Lead Acid Battery Self Discharge Question

Greenhil

I’ve stored my 80ah battery on the workbench in my unheated cellar (temp. about 50 degrees) since early November. Initially, it was fully charged - reading 13.0 v on my multi-meter. In the ensuing 12 weeks it’s self discharged down to 12.45 v - or about 85%. 

It seems to have stabilized at that level in recent weeks, but is that amount of discharge normal? I’ve read that the discharge rate is supposed to be fairly negligible. Last year was my rookie T@B year and I made the usual beginner mistakes while figuring out what the battery could do (not much). I’m concerned I may have damaged it. Thanks!

pthomas745

That is reasonably "normal". You don't say how old your battery is, or if it is an AGM or not.  The age of the battery and the chemistry will have different self discharge rates.

I have a 6 year old lead acid battery that I took out of the trailer back in late October.  It has dropped from about 12.6 to about 12.45 when I checked it a few days ago. 

Greenhil

pthomas745 said:

That is reasonably "normal". You don't say how old your battery is, or if it is an AGM or not.  The age of the battery and the chemistry will have different self discharge rates.

I have a 6 year old lead acid battery that I took out of the trailer back in late October.  It has dropped from about 12.6 to about 12.45 when I checked it a few days ago. 

Thanks! It’s a flooded battery (not AGM) that’s a little more than a year old.

ScottG

As batteries age their ability to take and hold a charge decreases. You will probably notice after each year of use the point at which it stabilizes after a full charge will get progressively lower, and it may reach that point more quickly. You may also notice that it discharges more quickly when in use.

If you hone your battery whispering skills you will develop a sense of when it's time for a replacement. For now though, I'm betting your battery still has some good life left.

ScottG

Your question inspired me to check my own 2-year-old wet cell. It's been sitting since late October when I brought it inside and gave it a full charge. I was pleased (and a little surprised) to see it was still showing more than 12.8V. It does get used pretty gently as I am miserly with power and keep a solar panel deployed full time.