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BQ78350-R1A: battery Blocks in parallel

rens van bolderik
Intellectual 396 points
Part Number: BQ78350-R1A
Other Parts Discussed in Thread: BQ78350

Hello I working with the BQ769x0 and the BQ78350 I get the question about parallel four battery packs each with there induvidual BMS circuits.

What will do the system when one of the packs is start failing an been switch off by it's BMS (BQ78350) then the other wil go on. and w start charging the other battery. After this we connect the extra battery we will get extreem charge curent to this battery (from the other three). I assume over charge current will switch off by the BQ78350 is this correct?

can we for example switch off the other three bateries when there is one failning this  by connecting for example the PRES signal of all four batteries togeher and controle this signal by the DSG output crerating some bus controll between the batterry packs?

Is placing bateries in parallel already perfomed with those BQ devices? if This is the case is there a paper written about it? or are there other devices from TI handeling this kind of battery topology?

  • 0
    TI__Mastermind 19195 points

    Hi Rens,

    Do you have circuit or block diagram of system you are describing here?

    Thanks,

  • 0 in reply to Nick Brylski
    Intellectual 396 points

    Hello Nick,

    Below you will see a block diagram of the kind of setup I'm thinking.

    So If there is one of the four packs is been switched off the PRES signal will go high. By connetting all tje PRES signals in parrallel by a bidirectional connection (isolated) the other three will also been switched off.

    If then the charger will be connected and trough the SMBus the control system is controlling the GPIOpin from the unit that have been switched of the PRES signal becomes acxtive again and the battery will been charged.

    Kind regrads
    Rens

  • 0 in reply to rens van bolderik
    TI__Guru* 81034 points

    Hi Rens,

    This looks like it should work in theory. We don't have any document or test results for this type of topology. One thing that comes to mind - when the first pack switches off, the other packs will need to drive higher current to the load until they are also switched off, so maybe something to keep in mind when selecting your current protection thresholds.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Intellectual 396 points

    Hi Matt,

    Thanks for your response on this. The main thing I'm trying is when one of four packs are switched off the other three are also switched off trough the PRES signal and this would prevent that the batteries have to much voltage diverance when the are switched on again and that one or more stronger battries deliver extreem high current to the others.

    kind regards

    Rens

  • 0 in reply to rens van bolderik
    TI__Guru* 81034 points

    Rens,

    This sounds like a good plan. Hopefully you will be able to shut off all of the packs close enough together in time so that there is no period when a single pack needs to supply all of the current.

    Matt