First DIY 18650 pack issues

Hi all,

I have assembled my firts 18650 pack, however I am facing some issues with it. Before assembling it, I measured all the cells voltage and they were around 4.12V, however, after having connected all the batteries in a 4s3p configuration, when I measure the pack voltage it is at 14.2V and the cells are at 3.56V and the BMS is therefore cutting the battery. If I measure the voltage of the parallel packs(from possitive to negative on each cell), the voltage measured is again 4.12V.

Any idea of what is happening here? Is there any problem in the connections or I just have to charge the complete pack? Since the individual cells were fully charged, I am afraid of over charging it.



Pics ?
Disconnect the bms
Measure voltage on each row
Measure voltage 1-2 , 3-4 , 1-2-3… s


I have dismounted the full battery, and measured again all individual cells and they are all at around 4.13V.

I have also tested to connect two single cells in series and I have again the same effect, only with two cells. Two individual cells at around 4.13V I connect them in series and measure and my reading is just 7.1V. Without BMS I have just connected the + and - of each 18650 and measure at the open ends.

Maybe broken cells?

What kind of série connection do tou use ? Pressure ?

Problem is now solved with the voltage issue. The voltimeter was working badly, giving wrong measure for single cells, new voltimeter gives correct readings for both single and series. However BMS still not working.

1 Like

Cheap multimeter with old battery (low battery) reads high and inaccurate, I’ve had the same issue in the past, was a major headache until I realized, replacing to a fresh new 9v battery solved the problem.