• Resolved

BQ25071: Recommendation for a Single Cell LiFePo4 Battery charger for Solar Input.

Part Number: BQ25071

Could you please suggest a battery charger which is an equivalent to the "bq24210 800-mA, Single-Input, Single-Cell Li-Ion Battery Solar Charger" but for LiFePo4 batteries instead.
The bq2507x seems to come close but no mention of Solar/DPM features.  The Bq24650 could be one other option but Bq2507x is more cost effective.
Any recommendations between these two parts or is there another part that we should be looking as well.
  • Hi Krishna,

    TI currently offers 3 chargers that charge LiFePo4 batteries and have solar input: the bq24650, bq25700A, and bq25703A. Unfortunately, none of them are equivalent to the bq24210. Here are some of the key differences between these chargers:

    bq24650: buck topology, charges 1-6 cells, standalone
    bq25700A: buck-boost topology, charges 1-4 cells, SMBus
    bq25703A: similar to bq25703A, but uses I2C instead

    Hopefully one of these chargers can meet your requirements!

    Best Regards,
    Angelo Zhang
    Applications Engineer | Battery Charging Products
  • In reply to Angelo Zhang:

    Hey Krishna,

    To add to Angelo's comments:

    If you have an MCU to control the charger, we also have a TI-Design for reference using the BQ25895 charger with integrated ADC to achieve a simple MPPT control scheme.

    You may find it here: ti.com/tool/tida-01556 with applicable design guide and source reference code.

    Joel H
  • In reply to Joel Hernandez II:

    Hi Angelo and Joel, thank you for the pointers. I went over them and I have few quick questions while I dig into it more.

    The BQ24650 comes close to what we need. We could use the VDPM regulation to have the input voltage regulated to 5.5v which is our PV module's VMPPT. We also have USB power that we feed into the same battery charger. The USB power and Solar power will be fed via a switch that will turn off the Solar path into the battery charger when the USB power is supplied. When USB power is supplied we will change the VDPM setting to regulate to 5V (for USB).

    1) Do you see any issues with this flow ?
    2) Any simplifications we could do ? Have a common VDPM setting for both USB and Solar and sacrifice some power?
    3) Should the USB input regulation be lower than 5V for safety.?

    Thanks a bunch for the great support that you and other TI engineers provide.
  • In reply to nack dack:

    Hey Krishna,

    I think you will want the VDPM threshold for the USB source to be lower than this. Possibly 4.5V depending on how much current you plan on drawing and the expected the max impedance there is between the charger input and the USB output. Otherwise, the charger may not regulate the system voltage or charge at all. However, it is not a safety concern; more of an overload condition concern.

    Other than that, my main comment about your flow is to make sure you have a way to detect the presence of a USB input.

    As far as simplifications, I think that is as simplified as you can get. Also consider whether you have a solar panel or a single solar cell in your application. While a cell shows similar V_MPP across irridiance, panels are a bit more complex especially when partially shaded or the temperature across it is not evenly distributed.

    Joel H
  • In reply to Joel Hernandez II:

    Thanks Joel. We have a Panel and a Cell would not give the voltage levels we need to feed into this charger.