Sunday, December 11, 2022

Battery for car's key fob

 My car has been giving me "key battery low" message for a little while, so it's time to get a new battery.  I still have a required CR2025 battery on hand (probably there for a couple years already), so went ahead to try it.  The key didn't operate at all with it.  I tested the battery voltage: the current one has about 2.92V, and the replacement has 3.2V.  This thread mentioned that old battery may not be able to deliver required current.  I tested the replacement battery (using 200 mA ammeter) and it started with about 150mA reading and quickly dropped to stabilize at 60 mA.  I also tried a CR 2032 I have (probably old as well) and that didn't work either.  That one reads about 60 mA too.  Maybe it's time to get some new CR2025 and see.

Update: the new CR2025s did work.  I measured the battery being replaced, and its current read about 90 mA.  The new battery has 3.3 V output (didn't measure the current).

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