jamurrin

15.5 volts does not seem very high to me...and...I would doubt would boil the battery...most especially in the recent frigid temperatures...don't through money and parts at the problem until you know what the problem really is!

FSM says alternator charges to 15.5 volts...you see 15.52. I would say that the alternator and the regulator are both OK...maybe the battery was bad/cracked/leaking.

If it does not seem warm to the touch, I would say you have no problems!

tech2

I thought 90mph was everyday cruising for you Tahoe owners.

tech2

ditto

byacey

15 volts is too high, unless the ambient temperature is -30C or so. Above 0C charging voltage shouldn't be any higher than 14.2 to 14.3 volts. Above 0C, 15 volts will boil the battery.

tech2

maybe on an agm battery. yes, most constant charging for vehicle is usually 14.4V most lead acid can go to 15.5 for timed periods....there also is a sulfation mode which pumps out higher voltage for time blocks.
when i came into the trade...all trade manuals stated 13.5 to 15.5 as normal. it has lowered to extend life of the battery. What this tells me is check the product you are working on and don't assume they are all the same.

in some cases the intelligent battery sensor data will cause the ecm to crank up the voltage if it thinks the battery is bad

Gary Smith

Hello, New to this forum and i need some advice please. I have a 1967 chevelle i've had apart for a while from the firewall forward. Once i restarted the car the alternator was doing weird stuff. Short story is i've replace the alternator (twice), the voltage regulator ( three), the battery and the wiring harness. Still charges at 15 + volts. I've checked voltage drop on the grounds and can't find anything wrong. Battery has 12.6 volts and battery terminal at the alternator shows the same. Any advice about where to look would be appreciated. Seems like nothing i've chenged changes anything.
thanks

tech2

best to start a new t hread as this thread is titled for the op's problem. you won't get the right people looking at it unless you start a new thread.

I know they used ballast resistors on the ignition coil to drop battery voltage to the coil. an ything like that req uired elsewhere...I'm not familiar with something that old.