Hi guys, been reading here and other places that if you have an AGM, our 4runners need a battery booster. I've been running an Interstate 34R AGM battery the past 3 years, never put on a battery tender and I don't have a booster, but from reading everything, I've ordered one already.

My Scanguage II shows a voltage of about 13.7 when the car is running. Being afraid of damaging my battery, from what I've read, I put the car on a Noco tender in AGM mode right now until the tender arrives. However, after a few minutes, it already shows fully charged. That being the case, is it that the Interstate AGMs don't need a booster and ~13.7 on stock alternator is good enough? I haven't had any battery issues in the 3 years I've owned it. Or is the tender coming up to full charge on the battery not really indicative of a battery that is slowly losing capacity due to being undercharged?

If it's the former and everything is ok, I assume I should still use the booster but put it on low (+0.5V) anyways?

Most quality AGM's are not affected by lower stock alternator ranges in my 2 decades of experience. With that said, my Odyssey clearly states that it needs a higher range to charge so I went with the booster and have had no issues. It bumps up about .3-.4V which helps keep it more in the sweet spot for charging so for the small amount of investment I feel that it's worth it.

With that said if you're 3 years in and the battery is holding charge I don't think it's anything to worry about

Thanks, since I have one hopefully in the mail soon, I'll just throw it on low setting and not worry much about it then. Yeah if 3 years and no issue, I guess the Interstate doesn't need it -- was just worried since everyone was saying you NEED to have them or your AGM will die.

Did you set your NOCO to AGM?

Yep, it's on 12v AGM. I know it works as my other car has an AGM as well (but it was meant for AGM) and that one definitely takes some time to charge up every other week -- it sits most of the time (good weathered weekend sport car)

It's not a touchy feely question, but rather a simple matter of what your battery manufacturer says it needs for charging or float voltage and what your alternator supplies at a nominal engine RPM (not at idle). If those two don't match, then you'll need a way to solve for it. If the desired and provided voltages are in alignment, then there's nothing you need to do.

That all assumes you drive the truck regularly enough that the battery stays topped off. If you don't, then the NOCO or whatever charger set to AGM will work too.

Hey guys, this is an good topic that may interest other gen owners, so I'm moving this to General Discussion so more people can see this.

I've been searching around and can't find info on Charging Strategy for AGM batteries.

I purchased a "Voltage Booster Pro" for my 2021. I set it on "Low" which gives me 14.5Volts on cold startup.

Down the road when engine is up to temp, the voltage drops to 13.5V

My question... Should I switch over to "High" setting, or it perfectly normal to see this voltage drop once things get warmed up.

The battery doesn't need the higher voltage once its topped off?

I thought AMG batteries went in Golf Carts, but not totally sure on that. I just buy a replacement battery that is for my vehicle, in most cases I buy a factory replacement Interstate battery, why Interstate always had good success. Never quite understood why some buy expensive replacement batteries, maybe because they live and work in extreme conditions, but for me just spending money for something not needed. Sorry, just don't see the need for an AMG battery.

In my experience, the voltage dropping once the engine's warmed up is totally normal. AGM batteries don’t need constant high voltage once they’re topped off. 13.5V is usually fine for maintaining them after they’re fully charged.

As for the booster, if you’ve got it set to “low” and it’s getting you to 14.5V on startup, that should be more than enough. Switching to "high" might push the voltage a little higher, but it’s not strictly necessary unless you’re noticing charging issues or if the battery starts underperforming.