Classic cars forum & vehicle restoration.

[Ray White]

I have a battery that reads over 12 volts but when I connect it to the car (MG TC) it only reads 9.3 volts.

I am at a loss as to where the missing 3 volts are going because the engine is earthed with a new heavy duty metal strap to the bulkhead only about a foot from the similar battery earth cable bolted to the steel battery box which forms part of the bulkhead.

The battery cables are both new and tight.

What am I to do please?

[ukdave2002]

Are you are saying that the voltage at the battery drops to 9.3v when connected to the car?

If yes and the battery is good, disconnect it very quickly because it's the sort of volt drop that a load similar to turning the engine over would create, so something could be getting extremely hot!

Otherwise it could be a duff battery.

Dave

[Ray White]

Yes, the battery reading drops from slightly over 12 volts to 9.3 volts when I connect the leads to the battery terminals. Nothing seems to be getting hot so I suppose - despite the reading - that the battery has come to the end of it's life.


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I have given the battery a charge and it seems to have stabilised at 12.6 volts across the terminals with the cables attached.