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Hot water for off grid 12v cabin?

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Started 8 years ago by Taswegian
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Taswegian
Member

I am in the design process for a cabin that will have a small solar setup to power 12v lighting and 12v appliances so as to keep the build, battery bank and panel setup as small and economical as possible.

I decided that a gas hot water on demand continuous flow system would be the best option for this build to supply one shower and basin for dishes. It appears in my research though that the Bosch 17e requires a 240v plug in which is a spanner in the works; and that the Bosch 16h requires no such thing as it is pressure driven/ignited without the need for consuming electricity BUT apparently I would need a tank elevation of 5-6m to achieve the minimum pressure required which seems huge and a really big pain in order to elevate and collect water to feed it from that height.

So far I have only talked to one professional on the phone but he was pretty helpful. It later dawned on me that I may be able to use a 12v pump to feed the 16h or perhaps a power pack like laptops and caravan TVs have to power the 17e?

Or perhaps there is another method?

I'd like help with troubleshooting these ideas so that when I do the build everything runs as desired. Help?

Posted Thursday 18 Jul 2013 @ 8:41:27 am from IP #
johnmath
Member

You could use an inverter to provide 240 volts for the 17e, but that would be really wasteful and drain your battery even when not in use. Better to get a 12 volt caravan pump that only runs when needed and use it in conjunction with the 16h. You can get one a suitable pressure pump on fleabay from about $30.

Posted Thursday 18 Jul 2013 @ 1:39:33 pm from IP #
Taswegian
Member

I have read some terrible reviews for the 16h basically saying it is very unreliable when it comes to igniting. Multiple attempts are often required and it is very wasteful of water for that reason. Has anyone had any experience with either model?

Rather than a sinewave inverter I was wondering if the unit could be modded and I could get away with the 12v type of power pack/inverter that resides in the power lead? I don't know. I also don't know if this wold be drawig power on demand or constantly? Anyone?

Posted Thursday 18 Jul 2013 @ 4:04:28 pm from IP #
Benny
Member

I presume the 17e needs the 240V for the electronic ignition and other electronic controls - display + remote etc. There's a good chance that inside the 17e the 240VAC is instantly changed to 12VDC or maybe 5Vdc to supply the control circuit, although the ignition might be direct from 240V. If so maybe you could use 12VDC direct to the 17e "innards" ? I suppose Bosch would be reluctant to divulge this though and there would be warranty issues. Anyone got one and can advise what the innards look like ?

You mention that the 16h needs "5-6m elevation for minimum pressure" - are you aware the 17e also has a minimum pressure spec of 100kPa - which is 10m head.

Posted Friday 19 Jul 2013 @ 2:46:11 am from IP #
johnmath
Member

The Bosch 17e has anti freeze elements, fans, microprocessor and so on and chews up a bit of electricity. Have a look at this site, which has a good discussion of the issues of gas heated water in an off grid situation: http://solarhomestead.com/gas-tankless-water-heaters/

Have you looked on fleabay: http://www.ebay.com.au/itm/Country-Comfort-LPG-Gas-Portable-Camp-Instant-Hot-Water-Shower-Heater-/350665219854?pt=AU_HotWaterSystems&hash=item51a5469f0e&_uhb=1

Posted Friday 19 Jul 2013 @ 3:29:32 am from IP #
gazmo88
Member

Sorry if this is a bit left field but have you thought about an Eberspacher ?

http://www.eberspacher.com/products/heating-products/water-heating.html

That runs on a tiny amount of 12 volt power and uses a max of half a litre of diesel or kero an hour for approx 4000 watts output.

Will heat a water tank as well as run hydronic fan heaters.

Its a balanced flue so does not use any internal air from your cabin.

They are designed for boats and trucks. The boat models are much more expensive than the truck ones.

We had two in our boat and they are genuinely tiny marvels of German engineering.

No idea about distribution etc in Oz but you could also look at the Webasto:
http://www.webasto.com.au/products-and-markets/marine/ena/html/8651.html

Webasto was not as highly regarded as Eberspacher but I forget why now - maybe did not make ones that small.

Good luck

Posted Friday 19 Jul 2013 @ 3:59:39 am from IP #
Taswegian
Member

I have looked at the country comfort but it reminds me of my aquacube series II which flows at 4.5L per minute and only really sprays most of the body so you are left pretty cold when showering. I really want a upgrade from this for the build. I like it that the country comfort has it's controls mounted on the side of the unit though. On the aquacube they are on top and when you reach out of the shower to adjust the settings they pool with water which runs into the unit and kills my flame (terrible design.) The shower head/hose connections also leak (though I am going to see if the fittings will allow replacement with something more heavy duty.) The country comfort flows at 6L per minute which is an improvement but I don't know if it would be sufficient or not.

Hence why I have been questioning the feasibility of the two Bosch models. The 16h really is starting to push in front after reading the last two posts however.

Can I successfully overcome the elevation issue if using a 12v pump? If I went for a model of 12v pump that pumped more litres per minute than the country comfort is listed as delivering would that 1) give it a little more power/push 2)change nothing or 3) have a negative effect on how the system functions?

I also really want to have a setup that will allow adjustment of temperature whilst showering preferably with hot and cold taps. It may be possible to do this with the country comfort by running by running a second water supply and pump that would mix before reaching the shower hose but I am unsure as to how well this would work or how to devise it.

Posted Friday 19 Jul 2013 @ 4:01:09 am from IP #
johnmath
Member

Taswegian said:
Can I successfully overcome the elevation issue if using a 12v pump? If I went for a model of 12v pump that pumped more litres per minute than the country comfort is listed as delivering would that 1) give it a little more power/push 2)change nothing or 3) have a negative effect on how the system functions?

2. it wouldn't matter. I would be a little skeptical about the ratings of pumps anyway so it would be good to get one rated at 12 - 15 liters per minute, or match the heater if it is more. (My shower uses 9 liters per minute and has quite a good flow.)

Posted Friday 19 Jul 2013 @ 6:44:22 am from IP #
johnmath
Member

Taswegian said:
I also really want to have a setup that will allow adjustment of temperature whilst showering preferably with hot and cold taps. It may be possible to do this with the country comfort by running by running a second water supply and pump that would mix before reaching the shower hose but I am unsure as to how well this would work or how to devise it.

I prefer to run the hot water tap only and adjust the heater for the right temperature. That way with the maximum flow through the heater, there is less chance of it cutting and and having a cold deluge as a result. It would also be more efficient on gas to heat the water to the temperature required, rather than to, say, 60 degrees and then cool back to 40 by mixing in cold water.

