Quote:
Originally Posted by leftybass209
Minimum voltage required to charge a lead-acid battery is 2.15 volts per cell. That equates to 12.9 volts required to start charging a standard car battery. ....
In your case, the difference between the charging rate and the battery voltage isn't much, so you shouldn't expect to see hardly anything on your gauge.
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I've always heard that it was closer to 2.3 volts per cell to start charging, hence the 13.6 to 13.8V I posted. But anyway, it looks like we both agree that in this case the stock battery gauge should be reading very close to center with the 13.5V he measured at the battery.
Quote:
Originally Posted by leftybass209
A properly set up charging system with a functioning gauge really doesn't register much in regards to needle movement because the source voltage (battery) and alternator output should be as little as possible to maintain the battery charge. Of course, added electrical components can change the demands.
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I agree. The needle will normally stay near the center when the battery is fully charged and the alternator is able to supply enough current to meet the demands of the truck's electrical system. If the needle is reading towards the discharge side that means the alternator isn't keeping up with demand and the battery is supplying the extra current to meet that demand (discharging in the process).