battery charging question

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miller87t
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battery charging question

Post by miller87t »

Hello,

As a way of extending the range of an electric vehicle, could I take a small diesel single cylinder engine (like a 5hp Hatz) and run 1 or 2 hi output (maybe 80-100 amp) car alternators from it to charge the batteries? I realize that this setup wouldn't have enough power to run the vehicle down the road without batteries, but my thinking was that maybe I could add some range (30-40%). The project I'm looking at would just be to get my feet wet building a car that would get me back and forth to work a couple days a week. I would need the car to have a range of about 45-50 miles at 45-50 mph crusing speed over hilly (as in small rolling hills) terrain.

Thanks for any input.
Sharkey
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Post by Sharkey »

What you are proposing is called a "series hybrid", and it's possible, but few examples have been built that produced the desired result. The efficiency isn't very good, although it does provide a flow of current to extend the charge on the batteries.

The problem with using car alternators is that they are pretty much limited to the wattage that they are designed to supply. A 12 volt, 100 amp alternator can be made to produce 120 volts, but the amperage will only be about 10 amps. (12 volts x 100 amps = 1,000 watts, 120 volts x 10 amps = 1,000 watts)

An EV running down the road requires about 10,000 - 15,000 watts (assuming small vehicle, moderate speeds, level ground). Even two alternators would be less than 20% of what is required to run the car.

It all comes down to how much utility you will get for how much effort and $$$ expenditure. If you must do the series hybrid thing, look into getting a commercially-manufactured genset of 6-7,500 watts. You'll get more power with less fiddling around. Of course, a 7,500 watt diesel generator is going to be pretty danged large and heavy, which is going to cause more load on your EV and greater drag, which in turn requires more power to make up to prevent the batteries from discharging.

I went through all this when researching before I built the Pusher, and decided that series hybrid was not for me. I also had the brick wall that my EV's motor is only 24 horsepower, and would never produce more no matter how much electricity a generator could produce. I decided that if I was going to have to produce 35-50 horsepower to drive the car over mountian passes, I would be best off simply putting that power into the pavement rather than trying to pass it throught the car's electrical system.

I'm not trying to discourage you (not exactly, anyway), but this topic gets talked about a lot, and few people have built gensets into their EV's and been satisfied with the results. If the series hybrid model worked well, there would be many more EV's using them, and EV owners building them.

As it is, there are three Pusher trailers that I know of, maybe four. The limiting factor there is that few people have the skills or time to put one together.

Anyhow, that's my tooughts on the subject...
miller87t
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Post by miller87t »

I wasn't considering that the alternators would only put out 12 volts. Thanks for the thoughts.
Sharkey
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Post by Sharkey »

Automotive alternators are rather open-ended as far as output goes. I have in the past, belted a Chrysler alternator up to a 4hp Briggs engine and caused it to put out 120 volts DC to run small electric power tools when I was living back in the woods (this was before I got serious about renewable energy). It's all a matter of how much current you cause to flow in the stator. I removed the regulator and substituted a variable resistor connected to a car battery.

One of my curent projects is to outfit the Pusher with a second alternator (this one is a Motorola) that has had the integral regulator removed and replaced with a homebuilt regulator. The purpose it to allow me to pump power into my 24 volt home renewable energy system's batery bank in the event of a prolonged power failure of the utility grid. Having a backup power source in addition to the PV arrays will insure that I can keep the batteries from completely dying if we have a utility power failure and long periods of cloudy weather.

When I'm done, the alternator will have been converted to 24 volts, but I'm not certain about how much amperage I will be able to pull out of it. It's rated at 65 amps, and might put out that much at the higher voltage. The problem generally is that the alternator will not be able to cool itself fast enough to put out twice the rated power (12 volts x 65 amps = 780 watts, 24 volts x 65 amps = 1,560 watts). The windings in the alternator are good for the 65 amps, as are the rectifying diodes, but something's gotta give at the higher voltage, otherwise, what would prevent someone from using a tiny alternator to run a whole house (120 volts x 65 amps = 7,800 watts)? I think either thermal limits or belt slippage will step in and give me a reality check before I get that much power.
miller87t
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Post by miller87t »

I like your idea about having backup power on hand. Here in Arkansas we have an occasional ice storm that has been known to take away grid power for 2-3 days. I don't yet have a PV array, but hope to have one soon. For the moment, I've acquired enough old computer battery backups and extra batteries from the same to run some lights, TV, and 'frig for a day or so. After the batteries give out, I can charge them from a charger I made from a GM alternator and 3.5HP Briggs.

