Battery Balance

[Zerksies]

What's an acceptable cell variance for lipo batteries. I have a two cell battery one cell is at 3.759 and the other one is at 3.81 and dropping after 10 minutes to 3.795. I put it on the balance setting on my new charger and it seems to be leveling out. What % of a variance should I have between cells?

 

[Mrgoodwrench35]

That's a great question. One I've often asked myself but never found an answer to so I guess I'm no help to you. Personally, I think a tenth of a volt difference is acceptable. Beyond that I would be concerned. Most of my Batts have far less than a tenth of a volt difference between cells.

 

[Zerksies]

My charger said it was done at .02 variance

 

[Mrgoodwrench35]

That sounds well within acceptable limits to me.

 

[bill_delong]

balance at storage isn't really important, the main reason we balance the cells is to prevent them from being over charged at 4.20V and things don't really make much of a difference in terms of cycles until a cell hits 4.25V on a regular basis which will reduce the cycles from 775 to 500 which is fairly nominal:
https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

Most of our batteries will age long before we hit 500 cycles, ha!

 

[tntpoof]

a 1/10 of a volt is ok. I dont over charge cell ever thats Dangerous thing to do.you can make a cell plug to get them exact .from main battery plug to a 2 lead balnce plug the charge the lower cell to match higher cell.but if new charger is doing that for you just pass

 

[DavidB1126]

balance at storage isn't really important, the main reason we balance the cells is to prevent them from being over charged at 4.20V and things don't really make much of a difference in terms of cycles until a cell hits 4.25V on a regular basis which will reduce the cycles from 775 to 500 which is fairly nominal:
https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

Most of our batteries will age long before we hit 500 cycles, ha!

View attachment 181633

If I am reading this correctly, a fully charged LiHV pack would have less cycles than a regular LiPo? That could explain why us racers go through batteries? And maybe why my uncle still uses normal LiPos. But with LiHVs, you can still just charge to 4.2v and it will still act as a normal LiPo, therefore might have a chance of living more cycles?

 

[bill_delong]

If I am reading this correctly, a fully charged LiHV pack would have less cycles than a regular LiPo? That could explain why us racers go through batteries? And maybe why my uncle still uses normal LiPos. But with LiHVs, you can still just charge to 4.2v and it will still act as a normal LiPo, therefore might have a chance of living more cycles?

The article I referenced doesn't include any testing on LiHV technology so I don't think it's fair to make any assumptions that they will reduce cycle life.

I always charge my packs to 4.22V where voltage tends to sag to 4.20V for tech inspection to get max legal voltage for stock racing

 

[WickedFog]

The article I referenced doesn't include any testing on LiHV technology so I don't think it's fair to make any assumptions that they will reduce cycle life.

I always charge my packs to 4.22V where voltage tends to sag to 4.20V for tech inspection to get max legal voltage for stock racing

A drone guy I followed a long time ago suggested the same thing. He also charges his packs to 4.22. I am not a racer, so I don't mess with overcharging, but I have tried it a few times and had the same results. After settling the cells fell back to 4.2v.

 

[DavidB1126]

I always charge my packs to 4.22V where voltage tends to sag to 4.20V for tech inspection to get max legal voltage for stock racing

Oh I see.
I maybe was cheating and getting that extra voltage
Its only normal club racing, so really doesn't matter. Or does it.

 

[Zerksies]

These are new packs with a new charger. I wanted to test both of them out. I never really fully charged the packs, Maybe got them to about 70% and did a storage charge on them. I hope to use them this weekend and get them up to a full charge.