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BQ24650: +TPS43061 with sealed lead-acid battery problem

Vladimir Lobanov
Prodigy 80 points
Part Number: BQ24650
Other Parts Discussed in Thread: TPS43061

Hello.
I use BQ24650 to charge a 12V sealed lead-acid battery (I used the instructions www.ti.com/.../slva437a.pdf). The battery is shut off using a mechanical switch. The input voltage is 24V from the power source. The voltage from the battery is increased to 24V using TPS43061. An operational amplifier is used to protect the battery from full discharge. It switch off the ground when the voltage drops to a certain level.
The charger behaves strangely. If I first switch on 24V power to the input, and then connect the batteries, then charging does not start. Also, when the target voltage is reached, the current drops to almost 0, but the charging end LED does not light up. When the batteries are turning off, the charging indicator flashes several times.
Could you help to solve these problems?

1258.charger.pdf

  • 0
    TI__Mastermind 24075 points

    Hi Vladimir,

        When you turn on the input voltage of 24V and before you insert battery, can you take a scope capture at BAT close to C22, C23, along with VCC and PH? When you mention current drops to almost 0, what is the value of charge current you are observing? What do you mean by batteries turning off? STAT1 flashing while STAT2 is off, indicates charger is entering and exiting a fault condition.

  • 0 in reply to Kedar Manishankar
    Prodigy 80 points

    Thank you for your answer.

    The video, when I am turn on the input voltage and before insert battery, in the attachement.

    Speaking about current drops to almost 0, I meant value about 10-30 mA.

    The positive contact of batteries connected via mechanical switcher (switcher.png). 

  • 0 in reply to Vladimir Lobanov
    TI__Mastermind 24075 points

    Hi Vladimir,

       Can you show it to me in scope captures? The video link is faulty. I want to see if there is an issue with battery detection, when you insert the batteries. I don't see LED in the schematic. What is the voltage you observe at STAT2 when charging is complete, and is charger successfully entering float charge stage or not? 

    For termination, STAT2 will be low when termination current is hit, and target charge regulation voltage is hit. For 25mohm resistor termination current would be 160mA. Note that charger does not terminate as soon as it reaches target voltage. Charger will enter constant voltage phase (CV) where charger will regulate output voltage and allow charge current to gradually taper down until it hits the termination condition. However charger should have terminated before you see 20-30mA as termiantion current setting is at 160mA. How and where are you measuring this charge current of 10-30mA? (measuring current into battery not out of it into the TPS43061)

  • 0 in reply to Kedar Manishankar
    Prodigy 80 points

    The scope capture close to C22, C23 then the battery off (yellow line) At this moment STAT1 LED is blinking:

    The scope capture close to C22, C23 then the battery on (yellow line):

    I connect the labor power source to VCC and It show the current. On the second picture the current is about 0 A. At this moment STAT1 LED is swith off.

    LEDs connected to P1 Header 3x2 in schematic.

  • 0 in reply to Vladimir Lobanov
    TI__Mastermind 24075 points

    Hi Vladimir,

       From your scope capture, your CH1 has a scale of 1V, and you are only seeing about 1V to 2V on SRN?

    Can you run 2 tests:

    1) With no battery connected at all, plot PH, SRN, charge current and VCC on one scope capture so we can see them overlaid each other. Document STAT1 and STAT2 behavior

    2)Plot PH, SRN, charge current and VCC on battery insertion. Document STAT1 and STAT2 behavior after insertion.

    Is removing and re-inserting SLA battery pack part of your application?

  • 0 in reply to Kedar Manishankar
    TI__Mastermind 24075 points

    Hi Vladimir,

       Any update on the above tests?

  • 0 in reply to Kedar Manishankar
    Prodigy 80 points

    Dear Mr. Manishankar,

    Thank you for your concern.


    Unfortunately, now I am in a business trip, and I have no way to carry out the necessary tests. I will be back at the end of November and then I will continue to deal with these problems.

    With the best regards

    Vladimir Lobanov

  • 0 in reply to Vladimir Lobanov
    TI__Mastermind 24075 points

    Hi Vladimir,

      Not an issue. For tracking purposes I will close this thread for now. When you are back we can debug this issue. If thread has locked by then, feel free to open a new thread with this thread mentioned, or simply re-open this thread.