coin cell battery safety
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coin cell battery safety

by overout on Fri Feb 15, 2013 4:08 pm

So, I have two projects that are very simple, but I'm getting paranoid after reading various articles about battery safety.

First project: a 3V 2032 is powering five white LEDs in parallel, each having a 100K resistor.
Second project: a 3V 2032 is powering one amber and one red LED in parallel, each having a 100K resistor. Current seems to be 6mA.

Are these batteries in danger of exploding or doing other damage? I can't imagine that they are, but, as I said, I getting paranoid (and I'm the type of person who would wear suspenders and a belt together).

Thank you.
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Re: coin cell battery safety

by adafruit_support_bill on Fri Feb 15, 2013 4:20 pm

Typical max discharge rate specs for CR2032 are about 3mA continuous, 15mA pulse. Does that mean it will explode at 6mA continuous? Probably not, but the effective mAh will be reduced. If the cell is getting uncomfortably hot, I'd be worried.
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Re: coin cell battery safety

by overout on Fri Feb 15, 2013 7:32 pm

I've noticed no warmth from the coin cells at all. The resistors are 1/4 watt: might that be why no warmth, or am I just not leaving the circuit powered long enough? Is there anything I can add to the circuit to increase safety?

Thank you so much for replying.
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Re: coin cell battery safety

by adafruit_support_bill on Fri Feb 15, 2013 7:54 pm

High drain-rates will decrease effective mAh of the cells, but if nothing is getting hot, then safety is not an issue.
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Re: coin cell battery safety

by Zener on Fri Feb 15, 2013 9:20 pm

100k or 100 ohm? Don't think it will work with 100k
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Re: coin cell battery safety

by lyndon on Fri Feb 15, 2013 9:52 pm

Even then, I wouldn't be too worried. One of my "cautionary tales" happened early on my first job out of college at a tiny electronics manufacturer.

I was testing/repairing some real-time clock modules that had just been assembled and had removed the coin cells from the ones I couldn't fix. Not thinking, I put them all -- a few dozen -- into a big ziploc bag and placed it on the pickup table for restocking. Then about fifteen minutes later, our office manager picked up the bag and commented "Oh, this bag is nice and warm!" (it was rather cold outside).

My head snapped around when she said that because it had just hit me how stupid I was. Unfortunately, my boss was standing next to her as she said it and glanced down at the bag, then glared at me and stormed off into his office without saying a word.

So you're safe, just don't short the terminals together.
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Re: coin cell battery safety

by overout on Sat Feb 16, 2013 10:42 am

Thank you, all, for your replies: I really appreciate them!
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