I’m new to this forum, and looking for some direction. I’ve had trouble finding any info on the net, and I have an idea I’d like some of you more knowledgable guys to look at.
I don’t like the idea of a rechargable car at this point because I do a lot of cross-country driving. I don’t want to stop every three hours for five hours to recharge my batteries. Would it be plausible to run a generator off of a small(ish) gasoline or deisel engine to power a motor?
I was thinking if it could be done with a substantial savings in fuel, it would be worth the r & d. It is a similar idea to the Chevy Volt, less batteries, more engine. I know the electric motors are out there that will easily move my car ('89 Civic), but I was wondering what kind of juice would be required from a generator. Maybe a couple extra batteries to help from a stop.
At this point it is just an idea, but I would really like to hear your input. I know there are some carbonphiles out there, but I’m more willing to take small steps to get up the big hill.
well, you didn’t research much… its been covered on here before, as well as diyelectriccar.com
cross country driving - maybe an EV isn’t for you… just get a REALLY fuel economic car and drive it.
Converting gas, to mechanical, to electric to electric then back to mechanical is inefficient, and you’d need quite a large generator (greater than 10-15Kw) to cruise. It won’t get better gas economy when you convert the way you’re trying to do. You lose too much in inefficiency.
Plus, those engines don’t have cat’s on them, and can be MORE harmful to the environment.
Not quite correct. This is EXACTLY what the Chevy Volt does. Go more than 40 miles, and the Volt does exactly what he wants. It has a gasoline driven generator providing electricity to the drive motor. There is no direct mechanical connection between the ICE and the wheels in the Volt. In fact, the idea for the Volt, at least with GM, actually came from the EV1. The engineers were having problems with testing the car due to the limited range, so they rigged up a small generator to provide power to the car for their testing. It worked so well one of the engineers pushed to have this considered as a product, but GM wouldn’t go along with it. Until now.
It also only takes a 5HP gasoline motor to provide enough power to move a 3000lb car at 45MPH across flat land when that 5HP engine is driving a generator only, with a 36V electric motor providing the drive. Not only has this been done, it was done in the 1970s. With a carb on a cheap ICE, this vehicle also saw almost 90MPG. See the article for the exact details.
With a modern fuel injected ICE making 20HP, driving a slightly larger generator and a slightly larger motor, should be able to make highway speeds and see over 100MPG. You can also get a catalytic converter for such a small ICE if you wanted, but burning that little fuel in that small an engine, the emissions will be at least what the car puts out with its original ICE, or really should be less since there’s just so much pollution you can generate out of a gallon of gas. Eventually I hope to do this exact conversion.
Specs on the volt:
120 kW (160 hp) electric motor
1.4 L 4-cylinder for 53 kW generator
You’re going to need more than a 5Hp motor to keep a car at cruising, along with all the stop and go. Sure, it can extend range, but you’ll be still using bats with a small generator. if you go 60mph and get 300wh/mile@60mph in a car (reasonable number for wh/mi), thats about 18kW, just to cruise. WAY more than that to get it started. At a minimum, you’d need over 25 (so that extra 6-7kW can charge the batteries).
Read the article I linked to. Here, let me show you several. You can say you gotta have this or you gotta have that, but the fellow of which I speak built a car that will run all day long on a gasoline generator with three 12V lead acid batteries. Was a bit off on my previous post though, the guy was only seeing 75MPG with the cheap 5HP carbed lawn mower engine. Seriously, it doesn’t take as large a gasoline engine as you’d think to run this, because the ICE will be running at a constant speed. It doesn’t have to move the vehicle from a dead stop off idle, so can be sized much smaller.
So far as the generator goes, you just need one that’s large enough. Correct me if I’m wrong on this one, but if you have two identical electric motors, and you hook one to an ICE to act as a generator and drive the generator at 1000RPM, it should make enough electricity to drive the other motor, with a load on, at 1000RPM, correct? This is if we don’t take wiring loss between the two motors into account.
Read the article I linked to. Here, let me show you several. You can say you gotta have this or you gotta have that, but the fellow of which I speak built a car that will run all day long on a gasoline generator with three 12V lead acid batteries. Was a bit off on my previous post though, the guy was only seeing 75MPG with the cheap 5HP carbed lawn mower engine. Seriously, it doesn’t take as large a gasoline engine as you’d think to run this, because the ICE will be running at a constant speed. It doesn’t have to move the vehicle from a dead stop off idle, so can be sized much smaller.
Fair enough. 75mpg isn’t too bad though… it doesn’t take much to keep it going…just the stops and starts (uses the batteries)… then the gen needs to recharge what they discharged from accelerating them while driving. great links. I want to add an ICE range extender on my motorcycle (something like a 1500-2000W generator) inside something like a luggage case on the back of the bike. It works great for shorter ranges, but to do cross country… it’d take a bit higher Wattage.
So far as the generator goes, you just need one that’s large enough. Correct me if I’m wrong on this one, but if you have two identical electric motors, and you hook one to an ICE to act as a generator and drive the generator at 1000RPM, it should make enough electricity to drive the other motor, with a load on, at 1000RPM, correct? This is if we don’t take wiring loss between the two motors into account.
you ignore connection losses thats fine, but don’t take into account motor efficiency and generator efficiency. even if you operate in the most efficient range, you still need more power. There are power losses converting mechanical to electrical and back. That’d be perpetual motion. You have losses in the magnetic fields, brushes, mechanical conversion from rotation to current flow via electromagnetics, losses in the copper windings. it is volts per RPM, yes, but you won’t be able to load the motor and get the same RPM (for the most part). You won’t get the same volts out at 1000RPM as you need to run a loaded motor at 1000RPM.
