Lucianpoppy

Hey guys trying to get more knowledgeable in the hobby and want to get the appropriate batteries for my vehicles without asking my LHS for the battery that fits. I get all the other parameters on the batteries but my question is on the ESC manual , am I looking at the part that says continuous current to know what the minimum discharge rate would be for on the barttery or am I messing this. Ie I have xray T4, which has a hobbywing xr10 esc which has a continuous current of 80a. Do I have to find 2s Lipo batteries that say 80c or above for discharge rate?? Or am I looking in the wrong place all together. Hope I don't sound to silly but I figure I'm in the right place for this very thing.

ticedoff8

If you are using a Lithium based battery pack, the idea is that a battery has a maximum "C rating" and that is supposed to give you some idea of its maximum discharge rate.
The maximum discharge rate of the pack should be a little over the ESC continuous current rating.

EG: Lets say you are looking at a Lithium based battery pack with 2 cells, is rated at 3300mAh (aka "1C") and has a 10C rating for maximum continuous discharge.
The 2S indicates it is 2 cells in Series. In series, the cell's voltage add together. And each Lithium cell provides 3.6v minimum (fully discharged) to 4.2v (fully charged). That means the 2S pack will provide from 7.2v (fully discharged) to 8.4v (fully charged).
The 3300mAh means the battery is designed to deliver 3,300 milliamps (3.3 Amps) for 1 hour. At 1 hour the battery's voltage should be fully discharged (7v). So, 3300mAh would be 1C.
A maximum discharge C rating of 10 (10C) means that the battery will deliver 10 times the 1C rate for short bursts without overheating. So, the 10C battery would be able to deliver 33A (3.3 x 10) for short spikes of current draw and show no sign of heating up.

Your ESC may be rated for 80A continuous. But, an RC truck doesn't use 80A continuously. If it did, you would need a 80000mAh (80Ah) pack.
But, it may spike to 80A or 90A while you are tearing up the track. In that case, you may need a 3300mAh pack with a 30C max (3.3 x 30 = 99A). And, that battery pack would not be hot at the end of the run (a run may last maybe 5 or 6 minutes)

The problem is that the maximum C rating that is printed on the label of the battery is almost always BS. And it makes no difference on the price or the brand. They all lie.
So, it makes it tough to figure out what packs to buy.

I use the thread on RCG to get my up to date info on batteries: https://www.rcgroups.com/forums/show...st-Comparisons
But, if you belong to a RC airplane club, ask the guys who are flying EDF (Electric Ducted Fan) jets what brands they recommend.

rgburrill

Put another way, and much simpler, 1C is the capacity of the battery - the 3300 mAh example above. 25C would give you 82.5 max Amps.

See, you don't need a huge dissertation.

rgburrill

One more thing and I've said it before - max rating of the ESC is what the ESC CAN HANDLE. Max rating of the battery is what the battery CAN DELIVER. But the most important number is the max requirement of the motor - THAT IS WHAT THE MOTOR NEEDS AND DETERMINES WHAT THE OTHER TWO MUST BE AS A MINIMUM. Please stop thinking a 100 amp ESC with a 80C battery will drive a 20 watt motor to 60 MPH.

And kV IS NOT A POWER RATING. It is nothing more than RPM per volt.

Lucianpoppy

i think you just summed it all up for me. so Ill look at my motors manual to see what it says. the manual for my rtr losi didn't have the motor specs on it or maybe im just blind. so ill just google the actual motor itself an go from there. thanks a million

Lucianpoppy

wow thanks for such a well thought out response, I def appreciate you taking the time out to respond to my listing

Lucianpoppy

thanks not sure if my reply would reach you or not. not great with forum etiquette

jester_s1

Also, C ratings mean practically nothing. There is no objective standard for them, so they are little more than a way for manufacturers to give you a "good, better, best" set of options. One manufacturer's 40c pack will outperform another's 70c pack.

Lucianpoppy

good analogy. Do you get your batteries from your LHS or online ?

jester_s1

I buy them online.
The real test for batteries is to look at what the serious competitors are using. The F3A pilots have figured out which batteries give the most capacity for their weight, the racing and jet guys know which ones can sustain high amp draw (also the serious boat racers), and the car and helicopter guys can tell you which ones hold up their voltage best throughout a run. Professional drone pilots can tell you a lot about durability. You won't find any of them using the cheap Zippy or Rhino batteries, although for many of us they are perfectly adequate.

jester_s1

To the OP: Your actual amp draw will be determined by your motor Kv and your gearing mostly. Your tires and the terrain you run on will be a smaller factor. Battery choice for surface racing is about getting through the heat without losing too much speed toward the end of the run while keeping weight down as much as possible. But if you pick a battery that can't supply the amps that your system wants, the voltage will just sag and slow your car down some. As a beginner, that's not really a problem.
You will probably get more specific responses in the car forum. It's a little bit farther down on the page.