Parallel charging brain fart :(

[GreggyG]

Hi

I'm having a bit of an early morning brain fart during my research for a new charger and power supply. My question is -

If im charging 2 X 5000 lipos on a parallel charging board at 1c, will the charger need to be set at 10amps or just 5 ???????


I guess its quite straight forward but im not really getting it.

Thanks

[miniman]

10 Amps

Peter

[Sburv]

Parallel charging brain fart

Yep 10amp at 1C

[GreggyG]

Thanks

[Delarado]

Paralell the voltage stays the same but add the current together.

Serial add the voltage together but the current stays the same.

E.g 2 x 5000 mah 6s to charge at 1c:

Paralell = 6s (22.2v) 10 amps (2x5a)
Serial = 12s (44.4v) 5 amps (2x 22.2v)

[bulldog5046]

Series

[TheDarkPassenger]

Question on a question.

So, if 2 x 3S 2200Mah batteries, then charge 3S at 4.4amps.

If I have a five amp charger, is two of the above batteries the maximum for parallel charging or would they simply charge slower?

[Delarado]

Depends what voltage the charger can hold 5 amps at to be honest. Amps is not a good way to measure charger output as it is dependant on voltage. You need to measure it in watts really, then it becomes voltage independant and a true measure of charger power. When you push a charger past its limit it should just charge slower (providing it can charge at the right voltage)

So, if your charger is a 50w charger (Which many are) the theoretical maximum for that charger for 3s would be:

50w = 11.1 * X

So:

X = 50w / 11.1 = 4.5 amps

Ergo, you can charge at 4.5 amps with a 50w charger @ 3s. So paralell charging 2x 3s you could charge at 4.4 ok. Paralell charging 3x3s you could still only charge at 4.5 amps.

4.5a / 3 = 1.5 A per battery.

1.5a / 2.2ah = 0.6C charge rate.

I.e the batteries would still charge, but more slowly.

Take that 50w to 6s though:

50W = 22.2 * X

X = 50w / 22.2 = 2.25 Amps

So you can charge at 22.2v (6s) at 2.25 amps. Adjust the "C" Charge rate depending on what battery you are using! (FOr example a single 2200 mah 6s would charge at 1c there)

[robgt]

To the original question, it also depends on the charger you are using.
As this question is in the Optipower forum, I think you are looking at the Powerlab chargers?
When programming the Powerlab 6 or 8, you tell the charger at what rate you want to charge 1 pack, then tell it how many packs in parallel you are charging. The charger then works out the totals for you.

Cheers,
Rob

[miniman]

As soon as you conect two packs together in parallel, in your case 3s 2200mah, you get a single pack 3s 2p 4400mah. A 1c charge would require 4.4amps at 12.6v (fully Charged), or 55.4 watts

Your 5amp charger should cope with charging the pack at 1c

Peter

[Delarado]

Just to clear up any confusion, Miniman has used the maximum voltage of a 3s pack in his calculation (4.2v x 3 = 12.6V) and I have used the average voltage (3.7v x3 = 11.1v)

I tend to use the average voltage when doing charging calculations because if the pack is at maximum voltage, the charger will not be outputting full power to charge it (It will start to reduce the charge amps gradually to maintain 4.2V per cell)

Either way is fine though, Minimans is probably a slightly more true way of representing maximum charge capability though as it shows a chargers specified absolute maximum, where as mine shows more of a real world approximation and may not actually hit those figures!

Also remember not to connect packs together in paralell with different states of charge.

When I fly, I charge to full, then fly.

When I get home, I charge each pack individually to 4.2% or 3.82V per cell.

When Im ready to fly again I bung them all on together (6x6s 5000mah) and charge at 30 amps. Voila, I have 3 sets of packs ready to fly in about half an hour.