Although the answer might be easy, I am a newbie and want to ask before burning my house down.

I've seen a lot of battery packs tutorials. Now I have to use my knowledge to connect two 7S packs in parallel. Now I am worried that my tools aren't the best and the voltages of the two packs might be different and cause a big current flow that will destroy something in the dual BMS. I want to safely equalize the voltages between the packs. Everyone mentions how easy it is to balance a 2 cell battery but I didn't see anywhere how to balance two xS batteries. I am thinking of a resistor across them outside the bms and leave them until they equalize, what are your suggestions and is this a good idea?

  • \$\begingroup\$ What’s the ESR of the batteries? What’s the maximum allowed charge and discharge currents? \$\endgroup\$ – winny Apr 19 '18 at 16:52
  • \$\begingroup\$ Sadly, there is no way to know(the stickers on the cells do not show up on google). It's ebike battery that's 7S2P with dual bms but it refuses to charge the cells and i had to charge the packs manually, it works with discharging tho. \$\endgroup\$ – Pavel Stoyanov Apr 19 '18 at 16:58
  • \$\begingroup\$ I searched for similar batteries for my ebike, they say the continuous discharge current is 20A, they do not specify anywhere what the max charge current is and related specs. \$\endgroup\$ – Pavel Stoyanov Apr 19 '18 at 17:05
  • \$\begingroup\$ With 0.001V you should be on the safe side \$\endgroup\$ – PlasmaHH Apr 19 '18 at 17:07
  • 1
    \$\begingroup\$ You can use an 8W festoon 12V car bulb to equalize google.com/… \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Apr 19 '18 at 17:39

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