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Using alternator as starter engine

16401 Views 26 Replies 9 Participants Last post by  jared2009gregg

I'm building a hybrid vehicle, and for this I need to use (one of) the alternators attached to my internal combustion engine as a starter engine. My initial idea was to just use a starter motor, but since I can't use the retract function of this, it needs the starter engine to remain connected all the time, and (besides that this lower efficiency), it would also rip the starter engine apart due to the sheer force when running at full speed. So obviously I need to use one of the alternators as the starter motor.

The internal combustion engine I'm using is a 17 - 20 HP internal combustion engine. It runs at between 6000 - 7000 rpm (say 6500 rpm)
The most efficient rpm for the alternators (regular running, NOT starting !) is between 4000 rpm and 5500 rpm. So, I'll be using a 65/40 or 65/55 gearing in between the internal combustion engine and the alternators. I'll be using not gears, but a toothed belt for this, probably in a V-type setup.

The alternators are 2 Leece-Neville 8SC3009ZA's (well actually Prestolites, but these have the same specs as the Leece-Nevilles). They run at 24 Volt (output of the 2 is hence 48 V). Power curves are at

The batteries the alternators charge will probably be 4 batteries of 12 Volt (with 2,3Ah), in specific, these ones (as they're quickly rechargable):

I'll actually be using 2 sets of 4 batteries, so as to allow running the engine from 1 set, while charging the other set of batteries.

Anyway, the question I have is: won't this damage my alternators (as they're not intented to be run as engines, and I'll be starting (and stopping) the engine a lot), and is the power of the batteries (140 A @ 48 V) sufficient ? I assume so, from the power curve, but I still like to hear a second opinion, and hear that it is indeed possible to run these alternators as engines without damaging them.

If the above won't work, will some other batteries from cs-shop (in particular the 150A @ 12V, with 2,5Ah) be able to do it, and/or do I need still other batteries.

Note that the batteries have so little Ah mainly because I like to keep the vehicle very lightweight.
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I think we understand your conceptualizing and theorizing, but it seems you are woefully lacking in the knowledge and skills to actually design and build something based on your ideas. That's OK. This would be a difficult project for even the best designer/builder.

The good news is, if I understand your ideas and needs correctly, GM has already built this type of vehicle: the Volt( the Holden Volt in Australia and New Zealand, and with a different fascia as the Vauxhall Ampera in the United Kingdom and as the Opel Ampera in the rest of Europe.) A friend of mine has one, and he just loves it. He's careful to charge it whenever he has a chance, rarely buys gas, and yet can go on occasional long trips (using the gas engine) whenever he wants. The one drawback on long trips is that it's somewhat less efficient than conventional ICE cars because of the extra weight of EV hardware and batteries.

Volts are now available on the used market. If you really need to get your hands dirty, drive-trains and batteries are available at wreckers for Volt- based DIY conversions.
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I read the article about the GM Volt. It says that "the Volt operates as a pure battery electric vehicle until its battery capacity drops to a predetermined threshold from full charge. From there its internal combustion engine powers an electric generator to extend the vehicle's range as needed."
What you have conveniently left out of the quote from Wikipedia is the next line: " When the engine is running it may be periodically mechanically linked (by a clutch) to a planetary gear set, and hence the output drive axle, to improve energy efficiency"

So, YES the electric motor and the ICE CAN and DO run at the same time in the Volt. The designers at GM took a long time to work out the timing and sequencing of the electric motor and ICE to achieve maximum efficiency. It delayed the introduction of the Volt by many months, as I recall.
ed: You see initially GM had the Volt set up just as you describe your set-up with no mechanical link between the ICE and drive wheels. They quickly realized that in important driving situations such as hard acceleration, sustained freeway driving, low battery state, and others there was a distinct power and efficiency advantage to having a direct mechanical link between the ICE and the drive wheels. This is by itself or in combination with the electric motor/generators. The electric motors/generators and the ICE, through gear trains, clutches, and a lot of software, are set up accordingly.

As far as charging the batteries at a high rate and providing power to an electric motor at the drive wheels: there's no free lunch here. To do both and maintain normal driving abilities of the car (i.e. good acceleration and freeway speeds) you would have to have a more powerful, more gas guzzling ICE. This totally defeats the purpose of trying to increase efficiency and reduce gas consumption!

The Volt only partially recharges its battery from the ICE partly for this reason. Also, they do this because the cost of recharging the batteries from the ICE, if all the expenses are considered, is at least 5X the cost of recharging from the utility grid! They encourage you plug in whenever you can-to save money. The plug-in version of the Prius was also developed to take advantage of this cost savings

You're trying to reinvent the wheel here. To do it, you'll have to come up with a much better wheel!
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OK ed, obviously your not going to be constrained by the laws of physics or any semblance of logic in pursuing your dream. That's OK. You have to admire your tenacity and thickheadedness. As you build your dream machine, please take plenty of photos and chart your progress towards your dream. If it works out, I'll be the first to acknowledge your accomplishment. Be aware though, in my career and life, I've seen the scum of the earth-some of the most despicable human beings- push the most unbelievable crap as the truth.

If it doesn't work out, please let us and the rest of the world know. Maybe it'll prevent some foolish person wasting our time and leading us down some twisted, dead end, logic rat hole.

Then again, it could get you elected president of the United States!
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