Battery charger confusion

So I have a 13s4p 48V lithium ion battery with MH1 cells.
The battery charger supplied with it has specs of 59V 1.8A output.
My battery reads 53.7 V at full charge. The charger when tested has output of 56.5 V.
Something doesnt seem right? Thoughts?

Thanks.

That totally doesn't seem right. It shouldn't be going over 54.4... unless they're counting on the BMS to be cutting off the charge, which doesn't seem good either. 58.8 would be the next jump usually.... That seems oddly in between.

That charge sounds like its calibrated for a 13s pack of LiHV cells, which are designed to be charged to 4.35v.

Your BMS is probably protecting the cells which is lucky, although your voltage at 100% SOC should be 54.6v, so maybe there is something not right with the pack either, or the BMS is not accurate and is cutting off the charge a bit early (not really a bad thing). It may just be that because the charger is at a higher voltage, the BMS is detecting that voltage and cutting charge current before topping off the cells and then the cells are settling a bit below fully charged.

Id suggest a new charger, one that is rated correctly. You can keep that one for an emergency backup, though I would be weary using it. If the BMS fails to cut off the charge then your cells will be pushed to 4.35v which at best, will shorten their life and at at worse, will make them vent or worse.

lionman is absolutely right. You need a new charger with 54.6V output voltage (13*4.2V per cell = 100% DoD for MH1) or try to modify the existing one. There should be a potentiometer inside which can lower the output voltge. The main reason is safety but another reason is that your BMS immediately cut-off charging when reaching 54.6V, so there is missing CV phase of charging and so your battery is charged only to 85-90% of its full capacity. This explain your reading of 53.7V after charging.

Agree with lionman too, and Pajda adds some extra info about the charging protocol holding back your charging. I never knew that.

By the way, the same thing happened to me. Bought a 48V battery and vendor shipped me a charger that said 48V on the label, but also stated it had a 58.6V output. I'm sure I used it on all my 48V batteries for over a year. I guess the BMS on those batteries protected me.

Thanks for all replies.

I am suspicious that this is a 48V lead acid battery charger that was re-purposed for lithium ion, but not really spec'ed for the task.

The good news is that the bms will protect the pack, and has been. Till it doesn't some day.

I would not worry so much that its a lead charger, but I would open it up, and look for a tiny box with a screw on the top, right near the DC wire leaving the board. If you have that, tweak it down to 54.6v.


It is set to lead voltage, but if it was a lead charger, I'd think there would be some kind of label saying so on it.