Can OZ ditch alternators? (in cars) « Alternative Technology Assn Forums

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Can OZ ditch alternators? (in cars)

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Started 8 years ago by dbindoff
Latest reply from Bushwalker

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dbindoff
Member

I have been mulling over this question, like to know what others think.

Motivation: save petrol

method: buy a semi-flexible PV panel and 'glue' it to a suitable car surface, connect via regulator to battery, perhaps disconnect alternator altogether, replace headlights with led versions, take care not to drive long distance at night with accessories going and park where solar insolation is available.

Info: As far as I can tell the current drawn while driving is most likely less than 4A, perhaps a lot smaller but difficult to get a good info source. Cheap panels now available would give similar order of current but keep battery well charged continuously when not driving. Virtually nowhere in OZ needs cold weather conditions reliability that high current output alternators and high CCA batteries are designed for. Battery would probably last longer provided it does not break by doing the wrong thing but that can and does happen anyway.

Question: How much petrol/emissions would be saved if it works?
Have I forgotten to include any deal-breakers or counter to my info?
Has anyone done it or similar?

Thanks for your consideration.

Posted Sunday 15 Dec 2013 @ 5:24:58 am from IP #
Chip
Member

I like your thought process. On run of the mill cars, alternators don't use much power to turn once the battery is fully charged and if there is little drain on battery from lights, heated windows, etc. Solar panels on a hybrid or a fully electric vehicle would be worth considering and there are advances in coatings that will soon make car shells large solar pv panels. Emissions might be best reduced by calculating the $$ that would be needed to buy and fit solar panels, led lights, etc to car then spend that money on solar pv or hot water for house. A growing number of cars automatically stop the motor and then restart it at traffic lights so that indicates that fuel saved is greater than amount used by driving alternator to recharge battery after starting drain.

Posted Sunday 15 Dec 2013 @ 9:06:51 am from IP #
dbindoff
Member

Thanks chip, I've already achieved pv solar beyond residence consumption and almost completely solar hw, so just looking at how to lop some more off mv use, evs still too expensive. Do you have any feel for the order of saving I might get?

Posted Sunday 15 Dec 2013 @ 9:25:07 am from IP #
Bushwalker
Member

Well, you can order a PV roof on the Nissan Leaf overseas (don't know about here)

The opinion from those that have a Leaf is:

does the PV cell on the roof of the SL make a noticeable difference in any way?

No.

Marketing. Purely.

The 3rd gen Prius has a really nice solar panel on its roof. I think it can generate about 60 watts of power in good sunlight. But it just powers the ventilation fan

Useless

From:
http://www.mynissanleaf.com/viewtopic.php?f=31&t=12442

A solar panel on the roof of a car sounds like a nice idea, until you realise that the car won't see much sun in the carport or garage, in the city, under a tree, etc, etc. On top of that, the alignment of the panel won't be the best on a curved surface when the sun is tracking across the sky. I shudder to think what the derate would be in ideal conditions, and the everyday power produced wouldn't pull the skin off a custard.

If we have batteries in an ICE car that actually gets used, we need them to be kept charged and an Alternator is the current best way to do it. When you find a solar panel that will fit on the roof of your car and put out 60A in the shade then you may have an option...

Posted Sunday 15 Dec 2013 @ 11:11:53 am from IP #
dbindoff
Member

BW, my thesis in this topic is that we don't need very many amps from our battery even when running accessories like audio and fans, I'm not sure how much that is but surely we can engineer it to be less than 60A???

A fully charged battery ought to be able to start a car a few dozen? times, so as long as the accessory load when the car is resting is low, then a moderate PV panel will be able to keep the battery charged ,in that case it will be sufficient to confidently run the car under the stipulations I mentioned.

The query is how much load will the (currently over engineered for our conditions) alternator release to power the wheels if it is not being driven by the motor.

Posted Sunday 15 Dec 2013 @ 10:56:21 pm from IP #
Bushwalker
Member

Understand your thesis dbindoff, and I agree that there must be some savings to be made but honestly doubt that a PV charging system is the answer in any but the most ideal circumstances.

You do know that alternators with no electrical load present very low drag to the engine regardless of their rated capacity? Bear in mind that alternator load on the engine is dependant on current draw. If there is little load on the system then the alternator will be idling with little impact on engine performance. On the other hand, an alternator supplying 50 amps will be pulling roughly 1.0 horsepower to do the job. 17 amps, and it would be about 1/3hp.

If we went back to 1970 where there was minimal electronics in the cars, they were mostly manual gearboxes and could be push started, then I think there would be a chance.

The alternator and battery in modern cars is sized to cope with all running conditions the vehicle is likely to encounter. High electrical loads during starting and running, hot weather A/C, cold weather starting and battery losses, resistive glass heating, Lighting, Entertainment and Engine management systems. On top of all those parameters, the charging system has to cope with short run times and low speed idling in traffic.

We all like to think we drive long distances and the battery will have no problems maintaining charge but the reality is different, we drive short distances, our cars spend a lot of time at traffic lights and idling in traffic, and the charging system just copes with that until a component falters.

If you can eliminate many of these loads, then sure, you can downspec the alternator, but I would suggest a higher efficiency alternator rather than a lottery on PV charging.

