# Small vehicle power quandary

I'm building a Battle-Bot, and I need areliable power scorce. I have multiple AC motors, but will require a DC power scorce. Anyone know a good battery? I've already heard that a motercycle battery might be the way to go, I'm just looking for cheap alternatives. Also, please keep in mind that there is a 120-lb limit to the entire vehichle, so a car battery probably won't work.

Thanks, Cash

jim hardy
Gold Member
Dearly Missed
look at lawnmower/garden tractor battery, $25 at Walmart. in boat section you can get a battery box to match. Thanks for the advice. No adapters nessesary? The motor still has the power cord on it, and works when i plug it into the AC wall socket. (I've already stripped it down to the bare motor, it was a fan, and took it apart and cleaned it) jim hardy Science Advisor Gold Member Dearly Missed welll a 120VAC motor sure won't run on 12vdc. check into those power inverters that plug into a car cigarette lighter watts = volts X amps so check your little (i hope they're little) ac motors this'll help you size things:: 1 hp = 746 watts and a little fan is probably < 1/10hp or about 75 watts so a 200 watt inverter should start a 1/10hp motor. at 120 volts 200 watts is 1.667 amps so lampcord will do on motor at 12 volts 200 watts is 16.67 amps so use like #14 or #12 wire on input to inverter and an inline fuse about 20 amp slowblow or 30 amp fastblow. you might also consider switching over to 12Vdc motors. Junked luxury automobiles have an assortment of them - A/C & heater blowers, electric windows & seats, wimdshield wipers, and teeny ones for outside mirrors. Car blower motor is surprisingly powerul but pretty fast. You can pillage the speed control out of old dash panels, though...and learn about DC motors at same time. 80's Ford windshield wiper assembly includes a powerful reduction gear that'd be about right speed for drive wheels. It's a three brush motor which gives better speed regulation, and is another interesting device to study. It's a cousin to Model A car generator of about 1930. since you're enjoying the machine age, why not study up on the machines! have fun - old jim Last edited: If you want really dense power, about the most power per pound per$ is on Ebay. Batterys for Ebikes can really pack a wallop, and you can pull those large cells out of most.

However, if you do this, you'l need a good power supply (with a settable voltage and current limit) to charge them.

Also consider that you most likely do not want a liquid acid battery in something that can flip over. I used a liquid motorcycle battery in one of my projects years ago, and the acid and fumes caused a lot of damage. Gel cell batteries would be a much better option.
The second thing to consider is amp-hours vs load vs how long a match might last.

Thanks all for the terrific advics.
jhonbbahm brings up a valid point, in the setting in which this bot (Battle-Bot) will be used, it will be thrown all over the room, and any leaked acid results in a host of unpleasant reprecusions. I'm researching the gel cell batteries, and am very interested to know where i may be able to acquire them in a frugal manner (limited budget).
Thank you, Jim Hardy, your advice is most helpful. I have a small junkyard that I am allowed to pick parts from, and the car blower motor idea is much apprechiated.
Is there any way of creating a mobile AC power source? If not, is there a way to create a low-budget alternative to a power adapter?