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Battery Packs

Bob Sachsalber
Prodigy 60 points
Other Parts Discussed in Thread: BQ27510, BQ27500, BQ27210, BQ27541

Most of the battery vendors do not supply what electronic design is available inside a battery pack, especially a smart battery pack?

Do you have any insight as to how to obtain such information to determine what is required for Battery Charger design for these OEM battery packs?

Are there any common practices available to interface to these battery packs?

Is it expected that if you are a Smart Battery Pack that you support SMBus or i2C?

Thanks

  • 0
    TI__Genius 14985 points

    Bob,

    You should be able to get information from the battery vendor on the pack.

    If it's only got +/-/T connectors then it's probably not a smart battery, but if there are also one or two communication pins then you should be able to talk to it via HDQ, I2C, or SMBus, or some other protocol.

    You can find some of the SMB commands including identification here: http://smbus.org/specs/index.html

    Regards,

    David

  • 0 in reply to dMax
    Prodigy 60 points

    Thanks David,

    to paraphrase if you have an unknown battery vendor and one is designing a battery charger, then it would be wise to design a charger that supports +/-/T or HDQ or I2C or SMBus interfaces to allow flexibility to interface to any battery pack.

    To reduce design complexity are all battery manufactures migrating to SBS?  Would you know the roadmap for battery packs for portable devices?  Is it SBS or is there another battery system being developed?

    My design intent was to develop a battery charger for an off the shelf battery pack.  Is this a wise decision?  Or should the assumption be that any new portable design should expect to have a custom battery pack?

    Best regards,

    Bob

  • 0 in reply to Bob Sachsalber
    TI__Genius 14985 points

    Hi Bob,

    Now I understand your goal and it's a little easier to answer.  Your first post was so open-ended that it was tough to answer!

    Any notebook PC battery pack should be a "Smart Battery" with a gauge inside.  That's how your PC can show remaining capacity, time to empty, time to full, etc.

    Until recently most smaller single-cell packs (such as those for cell phones or small portable electronics) have been dumb batteries since they wanted to keep them cheap and didn't really require the smarts or accuracy of a fuel gauge.  The interest is growing for accurate fuel gauging in single-cell applications, but initially the gauges were placed on the system side rather than in the battery pack, again to keep them cheap and to work with existing packs.  Examples of these types of gauges are bq27500, bq27505, bq27510. These types of off-the-shelf packs will typically have only PACK+, PACK-, and Thermistor connections.  The charger would monitor the temperature using the thermistor in the pack so it could safely disable or scale back charging outside of a certain temperature window.  Communication with the fuel gauge IC can also take advantage of some of the gauge's features to control charging.

    Interest is also growing in putting fuel gauges inside the single-cell battery packs.  Our older gauges like bq27210 were typically used this way, as well as our newer bq27541 product.  These will have communication pins to talk to the host, but there will also usually still be a thermistor pin for the charger to use.  Again, gauge features also allow some information to be used to control charging if implemented properly.

    If you have a specific pack in mind for your charger, then try to find out from the manufacturer what's inside.  Otherwise you'll need to characterize it yourself and maybe tear it open to see what's inside.

     

    Regards,

    David

     

  • 0 in reply to dMax
    Prodigy 200 points

    hi ,

    i do have a baterry pack of 12V and 6600mAH . The problem i faced is when i by mistake connect these fully charged batterie in reverse polarity ( with no external DC charging source) the battery voltge drops to 6V . This remains same even if try to charge the batteries again..