charger help - what charge rate - RC-Monster Forums

lucias · **charger help - what charge rate -** 03.15.2011, 04:27 PM

So I bought a new Hyperion Duo 3 and it will charge up to 20 amp's, and I also bought a 40A Pro Tek Power supply.. How do you calculate how many amps you can charge a battery at by it's C rating??

simplechamp · 03.15.2011, 04:32 PM

Discharge C-rate and charge C-rate are two different values. Standard lipo charge rate is 1C, so a 5000mah pack (5Ah) would charge at 5A. Some newer packs can charge at 2C, or even claim up to 5C. Only attempt if it's clearly labelled on the pack that this is OK. Even then, there is some debate about if it affects the life and health of the pack.

BrianG · 03.15.2011, 04:33 PM

You mean how many amps for the PS input into the charger? If it's the Duo 3+, the max input is 40A @ 12v.

That charger (if its the duo3+) is rated 350w X 2 only when hooked to a ~24v supply. At 12v, you are limited to 40A max, which is 480w max. That will be split between the two charger channels (when charging two packs at once). Minus efficiency losses, yadda yadda, you are left with around 220w x 2 channels. What current you can charge at depends on the voltage of the pack.

lucias · 03.15.2011, 04:34 PM

I was looking at the Hyperion Packs and they claim you can charge a 5000mah pack in 12 minutes..

simplechamp · 04:44 PM

At 1C a pack should take about an hour to charge. So what that implies is that the said Hyperion pack can be charged at 5C (12 minutes, 1/5 of an hour). For that 5000mah pack a 5C charge rate is 25A. Any lipo pack should be clearly labelled with it's max charge rate.

To calculate charge rate you take pack capacity (in mah), divide by 1000 (to convert to Ah), and multiply by charge C-rate (1C, 2C, 5C, whatever value you want to charge at)

3000mah pack charged at 2C would be: 3000/1000 = 3, then 3 x 2 = 6, so 6A

lucias · 03.15.2011, 04:52 PM

thats kind of what I thought but thanks for the explanation it makes more sense now.. Charge on!

I also bought one of the Hyperion EOS SENTRY Battery Checker, kind of a cool device if you haven't seen one..

_paralyzed_ · 03.15.2011, 05:50 PM

well, it gets more involved. For simplicity, I will say a 6s pack is 22volts.

To charge a 5000mah 6s pack at 2c requires 220 watts. (10a x 22v = 220 watts.)

So you are limited to a 2c charge with a 6s pack with your setup.

5c charging a 6s pack requires 550 watts. (25a x 22v = 550 watts)

voltage x amperage = watts