3s 11.1v or 12.6v / 6s 22.2v or 25.2v?

[Nazar78]

Hi all, I need advises. Which volt do we see in lipo to calculate watt?

For 3s1sp 2200mah, isit:

11.1v x 2.2a = 24.42w
or
12.6v x 2.2a = 27.72w

11.1 is as advertised 3.7v per cell, 12.6 is max volt 4.2v per cell.

I wanna get rough estimation +/-5% for a power supply. Thank you...

[genexis]

If you are choosing chargers, try the following


Basically most chargers in the market takes only a 12-15V input power supply. And if you are going to charge batteries 4S and above, you will need to charge at a output voltage of 4.2 x 6 = 25.2 and above, which is higher than your 12-15V input. Thus, the charger will step up the voltage until it is high enough to charge the 6S battery, but in doing so, the current drawn is going to be a lot more. Thus, you need to choose a power supply that is way above your calculation.

Ok, now for calculation...

If you are going to charge 3S batteries, that is 2200mah, for lipos we charge at a standard of 1C, which means 2.2A. Theoretically, you will need a power supply that is 2.2 x (4.2 x 3 +++ ) = something above 27.7watt.

But why (4.2 x 3 +++)? Because if we want to charge the battery, the voltage of the charger output must be higher that the voltage of the battery for charging to be possible. So ... I don't know exactly whats the required power rating, but we should always get something above our needs.

Anyway, to keep things simple ...
1) Look for a REGULATED power supply that can give you a constant 12-15V output.
2) Look at the AMPS drawn at that output, is it 5A? or is it more. To see how much AMPS you need, you will need to decide how many chargers and the battery you need to charge.
3) I always get something that can last me a long time. Min i'll get 12-15V and 15amps ++ charger.

In the simplest case, 3S, 2200mah, then you only need to get something around 3Amps because you need AT LEAST 2.2 amps to charge, and probably more due to some inefficiency of the charger itself, hence 3Amps should be safe.

Hope this helps. It will be even clearer if you tell us exactly what you wish to charge.

[Nazar78]

hi broe, thanks for the respond, very informative.

So instead of using 3.7v each cell as advertised, we use the max volt 4.2 each cell. so its 4.2volt x 3cell = 12.6v, then x 2.2ah = 27.72watt. if 6s is 55.44watt~ thanks i got this part.

im actually figuring out:

1) which is better/faster when charging a 2x 3s1p 2.2ah, is it better to charge as 6s1p (2.2ah) or 3s2p (4.4ah).

2) currently im using psu 430watt, total 29amp on the 12v1/2+ railings, but my 10-18v/5a 6s charger is only 50watt output. so im scared this is too much current for the charger, thus wanna calculate to get a lower power supply.

[genexis]

in my opinion, parallel, 3S2P

At 6S1P, your charger will need to step up the voltage, so it will draw more current, but in this case, it should not be an issue to your power supply.

I don't think any of this will spoil your charger, it will just not be able to perform at your expectations. Chances are it will draw less current and under perform.

In any case, you can choose to charge lower than 1C, like maybe 0.8C.

So when charging at 3S2P, you are basically charging a 3S1P 4400 mah batter.
1C = 4.4 amps, so power = 4.4 x 4.2 x 3 = 55 watts > charger limits
0.8C = 3.52amps, power = 3.52 x 4.2 x 3 = 44.35 watts
It will take a longer time to charge, maybe 1 hour and 10 mins maybe? But it is still faster than charging two packs individually ( 2 hours ).

[Mazon]

2) currently im using psu 430watt, total 29amp on the 12v1/2+ railings, but my 10-18v/5a 6s charger is only 50watt output. so im scared this is too much current for the charger, thus wanna calculate to get a lower power supply.

the current drawn is dependent on the charger not the psu. so having a higher rated psu is fine.

powerloss is thru the current, P= I²R . So higher charging current will have higher powerloss , i.e less efficient. so u be more efficient charging at 6s1p. Thats y electricity is stepped up and transported thru very high voltages, then step back down again for use.

[madflurry]

wah pang i didnt know you are an electrical engineer

[Nazar78]

in my opinion, parallel, 3S2P

At 6S1P, your charger will need to step up the voltage, so it will draw more current, but in this case, it should not be an issue to your power supply.

I don't think any of this will spoil your charger, it will just not be able to perform at your expectations. Chances are it will draw less current and under perform.

In any case, you can choose to charge lower than 1C, like maybe 0.8C.

So when charging at 3S2P, you are basically charging a 3S1P 4400 mah batter.
1C = 4.4 amps, so power = 4.4 x 4.2 x 3 = 55 watts > charger limits
0.8C = 3.52amps, power = 3.52 x 4.2 x 3 = 44.35 watts
It will take a longer time to charge, maybe 1 hour and 10 mins maybe? But it is still faster than charging two packs individually ( 2 hours ).

ooo, ur .8c parallel recommendation should work great wit my configs. i initially thought 25.2v has the same charging time as 4.4ah. hehe thanks alot...

[Nazar78]

the current drawn is dependent on the charger not the psu. so having a higher rated psu is fine.

powerloss is thru the current, P= I²R . So higher charging current will have higher powerloss , i.e less efficient. so u be more efficient charging at 6s1p. Thats y electricity is stepped up and transported thru very high voltages, then step back down again for use.

bcos previously my old 12-15v 2a 3s charger smoked when using car batt 35amp. not sure y but thanks for da assurance.

errr, so charging 6s1p is better or faster than 3s2p? this is my 1st time charging 2x3s1p together...

[Mazon]

bcos previously my old 12-15v 2a 3s charger smoked when using car batt 35amp. not sure y but thanks for da assurance.

errr, so charging 6s1p is better or faster than 3s2p? this is my 1st time charging 2x3s1p together...

the charging time depends on the charging current.

i.e at 1 C rate, charging 6s1p at 2.2amps will take roughly same time as charging 3s2p at 4.4amps.

if u want to take care of the lipos, its best u charge them individually with a balancer.

[Nazar78]

the charging time depends on the charging current.

i.e at 1 C rate, charging 6s1p at 2.2amps will take roughly same time as charging 3s2p at 4.4amps.

if u want to take care of the lipos, its best u charge them individually with a balancer.

oh ok, noted. tankz all...

[Nazar78]

updates;

3packs 2200mah 30C (all 9 cells ard 3.7Xv) fast charged in parallel 3s3p @ 2.5amp, took est 1hr40mins for all 9 cells to reach 4.19v. Haven't got the time to test charge at 1c, mayb next ff hehe. Thanks broe genexis/Mazon...