Battery mystery

[WoodSpinner]

I was given a 12v deep cycle battery to play with in conjunction with my attempts at making an alternator.  This battery sat for an unknown period of time in a field, then in my friends yard for about 6 months.  When I brought it home it read about 6v, I put it on a charger the other day at 6amps and forgot about it until the evening. I ran out and disconnected it and checked voltage which showed about 15.5v. I waited 2 days and checked it again thinking it would drop down a little and it was still at 15.5v, I then attached a 24vdc motor to it and checked the voltage. I expected it to go down at least a little but it appeared to climb instead until it was at almost 17v.  I checked amperage draw of the motor and it was pulling about 1.1v.  All of this seemed so wrong to me I assumed it was a bad meter, so I pulled out my cheapie meter and checked again, and the voltage was still almost 17v.

am I delusional? are my meters that bad? is the battery about to explode?

any clues to this mystery would be appreciated.

John

[Flux]

" I checked amperage draw of the motor and it was pulling about 1.1v. "

That doesn't make sense.

A 12v battery not on charge and supplying a load is not going to produce 17v.

You have a meter problem or you are doing something wrong.

Normally even cheap meters are fairly close but some of the very cheap ones do strange things when the battery is flat. Better ones shut down or show a battery error and still give sensible answers.

The 15.5v when on the charger is perfectly normal but off charge it will soon drop to about 12.8v.

You can get some errors with prodding batteries with acid on the connections if the prods are of dissimilar metals ( additional cells) but this is never going to give you an extra 4 volts.

Try your car battery, about 12v with lights on or near 14v with engine running and alternator charging. If these figures are way out then yes you have meter problems.

Flux

[WoodSpinner]

the "1.1v" was a typo, its was supposed to be 1.1a, I'll try the meters on the car and get back to you.