• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 269 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Single li io battery charging from less power solar cell

Jo Varghese
Prodigy 160 points
Other Parts Discussed in Thread: BQ24253, BQ24210

I'm doing some initial research for a project. The design could use single cell  Li-Ion battery. The power source can switch between solar OR 5VDC in. My requirements is like output from solar cell hardly 7V, 50mA with this i need to charge my 3.7V , 2000mA Li Io cell.

So kindly request to suggest some device which will receive this input range and atleast provide output current which is sufficient to charge the Li Io cell within 6 Hr.

  • 0
    TI__Guru**** 166416 points

    Hi Jo,

    To charge a 2000mAHr in 6 hours means you need to charge at >2000mAHr/6 = 333mA per hour.  You will not be able to do that with a solar cell having VOC=7V, ISC=50mA and VMPP=7V*80% = 5.6V.  Your solar cell would need to provide 333mA*3.7V/5.6V = 220mA just to get the cell to 3.7V, more if you want to fully charge to 4.2V.  The BQ24210 is a linear charger that is designed to work with solar cells or 5VDC sources.  Its quiescent current is a bit high for a 50mA solar cell but it is simple to use.  We have some switching chargers (e.g., BQ24253) with MPPT (VINDPM) that might work by burst charging but they are designed for much higher power sources than 5.6V/50mA so the charge current might come out in short, infrequent bursts as the input capacitor droops.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 160 points

    Thank you Sir for your advice,

    I have one more doubt , if am using 3.7V , 1000 mAh battery and also I don't need to fully charge my battery through solar cell at least 60% charging is sufficient.

    Because my application just need 120 mAh load current for 4 hr.

    1000×60%= 600mah

    600mAh/6hr= 100mah

    100*3.7/5.6=66mA

    So pls help me to find a better device

  • 0 in reply to Jo Varghese
    TI__Guru**** 166416 points

    Hi Jo,

    All of our standalone chargers charge to 4.2V.   BQ24210 linear charger is the best fit for your solar cell and battery.  A slightly more efficient switching converter based charger with external VINDPM is BQ24253.

    Regards,

    Jeff