I have a Li-Ion battery pack made with twelve 18650 in a 3S4P configuration, using an off the self Battery Management System (rated for 25A), that I purchased on aliexpress. I tried to charge it using a 5A, charger, at 12.6V, But the problem is, the BMS seems to max out the current supply and the charger is blown off. I have following questions:

  1. Should I supply more than 12.6V to charge the pack? Will this reduce the current drawn?
  2. Is there a way to limit the current drawn by the BMS circuit externally?


  • 1
    \$\begingroup\$ Since the charger is blown, use this chance to buy a better chargee that can limit the charge current itself. Although such a charger would also be able to charge the battery without the BMS. \$\endgroup\$
    – DKNguyen
    Jun 12, 2019 at 5:00
  • \$\begingroup\$ BMS drawing more Amos than input?? You mean more heat maybe. Did you verify the charge imbalance and understand how it works before your cooked it? next time start with a lower current limiter. it.s only supposed to balance at low currents after it reaches CV mode. \$\endgroup\$ Jun 12, 2019 at 6:40
  • \$\begingroup\$ @SunnyskyguyEE75 What is a lower current limiter? \$\endgroup\$ Jun 12, 2019 at 6:54
  • \$\begingroup\$ A soft start circuit. WHat are the symptoms , measurements of your failure? details.... \$\endgroup\$ Jun 12, 2019 at 15:30
  • \$\begingroup\$ There is no way BMS would cause charger to "blow off". Furthermore, even cheap Li-Ion charger should limit the current to what it can handle. Are you sure you connecting everything properly? \$\endgroup\$
    – Maple
    Apr 12, 2021 at 8:03

1 Answer 1


BMS chips are typically for protection from over and under charge... You still need a properly designed Lipo charger that is CC/CV.

BMS systems typically just have FET transistors that disconnect the battery from the circuit in the even of over or under charge.

Unless you are using the term BMS wrong, they are not intended to be used as a charge controlling device or a primary charger, just a safety to keep a pack from exploding during or after charge.


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