Cell voltages not consistant

[knucklehead]

Hey everyone and Happy New Year!
Hoping I can get some light shed on my particular question. I have a new PL8 v 3.31
and my concern is voltage inconsistency from cell #1 to cell #6. Doesn't matter if I'm charging 1 pack or multiple packs in parallel. I get the same end result. I'm using FMA's MPA board and the charger is set to JST-XH wiring mode. Upon completion of a charge cycle, charger displays cell voltages of 4.200 - 4.198. When I check them with a stand alone balancer / checker, doesn't matter which brand, I see voltage levels from 4.198ish down to 4.150 descending from cell #1 down to cell #6. I just don't want any long term effects from cell # 6 starting lower than the rest of the pack. I haven't used them directly off the charger because I place them on my Hyperion 1420i to compare, and this charger brings all cells up to 4.20 - 4.19. Any comments, suggestions or answers would be greatly appreciated.

Thanks,
Ed

[Gregor99]

Which preset are you using? What is the age and approximate cycle life of the packs? Do you have a digital voltmeter?

If you move the cell checker up so that only the top two pins on the pack are connected to the bottom two pins on the cell checker, does it give the same voltage reading as when all pins are connected to the cell checker?

[knucklehead]

Using preset 3 high power. For shits and giggles I used preset 2 on my "test" pack, and it actually finished with a much closer group of #'s. This pack is an old nano puff 6s 3500mah I use for setup purposes and all 6 cells finished within .02v of each other. This pack is probably 2 1/2 years old with countless cycles on it.

My guess is high power charging is not as accurate? I set the current with this pack @ 2C in preset 2 and it took 41mins. to complete versus 18-20 mins. on high power charging @ 10amps. Is this correct? BTW, I did use a dvm and checked the individual cells and they matched what was displayed on my cell checker.

[Gregor99]

The high power preset uses a CV termination setting of 10% of the set charge current. The same is true for preset 2. But with preset 2 you'll be limited to 10 amps max so the termination current is about 1 amp. For the highest level of accuracy, use preset 1, accurate charge. The charge termination is set at 5%. Reading through your results its sounds like your second test was with preset 1, instead of preset 2.

The voltage mismatch on the high power setting sounds about normal for a pack of that age and condition. As cells age their rate of voltage sag after the charge cycle increases. Its common for packs that are not well matched for the sag rates to be uneven across the all cells in the pack. Using a preset such the accurate preset with a lower termination current does help to mask the issue. But it may not be the best choice as the cells with the higher rate of sag are getting charged slightly more than the other cells on the pack.

[knucklehead]

My test pack was charged on preset 2. My flight batteries are pulse 3300mah 6s 45C and thor 3300mah 6s 45C. I cycled them on the PL8 using preset 2 and preset 1 and they charged great. All cells in all packs were within .01 - .015v of each other. Charge time was longer but that's fine.

Thanks for the info. I managed to read thru the operation manual on revolectrix's website. And it explains what you were saying.