Posted Friday 19 Jul 2013 @ 6:47:31 am from IP #
dbindoff
Member

I'm pretty sure I had a 16h installed several years ago for offices, while I was around it seemed to be working fine, we did have reasonable pressure on the mains. When I researched it, as I recall the only negatives users were having were related to low pressure.

Posted Friday 19 Jul 2013 @ 7:18:49 am from IP #
Taswegian
Member

johnmath said:(My shower uses 9 liters per minute and has quite a good flow.)

What heater do you run and is it installed indoors or outdoors?

I was thinking that if I were to install something indoors (they say not to) I could make it safe bu having a vent at the bottom of my entrance door like caravans have so that any potential gas leak would escape due to it being heavy and sinking through the vent. I can't see any problem with that other than it would take up valuable space and I could probably just as easily build an adjoining deck and have an outside bath/shower setup with the unit housed on the exterior cabin in a protective box with vented door.

Posted Friday 19 Jul 2013 @ 3:13:40 pm from IP #
MoreBikesPlease
Member

Taswegian, I've set up a weekender cabin just as you describe. All electrics are DC - I haven't added an inverter yet. I started with a 12V system, but then upgraded it to 24V (with converters to power 12V lights and cigarette sockets).

Supplying a Bosch Hydropower 10H with a single caravan-style 24 volt Shurflo 2088 pump, the hot water flow was NOT reliable enough. But now that I've added a second identical pump plumbed in parallel, showers are great!

My system also has a small caravan-style pressure tank after the pumps, to smooth out the flow. The pressure in the air pocket can be topped up with a bicycle pump. I did try a variable-flow shurflo which supposedly removes the need for a pressure tank, but it turned out to be faulty. The 2088s seem bombproof.

Posted Saturday 20 Jul 2013 @ 4:35:31 am from IP #
MoreBikesPlease
Member

Oh a couple of things to add:
- My Bosch 10H is installed outside, but under a carport. No problem in heavy frosts.
- If it hasn't been used for a week or more, it does take a long time for hot water to start flowing. That's OK once you're used to it - use the hot tap for all your hand washing, cooking etc. After a while the hot water comes through. I guess it's taking a while for LPG to work its way through the pipes.

Posted Saturday 20 Jul 2013 @ 4:37:01 am from IP #
yabbietol
Member

Hello below is something I posted in another forum topic

"Please be careful with WA instantaneous water heaters, some years ago we had one I cannot recall the brand name. We had no end of problems not because the heater was not good quality, but that it was designed for WA which does not have very cold winters. The problems we had with the heater all related to the heater partially freezing and damaging itself and leaking.
We followed the advice of a local plumber and installed it outside our house and every winter had problems."

I do not know if these problems apply to other instantaneous HWS but be careful with outside installs in cold areas.

Posted Saturday 20 Jul 2013 @ 6:42:20 am from IP #
Taswegian
Member

MoreBikesPlease said:
Taswegian, I've set up a weekender cabin just as you describe. All electrics are DC - I haven't added an inverter yet. I started with a 12V system, but then upgraded it to 24V (with converters to power 12V lights and cigarette sockets).

What was your reason for switching to 24v. How have you found it and what is your solar setup? I was thinking I could getaway with 2-3 deep cycle batteries on rotation being topped up by one or two camping solar setups maybe to run small LCD tv, charge mobiles, laptop and 12v caravan lights; so I'd be interested to compare your needs and find out what your setup is and how it copes.

MoreBikesPlease said:
Supplying a Bosch Hydropower 10H with a single caravan-style 24 volt Shurflo 2088 pump, the hot water flow was NOT reliable enough. But now that I've added a second identical pump plumbed in parallel, showers are great!

My system also has a small caravan-style pressure tank after the pumps, to smooth out the flow. The pressure in the air pocket can be topped up with a bicycle pump. I did try a variable-flow shurflo which supposedly removes the need for a pressure tank, but it turned out to be faulty. The 2088s seem bombproof.

Was the pressure too weak or did it cut in and out? How many litres per minute was it delivering? Also this secondary tank (pressure tank) is not something I knew about. What reading should I be doing regarding this?

Posted Saturday 20 Jul 2013 @ 10:08:33 am from IP #
MoreBikesPlease
Member

Hi Taswegian. I've only got two 12V nominal, 80W solar panels. Originally wired in parallel, now in series to give 24V nominal.

My regulator is a Plasmatronics PL40. Aussie-made and very tough. When you look at specs, don't be confused by the 7 amp "load" rating. That's only if you hook up your loads (appliances) to draw out of the regulator. Actually you can run the loads off the battery, without going through the regulator.

My initial battery was a big 220AH 12V sealed AGM unit I got on special. Too heavy for one person to lift! It died prematurely, probably due to summer heat in the attic where I set it up. Since I had to replace it, I took the opportunity to increase the overall storage, going for four 6V , 200AH batteries:
item NPD62000A at http://www.yhipower.com.au/main/product-1.1.4.html. Combined in series they make up 24V, 200AH. This is one reason for going 24V - when you've got multiple batteries of a manageable size, a series connection is better than parallel. This is because they all get drained identically so they don't get unbalanced. Other reasons:
- The current through your wires and components is halved, and resistance losses are quartered, so they can be less beefy and cheaper. Any voltage drop that occurs is smaller in comparison to the starting voltage, so less significant.
- It becomes more practical to run 240V appliances in the future, if I wanted to. On mains power, a standard 240V powerpoint is on a circuit fused at 10 amps, so it can run appliances up to 2400 Watts eg toaster, microwave, hair dryer etc. To run 2400W through a 12V inverter, the battery must supply 200 amps, which needs a super-thick expensive cable, unusual circuit breakers etc. A 24V battery has to supply 100 amps, which is more do-able.
- 24V nominal solar panels with 72 5-inch cells have become common and cheap, relative to 12V panels. Although the trend now is towards even bigger panels with 60 6-inch cells that would need a MMPT regulator to charge batteries.
- Running lights and sensitive electronics directly from a solar system is not ideal. The voltage at the battery terminals varies from 12V up to 18V or so when it's being charged, which is harsh on these appliances. Depending on your charge regulator, lights may flicker as the voltage pulses. A 24V to 12V converter outputs a nice stable voltage for them. On the other hand, motors can handle voltage fluctuations much better. Running 24V DC pumps, camping fridges and extractor fans directly off a 24V DC solar system works very well.
- 24V system voltages are basically as safe to work with as 12V and still classed as ELV (extra-low voltage).

I run a camping fridge, water pumps, extractor fans, 12V compact fluoro lights, a car radio with big speakers, small TV, cordless drill charger, laptop charger, phone charger etc.

