How often should I balance my cells if I don't have BMS

Hi,

Six months ago I setup a small 200AH 12V Lithium battery for emergence lights at my parents' house. The battery is charged by grid

In most cases the battery remains idle as they have few power cuts. I just realized I completely ignored need of an active balancer for the cells

I just wanted to know how often was I supposed to be balancing it while waiting for the active balancer to arrive from China. I can imagine the cell can have less than 10 full cycles in a month

Thanks, Innocent

Balance them when they are our of balance enough to be a concern. If they are LiFePo4 and if you have top balanced them they might be just fine as long as you don't take them down too low. I set up a similar system recently. it is to be expected that one cell might have more capacity than another cell. The voltage will start showing differently when you cycle them fully down and up than if you don't take them to the extremes.

You might want to add a BMS or add a cell level monitor.

If the cells are half decent and initially balanced and with a BMS then an active balancer should not be needed.

The AC charger should be set to a charge voltage that is correct for the cell group.
The BMS should stop the cells from being over charged or over discharged. An active balancer will not prevent over charge/discharge.

Even if the cells are not top balanced and just put together as a battery, it should not be a problem with a BMS fitted, you will be loosing some battery capacity but still have a usable battery.

If you are operating without a BMS then there is a danger of the cells being damaged beyond recovery. You need a BMS not an active balancer.

Mike

It's just a matter of time without a BMS --- We'll be seeing one of your cells bloated or dead -- that's unless you sit there and monitor them every Discharge and Charge cycle