Noob to brushless
 

Hey guys, just thought I'd give a little hello here. I currently have a fully built "wheely king" crawler, that has just about nothing left from a wheely king haha, and also a brushless sand rail that I built out of slash parts and brakeline. I joined the site because I am seriously thinking about picking me up a savage flux and running it on 2 thunderpower 3s 25C 5400mah lipos, they should be able to deliver the power the truck needs? Touch worried about the C rating though.I am also VERY impressed with the knowledge on the site. I have been doing some lurking the past couple days and learned a lot of important info. Anyways, the sand rail is up for sale so I will post up some pics of it, and maybe if I get a few minutes I'll post some pics of the crawler up too so you guys can have a looky-loo.

-Matt

Also, I'm canadian eh.

HEHE, another canadian!

Those lipos will be fine.

Thanks for the reply! The whole "C" rating thing is still taking a while to sink in, but from what I gather the higher the mah, the less "C" you could get away with, correct? Is it how FAST the battery can discharge or by how many amps/volts it can draw for a length of time? Does the "C" rating just stand for current?

YES! Another Canadian on the forum! The lipos will be fine. C rating is how many amps a cell can deliver for the given mAh. So, a 10C 8000mAh pack will deliver 80A cont. You get 80A by multiplying the cont. C rating by 8.000 since the pack is 8000mAh. Just move the decimal place 3 times to the right and multiply that value by the cont. C rating to get the cont. amps said pack can deliver. Another example would be a 4900mAh 25C pack, which can deliver 122.5 amps cont. I hope this makes sense....

http://www.youtube.com/watch?v=7j8UH84h0-M

I agree with those two, they'll be fine!

The C rating indicates how much the battery can discharge in Amps, and the higher, the better. Especially for brushless setups and when your hammering on the throttle. Having too low of a C rating can cause the battery to heat up beyond the safe 150F mark and can stress out the ESC causing it to fail or even burn up. Both of which are very bad.

Excerpt from LiPo Tutorial

http://www.robotwars.00server.com/tutorials.html

The C rating is also known as the discharge rating. This is a measure of how much current ( in amps) the battery can output before it will overheat and become damaged. Most lipos have the C rating listed in their specs, but this doesn’t actually tell you how many amps the lipo can ouput, there is a very simple sum however:

Mah capacity x C rating / 1000 = output potential.

For example, a 10C 5000mah pack can output 50amps, and a 20C 4000mah pack can produce 80amps. This however is assuming that the C rating on the pack is accurate. If you are in doubt, there is fool-proof way of determining the C rating, but it requires additional equipment. Using an Eagletree data logger or similar, you can record the voltage level of a lipo in relation to the amount of current that is being drawn from it. If the voltage level remains at about 3.0v or higher per cell at the specified C rate in amps, then it is accurate. If not, then it is over-rated. An example of this would be a 20C 5000mah pack outputting 100amps and staying at about 3.2v per cell. The graphs can sometimes be hard to interpret, but if you have the current and voltage graphs on the same chart, you can easily locate the voltage at any given current output.

One important thing to concider when choosing a pack based on its C rating vs mah capacity is that 10C packs will drop their voltage heavily when taxed to more than about 12-15C (the typical peak or burst rating of 10C packs). A 25C pack will happily deliver in excess of 35-40C before its voltage output drops, so dont always assume a 10C 8000mah pack will be just as good as a 25C 5000mah pack in a high-drain application; that would be a false economy. For low drain setups however where runtime is more important than current output, you would be fine with the lower spec, higher capacity pack.

Thanks for that LOL.

We deffinetly say "eh" a lot, without even realizing it...However we DO NOT say "aboot", it's about. I am not sure who decided we say "aboot":na:

Well, I say a-boot. You're not Canadian enough.

Where aboots are you from?

It's true...I asked my mother one time what "nationality" I am, she said heinz 57....

I'm from Temagami, Ontario. A-boot 5 hours north of Toronto. Where a-boots are you from?

Red Deer Alberta eh, right in the center of the hell-storm the economy created. grr.