Bad Battery or is this normal reading?

V

VQLT

Joined
Feb 5, 2018
Messages
270
Location
So. Cal
disconnected battery and fully charged (trickle charger). after charging battery was 13 volts. Few days later 12.59 volts then as follows
5/10 - 12.55
5/11 - 12.53
5/12 - 12.51
5/14 - 12.47
5/17 - 12.42
5/20 - 12.39
battery has remained disconnected the entire time.
 
after one month of sitting car was completely dead. thought I had parasitic drain but reading was only 20milliamps which seems normal.
 
Not terrible, but I wouldn't use it if car stopped over 10 days. If you can disconnect (-) then not problem 10-15 days.
It would be normal with little consumption (30 mA), so battery is not perfect.
 
Continue this experiment if you can, I wonder if it will level out in the low 12's.

I also wonder if your trickle charger really, really fully charged it. Starting with a surface charge of 13 may not be 100%.
 
eljefino said:
Continue this experiment if you can, I wonder if it will level out in the low 12's.

I also wonder if your trickle charger really, really fully charged it. Starting with a surface charge of 13 may not be 100%.
Click to expand...

Usually if you check it a few hours after it's been removed from the charger, that voltage reading is it's true actual state of charge. Since he checked it a few days later and it was at 12.55V, you'd expect it to stay at that voltage for a while.
 
what is the date code on the battery? you bought it 6mo ago, but wondering if it sat on the shelf a while first. regardless this is one case where the Costco warranty should rightly be used. new battery should not self discharge that quickly.
 
VQLT said:
disconnected battery and fully charged (trickle charger). after charging battery was 13 volts. Few days later 12.59 volts then as follows
5/10 - 12.55
5/11 - 12.53
5/12 - 12.51
5/14 - 12.47
5/17 - 12.42
5/20 - 12.39
battery has remained disconnected the entire time.
Click to expand...

I think those figures are terrible. No way should a disconnected 6 month old battery lose nearly half it's capacity in 10 days. It's faulty.
 
looks like it may have stabilized but still a slight drop.
5/23 - 12.37
5/24 - 12.36
 
VQLT said:
looks like it may have stabilized but still a slight drop.
5/23 - 12.37
5/24 - 12.36
Click to expand...

It still should not have lost anything like that much voltage in only 2 weeks.

I have a 12 year old battery sat on the garage floor that I took out of my car 5 months ago. Thinking of your issue I put a meter on it today and it read 12.4 volts. Besides indicating I might have replaced that battery prematurely it shows yours is faulty.
 
13.4 volts fully charged at about 70 to 75 degrees is what I always used as a standard. If you just charged it I would put the lights on for a minute and wait ten min to test.

The voltage seems to be dropping a bit hard but could be a drain as well. As a bad or weak battery
 
okay well I have a Costco 24F from 2014 in my basement. I kept it as a spare rather than return it for a measly core fee. I charged it and did the same experiment you did.
5/21 - 12.87v 3hrs off charger
5/22 - 12.77v
5/29 - 12.77v

This battery has a 700cca rating. I replaced it because the van was cranking slower and it measured 450cca with my tester. After a few rounds of desulfation charging it now measures 580cca. good enough for a spare.

but the point is --- your 6mo old battery is toast. take it back to Costco asap. it will only get worse from here.
 
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