Adafruit 18650 LiOn Battery Trip Time

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suvratjain
 
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Joined: Thu Jul 01, 2021 4:32 pm

Adafruit 18650 LiOn Battery Trip Time

Post by suvratjain »

Hello!

I am using the following lithium ion battery for my project: https://www.adafruit.com/product/1781#technical-details

I have designed a circuit with PTC fuse in hopes to reset the battery in the event of a short. However, it seems like that the battery's internal protection circuit is kicking in a lot faster than the PTC fuse. Is there any info on the trip curve of the internal battery protection circuit so that I can spec a fuse that trips faster? Essentially, I'd like the system to shut off in case of a short but turn back on when the short is gone without unplugging the battery. Currently, I have to unplug and re-plug the battery back into the system after a short.

Let me know if you have any questions. Any help would be greatly appreciated!

PS: The PTC fuse in question is this: https://www.digikey.com/en/products/det ... iALoC%2BQA

Thank you!

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adafruit_support_bill
 
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Re: Adafruit 18650 LiOn Battery Trip Time

Post by adafruit_support_bill »

The battery specifications do not specify a time for the short-circuit overcurrent protection to activate. They only specify a maximum surface temperature - and that there is no fire or explosion.

tighter specs on your fuse might help. The fuse you are using has a 9A trip current and a trip time of 2s. The maximum discharge rate of the cell is 4.4A. There are resettable fuses with trip currents of 5A with trip times of 1S or less.

If your normal circuit draw is less than 5A, you can find fuses that react in less than 1S also.

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