Battery voltage

[Andy LS7]

I noticed this weekend that my battery voltage is only about 11, then when I start the car it goes up to nearly 13. After a little while of driving, the voltage seems to drop back down to about 11 again. The car seems to start ok and I don't appear to have any other problems. Does this sound like the battery is dead or something more sinister? Thanks. Andy

[Steve_D]

You should be getting about 14 volts at the battery with a few revs on. If not then the first culprit has to be the alternator.

Steve

[V8Dom]

Steve_D said:

You should be getting about 14 volts at the battery with a few revs on. If not then the first culprit has to be the alternator.

Steve

also a point to note is if air con is on my voltage drops when the engine is running..

dom

[GtrSimon]

You need to check if ECU Lambda sensors and pumps are all fed though the ignition switch, if so you will soon burn it out.

[Andy LS7]

V8Dom said:

Steve_D said:

You should be getting about 14 volts at the battery with a few revs on. If not then the first culprit has to be the alternator.

Steve

also a point to note is if air con is on my voltage drops when the engine is running..

dom

Thanks Dom - switching the air con off gets me to about 13 volts, so hopefully not really a problem. Cheers. Andy

[crafty]

Thin green wire from AC fan to Ign switch is too thin.

[V8Dom]

Id still put a volt meter across the batter and double check charging... should be 13.8 volts with no aircon, lights etc etc...

also check voltage without engine running....usually 12.5 volts if battery in good shape..

Dom

[GtrSimon]

The voltmeter just measures the voltage at the point it is connected too if the battery is at 13+ Volts and the Voltmeter is saying 11 something is getting hot and turning the A/C off just reduces the problem! but does not fix it. the LS7 installation uses a shed more power than a SBC and if it’s just been added to the existing loom beware. Simon

[spatz]

yes fuel pumps alone are sucking 20 amps or more, and I have rewired the loom because of this problem.

[Gulf -LS2]

GtrSimon said:

The voltmeter just measures the voltage at the point it is connected too if the battery is at 13+ Volts and the Voltmeter is saying 11 something is getting hot and turning the A/C off just reduces the problem! but does not fix it. the LS7 installation uses a shed more power than a SBC and if it’s just been added to the existing loom beware. Simon

please bear what simon has said in mind and check how the ecu etc is wired, the LS installs run a 100 amp alternator as the system requires a lot more juice for the ecu,fuel pump, etc etc.