Could you direct me to some websites that I can learn about converting alternators to high voltage outputs?

Thanks for you help.
Mark R. Obtinario
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Post by Mark R. Obtinario »

Sharkey, why don't you start with a 24V alternator? A 65 Amp 12V alternator isn't going to put out much more than 35 Amps at 24V.

MCI-7's had belt driven 24V alternators that were rated at 250 amps. Some were oil cooled by the engine lube oil but most were air cooled. And since the alternator was mounted on the back side of the engine (which on a rear engine coach that means it was buried back by the bulkhead underneath everything) it didn't get that much air flow except for what was created by the blower fans coming down from the radiators.

I know Luke @ U.S. Coach in NJ has the belt driven 24V alternators in stock all the time.

Just a thought.

Mark O.
Castle Rock, WA
Sharkey
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Post by Sharkey »

The 65 amp Motorola has several attractive features, not the least of which is that I already own it. Mounting it to the engine will be a bolt-on, as it's OEM VW, and designing and building a 24 volt regulator is a trivial task for me. If I can only get 35 amperes out of it, that's fine too, that relates to a C/10 charge rate for my 350 ampere-hour battery bank.

The purpose of this project is to have some manner of secondary backup power to replenish the batteries should the utility power fail for an extended period of time with no appreciable sun to power the PV array during that time. If I was serious about making power full time with a diesel engine, I'd run an 1800 RPM AC generator and recover all of the heat from the engine to heat water for domestic use and space heating. Like many of my projects, I'd be surprised if I even need to fall back to the generator, but knowing it's possible to keep the batteries from completley draining is reassuring.

My last project was to install a Bosch LPG instantaneous water heater in series with my electric water heater. The Bosch can take pre-heated water and adjust the flame to heat it to normal temperature. I have the bottom heating element in the electric heater connected as a dump load for my PV array, so if I have excess power, it heats the water, sometimes so much so that I don't have to turn the top element on to have hot water for showering and clothes washing. Now I no longer have to be concerned about hot showers if the power fails. Any leftover heat in the electric heater tank will temper the water going into the gas heater, and save me $$$ (LPG is going for about $3/gallon these days!). Two valves bypass the Bosch when the electric heater is operating normally.
Tim Clevenger
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Post by Tim Clevenger »

I was thinking about a small car engine, such as a 1L 3-cylinder from a Geo Metro or Honda Insight. Much better emissions, quieter and longer lasting. Can you mount a gasoline engine on its side? Or do you have to do something special to lubricate it properly?
Sharkey
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Post by Sharkey »

Turining an engine on it's side is possible, but would involve some custom fabrication for the crankcase sump and oil pump pickup tube. You would also have to be very aware of oil return galleries that allow spent lubricating oil from the valve train to return to the crankcase.

The engine in my Crown is a standard Cummins 220 turned 90 degrees. It has a custom cast crankcase, and being a puch rod engine, the oil drainback is fairly simple. As long as you were using a fuel injected engine and not carburated, I can't see anything else that would be a major impediment.

Might be better off to find an engine in the configuration that you need to begin with. Subaru makes flat 4 cylinder engines, and VW made a flat four "waterboxer" used in the Vanagons for a time. Most VW watercooled engines from the last 25 years are "slant" engines, that is they are mounted in the cars at a 15 degree angle or more. Some of the Vanagon engines are laid over much farther and already have the sump modifications.
marco

alternators

Post by marco »

Hi i'm wondering if it's possible to get power from alternator connect to the back wheel logicaly if the wheel turns and the alternators turning I should be able to create power ?
Sharkey
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Post by Sharkey »

This topic:

http://www.diyelectriccar.com/forums/sh ... hp?t=13644

should answer your question. Basically, what you are proposing is perpetual motion (doesn't exist).
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