Charger cutoff current

[nikolay]

Hi all,

I have a charger for my 13S battery which is not cutting the voltage when it reaches the low current at the end of the charge. It just have green LED which turns on when the current is about 150 mA. But it never cut the voltage. My BMS is like this one: https://enerprof.de/en/accessories-components/bms-pcm/13s/756/bms-13s-20a-for-li-ion-batteries-48v-in-reention-case?c=153

I saw that even Grin's smart charger never cut off the voltage. It just shows you the battery is charged by detecting the low current but the voltage is not stopped. As far as I understand this is because of the balancing as it might read very low current but still needs some topping. I know that keeping the battery connected forever to the charger especially on 4.2V/cell is not good for the cells. Does it means the BMS will cut off the charging when the voltage on all groups reaches 4.2V ? Then there is no problem the charger to provide the voltage forever...?

 

[john61ct]

I am very surprised about your statement wrt to Grin not fully shutting down. Personally, I would not want the cells to be subjected to voltage once my definition of Full is reached, even without any current flowing.

In fact there really is no need for LI to have **any** CV / Absorb stage at all,

in fact depending on C-rate and termination voltage setpoint a CC/Bulk stage only "just stop at X.xx volts" profile

may be more conducive to good longevity, even if X = 4.05V

You may want to figure out how your BMS HVC works to protect against overcharge, and then test to verify.

IMO a cheap BMS (less than say $500 dollars) should only be used as failsafe backup protection, for when the primary "user space" circuitry fails.

A simple adjustable pack-level HVC can be rigged to either trigger a remote switch terminal OFF on the charger, or cut its upstream input supply.

In expensive rigs, the BMS uses CAN or another comms protocol to control the charger, and then has independent per-cell HVC logic.

 

[TommyCat]

Hi nikolay,

When the green light came on, did the current stop completely?


Regards,
T.C.