reading charging voltage

[William F.]

Where do you place probes to accurately "read" voltage that charging system is supplying? Do you read it across battery terminals with engine at or above 1500 rpm or will you get a false adequate reading just from a new "hot" battery itself even if the charging system is not putting out? Measured across batt terminals, I get high13's, but my ammeter shows slight discharge and a Wal Mart plug into cig lighter socket V meter shows only mid to low 12V's.This plug in meter shows good voltages, which I believe to be correct, when tested in my newer non Corvette vehicles. Charging problem or problem with ammeter wiring?
Thanks

[Michael H.]

Re: reading charging voltage

Bill,

I did mine across a fully charged battery at 1500 rpm with lights on and I got 14.2 volts. Originally when I installed the restored VR I was getting 14.8 volts ( was smelling battery acid fumes ) then I adjusted my VR down to 14.2 and everthings been fine, no more smell of fumes.

Mike

[Edward J.]

Re: reading charging voltage

Bill, you should use a voltmeter across the battery termails, normal charging voltage is generally 13.8/14.2,The standing voltage of the battery without car running on a fully charged battery is 12.66,This voltage is also the sign of a healthy battery. For each .10th of a volt the battery state of charge is the battery drops 10-20%,

[William F.]

Re: reading charging voltage

Thanks, Ed,
But why do I read a lower voltage with plug in meter in cig outlet and why does my ammeter show slight discharge when I read 13.8V across battery terminals?Problem with firewall connectors or horn relay?

[Edward J.]

Re: reading charging voltage

Thanks, Ed,
But why do I read a lower voltage with plug in meter in cig outlet and why does my ammeter show slight discharge when I read 13.8V across battery terminals?Problem with firewall connectors or horn relay?

Bill, It maybe that the voltage at the lighter may vary somewhat, due maybe to the wire or the lighter housing but only a few tenths of a volt. and maybe just how accurate the meter you are using in the lighter housing. what really matters is at the battery, if your reading 13.8 thats great, the 13.8-14.2 is a good area for the charging rate. sometimes when your cars battery is not healthy the charging rate maybe a little lower, as in the 13.8 range, and when the battery is healthy(12.6) You may see a little higher charging rate.

When seeing a amp. meter in the neg. side of the meter there maybe a situation of the idle speed to low, add another 100rpms and see what happens. doesn.t mean there anything wrong with charging system. sometimes with high current draw such as the headlamps or fan speed on high it may go into the negative side.