Motor to drive alternator?
02-10-12, 11:48 AM
#26
Old [Sch|F]ool
...on a points ignition car.
I forget where I saw it, but someone was experimenting with system voltage on an MSD equipped engine on a dyno. HP dropped as system voltage was gradually lowered from ~14v to ~11v. The power loss was on the order of 20hp when voltage was dropped from 14v to 12.5v.
sen2two, nobody's denying that an electric motor will turn an alternator. But, excite the field windings, put a load on the alternator, and monitor the current going into the electric motor. My bet is, the electric motor will stall down to the point where the alternator's output drops to a level manageable by the electric motor despite the field being fully excited.
In other words, you won't get any effective charging out of the alternator, so the effort is pointless.
Sure, some other guy did it. I can show you pictures of all sorts of things that don't really work well or at all. Hell, go into any porting thread and find pictures of 6-port end housings wallowed out into one giant port, with an IC line around 85-90abdc, with a huuuuge banana-sized bridge port on top for good measure. Like someone else said, funny how you only ever see ports like that pulled out of a scrap pile and not nice and clean from a running engine getting refreshed/reassembled...
02-10-12, 12:13 PM
#27
I recently removed the motor to drive my water pump and ran that back to the crank. Then hooked it up to my alternator. Let the car idle for a few minutes than drove it around a little. Checked the battery voltage before and after with no change...
Will it work on a daily driver...? Most likely not. Will it work on race cars, I know it will. The power draw from these motors are so low it shouldnt effect anything. But with a daily driver with radio, a/c, lights, ect. it might just be to much. But on a race car, especially if it's a carbed distributor type set up, it should be plenty fine...
It's a small pic, but it's there... (not my car)
Will it work on a daily driver...? Most likely not. Will it work on race cars, I know it will. The power draw from these motors are so low it shouldnt effect anything. But with a daily driver with radio, a/c, lights, ect. it might just be to much. But on a race car, especially if it's a carbed distributor type set up, it should be plenty fine...
It's a small pic, but it's there... (not my car)
Here's why it won't work:
FWIW a lot of this was stated above... but here it is again for review
IF this were an "ideal" system in an "ideal" world, where none of the energy used by the motor or converted by the alternator was wasted to the environment (100% efficient system), the motor might be able to turn the alternator indefinitely... the only drain on the battery would be the energy that was used to get the drive motor up to speed initially... after that, all the energy made by the alternator would flow through the battery and back to the drive motor... and that's what makes this idea seem possible. If you were to stop and start the above "perfect" system multiple times you would run the battery dead from using stored energy in the battery to spin up the drive motor again. This system would never be able to add any more energy to the system than the amount that was initially stored in the battery.... even if you messed around with the pulley sizes!
We don't live in an "ideal" world so we aren't working with a 100% efficient system in real life. The problem is that there are tons of places that the system loses energy. It loses some of the energy to heat (since the alternator and motor heat up as they are spinning no doubt), to over coming friction in the bearings in both motors and to making noise (noise is energy too!). Charging the battery isn't 100% efficient either and some energy will be lost there too. So, you lose a bunch of energy (that should be recharging your battery) to the environment just by having it running. Then you lose some at the battery level too when you are trying to stuff all that energy back into there! And then, on top of that, you are taking more energy from the battery to run the ignition system (and other in-car accessories), which you would never get back with this system anyway. It will always drain the battery the way you have it hooked up. It just won't work in the way you are intending. Just pull the motor and alternator off and save the weight at the drag strip. Keep the alternator hooked up to the engine on your street car.
BTW, The reason the alternator can charge the battery when driven by the engine is due to the fact that the energy to drive it is not coming from the battery... it's coming from the energy stored in the gasoline.
So, in short, You can't get something for nothing.
And that's all the hating I have to dish out today.
02-10-12, 12:19 PM
#28
02-10-12, 12:31 PM
#29
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Ok, let me put this in plain English why this won't work.
It takes more power to run the electric motor than the alternator will make. The extra power required to run your alternator off a electric motor will come from your battery. If you hook this up you will basically be adding 30lbs of dead weight that will be draining your battery.
It would be more efficient to run no alternator at all then the setup you're proposing.
You're either trolling or are incredibly dense.
It takes more power to run the electric motor than the alternator will make. The extra power required to run your alternator off a electric motor will come from your battery. If you hook this up you will basically be adding 30lbs of dead weight that will be draining your battery.
It would be more efficient to run no alternator at all then the setup you're proposing.
You're either trolling or are incredibly dense.
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