This is the kind of voltage converter to use. You can run 24V to somewhere close to the appliance, and then convert to 12V. The really small flimsy converters are no good.
http://www.ebay.com.au/itm/DC-DC-Converter-Regulator-24V-Step-Down-to-12V-20A-240W-/280821951077?pt=AU_B_I_Electrical_Test_Equipment&hash=item41624aea65&_uhb=1

Here are some good tips on cable sizing. You can also find online calculators and tables.
http://www.smartgauge.co.uk/cable_type.html

Using several batteries on rotation would be annoying I think. It's also better to have your whole capacity working together, because batteries like to have a small current drain, relative to their capacity.

Your usage looks pretty similar to mine, apart from the fridge. If you're not going to use a camping fridge, and you can rule out ever running power-hungry stuff like a toaster, I'd guess you'd only need about half or a third of my system. But watch out for appliances' starting amps. When you turn on a motor it typically draws an initial spike of current that's several times higher than when it settles down. Your system has to cope with that, plus whatever else is running at the same time. Electronics and lights don't have a spike like this.

In hot weather, batteries should be charged more gently than normal, and vice-versa in cold conditions. So it's a good idea to use a regulator that adjusts its charging to the battery temperature. This needs a wire from the regulator to a temperature sensor on the battery casing.

With sealed batteries at 12V or 24V, the main safety issue is short-circuiting from positive to negative. A big battery can instantly melt/vaporise a spanner, wristwatch etc!! Use good terminal covers, and a circuit breaker or fuse close to the battery. With flooded batteries you also have all the issues with acid, potential hydrogen off-gassing etc. Even a sealed battery could theoretically off-gas, so you have to allow for venting.

Pump specifications give a flow rate in litres per minute, but this is only the rate at zero pressure, ie no restrictions to the flow. When the pump has to push water through plumbing, up to a shower head etc, back-pressure builds up, the pump has to work harder and the flow rate will be reduced. This flowrate/pressure relationship is shown on a pump curve.

A standard caravan pump has a simple pressure switch. The pump runs until the pressure at the pump's outlet reaches a certain level, then the pump stops. When you open a tap water flows out, pressure is relieved, and the pump starts up again. So the water out of the pump tends to pulse rather than flow, and the hot water system is unlikely to work reliably. Here's some info on pressure tanks /accumulators:
http://caravansplus.com.au/catalog/help-tips6.php

Hope this helps!

Posted Saturday 20 Jul 2013 @ 11:52:44 am from IP #
Johnnojack
Member

Solar HWS? How often do you use the cabin? Even in not so sunny Tassie 5 days sun will give you hot water for the weekend. Does the Bosch 10H have a pilot light which stays on? Gas bottle empty after no use for 2 or 3 weeks.

Posted Saturday 20 Jul 2013 @ 2:24:46 pm from IP #
MoreBikesPlease
Member

Johnnojack, I thought about a solar HWS but the cost was too high for a weekender. These days there are some cheaper solar systems though...

The Bosch Hydropower units have no pilot - they use the power of the flowing water to drive a sparking igniter. Using gas just for cooking and hot water, a bottle lasts forever!

Posted Saturday 20 Jul 2013 @ 9:08:10 pm from IP #
Taswegian
Member

I am looking at spending extended periods of time. Weeks/months on end for Mountain pepper harvesting and doing the cabin up with add-ons or to sell on as it is easily transportable.

The latitude is about 41.36, average elevation is 561m above sea level with highest point being 1330m. Plan is 6m long high cube shipping container either on top of a hill (no shade on panels/frosts minimised) in a generally rainy, cold highland area of Tasmania.

It will either be near a shed on the hill (storage/water collection) or down in front of the hill (gravity fed water from hill, less wind but closer to water holes and colder with some shade) I want to have it on four concrete anchor points to raise it a bit and put a barrel heater in there a window and a door.

For maximum solar exposure I am going to place it lengthways facing true north to put panels on a right angle triangular roof which will either become a sleeping loft or storage. There will be an outdoor platform with roof for showering over a bath and I will either dump the water as the site is well drained or plumb it to a collection tank for gardening. I will have a long drop toilet similar to the one I grew up with. I want to keep this cheap but functional with minimal power consumption/wastage so I won't be running any 240v appliances if I find I need to I will use a generator same as will be used for the angle grinder when modifying the container.

I am not convinced solar hot water is good enough for this project given the area and climatic conditions. Nearby neighbours have power a power pole but it would be around five grand to get it to the site and I have no desire to pay that or get a power bill. I am going to charge everything 12v. For refrigeration I will use a zeer pot in a cage to keep possums away and hole lined with bricks with a lid. I want to run a 12v freezer small LCD TV, laptop without the need to be turned off, 12v caravan lighting, probably 12/24v water pump, gas cooker and gas hot water. I have plans drawn that are evolving.

I need to figure out the most sensible way to do the HWS and the solar setup I will use but other than that I have a good basic working idea as to what will be sufficient. Down the track I may have a wetback fitted to the barrel heater but I don't see it burning much as the space will heat VERY quickly and need ventilation (thinking whirly bird and cross ventilation from container doors and window at other end) hence the desire for gas HWS especially for when it is warmer.

I am not a natural with maths and advanced stuff is beyond me so solar system technicalities tend to confuse but I have been left with the impression from some reading that a 24v system once "converted" to 12v for appliances isn't always converted but stepped down with less being drawn fro the panels and the potential power draw/storage is halved and potentially stored power is wasted. I think I may have confused the matter though.

I know I won't need a big/expensive setup though and that the neighbours had the power disconnected and were using a barrel heater with wetback in a far lager space, long drop, LED lighting, charging phones and using a laptop and LCD TV for at least 6 hours or so a night with one battery and one 120w panel. I can't see the wetback being as practical for me as for them and want gas so I am asking as many questions as possible before I part with my money as it isn't much.

Posted Sunday 21 Jul 2013 @ 1:41:53 pm from IP #
MoreBikesPlease
Member

Mountain peppers are a new one to me - interesting!

Learning from or copying the neighbours is always good! However it sounds like their 12V system is just running electronics, no motors. Your freezer and water pump will bump up the consumption, and also have the "spike" effect I mentioned.

Yes converting from 24V to 12V involves losses, but they should be only about 15%, not 50%. You value simplicity, so going up to 24V may not be worth it. Your demands are frugal, but the freezer is the big consumer.

It's good that you'll have a generator given your location. You could add on a 240V-driven battery charger to give your battery a boost when it gets low. And while the gennie is running you could always run some of your appliances off it if they are 240V / 12V switchable, eg laptop, TV, freezer. The Zeer pot sounds cool!

I think you need to make a list of your planned electrical appliances, and look up from specification sheets how much current (measured in amps) they draw. If the spec only gives the power in watts, that's ok because current (amps) = power (watts) divided by voltage (volts).

