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Original question:

BQ24650: Charging 1-cell lead-aсid battery

BQ24610: 1-cell lead-acid battery charging

Vladimir Naumenkov
Expert 2970 points
Part Number: BQ24610

Dear Kedar, good morning

I’d like to charge 1-cell lead-acid battery. I have 5.1V, 5A power supply.

You recommended to use bq24610. Please, see figure 19 of bq24610 datasheet, page 26.

Please, answer:

1) I need not in Input Adapter Current Regulation. Can I set RAC resistor = 0 Ohm and feed low voltage (e.g. 0.5 V) to ACSET?

2) I need to connect load to VBAT only (PACK+). Can I remove Q3 transistor?

3) If I remove Q3 transistor, then can I remove (to “short”) Q1 and Q2 transistors?

4) R11, R12, R13 are 10 k. But for LEDs a current of 2...5 mA is needed. With such values of resistors, the current will be much less. Maybe should do less R11, R12, R13 values?

5) As I charge lead-acid battery, I need a temperature compensation. I see circuit on the figue 2 in SLVA437A and Rtc =100 k thermistor (in parallel with R23). Please, advise which type of thermistor Rtc to use?

6) There are equations (1) and (2) in SLVA437A, page 3. It seems to me that instead of Vref there should be VFB. On page 5, instead of Vref, the value of 2.1 V is substituted - I think 2.1 V it is right, and this is not Vref (3.3V).

TIA

Sincerely,

Vladimir Naumenkov

www.agat.by

  • 0
    TI__Mastermind 24075 points
    Hi Vladimir,
    1,2,3: This is a frequently asked question, and is answered in this E2E FAQ: e2e.ti.com/.../791790
    This FAQ will also help some other questions that might come along the way when designing the schematic.
    3: Yes you can remove the back-to-back Q1,Q2 FET but a reverse blocking diode would still be needed to protect against reverse polarity battery insertion.
    4. This depends also on what your pull-up source is, whether it is VIN or VREF, but yes you can change the resistor accordingly
    5. Finding the appropriate thermistor for your system is trial and error, but the SLVA437A app note section 2 Circuit to Implement Temperature compensation shows how to calculate required based off of a thermistor's datasheet.
    6. Yes 2.1V is the correct value. Here they are referring actually to VFB, and this 2.1V would correspond to max charge regulation voltage of the battery. Not referring to 3.3V VREF pin on IC. We are looking to update this app note to clear confusion.