DIsconnected new battery, small loss overnight

[mike42]

Hello All

I wonder if some kind person more knowlegable than me can answer this?

Been having some problems with the battery going flat. One test I did was to disconnect the -ve lead at the battery and then hooked up a trickle charger for a few hours. I left it until 12.49V.

Then in the morning I checked and it was 12.44V. I mean shouldn't it hold rock solid at 12.49V ?

Does that mean the battery is already fried?

Sorry if that is a stupid question.

[GreenV8S]

It's perfectly normal for the battery voltage to settle a little after you stop charging it. That tiny voltage change doesn't matter at all.

By the way, the battery should read about 12.6V when it's fully charged so your battery is not fully charged at the moment.

[mike42]

Brilliant - thanks a lot.

I'll fully charge it then monitor it again over perhaps a longer period.

[paul_c123]

Voltage alone won't give a good indication of the state of charge, and definitely won't help find the state of health, of a battery. You want to be using something like a Topdon AB101 battery tester.

[GreenV8S]

paul_c123 said:

Voltage alone won't give a good indication of the state of charge,

There is a predictable relationship between the voltage of a lead acid battery, and the state of charge. That doesn't tell you anything about the battery health or capacity, but does tell you the state of charge. Hence my comment that the battery voltage indicated it is not fully charged.

[mike42]

paul_c123 said:

Voltage alone won't give a good indication of the state of charge, and definitely won't help find the state of health, of a battery. You want to be using something like a Topdon AB101 battery tester.

Thanks. I had a look at that one and correct me if I'm wrong but I don't think it does much a multimeter can't do? FOr example, the crank test could be done with a multimeter with a MIN setting. Parasitic drain test again by any multimeter with a decent amp rating (e.g. 10 amps plus?) .

[mike42]

So I charged it up to what the "smart" charger said was the maximum. It measured 12.90v.

Over the past 24 hours I measured the voltage out of car:

Time Volts
13.17 12.90
18.53 12.87
22.54 12.85

NEXT DAY
13.14 12.82


Battery isn't brand new its about 5 months old. Can I pretty well rule out the battery as being faulty or is that too big a drop?