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BQ24650: Charging 1-cell lead-aсid battery

Vladimir Naumenkov
Expert 2970 points
Part Number: BQ24650
Other Parts Discussed in Thread: BQ24610,

Dear Sir, good morning

I have 5.1 V power supply - conventional power supply, is not a solar panel.

Please, answer:

1) Can I charge 1-cell lead-aсid battery? ( "bulk voltage" = 2,47 V;  "float voltage" = 2,35 V). Battery charge will occur in the temperature range from minus 40 to pluis 60 C. 

2) Can I set 3A charge current during CC charging?  (as I have 25AH  2V cell and I would like to charge it quickly).

3) I see, that circuit on the figure 2 has two outputs: System Load and Battery Pack. Can I connect load to Battery Pack out? If  connect the load to System Load out, then the voltage on it will be less by the amount of the drop on the diode D3. 

4) What voltage I need to feed to TS input?

TIA

Sincerely,

Vladimir Naumenkov

www.agat.by application note bq24650.pdf

  • 0
    TI__Mastermind 24075 points
    Hi Vladimir,
    If not using solar input, you can use BQ24610 as the external circuit to set float charge using STAT2 pin in BQ24650, can also be used on BQ24610. With BQ24610 you can also set charge current and precharge current separately. To answer your questions:
    1. Yes you can charge 1cell lead acid battery, as BQ24650/10 support down to 2.1V VBAT, and you can safely set your float charge voltage to 2.35V as it is above the minimum limit.
    2. BQ24650 sets charge current based off of the value of the sense resistor. Ichg = 40mV/Rsr and you can calculate appropriate Rsr for 3A charging, however precharge and termination will also be off this value, meaning you will have a precharge current of 1/10 fast charge current (0.3A). BQ24610 supports 3A charging based off of the ISET1 voltage and your Rsr. Ichg = Viset1/(100*Rsr), and separate precharge/termination based off of the voltage of VISET2.
    3. Yes you can connect system load at SYS or BAT according to your application if SYS is to track battery voltage. If using BQ24610 this has powerpath feature with integrated gate drive controlling PFET between BAT and SYS so SYS = VBAT - Iload*Rdson or SYS tracks VIN depending on if adapter is connected or not.
    4. Source between 40%-70% of 3.3V (VREF) so charger does not go violate cold and hot temperature and suspend charge.