Been researching for a while and now I have enough cells that I would like to get a pack together. I have quite a few 19650 li-ion cells around 2500mAh.
I would like to try out diyBMS on it. It seems that 48V would be a good voltage to eventually build a pack for, but I still need to have a look at it further. for the moment, will build 3.7V packs that I can then connect in series at a later stage.
My question is, using one diyBMS module, how many cells do you guys recommend connecting in parallel? I would prefer a number based more on safety than cost at this point.
I think that the cost of the BMS must have a point where it is protecting a enough number of cells that will be optimum. as an example, using one module to protect one 2500mAh cell is the safest but not cost effective.
Would like to hear from you guys on your experience.
Hi, I would say that it depends on how many amperes you are going to charge the battery pack with, the module needs to be able to balance the battery and if it is a very big pack the balancing will take a very long time and if the charge current is very high the balancer will not be able to keep up. I would say build the battery as large as you want it but the first time you charge it keep the charge very low (maybe 1A) to let the pack balance, once it is balanced and fully charged these modules should be able to keep up without a problem to have the battery keep in balance. These modules should be able to balance at 2A, but when they start balancing they heat up and the current drops. It’s possible to use the rules to set it up so you can start fans on the modules when they heat up or even stop the charging to let the balance do its thing and then start charging again when the balancing has caught up with the charging.