this might be a stupid question but what does the number with a (c) at the end mean (40C) and should you buy batteries that have a higher number or a lower number?

C is the burst rate. It depends on what u need it for or application you want

its going to be used for a slash 4x4 and a 2wd buggy (stock)

http://www.youtube.com/watch?v=yWixnDjUyss
this will help. dont watch the video. just read the comments.

Go for a 40-50c that will be fine. Maybe a Gens Ace.

yeah im just figuring out which one i should get.

If price isn't important go for the 65c batteries. Gens ace are pretty easy on your wallet so you might as well go for the better option. Turnigy nanotecs are very good batteries as well.

On the slash I would def run 65c I run 65c 6600 mah on my scte but they arent
Cheap $130 each. But on my 2wd buggy it would depend on the track. I'd usually run a 25-30c pack because you get a smoother acceleration than with a higher C pack

My 6600 65c NanoTechs ran me about 40 bucks each that I use in my SCTE with great success (and to keep things simple, also run in my 2wd buggy).

Don't use the battery C rating to reduce your output. This should generally be controlled by, in order:
1) finger control
2) current limit/punch setting on ESC
3) appropriate slipper setting for the track
4) expo/rate setting on transmitter


For the OP:

Running a pack that doesn't have the output rating (C, but not just C) needed for a given application can be bad, overdrawing the battery and leading to puffing. Running a pack with too high rating is never bad, it just means you don't use all the potential of what the battery can output, and may have spent a couple bucks more than you needed to. But you may be happy to have it when the next vehicle you buy needs more instead of having to replace the batteries to support the new vehicle.

That being said, your average 2WD car/truck driven by the average driver won't be able to make use of much more than 30-40C on a 5000+ mah pack. If you're going with a smaller "shorty" pack that is something like 3300 mah, then having a higher C pack may be helpful. For a heavier 4wd SC, I wouldn't suggest less than 50c on a 5000 mah pack (though I've done a 5300 at 35c a couple times while waiting for my better batteries...but it was obvious that I needed more from the pack).

To clarify briefly why the above is true (so you can't just look at C), a battery's max output is roughly equal to the mah multiplied by the C rating. If you have a lower mah battery, you need more C to get the same max output.