I don't understand my balance charger, Thunder 1220 charger. I have two battery packs: 1) 12S1P - 8ah, and 2) 12S2P - 16ah.
The charger has a 180 minute time limit for charging. I set the charger to target 4.2v per cell.
When I balance charge my 12S1P it takes about 90 minutes. Cells 8 & 10 are over 4.2v and the rest are under.
My 12S2P is brand new ... the four batteries were fresh from the factory. The first time I balanced charged the charger timed out at 180 minutes. Cells 8 & 10 were over 4.2v. The rest were under. The total charge was 49.5v. I didn't start my charger over. I just used the battery. Went 22 miles and the battery was down to 45.2v at rest.
I balance charged again. This time I let the charge run for 170 minutes - then I needed to use the battery and I figured in the last 10 minutes it wasn't going to level all the cells at 4.2v so I just stopped the charge cycle and used the battery. But I shot video of the cell levels:
As you can see - the charger reports cells 8 & 10 are over and the rest are under. And the total charge is 49.75 - target is 50.4v.
Immediately after I took the battery pack off the charger I checked the cells with a hand held checker - this checker (Bluecell Lipo Digital Battery Voltage Checker - http://www.amazon.com/gp/product/B005HG ... UTF8&psc=1
) gets good reviews for accuracy on Amazon. I got two them. I shot video of the result:
AS you can see - no cell is over 4.2v. I don't understand. Doesn't my charger need to be most accurate so as to not overcharge a cell? But it appears the charger readings aren't accurate. And cells 8 & 10 are the ones the charger reports as over for both battery packs: 12S1P and 12S2P. The same cells (8 & 10) in both battery packs - that seems odd. I'm confused. I'm thinking this is operator error as this is my first experience with LiPo / RC / Balance Charging and everything.
Also, both the charger and the checkers report cell levels that are not within 0.01v tolerance of each other.
What gives - any insights would be greatly appreciated.