Originally Posted by r3meyer
Curious if you have done a full load test on them yet. Brought them all the way down to LVD and all the way back up to HVD (or very close to it). If so how close in balance did they stay? I think you stated you were choosing 14.5V as your max.
One thing I am finding with the larger AH packs is that those mini balancers you have do not have the needed amp capability to make a correction when you are charging with the higher amps that you are if you bring the packs down and up frequently.
Actually your finding is quite the opposite of most users.
Couple of thoughts here you need to decide if you want your pack to be bottom balanced or top balanced but they cannot be both.
I have mine top balanced because I think this is the way to go for an RV. Others think different.
It took me 2 full charge and discharge cycles to get them top balanced and stay that way.
Since then the packs are in use and have not been balanced in the last 3 month.
I just went out and took a picture of the attached meter. I don’t use that to balance by the way.
The min to max cell voltage is 0.014V all the balancing logics that I came across so far are starting to balance at 0.2V difference.
My Victron shows 11 complete full cycle charges and the pack gets used (fans) and charged (solar) daily.
If you experience that your cells stay not in balance then here is my recommendation.
A) if you bottom balanced your High Voltage cut off is set too high or if you top balanced your low cut off needs to be raised.
B) in all scenarios I have seen where packs want to chronically fall out of balance the internal resistance of the pack is not matched either up front when put together or when they age.
C) the C rating for the discharge is not matched to the capacity of the pack. So you install a 50Ah pack and expect it to deliver 250A, while possible and manufactures like to claim their cells can do it I think it is not practical.
And finally D) in the pack assembly there can not be a connection with a different resistance then the rest.
An external balancer placing a parasitic draw on a cell of 0.8 to 1A should be plenty for any pack size you can fit into an RV. It just needs time to do it. But you cannot use it to initially balance your pack.
I think my explanation is getting a bit long here ... anyways I own 14 lithium packs from 12V to 36V and this is what I have learned in the past 6-7 years of using them.