Yeah, that was 1970s tech he was using. With the stuff we have today I can’t see a vehicle not being able to meet the speed and acceleration standards of an all ICE vehicle, only running off generator-produced electricity and getting triple digit mileage. This would also save quite a bit of weight since you’d not need such a large battery pack.
If you could set up the controls correctly though, you could run off battery pack, and have the generator come on and off as needed to charge the batteries. Drain them to 80 percent (depending on battery makeup), then bulk charge back to 95 percent with the generator running flat out. The way I’m looking at going will require the generator to be on at all times when driving, so the generator wouldn’t be as efficient as it could be.
Don’t know that I’d want a generator on the bike directly, but one of those little travel trailers would work great and would even allow you to take a suitcase or two along. Hanging the generator on the bike would mean you’d be solo on the bike, and would need to beef up the suspension a bit since they aren’t light. Main concern would be that much weight that high off the ground. A Honda EU generator would be the way to go, according to the solar energy folks they have an econo-setting which allows them to run at 25 percent load efficiently. A 5KW would be able to provide all the juice you’d need on a quart of gasoline an hour, maybe less.
I didn’t think my little theoretical model was perpetual motion since there would be an ICE driving the generator. It did fail to take losses into account. I’m guessing you’d actually need a generation section about 20 percent larger than the drive section to overcome the loss, and really that would only be an issue if you planned to run the drive section flat out for an extended period of time. If you were running at half speed on the motor, the generating section would not need to produce more than what the motor used plus losses between the motor and generator. You would want some extra on the generating side, since there would still need to be batteries (dammit) and you’d want to be able to charge them back to max while driving. You’d also want to be able to operate accessories in the vehicle.
Don’t know that I’d want a generator on the bike directly, but one of those little travel trailers would work great and would even allow you to take a suitcase or two along. Hanging the generator on the bike would mean you’d be solo on the bike, and would need to beef up the suspension a bit since they aren’t light. Main concern would be that much weight that high off the ground. A Honda EU generator would be the way to go, according to the solar energy folks they have an econo-setting which allows them to run at 25 percent load efficiently. A 5KW would be able to provide all the juice you’d need on a quart of gasoline an hour, maybe less.
The little 1.5 and 2kW models are fairly light… and it’d be on a side saddle, not on the top. I don’t mind being solo either, its a commuter, not something to take people on for longer trips. I’ve got an adjustable rear shock for added weight. Its just an idea… I want to get a small 1kW and see how well that works first. They’re about $100 and at 1000W, it’d help a little. With my charging system at ~800W, with 16A output at 48V, every little bit helps. I’m limited because my charging system charges each battery at 5A/12V.
I’m guessing you’d actually need a generation section about 20 percent larger than the drive section to overcome the loss, and really that would only be an issue if you planned to run the drive section flat out for an extended period of time.
That was my thought too, about 20-30% over should be fine. Flat out, or stop and go is going to hurt ya.
Its all about calculating the power required by motor over the length of a drive (wh/mile will work), add in some overhead for stop/go and hills, add in accessory power, and size the generator accordingly. You need to add the hills and stop/go because the generator will still be recharging the 2-3 bats you have for “pulse” starts, after the pulse is done.
Hmm, if it works it would be worthwhile to upgrade the charging system to accept the generator’s full output then. I could also see building a section to set the generator directly behind the bike, without a trailer, if having it on the bike isn’t an issue. Having the weight on one side seems like it would cause problems, although I’ve not ridden a saddlebag-equipped bike so I can’t say for certain. I’ll be waiting to see what your results are, suspect you will be very pleased.
If I do this, and I’m pretty sure I will, I’ll be sizing the generation section to be large enough to run a charge to the batteries, run flat out and operate accessories. Since running flat out won’t be happening often, there should be enough capacity to recharge the batteries fairly quickly. I don’t see stop and go as being a real problem either, since if the batteries are low on juice the generator would be running when stopped, and thus would be dumping its full charge to the batteries as fast as they can absorb the juice.
Hmm, if it works it would be worthwhile to upgrade the charging system to accept the generator’s full output then. I could also see building a section to set the generator directly behind the bike, without a trailer, if having it on the bike isn’t an issue. Having the weight on one side seems like it would cause problems, although I’ve not ridden a saddlebag-equipped bike so I can’t say for certain. I’ll be waiting to see what your results are, suspect you will be very pleased.
Charging systems that I’ve seen don’t go much over 10A at 72V (720W) anyway. Size is my concern, I have a motorcycle and can’t fit in a larger charger. Maybe with a LiFePo solution, I could charge at a faster rate (higher C) but not with these lead. 10A is about max. The charging system I’ve got is modular (charges each batt individually at 12V 5A) and is a prototype. It will be upgraded to take 1500W (normal plug in power). No need to go over that really. Its just proof of concept if I put a gen on. They’re not huge either, and I’d put gas and the electronics for the generator on the other side to offset it somewhat. Hell, toss another battery in.
This is way down the road, first step, new batteries, 120VDC of em, new controller, install new charging system and build a display for it.
Seriously, it doesn’t take as large a gasoline engine as you’d think to run this, because the ICE will be running at a constant speed. It doesn’t have to move the vehicle from a dead stop off idle, so can be sized much smaller.
Seriously, it doesn’t take as large a gasoline engine as you’d think to run this, because the ICE will be running at a constant speed. It doesn’t have to move the vehicle from a dead stop off idle, so can be sized much smaller.