Estimate how many hours per day each appliance is likely to run. From that you can estimate how much battery storage you need, and also estimate the maximum "spike" power / current your system needs to support. Number of panels comes later.

For example if you used a 12V Shurflo 2088 pump, it would draw about 5.6 amps of current while it is working quite hard, delivering 30 PSI of pressure.
http://www.shurflo.com/files/RV-Product-Data-Sheets/Classic-Series-Pumps/Classic%20Pump%20-%20pds-2088-422-144_444_.pdf

Lets say this was running for 0.5 hours a day to wash hands, wash dishes, prepare food etc. No toilet filling 'cause you're using a long drop. So it will consume 5.6 x 0.5 = 2.8 amp-hours of energy.

If you're running a Bosch 10H for your shower, your second 2088 pump kicks in as well. Worst case, both pumps are running continuously during your shower. 12 minutes of showering per day (one fifth of an hour) consumes 5.6 x 2 x 0.2 amp-hours = 2.24 amp-hours of energy.

So per day, your water pumping will deplete your 12V battery by 2.8 + 2.24 = 5 amp-hours. Actually it will deplete a bit more thanks to resistance losses in the cable and switches between the battery and the pumps.

For the freezer, let's say you had a Waeco CF-50 running on 12V. While the motor is running it draws about 5 amps of current. When the motor starts, it might draw a spike of 10 amps instantaneously. Over an hour, the fridge cuts in and out to maintain the temperature. When running as a fridge, its average current draw is 0.84 amps. When run as a freezer its draw is a bit uncertain. You can maybe get away with 2.5 amps average if it's in a cool spot and you add some extra insulation eg underneath the freezer. So over 24 hours it will deplete your battery by 2.5 x 24 = 60 amp-hours of energy.
http://www.waeco.com.au/products5.asp?id=334&catId
http://www.caravanersforum.com/viewtopic.php?f=2&t=8487

Your other appliances should be easier to work out than these.
Laptop: I think you will need to turn off or hibernate when it's not in use. Say 30 watts at 12 V draws 30 / 12 = 2.5 amps. 4 hours per day = 10 Ah.
Lights: 2 amps for 5 hours = 10 Ah.
Small TV: 2 amps, 2hrs = 4 Ah.

With these assumptions, your daily current draw is about 90 amp-hours (Ah) of energy. How big does the battery need to be? The rule of thumb to maintain its health is don't deplete it by more than 50%. We might allow for two rainy days with no solar charging. Actually the panels will still charge a little, but the cloud might persist for longer. In a string of cloudy days you start to rely on your generator. So we need a battery capacity of 90 x 2 x 2 = 360 amp-hours.

Looking at sealed 12V AGM lead-acid batteries as an example, you could get two NPD63800 six volt batteries, each with a capacity of 380 Ah. Then connect them with a fat cable to give a combined battery of 12V, 380 Ah capacity.
http://www.yhipower.com.au/main/data/neutonpower/NP_DCS_VRLA_AGM_A4.pdf
Flooded batteries would be cheaper of course.

Your maximum "spike" current is when you're having a shower and the freezer kicks in: 5.6 x 2 + 10 = 22 amps. But you'll have to allow for your other appliances running at the same time too, say 35 amps total amps. You might use a 40-amp circuit breaker on your battery. If the current draw on the battery exceeds this, the circuit is broken. Now your cable from the circuit breaker to your distribution box / fuse box needs to be rated to at least 40 amps. Perhaps AWG 6 (American Wire Gauge) which has a conductor about 4mm in diameter, or 13 square millimeters in area.

Then I'd use a box something like this:
http://www.narva.com.au/pressreleases/asset_id/116/cid/1/parent/0/t/pressreleases/title/new-12-way-fuse-box-eliminates-messy-wiring

And thinner cable out to your appliances. Not too thin or you'll have resistance losses. If the freezer is say 5 meters away from the box I'd use a cable with conductor area say 5 square millimeters, or AWG 10.

Posted Monday 22 Jul 2013 @ 1:04:21 am from IP #
Taswegian
Member

MoreBikesPlease said:
When you look at specs, don't be confused by the 7 amp "load" rating. That's only if you hook up your loads (appliances) to draw out of the regulator. Actually you can run the loads off the battery, without going through the regulator.

I could be reading this wrong but; you're talking about using power converted as it comed from the panel direct as opposed to the battery?

MoreBikesPlease said:I took the opportunity to increase the overall storage, going for four 6V , 200AH batteries:
item NPD62000A at http://www.yhipower.com.au/main/product-1.1.4.html. Combined in series they make up 24V, 200AH. This is one reason for going 24V - when you've got multiple batteries of a manageable size, a series connection is better than parallel. This is because they all get drained identically so they don't get unbalanced.

I am not sure whether to go for a series of batteries or one one enormous battery with a huge amount of amp hours and the relative pros/cons

MoreBikesPlease said:
Other reasons:
- The current through your wires and components is halved, and resistance losses are quartered, so they can be less beefy and cheaper.</bolckquote>
cheaper?

MoreBikesPlease said: Any voltage drop that occurs is smaller in comparison to the starting voltage, so less significant.
- It becomes more practical to run 240V appliances in the future, if I wanted to. On mains power, a standard 240V powerpoint is on a circuit fused at 10 amps, so it can run appliances up to 2400 Watts eg toaster, microwave, hair dryer etc. To run 2400W through a 12V inverter, the battery must supply 200 amps, which needs a super-thick expensive cable, unusual circuit breakers etc. A 24V battery has to supply 100 amps, which is more do-able.

When you say mains power you mean 240v not grid connect right?

MoreBikesPlease said:
- 24V nominal solar panels with 72 5-inch cells have become common and cheap, relative to 12V panels. Although the trend now is towards even bigger panels with 60 6-inch cells that would need a MMPT regulator to charge batteries.

What is a MMPT regulator and how other than price is this significant precisely as this is all new to me?

MoreBikesPlease said: - Running lights and sensitive electronics directly from a solar system is not ideal. The voltage at the battery terminals varies from 12V up to 18V or so when it's being charged, which is harsh on these appliances. Depending on your charge regulator, lights may flicker as the voltage pulses. A 24V to 12V converter outputs a nice stable voltage for them. On the other hand, motors can handle voltage fluctuations much better. Running 24V DC pumps, camping fridges and extractor fans directly off a 24V DC solar system works very well.

I was thinking I would run these lights:
http://www.ebay.com.au/itm/290942035498?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

MoreBikesPlease said:
- 24V system voltages are basically as safe to work with as 12V and still classed as ELV (extra-low voltage).

I run a camping fridge, water pumps, extractor fans, 12V compact fluoro lights, a car radio with big speakers, small TV, cordless drill charger, laptop charger, phone charger etc.

