What differences should I expect going from 7.4v to 11.1v?

[mjr_larkin]

Hello all. I'm rather new to batteries and all. I have a gaui 200 se on order and I see some people use 2S batteries and some 3S. Yet another distinction is that some are rated 11.1v and some are 7.4v. The battery that was suggested for my setup is a 3S 11.1v. What would happen if I switched to a 3S 7.4v? I assume switching to a 2S would result in epic loss of headspeed.

Someone please sort out the 7.4v vs. 11.1v difference.

Thank you!

[int2str]

Just to clear up some confusion:

Lipo cells are rated at a nominal voltage of 3.7V per cell

2s, 3s, 4s etc. refers to the number of Lipo cells connected in series, effectively multiplying their voltage.

So...

1cell = 3.7V
2s = 2 cells = 7.4V
3s = 3 cells = 11.1V

There is no such thing as a 3s, 7.4V battery.

As for what the Gaui 200 runs on, I'm not sure. I'll let the 200 experts sort that one for you.

[mjr_larkin]

Thanks for that key clarification!

I think the rest makes sense now.

[Pinecone]

With the stock motor, you want to run 2S. Motors are rated in Kv (RPM per volt). So it you go from 2S to 3S (7.4 volts nominal to 11.1 volts nominal) you will gain a LOT of RPM. And higher RPM will draw more current, which may exceed the capability of your ESC and/or motor, releasing the magic smoke.

You need to go to a small pinion to use a high cell count pack to keep teh head speed proper, but you may still be exceeding the capability of the ESC and/or the motor due to max commutation speed or max watts.

The stock motor is 4800 Kv. A 2S packs runs about 7 volts under load or 33,600 RPM on the motor. On 3S (10 volts under load) the motor is running at about 48,000 RPM.

[mjr_larkin]

What does the discharge rate have to do with things?

The discharge rate on the battery I ordered is 600mAh 25C 3S. I'd like to buy a 710mAh 3S battery but it's rated 13C. What difference will that reduced discharge rate make?

thanks

[Pinecone]

If you multiply the AH by the C rating, you get the max amps the battery can safely deliver.

So your 25C 600 mAH is 0.6 AH (divide mAH by 1000) x 25C = 15 amps max.

The 710 mAH 13C is a max amp rate of 9.23 amps.

The Hurricane 200 ESC is rated at a max of 12 amps, so in general you want a pack that will deliver at least that much. For long battery life, best is to draw no more than 80% of the pack's maximum. So for a Hurricane 200, a 15 amp or higher capable pack will live longer.

[rotorhead58d]

i don't think the 200's ball links will like the increase in headspeed. check them often.