Originally Posted by
brandrr
Why dont people just use a Dual 12V car battery,
that will give the low 24V, but at a very high amp, (ponders) because i keep seeing people
going to the big 2KW, Goals from some other fourms,
, the batterys I see are so low amps, 10a and 12a,
I mean 10a * 36v = 360watts,
or you can have a Dual 12v (car batt)but amps closer to like 500amps and UP
24V but at 600a = 14,400 watt's or 14.40kW
Is it because the motor control unit(mcu) cant handel that high of amp's?
or... IDK, is there a simple answer,
It doesn't really work that way. Sure a car battery can put out 500-600 amps. Usually a car battery manufacturer provides a cold cranking amps (CCA) rating of around 500-600 amps, which is a rating given to batteries to determine if they can do what it takes to turn a car starter motor in the dead of winter for a few seconds. And a few seconds is all you will get at that kind of current draw. Ever witness a car that won't start? After about 30 seconds or so the battery is already dead.
Unfortunately car batteries and all other lead acid batteries are subject to
Peukert's effect. The gist of Peukert's effect is that the more current you try to pull from a car battery, the less capacity it will give you.
Here's an example:
http://www.batteriesinaflash.com/flo...n?currency=USD
At the bottom of the page the specs are listed.
That particular battery is rated to provide 190 amp hours, but only if you discharge the battery slowly over a 20 hour period. Try and do it in 5 hours and you only get 155 amp hours out of it. That's Peukert's effect. Now imagine how much less capacity you'd get shortening the discharge rate to 15 minutes.
There's much more to it than just that. Generally speaking the higher the voltage, the higher the top speed of the motor. It has to do with counter-electromotive force limiting the top speed of the motor.
Hope this helps, have fun experimenting!