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BQ25601: Battery goes "bad" after a couple months in the field

Jason Harris
Prodigy 30 points
Part Number: BQ25601

We are using the BQ25601 in our application to charge a Li-ion 18650 from Battery Space

https://www.batteryspace.com/custom-li-ion-18650-battery-3-6v-2600mah-9-36wh-with-10k-thermistor---un38-3-passed.aspx

The power input is 5V USB and our load draws a ~100mA to 1A depending on what it is doing. Most of the time the system is powered off and only draws 60uA. When the system is powered on it should be charging most of the time and only be running exclusively on battery for around 5min per 1-2 hours of charge time.

After 4-6 months in the field (units are remotely located) over roughly 50-100 charge/discharge cycles we are starting to see "bad" Batteries. In the lab we found that the battery voltage is ~0V (0V is also directly on the cell when bypassing the protection circuit). If we connect a new battery to the same charging circuit from a defective battery unit, it works fine and charges the battery as expected.

I am trying to understand what failure mechanism may have caused the batteries to go bad and if we are looking at defective batteries, of have messed up the charging profile etc.

Thank you for your support in advance.

  • 0
    TI__Genius 11850 points

    Hi Jason,

    Have you been able to get in contact with the battery manufacturer or supplier? Since you mentioned that the BQ25601 can charge new batteries as expected, this seems like a battery issue rather than a charger issue.

    I don't see a datasheet provided anywhere at the link you sent, but I do see the following information in the table:

    What are the operating conditions like in the field? Is it possible that the temperature exceeded these ranges and stressed/damaged the battery over time?

    Best regards,

    Angelo

  • 0 in reply to Angelo Zhang87
    Prodigy 30 points

    We are sending a sample back to the manufacturer now. 

    Its an LG cell. www.batteryspace.com/.../5457_B4.pdf

    The field conditions should be better overall than the temperature in a car "cabin"

    There is NO possible impact of any environmental condition aside from temperature.

  • 0 in reply to Jason Harris
    Prodigy 30 points

    I find a "battery" issue a little strange because this is a high volume mass produced cell.

    Is it possible for settings in the charge to be set incorrectly to cause such a problem?

  • 0 in reply to Jason Harris
    TI__Genius 11850 points

    Hi Jason,

    Thanks for sending the datasheet!

    Again, based on the fact that the BQ25601 can still charge new batteries as expected, I suspect that your batteries have been stressed over time such that they fail after 4-6 months in the field. What is the failure rate you've been experiencing?

    We've already discussed the possibility of high temperatures stressing the batteries, but what are your charge current (ICHG) and charge voltage (VREG) settings? If these are too high, then they could also stress the battery over time.

    Also, you mentioned that the system runs exclusively off the battery for about 5 minutes per 1-2 hours of charge time. Do you know how much current the system draws during this time?

    Best regards,

    Angelo

  • 0 in reply to Angelo Zhang87
    TI__Genius 11850 points

    Hi Jason,

    We haven't heard back from you. We are assuming you were able to resolve your issue. If not, just post a reply below or create a new thread if the thread has locked due to time-out.

    Best regards,

    Angelo