Dual AGM battery questions

Anyone here who has AGM dual battery setup? Right now I have single AGM with AGM tuned. Can I just get a isolator and hook them up together or I need to get off grid stuff? I don't want to spend $1000 for the parts only(without battery).

 

Remember, you also need to modify the charging circuit to properly charge the AGM batteries

 

A few members have said this is bologna and had ran AGM for years with no issues.

 

The answer to that question is printed on the battery - the charging voltage. AGM batteries require a higher charging voltage to get to full charge. Yes, they will work on lower voltage, but their overall life will be shortened.

That said, to run dual batteries on these trucks (most any new truck these days), you need to isolate the batteries and use 2nd battery charger to charge the 2nd battery. This has to do with how the "smart" alternators work.

I run a CTEK charger for my 2nd battery. If curious, you can see my setup in my really-needs-to-be-updated build thread (near then end.)

 

I set a reminder in my phone for 1 month before the Costco warranty expires, problem solved for me.

 

you can run them at flooded lead acid charge levels but they’ll need a top off every now and again to maintain rated amp hour specs

 

I have Off Grid's dual battery setup with the Blue Sea isolator, and two AGMs. The trays, the wiring, and the isolator are all well done. I just went and checked the resting state of batteries. The starter is at 12.69v, and the auxiliary is at 12.82v (nothing is hooked up to at the moment, but a fridge is why I have it). If I was doing this over, I'd go with their Redarc setup, which I think is all they now sell. I realize it's pricy, but no regrets.

 

The RedArc is a great option for keeping the starter battery lead acid at stock voltage and going to agm voltage on the 2nd battery. That's how I roll in my 3rd gen.
For older trucks like 2nd gen Tacoma, where you can easily boost voltage with hkb, I'm thinking it's cool to go with just an isolator unless you really want solar input capability since you most likely would do dual AGM's and charge them at the same voltage.

The 3rd gen needing a tune to boost charging voltage makes the RedArc a really good option for the 2nd battery.

 

I have a sdhq dual setup with agm, it has the bluesea. Also I have a cascadia 4x4 solar hood panel. Kdmaxx tune for the battery. Seems to working out fine. But I think in the first post you mentioned cheap. I don’t even want to total it all up.

 

https://www.egismobile.com/shop/7610b-th-series-12v-automatic-charging-relay-acr-160-a-bulk-5418#attr=

I run this for dual LA batteries, but if I were to switch to AGM, this would still be perfect for it.

 

The battery makers will tell you completely otherwise, but whatever

 

Do the voltage boosters adjust for temperature? AGM data sheets I’ve seen call for full voltage at something like 75 degrees F and reduce it as temperatures go up.

 

https://www.tacomaworld.com/threads...-booster-upgrade.604478/page-62#post-29016347

Options:
1. Adjustable and change based on seasons
2. Non-adjustable and enjoy without overthinking it

I'm an option 2 guy

 

Hmmm ok. Now I’m curious what temperature my battery sits at on a hot day. I suspect the desired voltage in the summer is closer to 14

 

Sounds like the way right there. I love my RedArc Tow Pro, will have to look into their dual batt option.

 

In the beginning of July I was up in the mountains, hot sunshiney day, well over 75. Had my fridge running and then used my air compressor, truck was turned off. I checked my voltage it was 14.3

 

Love my Redarc. Been running the

$464 BCDC1225D REDARC 25A in-Vehicle DC to DC Charger with MPPT — Dual Input for Solar & Alternator Charging, Green Power Priority - 12 or 24V Battery Charger Suitable with AGM, Gel, Lithium LiFePO4 Batteries

BCDC1225D since March and it’s been great. Just added a solar panel to the mix and it couldn’t have been easier.

I’ve had a fridge in my truck running 24/7 since April and my second battery (100ah lithium) hasn’t gone below 60% even when it’s 90 degrees and I haven’t started my truck for 15+ hours.

 

Did you install this yourself? Like you I’m planning to have fridge running 24/4. I’m planning lithium fe phosphate battery and solar .

 

Yeah did it all myself. Hardest part was running the wire from the starter battery into the cab all the way to the behind the back seat. They make a nice wiring kit too. It’s pricey but has everything you need.

 

I know this is a year old thread about dual batteries, but a question about adding an isolator in the engine compartment as some have mentioned they’ve done. Mine calls for a “true ignition power” connection that stays on during engine cranking. Where might this be found in the engine bay of a Gen 3? Thanks