# Thread: I don't understand batteries anymore :0

1. ## I don't understand batteries anymore :0

My 11.1v 3s lipo is charging up to 12.9v and my 7s nimh pack is charging to 9.7 (about) ???? Also what can each cell in a lipo battery be safely be discharged to?

2. Your lipo is over charging by 0.3V
the 7cell nimh should be 10.5V (about)
3V per cell is the absolute minimum the lipo should go down too. But there is no need to discharge them.

3. Voltages marked on the pack are nominal.

LiPo:
Full = 4.2v/cell
Nominal = 3.7v/cell
Empty = 3v/cell << You really do not want to ever empty a LiPo.

NiMh:
Full = 1.4-1.6v/cell
Nominal = 1.2v/cell
Empty = .9-1v/cell

4. Thanks it helps :P. now about the mah rating, when they say 6400 mah do they mean until lvc kicks in? Or is that until you completely drain the battery and reverse its polarity.

5. LiPo's polarity cannot be reversed.
Capacity (mAh) rating is not always completely useable... depends on the quality of the pack. I have seen packs able to deliver over their stated capacity and I have seen packs not capable of their stated capacity. Discharging is not done by capacity anyway... it is done by cell voltage... and it should be that way for charging as well.

6. Originally Posted by Jimmie Neutron
LiPo's polarity cannot be reversed.
Capacity (mAh) rating is not always completely useable... depends on the quality of the pack. I have seen packs able to deliver over their stated capacity and I have seen packs not capable of their stated capacity. Discharging is not done by capacity anyway... it is done by cell voltage... and it should be that way for charging as well.
Oh ok my dad said that's what happens when discharge them to much. :P as with the mah I meant (example) at 4.2v one of the cells have all of there 6400 mah in them. Then when you start to use up the storage the voltage starts to drop. So at 3.3v when lvd cuts in is almost all of the storage gone (500 mah left of is there still half a pack worth of storage left in there?

7. Next time I run my pack down I'll report back how much mAh I used vs the stated capacity. I even have new battery coming tomorrow... or Tuesday.

8. Thanks .

9. Battery came in...

Labeled as a 5S 5000mAh 40C.
Cycled down to 3v/cell on my iCharger and balance charged it to 4.2v/cell.... 4983mAh was put into the pack.

Keep in mind that it takes a few cycles to get full performance out of any LiPo.

Ran it today with the ESC set for 2.6v/cell, but the ESC I was using recognizes the 5S pack as a 6S pack... which means when the pack voltage hits 15.6 the ESC reduces power to less than 50% for just long enough for you to drive the RC back to you... most of the time lol. This also means, in theory, that I am setting the LVC to 3.1v/cell... but I think the ESC must watch dipping voltage quite closely because as soon as it hits LVC cell voltages range from 3.3-3.4v/cell and 3.5-3.6v/cell 15 minutes after the run.

Once I charge it up for a run tomorrow I will tell you how much mAh was used in today's run.

10. 4724mAh back in after a run.

11. Thanks. I didn't get the best of results with my 6400 mah pack I ended up with ~2600 mah left unused in the pack. :/

12. Oh the battery is a traxxas 3s 25c 6400 mah pack

13. What were your cell voltages and what is the LVC set at?

14. Esc is vxl-3 so I don't know and I think the whole pack was 10.5v

15. That figures to be about 3.5v/cell.
Are they new or old?

16. Fairly new, about 20 cycles

17. Something isn't right... your LVC is about where it should be. Any lower and you could ruin the pack, but you should be draining more mAh than that out of it.

18. Could it be because of the c rating? Because with a higher c rating you get less battery dip right?

19. The C rating is out of equation if the end voltage is 10.5v for the pack.

20. Oh do you think that the issue will fix itself after a while?

21. Oh do you think that the issue will fix itself after a while?

22. Hard saying since we don't know what the problem is.

23. Yes, that might be a problem.

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