This is the kind of voltage converter to use. You can run 24V to somewhere close to the appliance, and then convert to 12V. The really small flimsy converters are no good.
http://www.ebay.com.au/itm/DC-DC-Converter-Regulator-24V-Step-Down-to-12V-20A-240W-/280821951077?pt=AU_B_I_Electrical_Test_Equipment&hash=item41624aea65&_uhb=1

Here are some good tips on cable sizing. You can also find online calculators and tables.
http://www.smartgauge.co.uk/cable_type.html

Using several batteries on rotation would be annoying I think. It's also better to have your whole capacity working together, because batteries like to have a small current drain, relative to their capacity.

Your usage looks pretty similar to mine, apart from the fridge. If you're not going to use a camping fridge, and you can rule out ever running power-hungry stuff like a toaster, I'd guess you'd only need about half or a third of my system. But watch out for appliances' starting amps. When you turn on a motor it typically draws an initial spike of current that's several times higher than when it settles down. Your system has to cope with that, plus whatever else is running at the same time. Electronics and lights don't have a spike like this.

Our usage looks very similar I was thinking about buying 4x 250w panels either:
http://www.ebay.com.au/itm/350835973245?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

or:
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=221258095946

I first need to find out what would be compatible regarding batteries/leads/plugs and fuses first though.

MoreBikesPlease said:
In hot weather, batteries should be charged more gently than normal, and vice-versa in cold conditions. So it's a good idea to use a regulator that adjusts its charging to the battery temperature. This needs a wire from the regulator to a temperature sensor on the battery casing.

With sealed batteries at 12V or 24V, the main safety issue is short-circuiting from positive to negative. A big battery can instantly melt/vaporise a spanner, wristwatch etc!! Use good terminal covers, and a circuit breaker or fuse close to the battery. With flooded batteries you also have all the issues with acid, potential hydrogen off-gassing etc. Even a sealed battery could theoretically off-gas, so you have to allow for venting.

I don't know whether to go for one battery like this and if it would work for me:
http://www.everybattery.com.au/proddetail.php?prod=6PVV900PPOL

or whether to go for a bank of batteries that hold less amp hours and why exactly.

MoreBikesPlease said:
Pump specifications give a flow rate in litres per minute, but this is only the rate at zero pressure, ie no restrictions to the flow. When the pump has to push water through plumbing, up to a shower head etc, back-pressure builds up, the pump has to work harder and the flow rate will be reduced. This flowrate/pressure relationship is shown on a pump curve.

A standard caravan pump has a simple pressure switch. The pump runs until the pressure at the pump's outlet reaches a certain level, then the pump stops. When you open a tap water flows out, pressure is relieved, and the pump starts up again. So the water out of the pump tends to pulse rather than flow, and the hot water system is unlikely to work reliably. Here's some info on pressure tanks /accumulators:
http://caravansplus.com.au/catalog/help-tips6.php

Hope this helps!

Very helpful. I am starting to look at the country comfort as a more viable option however it seems to first heat water a set amount of degrees above it's ambient temperature (20-30 from memory) and to cut off and not heat above 50 celsius. This sounds like you would have to setup a system to have water run back through it a second time to be warm enough in really cold weather though.

I was also thinking that any low pressure issues could be countered by running two setups and two shower heads aligned to spray the same area. Just a thought. In the process of modifying my aquacube at the moment and building an enclosure first to see if it could still be incorporated into my cabin shower idea for extra flow.

Posted Thursday 25 Jul 2013 @ 12:13:27 pm from IP #
Taswegian
Member

MoreBikesPlease said:
Mountain peppers are a new one to me - interesting!

http://www.diemenpepper.com/plant.html

Not my enterprise but I am hoping to either supply or start my own venture as the family has harvested them in especially fruitful years ad we dried everything and sold it for a pittance without much in the way of story or packaging which I want to change since a growing market is emerging.

The property is isolated and the desire to be on the land is high hence the cabin. I don't have much money and get very few hours but have a bit over 5 grand. putting a container up there with a barrel heater in it with a pot/kettle attachment will cost me 2,700 roughly. I know a couple of people that are good with metal fabrication and welding which can held with making window frames to put second hand windows in.

I figure the left over funds will be spent on 1000L $80 tank for shower, shower system probably the country comfort in conjunction with aquacube to achieve 6-10.5L/pm and a solar setup. Will look at foilboard on the inside and maybe ceramic paint (depending on the cost) or battens with insulation and covering on the outside later on.

As the leaf is the only thing available year round and the fruits aren't reliable in appearing or bearing great quantity from year to year when it does happen you have to be there all the time to put all your effort into collecting and drying. One of the next door neighbours is my eldest sister's mother and she used to run a herb farm so she has drying sheds and incidentally knows a lot about extracting oils and making tinctures which I am considering may be a viable secondary line of products.

Posted Thursday 25 Jul 2013 @ 5:09:58 pm from IP #
MoreBikesPlease
Member

Taswegian said:
I could be reading this wrong but; you're talking about using power converted as it comed from the panel direct as opposed to the battery?

Your system will do that naturally - power you are using will get "skimmed off" before the solar charge makes its way into the battery. I was just referring to an additional feature of this regulator (and others). As well as taking power from the battery, you can take a limited amount from the regulator.

Taswegian said:
I am not sure whether to go for a series of batteries or one one enormous battery with a huge amount of amp hours and the relative pros/cons

The main advantage is transport - how are you going to get a single enormous one up to your cabin? Also redundancy. A battery is made up of multiple cells, each at about 2 volts - so a standard 12-volt battery has 6 cells. You may have seen this in your car battery when topping up the water. Occasionally a cell dies, in which case you have to replace the battery. If you have a series of batteries, then you only have to replace part of your setup.

Taswegian said:
When you say mains power you mean 240v not grid connect right?

Yes, it was just an example.

Taswegian said:
What is a MMPT regulator and how other than price is this significant precisely as this is all
new to me?

To charge a battery, you have to force a current of electricity into it. This requires a higher voltage than the battery voltage. Like to pump up a tyre, your pump must deliver a higher pressure than the pressure of the tyre. To treat the battery well, the voltage should be managed as the battery gets charged up - lower at first, then higher at the end. Eg 15 volts to finish charging a 12V lead-acid battery. The current should be managed too. When the battery is low, you can safely pump a lot of current into it quickly ("bulk charging" stage). Then when it is near full, the current must be reduced ("absorption" and "float" stages). Then it must be turned off, or you damage the battery (like popping the bike tyre!).

