Charging system turns off ??

[spyderrider]

New to me 2008 Denali with a question. Very pleased with the truck and noticed something strange and maybe it's supposed to do this. My radar detector shows battery and charging voltage. The other day I noticed while driving it showed battery voltage only 12.7v, no warning lights or message on the dash. Took the truck back to my shop, volt meter on the battery, at startup 14.5 then it slowly drops to 12.7v. When I put on all the accessories, alternator kicks it back up to 13.8. The last 2 days normal voltage 14.5v, I've been watching to see if it happens again. AC Delco battery load tests fine, cells are good. Thoughts?

 

[swathdiver]

New to me 2008 Denali with a question. Very pleased with the truck and noticed something strange and maybe it's supposed to do this. My radar detector shows battery and charging voltage. The other day I noticed while driving it showed battery voltage only 12.7v, no warning lights or message on the dash. Took the truck back to my shop, volt meter on the battery, at startup 14.5 then it slowly drops to 12.7v. When I put on all the accessories, alternator kicks it back up to 13.8. The last 2 days normal voltage 14.5v, I've been watching to see if it happens again. AC Delco battery load tests fine, cells are good. Thoughts?

Look up RVC and EPM. The alternator runs like a smart charger, when the battery is charged up, it cuts output under certain conditions. This not only gives you an extra .0001 mpg, it dramatically extends the life of the battery.

 

[OR VietVet]

GM electrical power management system senses needs and adjusts accordingly. My 2005 does the same thing and is all good. When the time comes, I have an AGM battery in mine and some say don't do it.

 

[spyderrider]

Look up RVC and EPM. The alternator runs like a smart charger, when the battery is charged up, it cuts output under certain conditions. This not gives you an extra .0001 mpg, it dramatically extends the life of the battery.

Look up RVC and EPM. The alternator runs like a smart charger, when the battery is charged up, it cuts output under certain conditions. This not gives you an extra .0001 mpg, it dramatically extends the life of the battery.

thank you, I knew something was different, my 04 doesn't do this, and see this change from late 2005 and up. Pretty cool

 

[swathdiver]

GM electrical power management system senses needs and adjusts accordingly. My 2005 does the same thing and is all good. When the time comes, I have an AGM battery in mine and some say don't do it.

Nothing wrong with an AGM battery. The charging systems in the GMT800s and GMT900s are not optimized for them so they will not last as long as they could have. If memory serves, they liked to be charged "faster" and have a lower voltage threshold, like 14 volts compared with a lead acid battery.

 

[OR VietVet]

I should have been more clear. I have the AGM battery and have no problems at all and am very confident in that battery. Others say that the AGM battery is not the way to go.

 

[Joseph Garcia]

^^^x2^^^

All is good.