Dead battery help AGM

Just replaced my alt last night took a crap on me. Thinking should I replace both my agm batteries idk if there bad or not. They where both replaced with the alt 4 years ago. When I drive my voltage read 14.4 solid while driving reg. If I come to a dead stop it will drop to 13.8. Then go back up to 14.5 back to a steady 14.4. Any help please thankyou.

 

New or remanufactured alternator? Not uncommon for remanufactured parts to be questionable.

 

Have the batteries tested at your nearest vatozone.

A healthy AGM will have a resting voltage of 12.7, after 24 or greater hours of not being charged.

Voltage in use doesn't mean much unless you have a coulometer to show the net momentary draw or charge. Its not a hard rule of thumb, but for me it seems like every amp of draw will make the voltage read about 0.1 lower than what it would be at rest state.

 

New alt from napa

 

Willet them sit for 24 hours drive other vehicle and check it.

 

What could be causing the voltage to.drop and fluctuate???? Or when I drive it will go to 14. 8 then Drop back down to 14.4 and stay while im.driving a constant 60 or soo for 1/2 hr then if I stop it drop to 13.8

 

Normal alternator cycling. Most systems will put a float charge at 14.4 and cycle off. A natural max voltage of batteries is at 13.8, which if left to rest, will eventually settle down to 12.8-12.6.

But again, voltage doesn't tell the whole story of battery capacity. A computerized draw down test will give you a good picture of how much life is left in them.

 

So what are you saying????

 

Gonna get it checked soon. What could cause the voltage to drop soo low when I come to a stop light o sign? From 14.4 to 13.0 feel like the car gonna die out

 

1 battery good one was fairly discharged

 

Replace them both then, sell the good one. Batteries tied together should always be bought together.

 

Is this normal....

Driving charge at 14.3 when I come to a stop it will drop to 13.8 13.6.. then when I move again. I spike to 15 then drop to 14.3

 

Also could it be a bad voltage regulator? How I check and where is it located?

 

Bumpp

 

How I know if a Diode dead or bad I put 2 in line with the sense wire upping the voltage. Been on the electricial sense wire for the alt for over 10 years

 

Bumppp

 

How I check if diode are still good?

 

Nothin’ to check. Everythin’ runnin’ just as it should. AGM’s need to charge at a higher voltage. Mine does exactly that & I’ve had no issues to speak of.

 

Purchase a medium quality “multi meter”.
Read it’s instructions, or YouTube or speak to any guy who knows how to dial a number on a phone.

Check the disconnected diode for resistance.
Check the disconnected batteries for voltage.
Check the serially connected batteries with engine off for current.

State the findings to the guy who will tell you precisely the problem.

 

Well seem lower with new alternator. Use to charge at 14.9 with the other alt. This one charges at 14.3 same brand..setup