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BQ24650: Charging of 24V lead acid battery

Prashant Chavan6
Intellectual 320 points
Part Number: BQ24650

Hi All,

Now I have switched to BQ24650, I have two batteries each of 12V in series, So following points are my requirement

1) Lead acid battery of 24V contains 12 Cells

2) Input Vtg. to charge Lead acid battery is 28V DC

3) Charging current required 2.5A

4) Operating temp. -40C to +125C

So I need confirmation on above parameter ( specifically point 1) that BQ24560 will suite perfectly for the application  , In addition to that is thermistor compulsory to use???.

Any help will be appreciated!!!

Prashant

  • 0
    TI__Mastermind 20570 points

    The bq24650 should meet your requirement. Please use the app note below for Lead acid battery charging using bq24650.

    http://www.ti.com/lit/an/slva437a/slva437a.pdf

    The thermistor is not mandatory. You can put a fixed voltage at TS pin to bypass this function.

  • 0 in reply to Jing Zou
    Intellectual 320 points

    Hi ,

    Thanks for your instant reply, I have gone through the pdf of bq24650 to Charge a Sealed, Lead-Acid Battery. But I have following queries

    1) Why pulse current charging algorithm during the constant voltage phase of the charge profile that is used to charge the sealed lead-acid battery??? if you have pdf please send.

    2) Vbulk voltage of battery is adjusted using thermistor(Rtc) at battery side with respect to raise in temp. In my application charging temp. around 55C, so is it necessary to add thermistor??? If yes then please provide connection dig.

    I hope you will provide above information, waiting for positive reply.

    Prashant

  • 0 in reply to Prashant Chavan6
    TI__Mastermind 20570 points
    regarding 1, what the charger does is cc, cv, and float. If you look at figure 1, the current reaches termination threshold, then the charge current goes to 0 and let the battery voltage float. When the battery voltage drop down below the recharge threshold, the battery charging restarts. Thus you see the pulse charge.
    Regarding 2, figure 2 in the app note link I shared in my previous post has the thermistor connection already. The app note also has the equation for the resistor divider. What other info are you looking at? Is your battery temperature going to always be fixed at 55C? I would suggest you to consult with your battery manufacture for appropriate charging profile.
  • 0 in reply to Jing Zou
    Intellectual 320 points

    Hi, 

    satisfied with your first point, Now could you suggest type of thermistors used to sense temp along with Mfr. name which will suite my app.

    And Battery will continuously charge around Min. 55C, If you know then suggest battery as well.

    Thanks

    Prashant 

  • 0 in reply to Prashant Chavan6
    TI__Mastermind 20570 points

    The bq24650 uses voltage based TS function. Any type of thermistor should work. You can use 103-AT type of thermistor.

    We do not have specific lead acid battery suggestions..

    What is the reason that you choose to use lead acid battery?

  • 0 in reply to Jing Zou
    Intellectual 320 points

    Hi Jing Zou,

    Good day and Thanks for reply!!

    LA batteries are inexpensive, and maintenance free. And low self discharge that set.

    Do you have any good option for LA by considering higher temp. 

    Thanks!