lipo 'C' rating question.

[Dandare]

Im i right in saying that, for example a 5000Mah 30c 2s battery can discharge safely at 150amps continuous ?

My question is how do i know what amps I'm drawing through the motor/ESC ?

[chris_dono]

Originally Posted by Dandare

Im i right in saying that, for example a 5000Mah 30c 2s battery can discharge safely at 150amps continuous ?

My question is how do i know what amps I'm drawing through the motor/ESC ?

Yes if the c rating was true, then 150amps is correct.

I know of only one speedo that tells you how many amps it drew, which is the GM 2010 version (after you store the telemetry data after a run).

[MrMagoo]

Fussion Exceed Pro can give you (from memory) peak and average current draws as well as motor RMP and the like.

[MattW]

In theory 150A continious, yes. Good luck finding any wire / connectors that can though!!

[F1END]

How does that work then?

MaH/1000 * C = Continuous Amps?

Therefore an Orion Carbon 6500 90C = 585 Amps?

[Matt Butcher]

The 90c that Orion state is Burst and not continuous. a nice bit of marketing there

[F1END]

Really? That's cheeky!

So what is the C rating of the Orion 90C batteries? I was tempted to buy one

[chris_dono]

Originally Posted by MattW

In theory 150A continious, yes. Good luck finding any wire / connectors that can though!!

Would love to see it as well !


don't forget it won't last as long if you pull more out of it either..

1 hour at 5a continuous
30 mins at 10a
15 mins at 20a
etc etc etc

so if you get to a point where you do pull 150a out of it, the wires would pop off and the battery would flatten almost instantly

Originally Posted by F1END

How does that work then?

MaH/1000 * C = Continuous Amps?

in theory yes, but reality is very different

[Dandare]

So regards to my 5000Mah 30c saddles, I don't really need to know what the 'C' rating is as I could never pull enough current to damage anything ?

I still can't grasp why we need to know it, lol.

[VintageRacer]

Originally Posted by MattW

In theory 150A continious, yes. Good luck finding any wire / connectors that can though!!

According to this table: http://www.powerstream.com/Wire_Size.htm you would need wire with a conductor diameter of around 6mm!!!

[VintageRacer]

Originally Posted by Dandare

I still can't grasp why we need to know it, lol.

I'm not certain about this, but my belief is that cells with a lower C rating will have a greater drop in voltage for the same current draw. But I may be wrong as that is just based on my logic and not any particular knowledge of how lipos work.

[Dandare]

Well if my 5000Mah 30c pack has 150amp discharge rate ie, well over what it would be asked to deliver why do people say It's best to get a battery with a high 'C' rating as possible, wouldn't it be pointless having a 90c for example ?

[VintageRacer]

Originally Posted by Dandare

Well if my 5000Mah 30c pack has 150amp discharge rate ie, well over what it would be asked to deliver why do people say It's best to get a battery with a high 'C' rating as possible, wouldn't it be pointless having a 90c for example ?

If my voltage drop theory is correct, a fully charged 8.4v 30C battery delivering 30A might drop to 8.1V whereas an 8.4v 90C battery might only drop to 8.3v. The difference will be greater the higher the current draw which occurs on heavy acceleration, so a higher C rated battery has more punch.

(note: all batteries have an internal resistance so their voltage under load is less than the voltage read with a meter, however, I don't know for sure if C rating effect internal resistance, just my theory).

[MattW]

As is normal for the RC industry and batteries, the figures get blown out of all proportions and the battery manufactures rely on the fact that no one really understands them.

"50C" means that the current (amps) that the battery is capable of delivering is 50 times the capacity. So for a 5000 50C battery the first thing you need to do is 5000/1000 to get the capacity into A/h rather than m/Ah, and then it's 5 x 50 = 250A.

So the current from a 3000 50C battery, and a 5000 50C battery isn't the same!

Then you need to worry about weather that figure is burst or continious! and ask youself the question of weather one manufacture "really" has batterys that are soooo much "better" than anyone elses