I want to use this 3.7V 40Ah powerbank to power my e bike's 48V hub motor. So would it be a bad idea to step up 3.7V all the way up to 48V? Would there be a huge Ah loss?

  • \$\begingroup\$ What wattage is the motor? What current maximum might you need? \$\endgroup\$
    – Andy aka
    Jun 8, 2018 at 17:59
  • \$\begingroup\$ The wattage of my motor is 1kW. I guess I would need at least 20Ah. \$\endgroup\$
    – Spoods
    Jun 8, 2018 at 18:13
  • \$\begingroup\$ 1000w / 48v = too many amps for your little batteries. \$\endgroup\$
    – dandavis
    Jun 8, 2018 at 20:05

1 Answer 1


No, this is not a good idea.

First, 20 3Ah primary cells form a 60Ah battery, not 40.

Second, up-converting voltage with 1:13 ratio will yield not a very efficient converter, losses go up as the duty cycle goes down.

Third, 20 cells in simple parallel won't last long, due to uneven wear of cell and overcharge of strong cells, unless the battery pack has individual cell management.

A better idea would be to re-built the battery into series configuration, 13S, and employ a BMS. But again, it will require a serious re-engineering.


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