This management of voltage and current is what a regulator does. Traditional regulators use PWM
(Pulse Width Modulation). This is just a very fast switch turned off and on to manage the current. The input voltage must be at an appropriate range - high enough to charge the battery,
but not too high or the potential power of that extra voltage is wasted. So with a PWM
regulator, you need a solar panel with an appropriate voltage. Panels designed for charging 12
volt batteries are nominally 12V panels, but actually deliver a higher voltage, up to 18V. Some
of the panel's capability is wasted, especially in the bulk charging stage. But PWM regulators
are relatively simple, robust and cheap.

A newer development is the Maximum Power Point Tracker (MPPT) regulator. These have more
flexible management of voltage and current. If a panel is delivering 5 Amps at 26V, the regulator can convert it into say 10A at 13V, or some different ratio. It considers both the
current appropriate for the battery's stage of charge, and the current at which the solar panels
will deliver maximum power (the Maximum Power Point). The two main advantages of MPPT regulators over PWM are:
- Much less power from your panels is wasted due to mis-matched voltages.
- You have more freedom in selecting panels, as you no longer have to match your panel voltage to the battery voltage.

Taswegian said:
I was thinking I would run these lights:
http://www.ebay.com.au/itm/290942035498?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

The specs look good to me!

Taswegian said:
Our usage looks very similar I was thinking about buying 4x 250w panels either:
http://www.ebay.com.au/itm/350835973245?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

or:
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=221258095946

The first one look great, you can use a PWM or MPPT regulator. The second one is nominal 24V - too high for PWM, but great for MPPT.

Taswegian <a href="http://www.ata.org.au/forums/topic/10374#post-

45695">said:
I first need to find out what would be compatible regarding batteries/leads/plugs and fuses first though.

I don't know whether to go for one battery like this and if it would work for me:
http://www.everybattery.com.au/proddetail.php?prod=6PVV900PPOL
or whether to go for a bank of batteries that hold less amp hours and why exactly.

If you look at the specs on that battery, it is 2V. It is designed to be connected together in series to make up a useful voltage. To get 12V you would have to string six of them together. Then the combined battery will have 932 Amp-hours of energy storage, which is almost three times the battery size I estimated you would need.

From that website, I would go for:
http://www.everybattery.com.au/proddetail.php?prod=DC400-6
String two of these together to give 12V, 400 Amp-hours. These are AGM (Absorbed Glass Mat) batteries - the acid is encased in glass matting and the batteries are sealed, so they are pretty foolproof.

If you go for flooded batteries (cheaper), you have to learn how to do monthly maintenance. Check out the buttons "Battery Safety", "Battery Set-up" and "Testing" on http://www.rpc.com.au/information/faq/batteries/maintenance.html.

Taswegian said:
Very helpful. I am starting to look at the country comfort as a more viable option however it
seems to first heat water a set amount of degrees above it's ambient temperature (20-30 from
memory) and to cut off and not heat above 50 celsius. This sounds like you would have to setup a system to have water run back through it a second time to be warm enough in really cold weather though.

I was also thinking that any low pressure issues could be countered by running two setups and two shower heads aligned to spray the same area. Just a thought. In the process of modifying my aquacube at the moment and building an enclosure first to see if it could still be incorporated into my cabin shower idea for extra flow.

The Country Comfort is an instantaneous gas system, like the Bosch hydropower units. It's certainly aimed at your sort of application. If you've heard that it only heats 20-30 degrees, that will not be enough! Running water through twice would be very difficult.

The Country Comfort talks about being connected to a garden hose, and the specs say "Operates with 30-80 PSI of water pressure". So you still need to supply some good pressure. Two setups side by side would only make things worse. That would try to draw more water, reducing the pressure. I think to run an instantanous gas system you can't avoid a decent pump or a high header tank.

Posted Friday 26 Jul 2013 @ 12:29:13 am from IP #
Taswegian
Member

After talking to a guy at Jaycar and a guy at Every Battery I have come to the conclusion that the initial idea of the biggest wattage panels possible is not the greatest idea as I am going to go the route of mono-crystalline not amorphous; it seems a better idea to run more panels with lower wattage so that is they get leaves/anything that could partially obscure part of them I will be losing less power.

I had initially read the listing on the Every Battery site incorrectly as 12v. I like your suggestion of battery. I was looking at spending around 1k on batteries and the same on panels but now think my batteries will be the greater cost i my budget.

If I were to buy two of those batteries and run 12v and connect a MPPT regulator would I then be able to run all of my panels to my batteries okay? I was thinking maybe eight 100w panels? Possibly these:

http://www.ebay.com.au/itm/251090817167?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

or these:
http://www.ebay.com.au/itm/271241288428?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Issue with the first listing though is they don't ship to Tasmania or allow pick-up so I would have to ship them to friends in Melbourne then arrange courier. I am first contacting a friend who works on the Spirit of Tasmania ferry service to see if he would be allowed to bring them over potentially one at a time as I imagine they have weight/size limits to what they can take.

My partner is also contacting a friend who's parents have the contract for the yelllow pages phone book and periodically need to ship large volumes of them, so we thought we'd ask if panels could be squeezed into a shipment maybe.

Regarding the Country Comfort I was thinking about using one in conjunction with my aquacube, more hassle but two heads angled right would effectively give me 10.5LPM, I expect the 12v pump is unavoidable and two wouldn't be much more hassle however the two bottles and sets of knobs could be a pain in the rear.

I saw this:
- Rises ambient temperature by 25-30 degrees C
here:
http://www.blackdiamondsupplies.com.au/index.php/store/country-comfort-complete-portable-combo.html

So I emailed the company asking for clarity and received this reply:
Jul 24 (4 days ago)
"Me
How hot does the rio grande heat water? to what temperature/ambient difference in temperature? Also are the water hose fittings standard and threaded?

Info@blackdiamondsupplies.com.au

Jul 24 (4 days ago)

to me
50 deg c and standard and fittings supplied"

Which makes me think it would need to be run like a bath when especially cold then I'd have to dump a submersible pump in the bath and stand in in and shower as it cycled through for the second time at a higher temp. I don't know.

My initial idea of a barrel heater I realised would be far too powerful and have now talked to a boilermaker/welder friend who has made outdoor heaters/water heaters and she has agreed to make me one for free from a 9kg gas bottle which will be thick and better heat the space. I just need to salvage/purchase materials and draw up the plans and she will make it.

Now I have to research dampers, baffle plates, and more. Will work out far cheaper and possibly even more efficient may even attach a little wetback but I really do rather the idea of a consistent temperature. As a kid we lived in a place with wetback barrel heater ad I never liked the hot water being super hot.

Not sure what the best thing to do about insulation will be. I really like this video:
http://www.youtube.com/watch?v=DsVxgOjNLbA&list=PLIQwKbrJcxnGjdXq6Aij0XUPFwkeiLkNV

but wish she talked more about the insulation specifics.

