will 14s bms be ok for 13s battery

Hi I was sent a 14s bms from ebay [https://www.ebay.co.uk/itm/48V-13S-45A-Li-ion-Lipolymer-Battery-BMS-PCB-with-Balance-For-Ebike-Escooter/352110181143?hash=item51fb66fb17:g:GWEAAOSwFdJZtikT]here. I ordered a 13s one. I am requesting a return. But would it be ok to use using only 14 of the 15 balance pins or will cut off voltages still be for a 14 s battery ie about 56 v fully charged and 42 v discharged.

You would have to test it. I have a bunch of loose 18650's from recycled makita batteries that I use.

You connect the cells starting from B- and see if you get the full pack voltage at P- with only 13s.

If it won't turn on then try to connect the 14th cell balance wire to the 13th one.

It should work fine. The BMS only looks at the individual cell voltages, not the pack total. The Cell 13 and 14 wires should be tied together.

Yeah, I thought that method works for all BMS, but I recently tried that on a Bestech: http://bestechpower.com/518v14spcmbmspcbforli-ionli-polymerbatterypack/PCM-D452V1.html
and it didn't work.


But the HCX D131 and a few other work with 10 to 24 Cells, and you don't even need to short the balance leads 8)

Thanks for reply. I,ll try your suggestions. so i short 15th balance wire with 14th one.I presume this would be on the positive end right? Why cant i just ignore the 15th wire and cut it off

You need to tie the unused balance wire to the top cell. If you just cut it off, it will pick up noise and false trigger a shutdown.

With the Bestech power unit, the design is different and you have to place a jumper across pins on the chip to lower the cell count. Based on the picture in the link, the unit he's working with will work just by jumpering the unused cell connections.