Found via google:

Sizing Up Your Alternator

Accessories Amp Draw
On Board Computer 0.2 – 0.3
Electric Fans 5 – 18
CDI Ignition 5 – 30
HEI Ignition 5 – 10
Electric Fuel Pumps 3 – 9
Electric Water Pumps 5 – 12
Instrument Panel 1.5 – 3
Brake Lamps 3 – 5
Running Lights 3 – 5

If we want to eliminate alternators in OZ cars, we need to go back to old cars

BW

Posted Sunday 15 Dec 2013 @ 11:40:00 pm from IP #
franks
Member

Assume 100amp alternator and 50% mechnical to electrical conversion efficency, will take up to 2.7kW from motor, with a average 100kW motor thats aprox 2.7% loss.
If it is a good idea it would be done already ??

Posted Sunday 15 Dec 2013 @ 11:43:47 pm from IP #
dbindoff
Member

BW thanks for the list.

Franks, I'm hoping a brave person has given it a crack already (and lived to tell the tale, psychologically intact)

If a Leaf can run total drive including accessories on 120wH per km on flat ground at 60km/h, then we can infer average power used from the battery is 7.2kW. If we do an iteration to see if there is any consistency and assume the accessory load is 500w average, then the leaf battery is using 6.7kW to drive the electric motor. Going back to the ICE, the alternator, using 50% conversion estimate requires 1kW from the motor on average to do the same job of running the accessories. If we ditch the alternator load altogether the ICE will presumably have 1kW extra to convert to wheels at say 40% conversion so provides an extra 400w at the tarmac. If we assume the leaf has 80% motor and drivetrain efficiency the 6.7kW above is actually 5.4kW at the wheels, so the expected benefit at the wheels from ditching the alternator is 7.4% , no or yes??

Hence, provided my battery can be charged to my satisfaction, I might improve emissions by around 7-8%. Providing 500w for extended periods is not feasible for the practical PV size I can use.
On the other hand if the real average load is 100w or even 200w, I could provide that for the practical drive times I expect but if I assume the alternator does a reasonable job of following the load and lowering its demand on the ICE, I will get less of an improvement than 7%. In addition , if the alternator averages 2kW against the ICE, I could potentially get greater than 14% improvement.

So 2 questions I need a practical answer to;
1) what is the real average power drawn by accessories under daytime driving conditions being very sensible with audio and a/c?

2) How good is the alternator at lowering demand on the ICE when it is working only to provide 100w say as compared to a potential 2.7kW. (BW reckons it's very good)

Posted Monday 16 Dec 2013 @ 12:54:58 am from IP #
Johnnojack
Member

Rather than the solar panel how about modifying the alternator so it charges more under deceleration and less when not. (I think some cars already do this not just the Prius). In traffic there would be plenty of "free" power available to keep the battery full.
One way may be to have 2 voltage regulators, a normal one and one which is set to a higher voltage and is activated by the brake light.

Posted Monday 16 Dec 2013 @ 10:45:44 am from IP #
Bushwalker
Member

Johnnojack said:
One way may be to have 2 voltage regulators, a normal one and one which is set to a higher voltage and is activated by the brake light.

Good idea johnnojack!

Rather than operate it off the brake pedal, run it from the accelerator - when you lift off, the regulator pulls up the field coils in the alternator.

Posted Monday 16 Dec 2013 @ 11:19:03 am from IP #
garyt
Member

There is a place that makes shock absorbers that make power to do just that with good results i can't remember where i saw it do a patent search or google and you should find it.

Posted Sunday 5 Jan 2014 @ 11:56:51 pm from IP #
Joe
Member

Most modern cars and light (12V) vehicles only charge to 80% to stop gassing and fluid loss from the battery typically 12.6V whereas a float charge would be 14.3V tapering to 13.8V
I am led to believe that many EURO speck vehicles already have a 2 stage charge (smart charge) that does just what you suggest , don't know the details but Ford make this claim for their 4WD Ranger and warn that they do not recommend fitting a second battery (to run a fridge etc) as the smart charge system won't charge the 2nd battery
The EURO market claims the smart chargers save energy as the alt doesn't cut back in till battery drops below 13.6v after braking (however with day time driving lights and other electronic driving aids this period may be quite short)
As a motor mechanic I find the claims to be more sales than actual savings
I have a small solar panel on the dash of all my vehicles to trickle charge the battery and find it works well on a sunny day as cranking volts are definitely higher in winter when most batteries fail
Hope this helps
Joe

Posted Monday 6 Jan 2014 @ 12:45:37 am from IP #
Joe
Member

Correction the 12.6v above should be 13.6V
Joe

Posted Monday 6 Jan 2014 @ 12:47:16 am from IP #
Bushwalker
Member

I agree re the charge voltage Joe.

There is an enterprising seller on ebay who has designed an Alternator Voltage booster to boost the voltage on vehicles needing the extra charge for dual batteries etc.

eg: http://www.ebay.com.au/itm/Prado-Hilux-LandCruiser-Alternator-Voltage-Booster-MK1-/321290702989

Apparently, works well.

Posted Monday 6 Jan 2014 @ 1:49:04 am from IP #

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