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Recommended battery charging IC for 7.4V LiPos?

David__
Genius 3585 points
Other Parts Discussed in Thread: BQ25010, TPS61089, BQ24170, BQ24253, DRV8833

Hi, I'm trying to design an RC Car that uses the TI's SimpleLink products.

I'm trying to use a LiPo battery like this one.

I created a PCB a few weeks ago that uses TI's BQ25010RHLR, a Buck converter + LiPo or Li-ion USB charging IC.

In that case, the battery used 3.7V. However, in this new project, I doubted whether the BQ25010RHLR can charge 7.4V LiPo battery.

 

To sum my questions,

 

0) Can the BQ25010RHLR charge 7.4V LiPo battery(like the one on the above link) via Micro B USB?

 

1) If not, I wish to receive recommendations that can charge 7.4V LiPo batteries.

 

  • 0
    TI__Genius 13700 points
    Hello David,

    The bq25010 is only designed to have 1 cell in series meaning that it will not support a 7.4V battery pack.

    The challenge that you might encounter is that if you are trying to charge this battery via a USB input you need to boost the voltage up from 5V to something closer to 9V so that it can charge all the way up to the cell pack voltage of 8.4V.

    That said TI does not currently have any released boosting battery chargers. With that in mind I would recommend looking at using a TPS61089 and something like the BQ24170.

    Now looking at that pack there is hopefully integrated protection but as with any Li-Ion battery please treat it carefully and with the utmost respect. Batteries can be vary dangerous if not handled and used properly.
  • 0 in reply to Ryan May
    Genius 3585 points

    Hi, Ryan. Thanks for your reply.

    0) Then can you provide an example schematic when using TPS61089 boost converter and the BQ24170?

    I can't imagine how to connect both together to charge the 7.4V Li-Po.

    If the schematic cannot be provided, should I just use the 3.7 Li-Po battery, charge it using BQ25010, and power the motor driver using the TPS61089 boost converter?

    1) About the

    Ryan May said:
    That said TI does not currently have any released boosting battery chargers.

    , are you mentioning these products from Linear Technology can be an alternative solution for me?

    I do wish to use TI products, though. However, since TI doesn't have the product which I want, I don't have many options.

  • 0 in reply to David__
    TI__Genius 13700 points
    Hello David,

    The basic idea for how you could make the TPS61089 + BQ24170 solution work would be the following

    USB/5V source -> Input of the TPS61089 EVM -> Output of the TPS61089 EVM -> Input of the bq24170 EVM -> Output of the bq24170 EVM -> Battery

    That said the bq24170 is optimized currently for 5Vin and 1S charging.

    Question?
    Do you need to be able to charge from a USB input or could you use a 9V or a 12V source? If you can supply a higher voltage source then using a single device such as the bq24170 would work and no boosting would be needed.

    Regarding your question about the Linear Tech device. The topology of this device is rather complicated and finding the right coupled inductor could be a challenge. The other issue with me trying to answer any question about a Linear tech device is that this is a Texas Instruments forum and it is difficult to discuss devices from other supplies in this setting.

    All that said. The simplest solution would be to get a wall wart or a power brick that supplies 12V and then use that to supply your 2S charger to charge this battery pack.

    Let me know if there are any other questions.
  • 0 in reply to Ryan May
    Genius 3585 points

    Hi, Ryan.

    0) In the case of bq25010, this can be used as a buck converter as well as a battery charger.

    The BQ24170's typical application page seems difficult compared to bq25010.

    Does BQ24170 has a buck converter to provide 3.3-volt output for microcontrollers as well?

    1) Since this BQ24170 is complicated, how about this configuration below?

    Use bq25010 for supplying 3.3-volt output and charging 1 cell (3.7~4.2V Li-Po/Li-ion) battery ->

    Connect the battery to TPS61089 for constant high voltage (6 ~ 9V) ->

    Connect TPS61089's output to the motor driver (for instance, DRV8833CPWPR)

    I expect the motor driver will draw 3A max. Can you evaluate this method if I change the battery?

  • 0 in reply to David__
    TI__Genius 13700 points

    Hello David,

    Sorry for the delay.

    If you want to configure your solution with a 1S battery pack the bq25010 could work but it will take quite a while to charge any battery of decent size. I would recommend looking at the BQ24253. This is a charger that has a similar structure to the bq25010 in that it is a switch-mode charger with an integrated LDO (not a buck converter) but it supports charging up to 2.5A which is 5x higher than the bq25010

    That said if you use a 1S battery pack then you could use something like the TPS61089 to boost the 3V - 4.2V up to a higher voltage for you battery which will then be controlled by a part such as the DRV8833.

    Note that when the battery voltage is down close to 3V and if you are wanting 9V out at 3A it will be close to the limits of the boost converter. It may have a hard time supply locked rotor current.

    Let me know if there are any other questions.