AGM battery has been great in my jk. If your battery tender is a smart charger ie the brand is battery tender yes it will work.

 

Are the JK charging systems ok with these?

Good question. Many people use AGM batteries and say they are great. When I recently replaced my battery, I was going to buy an AGM until I started researching them. AGMs have pros and cons, but the thing that concerned me most was the 'float' charge. AGM batteries require a lower voltage float charge than a flooded lead acid battery. The JK system is set up for a flooded lead acid battery (afaik, there isn't any info to the contrary in the Factory Service Manual). So, it may be possible for the JK system to overcharge an AGM battery over a long period. My concern was that my Jeep stays running for sometimes 8+ hours at a time, so I did not want to risk overcharging.

As a matter of fact, the FSM for my 2014 JK states that the batteries are different between the gas and diesel, with the diesel engine JK using an AGM battery, and it states not to charge over 14.4 Volts or the AGM battery could be damaged. However, the gas engine JK system will regularly charge over 14.4V.

More info on AGM batteries:
https://batteryuniversity.com/learn/article/absorbent_glass_mat_agm

 

We swapped over to an AGM battery, I can't really see why you would go with a lower grade battery.
I have used AGM batteries in a variety of vehicles, ranging from Moto Guzzi motorcycles to this JKU to a lawn tractor. I have yet to run into an issue with the AGM battery being "over charged". In my experience a more likely concern is the AGM battery not being charged at a high enough voltage. I haven't had that issue yet, but it can be a concern with a Moto Guzzi and its charging system. With Moto Guzzi's, where we fear undercharging, some people will put the AGM battery on a real battery charger every so often (not a tender style charger but a full blown charger).
This is the first I have heard of people being concerned about over charging an AGM. But then, the main brand of AGM batteries we use are Odyssey.

 

In my experience a more likely concern is the AGM battery not being charged at a high enough voltage. ...
This is the first I have heard of people being concerned about over charging an AGM. But then, the main brand of AGM batteries we use are Odyssey.

The Odyssey AGM wants to be charged at 14.7V, but only if you are charging from a discharged state, and only for a certain amount of time until the battery is fully charged. After the battery is charged, the Odyssey float voltage must be dropped down to 13.6V.


Many automotive voltage regulators are set to regulate below 14.7V (as you pointed out, not charging at a high enough voltage), so they will not quickly & effectively recharge a discharged battery. But, they will also maintain a voltage of well over 13.6V any time the engine is running. So, once the Odyssey battery is fully charged, the Jeep will continue to overcharge the battery.


Tech info on charging Odyssey batteries:
https://www.odysseybattery.com/documents/US-ODY-TM-002_1214.pdf

 

I agree with @GuzziMoto. My observation say we have a pretty smart alternator. I monitor my batteries via the G-Screen monitor on my switch pod. When my batteries have been deeply discharged I see 14.7v, normal discharged state, 14.4v and fully charged 13.6v. Rarely if ever is your battery fully charged and about the only time I every see it fully charged is after I have charged it over night, at least a 12 hour process or when on a long trip.

 

Odyssey in my JKUR for 8 months and 4K miles. No issues.

 

5 years here so far. No issues.

 

So, chickenman o5, the only way to know if the JK charging system is really OK for the AGM installed would be to find out the charging specifications for the AGM battery installed, then see if the JK charging system will properly charge it. Otherwise, it was put in under warranty, so don't worry about it until it is eventually time to replace it.

 

There are people who have run AGM's for years. In fact it is probably the most popular battery with dual battery set up folks.

 

My fist set of Odyssey (Sears) batteries lasted 4 years. Now before you say that is not very long you need to understand how my system works. Once the volts drops below 12.7 volts my main battery is disconnected from the system. I have a pretty large drain on my batteries that I have not bothered to chase down. After about a weeks time my aux battery will drop to about 11 volts, after a month as low as 5 volts. And I am not very good about keeping my charger hooked up.

That first set of batteries was a 34/78 which will work in a Genesis setup. Because Sears drop there Diehard Platinum line using the Odyssey battery I had to move to a 34 instead. Otherwise I would of only had to replace one battery not both. Still works out to a battery every 4 years but I only except 3-5 year of battery life anyway.

 

Coming up on year 4 of my Odyssey and enjoy the cranking power and reserve, the winch has been used several times a year and have a lot of trust that the JKUR will start when far away from pavement. If I need to replace one day, the trust is worth the money.

 

I still have the stock battery in my '16. Probably should replace it before next winter.

 

one thing I have found with stock batteries is when they go they go fast. Like one slow start and the next dead as a door nail.