I noticed that my Auto start stop has been off and occasionally when I get in the truck I get the system switched off to save battery message. However never had a problem starting the truck
Today I hooked up my 800 mA maintainer to the battery. It is the original AGM battery
I had the maintainer connected for 9 hours and it was still registering as charging the battery. On the Schumacher the led light goes out once the battery is charged .
9 hours seems like a long time and I am thinking I messed something up. I know the maintainer is okay as I had it connected to a lawn tractor battery last week and it worked fine.
Did I do something wrong ?

 

You want the positive lead of the charger direct to the positive post on the battery.

The negative lead on the charger goes to a ground on engine or chassis, not on the battery terminal.

If something is staying on that is supposed to turn off, then the drain from that might be more than your trickle charger is putting out.

 

I don't think you did anything wrong. I'm no expert on batteries, but I use a 750 mA maintainer and I usually see it get to normal maintenance mode after about 24 hours. I don't drive my truck on a regular basis, so I often keep the maintainer connected. Even after driving the truck a considerable distance, then hooking up the maintainer afterwards, it always takes nearly 24 hours to get into maintenance mode. Another tip, connect the positive clip to the battery post, the negative clip to the ground on the truck (I use the one just off the battery). I've had good luck with this method.

 

I just got into this on the 21 forums with quite a brawl over it.
In short, the battery requirements are not understood.
An 800 ma maintainer is about 30 amps too small to do the job.
This subject gets very technical and needs you to research it to understand how an AGM charge phases are to be done properly.
For example, the first phase requires close to 30 amps for several hours before it goes to Phase two. then to float.
This total time interval can take as much as 18 hours to complete depending on the charge level begun from.
The truck's Alternator is capable of high charge current so has the capability but.... but must be applied enough time to do the battery recovery.
This means no continuous short time drives and re-starts. The battery cannot recover from this abuse and causes early aging/shorter life span.
This is where the issue develops from with various options not working due to low state of charge voltage.
You cannot fix it with a small capacity charger over a short time interval.
The proper charge phases and levels are already in the BMS program for the H6 size battery and is what is used for proper re-charge as long as the time to accomplish it is allowed to happen.
These trucks are so loaded with features and Modules that the H6 battery size is now marginal for capacity that size battery.
The same H6 size has been used for more than 6 years so now does not keep up with system needs as options and features are added., especially after several years of aging under low re-charge conditions.
The most obvious example is the failure of the Auto stop/start function because the battery is not being kept up to proper charge level by the way the truck is used.
It's not a design flaw or a faulty battery as long as the battery passes a load test. It's time and charge level related.
It is how the truck is being used that cannot be made up >>properly<< with a stinking little maintainer for even with days of charge, at that level.

 

I've use the CTEK MXS 5.0 charger maintainer. It's one of many smart chargers you can buy that charges in a multi step process as well as maintaining a battery after completing a full charge. Mode settings for AGM and FLA. I'll use it about once every 3 months to keep my original 3+ year old AGM battery topped off if needed. My current SOC while asleep is 12.7 but I always try to drive a minimal amount of milage and time on the engine to assure recharge recovery time. That works.

 

Your Lawn Tractor battery is a postage stamp size compared to your Truck battery. And even a different type.
The Maintainer is also too small for the job your expecting it to do.
That is why it does not bring the big AGM up the full charge the way you expect, in that short time.
Try to get the point of it.
The basis of this is the Ampere Hour Rating of the battery >>>and the charger.
Said another way; the total Battery Cell Plate area vs the very low Current applied.
It's like trying to Paint 1000 sq ft of area with a Pint of paint. Won't work very well unless spread very very thin and the (time)it would take to do that and the very little paint applied to the surface.

 

I recall two years ago when I began this journey and why I bought the the CTEK 5.0. It was recommended to me that I get one that will deliver at least 4 to 5 amps.

I do however, clip my negative lead at the BMS sensor on the leg the grounding cables are directly tied to. It is the same point on the back side of the sensor as a chassis ground point. Current flow still goes through the body of the sensor to the negative post of the battery.

 

Thanks to everyone who responded. I also read the thread referred to by Bluegrass
The truck is my daily driver. Two 30 minute drives ( home to office) spaced 8 hours apart. I noticed a while back that my auto start stop and the front passenger lock ( touch to open) had stopped working. I did read that these were two of the functions that were shut down to preserve the battery charge. I think the start stop has been off for a while, just hadn't noticed it.
Apart from those being switched off and a occasional message on the screen first thing in the morning the truck has started well and everything appears ok.
I tried my maintainer to see as an experiment to see if I could get those two functions back.
Maintainer was connected to the + red and the - negative AFTER the BMS sensor.
I was hoping to "top off" the battery with the maintainer.
One thing though. I left the hood up while the maintainer was attached ( doors were locked) would having the hood up "wake" the truck and draw a charge from the battery.?
A Question for Bluegrass you say that my maintainer is about 30amps shy of what I really need. All the maintainers I see are rated between 800ma and 2A so I am a little confused about that.

 

Maybe I missed it, but if you have the original battery, it probably needs replaced.

My 19 *** was doing the same thing and Ford replaced the battery. At that time The truck was 33 months old.

 

The NOCO Genius 10 is the best battery charger/maintainer I have ever owned.