Anyone know how to change alternator output for AGM battery

Does anyone happen to know how to change the alternator voltage to accommodate the higher charging voltage requirement for AGM batteries?
I've looked through techstream and couldn't find anything. Any help would be appreciated.

 

There are a few companies that have a jumper wire that goes between the alternator and the harness to trick the charging system. Not a techstream item though.

 

You can "test" the alternator voltage and increase it through techstream, but once you exit the test, it defaults back. There's gotta be a way somewhere in there to change it.

I've seen the boosters that go into the fuse panels on the earlier generations, but the 3rd gen doesn't have the fuse for it.

 

Instead of messing with the alternator or ECU, I just recharge my AGMs once a month with this

https://www.vmaxtanks.com/BC1215A-12V-15A-7-Stage-Smart-Battery-Charger-Maintainer_p_71.html

 

While someone still looks into the 3rd gen AGM charging, I went ahead and just put a solar panel and keep it charged through that

 

I hear ya, just would be nice to be able to keep it charged through the vehicle itself.

 

if you upgrade to agm battery charging needs to be different? I did not know. I just recently bought a NAPA AGM battery

 

The bulk charge from your alternator won’t go to 14.7V that your AGM battery has for a full charge. It’ll still charge it, but some members say only 80-90%.

Like I said above, an easy solution is to recharge on a 7 stage charger or similar once a month, you don’t have to take the battery out of the truck.

As you know AGM batteries are great if you’re discharging them with electrical mods, which they can down to 20% several hundred times.

 

Not sure how they wired it on 3rd gens
Anyone have the wiring diagram?

Most smart charge systems fail safe to full voltage if the circuit from the ecu to the alternator is cut

 

There’s an aftermarket higher output voltage regulator someone came up with for 2nd Gens. He couldn’t get it to work on the 3rd Gens.

 

ok new to me. thanks for the info


will it be detrimental if i don't use a charger to top off? how about using a harbor freight or similar battery tender?

 

AGM batteries another nope never again thing for me. I like the idea, but they can't handle cold weather at all.

 

I’m sure your AGM will last several years with doing nothing, you’re not going to kill it.

My understanding is a regular battery tender is for a SLA battery and better to use a multi stage charger for an AGM.

 

Maybe they’re not all manufactured equal. There’s drastic differences even in standard flooded batteries. AGM Odyssey says no problem down to -40F

http://blog.odysseybattery.com/2018/01/faq-benefits-and-care-of-an-agm-battery-in-winter/

 

I have an RV but I am not really all that knowledgeable about batteries. Nevertheless I thought that it was the Lithium batteries that can be drawn down very low but AGM, like lead acid, should only be depleted by 50% and then charged up.
I do know that the main advantages for AGM batteries is that they can be mounted in any position, so ideal for extreme pitch angle when off roading.
AGM batteries stand up to vibration pretty well.
AGMs are also idea for mounting inside an RV without needing a sealed vented box because they do not off gas.

 

I’m no expert, just try to read a lot. Here’s a good article

https://www.susprep.com/off-grid-power/batteries-101-part-1-depth-discharge/

 

According to that article, we are both right as it says that lead acid batteries can be drawn down to 20% charge remaining, however to maximize battery life, drawing down to 50% is ideal.

 

Smart man.

 

The charging system on a modern vehicle should have no problem charging an AGM battery. I have AGMs on the 911 and RX7 and their alternator amps are about 130. An AGM was a must due to moving it inside for weight distribution. An alternator will not, cannot charge an AGM to full charge. You'll need a battery charger.
I have them on a trickle charger to keep them happy.

For future reference to those who have drained it waay below and have a 6/12 volt charger, the charger will *think* it's a 6 volt battery and not switch over to 12v without a boost from another 12v battery *OR* a portable battery jumper.

 

Interstate claimed -20F, but it didn't matter they could stay in charged up good enough at 20F. I like the concept, but not venturing down that path again.