Technopro, You are going about this backwards. You need to figure out how many volts and amps the motors take to run, then get a controller that will hande that load. It looks like you have the amps figured out. Most Sabertooth controllers have a wide range of voltage that they will cover, but it is the motors that determine what voltage you need to supply.

ok well I know the motors came from another rc car that was powered by 4 AA batteries. 4 AA= 6v.

that drove them alright. it was the start ups in the other rc car that made me tear it apart.

I might have read your question wrong the first time. Were you looking for a battery, or a link for the Sabertooth? I thought you were trying to decide what controller to buy. In any event, the motors are designed to run at a maximum voltage. That is what your battery should be. If they came out of a car that ran on 6V, then that it what you should be looking at. I don't know much about small batteries to recomend a particular one. I am sure that someone here can help you with that. But, you answered your own question. 6Volts is what you will need.

Ok so the minimum voltage for the sabertooth.

If the motors take 6V, then the battery has to put out 6V and the Sabertooth has to handle 6V. Here's a Sabertooth that will work. It is a little pricey. You could probably find one cheaper. This one is regenreative. When you slow your car down, the braking energy is converted back into electricity that is fed back into your battery so that it doesn't run down as quickly. It runs 6V to 18V. It can handle two motors running at 5 Amps each and peaks of up to 10 Amps. Your motors sound like they are within that range. There are other motor controllers that are cheaper than Sabertooth. The important thing is to look at the specs (volts and amps). I wouldn't buy a real cheap one though. Well, I wouldn't do it again. I did that once, and got junk that didn't work. Shop around. Be smart about it.

yea. unfortunately that sabertooth has a peak of 10 A for a few seconds. with the 2 motors im using I need a 6A continues and a 12A peak

that's why I was going to use the sabertooth 2x12.

www.dimensionengineering.com/products/sabertooth2x12

it will supply the motors with all they need and no more. plus I could reuse it with larger motors.

I see. Yes bigger is better. You are correct about them not delivering more power than needed. You have to be careful about not applying too much voltage to a motor, but you can supply unlimited amperage. They will only pull what they need. Just a side note; If these are the motors that you posted pictures of in another thread, they look awfuly small to draw that much current. I don't mean to question you, I just wonder if you should double check that.

Here is what I have. These are awesome! Sabertooth 12 x 2 http://www.lynxmotion.com/p-562-sabertooth-2x12-regenerative-dual-channel-motor-controller.aspx

79.99 , but if you sweet talk them they might hook you up. When I told them about the Jarvis project they discounted the controller 10 percent off and discount on express shipping too ;)

Always try and sweet talk anyone, chances are they can move a little, more so if you have a big project where you can throw in a subtle advert for their products. I learnt that way back when I was heavy in the car modification scene (I paid no more than 50% for anything on my car, some was even free). If you don't ask you don't get but you have to ask the right way :)

Back to the topic in hand, I would also recommend the sabertooth 12x2 based on what I've read about it and the load you will require.

ok so a 6V battery?

Sure . or a 7.4v lipo , that's called a 2S lipo when your shopping by the way. A 2200ma is plenty

My only concern on using 6V would be if it drops below 6V when running low, the sabertooth may cut out. I don't know if it would, it's just a question that popped into my mind, someone else may know the answer.

As Josh mentioned, look at 7.4v 2S LiPos, they are cheap, light and hold a lot of power. But then a fully charged 2S LiPo is 8.4V, can the motors handle that? (I'd guess yes but don't take my word for it).

You could regulate the LiPo to 6V but when I was looking for my regulator the ones i found were 5A which is below your peek (and running) current.

You'll be fine with 8 volts especially when it gets dialed back to adjust speed with pwm. I'll do a write up on motors and applied voltage today.

Ok thanks guys.