battery question

[Bobg]

Can anyone tell me why my battery reads over 13 volts, and sometimes 12.6.  HOWEVER the battery is dead, it is a car battery in my 4 wheeler, when I turn the key on, (starter disconnected) the battery dives to a half a volt, turn the key off, it rockets back to over 12 volts.  If I switch it out with another battery the engine starts up just fine.
When battery reads over 12 volts, and I toucht the positive and negative terminals with a screwdriver there is no spark.  3 days later, the battery still reads around 13 volts.  But no spark across the terminals.  dunno, I always thought if a battery tests good with a dvm, you were good to go.  Bob

[KWKloeber]

Can anyone tell me why my battery reads over 13 volts, and sometimes 12.6.  HOWEVER the battery is dead, it is a car battery in my 4 wheeler, when I turn the key on, (starter disconnected) the battery dives to a half a volt, turn the key off, it rockets back to over 12 volts.  If I switch it out with another battery the engine starts up just fine.
When battery reads over 12 volts, and I toucht the positive and negative terminals with a screwdriver there is no spark.  3 days later, the battery still reads around 13 volts.  But no spark across the terminals.  dunno, I always thought if a battery tests good with a dvm, you were good to go.  Bob

Bob,

Yes, you can test a battery with a DVM, but you need to do a "load test."  Which is what you are doing, and she fails under load.

What has happened is the battery has no depth of charge to it -- ie. it 'thinks' it is full due to the internal resistance, so the charger stops charging, and there is no more acceptance.  What you have is a lead anchor, w/ one or more bad cells, and needs to be replaced.  How old is it?

Ken K

ken

[Noah]

A lead anchor with no holding power!