3V button batteries for car fobs

Thread Starter

john2k

Joined Nov 14, 2019
146
Just out of curiosity, if a car fob button battery is 3V but when you measure it with a multimeter it reads 2.7V can that indicate a weak battery? Is there a way to test if a battery is weak? I'm trying to troubleshoot fob issues. Thanks
 

dl324

Joined Mar 30, 2015
12,917
With a 2.7V open circuit voltage, the battery is pretty much gone.

This is for an Energizer 2032:
clipimage.jpg
You can see that once the battery gets to 2.8V with a load, voltage drops off pretty sharply.
 

Hymie

Joined Mar 30, 2018
983
I would expect a fresh 3V coin cell battery (e.g CR2032) to measure around 3.2V using a multimeter (under no load conditions) – a value of 2.7V (under no load) would definitely suggest the battery is flat/exhausted.
 

Thread Starter

john2k

Joined Nov 14, 2019
146
Thank you for the replies. Yes the multimeter is reading 2.7V with the battery completely removed without any load whatsoever.
 

du00000001

Joined Nov 10, 2020
65
Once upon a time I guaranteed the maintenance for a large automation installation. Our units had Li batteries of this type for memory buffering:
The Varta 2032 come NOOB with a Voc of 3.27 .. 3.29 V. Experience told me that they were useless at a voltage of 3.00 V "under load" (the memories draw 1-digit µA), meaning that the Voc in this case would be >3.0 V.
A Voc of 2.7 V is an indication that this battery should have been replaced months ago :rolleyes:
 

BobaMosfet

Joined Jul 1, 2009
1,821
Just out of curiosity, if a car fob button battery is 3V but when you measure it with a multimeter it reads 2.7V can that indicate a weak battery? Is there a way to test if a battery is weak? I'm trying to troubleshoot fob issues. Thanks
Get the datasheet for the specific battery- it will show you the battery expected life at expected current. Adjust assessment accordingly.
 

Hymie

Joined Mar 30, 2018
983
By coincidence I’ve just replaced the CR2032 battery in my car’s remote fob. The fob would work warm out of my trouser/pants pocket, but had to be close to the vehicle to work otherwise.

The removed battery measured 2.7V under no load.
 

Audioguru again

Joined Oct 21, 2019
3,305
Car fob batteries are not rechargeable. when they are exhausted then they are replaced.
Hey, sometimes I get exhausted but am not replaced (yet), so I am rechargeable.
 
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