• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 63 subscribers
  • Views 725 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ24250: Battery Safety Timer Operation

Tim Roberts80
Intellectual 470 points
Part Number: BQ24250

Hello,

I am just wondering if I could get some assistance with the operation of the BQ24250 chip.

We have one of these chips which works great 99% of the time. Every once in a while we experience a situation where we cannot turn on our device. The battery is dead and plugging in a charger doesn't charge the battery and also doesn't allow the device to start up. We found that we had to disconnect the battery and reconnect it for the system to start again or even charge.

Our assumption is that the system may have charged too long and tripped the safety timer. According to the datasheet if this happens, you need to disconnect the battery. I tested this out and simply reconnecting the power supply starts the charge again. Is this how this works? 

The datasheet also mentions the ability for the host to reset the timer. How is this done? I was unable to find a register setting that would reset the safety timer.

Also, the datasheet states that the default charge timer is 6 hours, the system reads that it is set to 6 hours, but it takes longer than that for the safety timer to trip. I have also checked and we aren't slowing the timer down during any conditions which may occur.

Is there any other way that the system could lock out a battery to the point that it requires the battery to be removed for it to start again?

Thanks,

Tim

  • 0
    TI__Mastermind 25800 points
    Hey Tim,

    Could you provide some of your test conditions? (I.e. input voltage, charge current, battery voltage, load current).

    Could you also provide the register read-outs of the charger? This can help us recreate the scenario on our bench here to identify the cause of what you're seeing.

    Are you using our EVM or your own board? If your own board, do you have a schematic you can provide?

    As far as the safety timer, 6 hours is just a typical value. There could be 10% variation in timing for this, but we don't typically test for min and max values. So more than 6hrs could be seen. Now, if you are seeing 2X+ timing, then something else may be occuring.


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Intellectual 470 points

    Hi,

    Input Voltage is 9V

    Charge Current is set at 1.13A

    Battery Voltage varies based on the charge

    Load current is approximately 1A (we are powering a beagle bone black which runs off of a 5V SMPS)

    We are unable to read the registers in this situation because our device is dead and it won't start up. We do not change the state of any of the registers, they are set at the defaults that we receive them in.

    This is our own board, schematic is attached.

    Power jack is on the far left, goes into the battery charger.

    We have a small micro which manages the turning on and off of the 5V regulator and monitors the status pin of the charger, the power push button and some voltages.

    Yesterday I started a charge at 9AM, hooked a load up to the battery and added 300mA to it to ensure it never reached full charge. By 5PM 

    (8 hours later), the system was still charging and hadn't timed out. I don't have an exact time on the charge timeout but could get a rough idea if I hook up some voltage measurement equipment to monitor the battery.

    Is there a way for the host to reset the charge timer? The datasheet indicates this, but it doesn't specify how to do it.

    Thanks,

    Tim

    Board.pdf

  • 0 in reply to Tim Roberts80
    TI__Mastermind 25800 points

    Hey Tim,

    The host can reset the safety timer through several means.

    You can toggle the safety timer bit in the register to change to Disable, back to a defined time value (i.e. 6hr --> Disable --> 6hr).

    You can also toggle the charge enable bit in the registers.

    And lastly, you can toggle the Hi-Z bit of the charger.

    All other resets of the safety timer come from either PORing the charger (through both input and battery), removing/replacing the input only, or removing/replacing the battery only.


    Regards,
    Joel H