This:
http://www.tincancabin.com/how-to-build/

is also interesting but his insulation looks really expensive. I want to be able to avoid corrosion/condensation. Ceramic paint like supertherm would be great but I suspect it costs heaps and also doubt I can find it in Tasmania.

Posted Saturday 27 Jul 2013 @ 6:03:07 pm from IP #
Greg
Member

I've used the spray insulation and would recommend it if you had easy access etc. Another idea might be just to protect the timber studs etc by coating them with a waterproofing membrane. There are a few on the market (liquid rubber) and are approved for bathroom waterproofing - very low odor, apply with a paint brush, wash up in water, flexible etc. Then you could use the foam board for insulation which again would not be affected by condensation. Might even be worth considering painting some on where the container wall and floor join to prevent rusting and add a small vermin proof drain.
If you wanted to go really alternative, have a look at Kevin Mclouds man made home. He built a toilet and bottled the methane produced. I also love his hotwater system which is just a hand made solid fuel boiler.
Keep the good information coming, great thread to read !

Posted Saturday 27 Jul 2013 @ 11:19:05 pm from IP #
MoreBikesPlease
Member

Taswegian said:
After talking to a guy at Jaycar and a guy at Every Battery I have come to the conclusion that the initial idea of the biggest wattage panels possible is not the greatest idea as I am going to go the route of mono-crystalline not amorphous; it seems a better idea to run more panels with lower wattage so that is they get leaves/anything that could partially obscure part of them I will be losing less power.

I had initially read the listing on the Every Battery site incorrectly as 12v. I like your suggestion of battery. I was looking at spending around 1k on batteries and the same on panels but now think my batteries will be the greater cost i my budget.

If I were to buy two of those batteries and run 12v and connect a MPPT regulator would I then be able to run all of my panels to my batteries okay? I was thinking maybe eight 100w panels? Possibly these:

http://www.ebay.com.au/itm/251090817167?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

or these:
http://www.ebay.com.au/itm/271241288428?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

The bigger panels you noted previously gave you more watts per dollar. And fewer, bigger panels makes less hassle with mounting, cables etc. I would just go for the bigger ones. If you are installing the panels in parallel, they will each be responding separately to shade anyway - I don't think smaller panels will make much difference on partial obscuration. Just try to keep the trees away, especially in winter.

A good MPPT regulator should be able to handle them fine. Your limiting factor will probably be the current (amps) coming from the solar panels. Let's consider these 24V panels you mentioned:
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=221258095946

The maximum current they can deliver at standard conditions is 8.7A (short-circuit current, Isc). Four panels in parallel will give 34.8A at 24V. Allow an extra 25% for extra performance in sunny, cold conditions -> 43.5A. That's a pretty high current! You'd run cables separately from each panel, then join them into a fat cable to the regulator.

So your regulator needs to support at least 44A of current. I don't have much experience with MPPT regulators, but Morningstar has a good reputation. Their Tristar MPPT-45 should be good. Note: another term for regulator is "controller".

If you went for 12V panels instead of 24V, the current would be doubled. Or you could muck around with hooking them up in series pairs to make 24V, then paralelling the pairs together.

On an average day with total sunlight equivalent to 4 hours of full sunlight (4 "peak sun hours"), one 250W panel as above would give you 8.17A x 4 = 32Ah of energy at 24V. The MPPT regulator will convert it to 64 Ah at 12V for your 12V battery. With four panels you'll get 64 x 4 = 256 Ah. This is a lot more than your daily consumption of 90 Ah. On a cloudy winter day you might get a quarter of that, back to 64 Ah. Even on a day like this your battery is only depleted by 26 Ah.

If you needed to reduce costs, I reckon you could cut back on the number of panels and get a smaller regulator to suit. See how much you are needing to use your generator. Then add more panels later if necessary.

Posted Saturday 27 Jul 2013 @ 11:48:38 pm from IP #
Taswegian
Member

MoreBikesPlease said:
The bigger panels you noted previously gave you more watts per dollar. And fewer, bigger panels makes less hassle with mounting, cables etc. I would just go for the bigger ones. If you are installing the panels in parallel, they will each be responding separately to shade anyway - I don't think smaller panels will make much difference on partial obscuration. Just try to keep the trees away, especially in winter.

I know and I am tight but figure 1)I am actually going to erect a right angle triangle roof with a pitch of near 60 degrees for maximum winter gain so I'm not worried about frames and their cost and 2) Cabling is relatively cheap and the guy at Every battery said as I don't plan on running any a very long distance thicknesses shouldn't make much difference.

Both people also said that I should run a bank if I can get away with it as it is easier in the batteries which I agree is a sound idea but I'm starting to think that if I run 12v that my battery bank would be two 6v batteries wired together which is pretty minimal and if I ran 24v it would be four wired together which would be twice as many batteries with double the cost and the same amount of amp hours but half the amperage draw. It appears to be much a muchness.

MoreBikesPlease said:
A good MPPT regulator should be able to handle them fine. Your limiting factor will probably be the current (amps) coming from the solar panels. Let's consider these 24V panels you mentioned:
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=221258095946

The maximum current they can deliver at standard conditions is 8.7A (short-circuit current, Isc). Four panels in parallel will give 34.8A. Allow an extra 25% for extra performance in sunny, cold conditions -> 43.5A. That's a pretty high current! You'd run cables separately from each panel, then join them into a fat cable to the regulator.

So your regulator needs to support at least 44A of current. I don't have much experience with MPPT regulators, but Morningstar has a good reputation. Their Tristar MPPT-45 should be good. Note: another term for regulator is "controller".

That shouldn't be an issue as far as I can see so far.

MoreBikesPlease said:
If you went for 12V panels instead of 24V, the current would be doubled.

Really? So it'd be in my favour?

MoreBikesPlease said:Or you could muck around with hooking them up in series pairs to make 24V, then paralelling the pairs together.

If you needed to reduce costs, I reckon you could cut back on the number of panels and get a smaller regulator to suit. See how much you are needing to use your generator. Then add more panels later if necessary.

I thought I may looking at running a small series battery bank and if it isn't sufficient at then buying more batteries and running several small banks so it would be [i]kind of[/i] paralell anyway but in effect but would also extend the battery life somewhat. Regarding the regulator I'll end up getting something that will cope with potential expansion but not to an enormous degree. I've been told to expect 4-500 for something really good which will be MMPT and cope with a lot which I am actually pretty relieved to hear.

Regarding refrigeration I am terribly close to buying the 40L 12/24/240v 40L Engel fridge/freezer from Rays Outdoors for $1100 (ouch but actually a big saving on the normal price) seeing as I can't find an Australian stockist or equivalent for this:
http://www.steca.com/index.php?Gefriertruhe_en

which frankly sounds fantastic but probably for the future.

