New Build battery cutting out

[John B]

I have just built my first battery, 36v 21Ah, 10S6P using new cells. When I connect it to a load, (my trike motor), the display flashes on for a brief second and then cuts out. The battery voltage remains unchanged at 40 volts. When I put another battery in its place everything works fine, so it appears my new battery will not pass any current even though it registers full voltage.

Any suggestions would be really appreciated, before I go and remove all the wrapping to check it out! Thanks.

 

[Diggs]

Is your new pack using a BMS?

 

[docw009]

How is the new battery held together? Are the cells spot welderd, or is it one of those spring/friction kits?

 

[molybdenum]

does it cut out under load (i.e throttle), or does it cut out as soon as it is connected?

 

[John B]

Thanks for the replies.
The cells are spot welded and I'm using a BMS. It cuts out as soon as it is switched on.
I think I've found the problem: one of the parallel groups is a much lower voltage than the rest,
so I'm going to replace that group. I think the BMS was shutting down as soon as current started to flow.

 

[Bandit1961]

you should balance all cells before building. Try charging the parallel group upto the same voltage as the other groups (you can do this in circuit). Also make sure all cells in that group are connected with your spot welding ... if some cells arent connected it can throw the balancing off quickly.

 

[docw009]

If one parallel group is much lower, and these are all new cells, try getting that group's voltage equal to the others before taking things apart. New cells are usually shipped around 3.4V, so they should have all been at that level. For the BMS to click off so fast, that low group must have been right at 3.0V.

Do you have a 4.2V charger available?

 

[gromike]

I've had that happen when I hooked up the parallel cell leads to the bms wrong. I had inadvertently swapped two leads and it drained one of the cell groups, and that was it as far as a functioning battery. Replaced that cell group and fixed the wiring and all is good.