Dual AGM Battery system

[TheJDMan]

I know that motorhomes and RVs use a system that will isolate the starter battery from the the coach batteries so you can always start the vehicle.

[Doug1]

I know that motorhomes and RVs use a system that will isolate the starter battery from the the coach batteries so you can always start the vehicle.

Here are a couple of short videos from a RV place that sells these type systems. In the DC-DC charger, it can charge an AGM to 100% because you tell the system it is an AGM. The one thing I am not sure about is the starting battery.

Does a standard alternator charge an AGM to 100% or not? Since most AGM batteries require a 4 stage charge to get to 100%, how can it get there with a standard alternator?

Smart Battery Isolator
https://www.youtube.com/watch?v=9jjh3Y4xIL8

BCDC charger

https://www.youtube.com/watch?v=0V2AfxKXHvg

Battery Management System
https://www.youtube.com/watch?v=Qgg9unSaXYk

[TheJDMan]

Does a standard alternator charge an AGM to 100% or not? Since most AGM batteries require a 4 stage charge to get to 100%, how can it get there with a standard alternator?

I suspect not 100%. The reason I say that is because every time I drive the car it charges and starts just fine but I always put a maintainer on the battery when it is back in the garage and it always shows the battery a bit low on the screen. I have no idea if this is a problem or not an issue. I also have a pair of Odyssey AGM batteries in my Silverado Duramax now for about 5 years with no charging or starting issues.

[Doug1]

I'm thinking the alternator would need a microprocessor to fully charge an AGM. In newer cars, it most likely has the capability but a stand alone alternator most likely doesn't get it there. To keep them topped off it looks like you need to hook up a smart charger / maintainer. Sort of a bummer that you constantly charge it to 80% and run from there, as the video seems to imply. That has to shorten the life of the battery.