How to keep Lifepo4 cells balanced without charging to 100%

[Cal]

3.4V can be at 70% state of charge if you charge at a decent rate.

That may be the case. However the cell is in the knee of the charging curve. Cell voltages have diverged. There's absolutely no problem initiating balancing at this voltage even at high charge rates.

 

[upnorthandpersonal]

That may be the case. However the cell is in the knee of the charging curve. Cell voltages have diverged. There's absolutely no problem initiating balancing at this voltage even at high charge rates.

If you have one cell at 70% state of charge, and another at 60% state of charge - both at 3.4V - and yet another cell (assume the lowest one) at 3.35V, you're going to take charge away from both the 70% and 60% state of charge ones to get the lowest cell up. If you were to turn balancing on at 3.5V, the 70% state of charge cell would reach this faster while the 60% one catches up. In the latter scenario, only the highest of these three will be used to bring the 3.35V cell up.

Edit: Anyway, I'm not trying to argue with you. If this works for you, perfect. I've seen issues with this in the past during tests; I'm just putting this out there in case others have. Anything that works is good

 

[Cal]

Edit: Anyway, I'm not trying to argue with you. If this works for you, perfect. I've seen issues with this in the past during tests; I'm just putting this out there in case others have. Anything that works is good

Yes, it works perfectly for me. High voltage disconnect is at 3.40V. At this point in time the processor determines the difference between the highest and lowest cell voltage. The lowest cell then gets charged for a time period determined by the delta voltage multiplied by a constant. The greater the cell voltage difference, the longer the time of the charge to the lowest cell.

 

[Ampster]

Please explain a Universal Dielectric Truth Model and it's calculations.

Dielectric? I know this was directed at @smoothJoey but it seems his comment was making a suggestion that new Lithium cells often need balancing. That has also been my experience. There is no Truth Model but an observation of the flatness of the charge curve has led many people to suggest that the same resting voltage of new cells is not a predictor of their equal State of Charge. It is simple physics if you want a scientific answer. Could you be thinking of a dialectical thinking model?

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