1.Why do BMS need parallel module?
It's for safety purpose.
When multiple battery packs are used in parallel, the internal resistance of each battery pack bus is different. Therefore, the discharge current of the first battery pack closed to the load will be larger than the discharge current of the second battery pack, and so on.
Because the discharge current of the first battery pack is relatively high, according to the law of conservation of energy, this battery pack is likely to trigger over-discharge protection first. If charged at this time, the remaining battery packs and the charger will charge this battery pack at the same time. At this time, the charging current is uncontrollable, and the instantaneous charging current can be relatively high,causing damage to this battery pack.So to prevent this risk happen, one parallel module can be necessary.
2. How to choose the BMS parallel module?
Parallel modules have different amperages, such as 1A, 5A, 15A, This selection is similar to the charger charging current selection. 5A, 15A refers to the rated charging current that the parallel module limited. When the battery pack is parallelled and the charging over-current protection is triggered, the parallel module will be turned on. If choosed 5A parallel module, the high voltage battery pack will charge the low-voltage battery pack with a limited current of 5A. Also, the limiting current determins the length of the mutual charing time. For example, if using 5A parallel module to balance 15Ah capacity, it will take 3h, but if using 15A parallel module to balance 15ah capacity, it will take 1h.So which parallel module to choose depends on how long you want the balancing time to be.
Post time: Jan-18-2025
