battery voltage question

lil red said
just brought out the express for the season tonight. When I went to start it the battery was quite weak from sitting and would barely roll over. I checked the voltage which was around 11.6v or so.

I hooked up the charger long enough to start it and went for a run around town for about a half an hour. When I went to start it, it again rolled over slow. I hooked up the charger again for about 2 hours while I cleaned up the garage.

once charged the battery shows about 12.6v or so when running and if I disconnect the alternator it shows about 12.4v (same voltage when the truck is shut off)

my question is most people I talk to tell me I should have 13 volts minimum when running and preferably over 13.5v. What do you think.....is the voltage to low and barely charging...

the dash guage shows positive when the alternator hooked up and negative when unhooked. The alt. is a 110 amp dual pulley one if it makes any diff.

thoughts fabo...........

Yeah that battery has been pretty deeply discharged at 11.6v. It'll take a some charging to get it back.... if it going to come back.

When you measure the votlage on the system the 13.8 to 14.2 optimum spec is at fast idle, AND with the battery fully charged. It does not sounds like you are measuring voltage at fast idle, and the battery is certainly not fully charged. Measuring voltages in those circumstances can mean a lot of different things and so no one can say what you really have for sure.

Put the battery on the charger for a full 12 hours.... no shortcuts. Then take it off for an hour and then measure the voltage. Then start and run the engine at fast idle for a few minutes, and then check the voltage across the battery with the engine still at fast idle.

Taking readings in this fashion is the only way anyone can get a good grip on what is going on; running the tests right is needed to get past educated guessing.