Yes you do. Any AGM battery requires a higher charge voltage than flooded type. Replace the alternator fuse with a voltage booster that replaces the fuse wire link with a diode.
Several threads here if you search on this and where to buy it

 

Do u have a link? I get that need to be done but don't see any place to get one

 

Here you go, plug and play and looks OEM vs some of the other options that look cobbled together:

Toyota | HKB Electronics

 

What one am I supposed to get? Lol

 

See Mikey's link

MK3 Mini blade 7.5A (Electronic fuse version) | HKB Electronics

The Alternator Voltage Booster was the first of its type on the market and is the only unit available that was has been purpose built for alternator voltage boosting.

www.hkbelect.com

 

There also used to be a HKB Electronics discount code for forum members (don't know if it still works), search for it.

 

Dirty Parts

www.dirtyparts.com

Here is another option. I need to order one of these too.

 

I have the Dirty Parts one. It jumped up my charge voltage by about 0.5 volts as promised.

 

When I haver a big draw ( usually when cold ) the HKB is touching 15v (14.98 - 14.99 ), routinely I'm at 14.55ish

 

Isn't 15v to high?

 

I've been using the HKB for quite a few years now as well.

 

Yeks 70$ for a fuse

 

Versus the cost of premature failure of an expensive battery....

 

Worth every penny.

 

Looks like the Tacoma guys are using this. Anyone ever try or have input?

https://www.oreillyauto.com/detail/b/littelfuse-4149/agriculture-hd-parts---accessories-19818/fleet---heavy-duty-20088/heavy-duty-a-c-parts-20120/hd-truck-a-c-relays---resistors-20307/22dde34136ba/littelfuse-1-amp-mini-diode/02400113xp/4414229

 

That is 1amp
HBK is 7.5amp

From HBK:

"The PTC device (electronic fuse) incorporated in the MK3 offers far better circuit protection than both the OEM fuse it replaces and all other types of voltage boosters. Should an electrical fault develop in the vehicles wiring other types of booster diodes will be destroyed and need to be replaced, this is not the case with the MK3 unit, in the event of an electrical fault occurring, the PTC device in the MK3 detects the excessive current flow and turns off preventing damage to the booster unit, the vehicles wiring, and alternator. Once the electrical fault has been removed the PTC device automatically resets and the booster unit will resume normal operation. "

Will the Oreilly one do this.....doubtful

 

Heh, for $4 worth a shot I guess.

 

I've got an Odyssey battery. I know the alternator will not put out sufficient voltage to fully charge it, so I bought a CTek MXS 5.0 charger maintainer. It's specifically set so that when it charges in AGM mode, it won't perform the high voltage "Recondition Mode", which will destroy an AGM. Especially since Covid, my FJ sits more than it's driven, so I have it to keep the Odyssey happily fed in the meantime. If I was driving more, I'd probably stick it on once every week to top it off fully. Eventually I may get the voltage booster though.

 

Ture it may be $1 worth of parts but paying for the knowledge, time and the ability to have it look OEM vs a cobbled together POS is worth every penny.

 

No reason that a properly designed electrical system mod, carefully made with the correct materials, should be a cobbed-together POS.

All my electrical mods are made with crimped & soldered terminations, MIL-spec or Deutsch connectors, teflon (rodent resistant) insulated aircraft wire, heat-shrink tubing, and are double-insulated with fire proof silicone-over-fiberglass sleeving. With a little time spent shopping on-line and minimal skills, just about anyone can do the same.

Granted, over the years I have seen many crude, totally POS electrical system mods, with lumpy twisted-together splices, big wads of electrical tape, primitive attempts at soldering using acid-core flux, wiring pulled tight against sharp sheet-metal edges or draped near exhaust manifolds, etc.

Probably not a bad idea to keep some mini-fuses in the glove box just as a backup in case your diode/fuse or diode/PTC thermistor module should fail when you're far off-road, at least you can bring your alternator back in service.

Realistically, the only risk I can see to either the OEM fuse or the diode modules is a short circuit caused by rodent-chewed wiring, and it would have to be the alternator's voltage-sensing wire that got the insulation damaged AND then shorted to ground.