• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 405 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.

BQ24616: Schematics review, had a small fire

Lorand Kertesz
Prodigy 50 points
Part Number: BQ24616

Hi,
we have a problem with a battery charger setup where one of the units caught on fire.
This is out of a batch of 25 and we are about to manufacture 1000 so I'm looking into this in detail.

when the event happened, the charger was on for at least 30 minutes and charging with full current from an 18V supply.
I can't pinpoint exactly what failed but it looks like Q35.

I've attached the schematics in PDF, if you hover the parts there's manufacturer part numbers and other details.

Any input will be appreciated, this needs to be rock solid, it's in a sealed metal tube with 26 lithium batteries.
I'm thinking the problem might be thermal.



pjer100_pcb146_jseis_4ch_daq__bms.pdf

  • 0
    TI__Mastermind 40305 points

    Hello,

    The schematic looks good. What is the current limit of the supply you are using?

    Thanks,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Prodigy 50 points

    Hi Mike,

    correction, the units where charging from a 12V supply (not 18V),
    supply is ripped from a PC, it's rated 800W and there were maximum 5 of these units in parallel

    I don't know how did my client use the ATX PSU but even on a single 12V output it can probably supply more than 20A-s.
    Our units have a 2.75A input current limit and a 5.27A charge current limit. When the unit failed it was probably in the input current limited state.

    Lorand

  • 0 in reply to Lorand Kertesz
    TI__Mastermind 40305 points

    Dear Lorand,

    Can you please confirm what you mean by, "there were maximum 5 of these units in parallel?"

    We need to confirm that the power supply can handle the input current limit of 2.75 A the way it is hooked up. If it is only rated for 2 A at 12 V as an example, the power supply voltage could crash as the power supply attempts to supply the required power for the charger.

    Thanks,

    Mike Emanuel

    Please click "Resolved" if this answered your question.

  • 0 in reply to Michael Emanuel35
    Prodigy 50 points

    Hi Mike,
    client just confirmed this, supply is rated 54A-s at 12V.
    Client also stated he usually charges up to 7 of these nodes (each with its own 2,75A limit) in parallel without a problem.
    When the fire happened there were only 5 nodes connected to the supply.

    On the battery side there are 13x 18650 parallel cells in a 2S configuration (26 cells in total), each ~3400mAh.

    kind regards,

    Lorand

  • 0 in reply to Lorand Kertesz
    TI__Mastermind 40305 points

    Dear Lorand,

    Can you please confirm the current rating? I am confused as to what is meant by the unit "A-s."

    Has the phenomenon been repeatable? What was the charge voltage of the batteries when this happened? Do you have any observations when this happened (you said, "When the unit failed it was probably in the input current limited state.")?

    Thanks,

    Mike Emanuel