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BQ24610: How to charge 2 battery packs in parallel

BERNARD FROMENT
Intellectual 270 points
Part Number: BQ24610

Hi,

We currently use the Texas BQ24610 chip to charge a 6.5Ah li-ion battery (robotics application).
In the new version of the robot, 2 packs of 6.5Ah Li-ion battery  can be connected in a parallel
- In standard: One 6.5Ah battery (as currently)
- Option: 2 batteries of 6.5Ah in parallel (same specifications, same states, same manufacturing batch).
Allowing, as an option, to double the battery capacity.
Info:
- We cannot use a pack of 13Ah for the option because  pack 6.5Ah is certified (FCC, CE, ...) and we must have to use 2 packs in parallel
- The space on the PCB does not allow to use two  BQ24610
- Each 6.5Ah battery pack has its own BMS (4-wires output: battery and Smbus)

Do we need  a battery balancing circuit for parallel connexion?
I think so because along time, even very identical at the beginning, battries age differently.
Must we balance only during charge and / or during discharge ?
Schematics to propose me?

Regards,

Bernard FROMENT

Electronics Engineer

  • 0
    TI__Guru**** 165866 points

    Hi Bernard,

    LiIon batteries in parallel self balance.  Even if one ages differently than the other, and therefore becomes more resistive, the cells will still self balance through their resistances.  Balancing batteries in parallel is complex, requiring independent gauges, isolation, discharge and charge switching circuitry for each battery.  I am not aware of reference design for parallel balancing.

    Regards,

    Jeff  

  • 0 in reply to Jeff F
    Intellectual 270 points

    Hi Jeff,

    If I understand well your answer you mean that I just have to connect the 2 batteries in // and that's all ?

    Their internal serial resistance will self-balance their charges/discharges.

    Even if they do not come from same  manufacturing batch ?

    Even if they get different ages when connected in // ?

    Only precaution I presume, is that they must have the same voltage when connected in // !

    Regards,

    Bernard FROMENT

    Electronics Engineer

  • 0 in reply to BERNARD FROMENT
    TI__Guru**** 165866 points

    Hi Bernard,

    Yes, all of the customers with whom I have dealt only connect their identical packs in parallel. It would be ideal if they were same age but not required.  And,yes, definitely only connect when discharged or charged near the same voltage level.

    Regards,

    Jeff