Posted Sunday 28 Jul 2013 @ 12:48:45 am from IP #
MoreBikesPlease
Member

Taswegian said:
I know and I am tight but figure 1)I am actually going to erect a right angle triangle roof with a pitch of near 60 degrees for maximum winter gain so I'm not worried about frames and their cost and 2) Cabling is relatively cheap and the guy at Every battery said as I don't plan on running any a very long distance thicknesses shouldn't make much difference.

That angle will be great for winter! Just watch out for those trees.

Taswegian said:
Both people also said that I should run a bank if I can get away with it as it is easier in the batteries which I agree is a sound idea but I'm starting to think that if I run 12v that my battery bank would be two 6v batteries wired together which is pretty minimal and if I ran 24v it would be four wired together which would be twice as many batteries with double the cost and the same amount of amp hours but half the amperage draw. It appears to be much a muchness.

If you went for a 24V battery bank instead of 12V then you would have four *smaller* batteries wired together. The battery bank would be roughly the same weight and volume as the 12V battery bank option, and would store the same amount of energy. To run an appliance (eg a 12/24/240V fridge) at 24V instead of 12V, the battery would deliver half the current but at twice the voltage. Power in Watts = current (Amps) times voltage (Volts).

Note that if you use a MPPT regulator, your panel voltage can be different from your battery bank voltage. Eg 24V panels feeding a 12V battery bank.

Taswegian said:
MoreBikesPlease said:
"If you went for 12V panels instead of 24V, the current would be doubled."

Really? So it'd be in my favour?

Sorry, there's no free lunch. Regardless of voltage, the same area of panels will produce the same power in watts. Compared to 24V panels, 12V panels will give twice the current but only half the voltage. So the power is the same. Higher voltage is no problem as long as it stays under 60V or so. But higher current is a drawback because it requires fatter cables and beefier regulator, switches, circuit breakers etc.

Taswegian said:
I thought I may looking at running a small series battery bank and if it isn't sufficient at then buying more batteries and running several small banks so it would be [i]kind of[/i] paralell anyway but in effect but would also extend the battery life somewhat.

Think of your battery bank as a "high maintenance" girlfriend. Mixing batteries of different types and ages is not a good idea. Due to imbalances, some end up working too hard, failing prematurely and bringing the good ones down as well. Ditto for putting batteries in parallel. I would advise to get a solid battery setup, treat it well (don't overheat, overcharge, undercharge etc) and don't mess with it until replacement time. Solar panels cope with change better, you don't have to be so faithful with them.

Taswegian said: Regarding the regulator I'll end up getting something that will cope with potential expansion but not to an enormous degree. I've been told to expect 4-500 for something really good which will be MMPT and cope with a lot which I am actually pretty relieved to hear.

That sounds great. A 45 amp MPPT would fit the bill I think.

Taswegian said:
Regarding refrigeration I am terribly close to buying the 40L 12/24/240v 40L Engel fridge/freezer

That's like my 50L Waeco, but Engel has an even better quality reputation. It should serve you very well!

You might consider allowing $150 for a couple of good crimping tools, eg "Ratchet Crimping Tool Insulated Lugs" and "Mini Hex Crimper 6mm2 to 50mm2" at:
http://www.electricianstoolsonline.com/crimping-tools

These work with lugs such as: http://www.rpc.com.au/catalog/lug-6mm-cable-6mm-stud-p-699.html You can get the smaller ones in packets from Middy's and Jaycar.

I found that these crimped connections were quick, and gave me much better confidence of a good connection than my amateur soldering skills. Write a label on a white heat-shrink insulating label from Jaycar, put it on the cable, strip the plastic sheath off the cable, put the lug on, squash the lug onto the cable with the crimper and shrink the label with a butane stove lighter! See the 22-minute mark at:
http://www.youtube.com/watch?v=kjSGCSwNuAg

Posted Sunday 28 Jul 2013 @ 5:08:31 am from IP #
MoreBikesPlease
Member

I was just checking the specs on the Morningstar MPPT regulators, page 58 at:
http://www.morningstarcorp.com/en/support/library/TSMPPT.IOM.EN.04.pdf

The current limit applies on the battery side, not the solar side. So, when charging a 12V battery bank, the MPPT-45 can only supply 45A, for a power of 540 Watts (they say 600 Watts, so there must be a bit of wriggle-room). Even their MPPT-60 can only deal with 800 Watts.

So, if you want to allow for four 250W panels (1,000 Watts of power) into a 12V battery bank, you'll need a bigger regulator. The Outback Flexmax 80 can do it, but it's a lot more expensive than the Morningstar MPPT-45!

I think you've got two realistic options:
(1) limit your system to 500W of panels.
- Eg 2 of these: http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=221258095946
(2) Upgrade your battery bank to 24V, and have the option of 1,000W of panels.

I would go for option (2).
Advantages:
- Your cables, switches etc will be slimmer, cheaper and easier to work with.
- You can run your Engel directly from the battery at 24V.
- You can get water pumps to run directly at 24V.
- Four smaller 6V batteries are easier to move than 2 larger 6V batteries.
- You are free to use a PWM or MPPT regulator, from 24V panels.
- If you ever want to add an inverter later, it will be easier.

Disadvantages:
- 12V appliances (eg laptop from a car charger) need a 24V->12V converter, incurring losses of about 15%.

Posted Sunday 28 Jul 2013 @ 6:25:46 am from IP #
Taswegian
Member

Oh am I ever conflicted. I just got offered the shed which is 6mx8m to fix up fix up if I wanted with the offer of the old man throwing money at it for batts and a concrete floor and the option of him letting us take the panels and water system and buying us out if we ever want to use it o a block that is completely ours and buying us out on whatever we put into it or alternately beqeauthing me his controlling 33acre share in the 66 acre block and with the option of later buying out the others who bought into it in the 70s and now live on the mainland and have no interest in it.

This would potentially be great but throws problems up regarding the fact it is close to but not exactly true north and the roof pitch.

I had a look today at the Engel 80L which has the DC power consumption listed as variable from 0.5-4.2 amps using 12kw per month.

Now the 40L is says it's power consumption is variable from 0.5-2.5 amps and uses 10.5kw per month.

I don't know how that will translate difference margins in battery drain and if how what panel will be needed but the kw difference doesn't sound much and I am now tempted by the 80L as it works out cheaper than buying the 40L twice and would allow for storage of frozen meals to be reheated as well as storage of ingredients.

Can somebody please offer some advice?

Posted Sunday 28 Jul 2013 @ 12:14:34 pm from IP #

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