Battery loses and recoveres voltage without charge

Thread Starter

Luminnion

Joined May 14, 2021
2
Hi all, I've had an odd thing happen to me. I'm working on a project that involves a 12v battery. I´ve tested it´s voltage and it's at 6.5v, so It's a bit on the low side, but I don't think It's the issue. Anyway, I connected it up to a voltage regulator that puts out 5v. What's odd is that the output is 0.4v and the battery voltage goes down to 2v. When I take the regulator off, the battery slowly starts creeping up to about 6v in 15 minutes. I tried connecting directly to a dc motor, but it doesn´t work either. So I connected the voltage regulator to 4 3v batteries in sequence and the regulator worked fine. So it's a battery issue.
What i'd like to find out is how and why this is happening, so any answers will be apreciated.
 

Yaakov

Joined Jan 27, 2019
3,167
What is the chemistry off the battery? A fully discharged lead aside cell will be at~1.75V, which means the battery should never be lower than ~10.5V.

A terminal voltage of 6.5V means there are bad, probably shorted cells. As soon as you place a load on the battery, it tanks. When you remove it, the good cells raise the voltage back up a bit.

If it is a standard lead acid battery you may be able to recover it with a decent battery charger but it sounds like it may be toast.
 

BobaMosfet

Joined Jul 1, 2009
1,776
Hi all, I've had an odd thing happen to me. I'm working on a project that involves a 12v battery. I´ve tested it´s voltage and it's at 6.5v, so It's a bit on the low side, but I don't think It's the issue. Anyway, I connected it up to a voltage regulator that puts out 5v. What's odd is that the output is 0.4v and the battery voltage goes down to 2v. When I take the regulator off, the battery slowly starts creeping up to about 6v in 15 minutes. I tried connecting directly to a dc motor, but it doesn´t work either. So I connected the voltage regulator to 4 3v batteries in sequence and the regulator worked fine. So it's a battery issue.
What i'd like to find out is how and why this is happening, so any answers will be apreciated.
it's called battery chemistry.
 

DickCappels

Joined Aug 21, 2008
7,442
A lot of batteries do that. As a child we would play with our flashlights (with carbon zinc cells) until they be came to dim to be fun, then we would switch them off and wait a while and the fun would resume.
 

Thread Starter

Luminnion

Joined May 14, 2021
2
Thanks for the replies, I’ve asked for another battery, I’ll just make sure it doesn’t go to low. Interesting to learn about the reason it came up a bit too. Thanks for the help everyone :D
 
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