AGM Dual battery setup

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Tooolman

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I have a 2017 Tacoma Off Road and I'm interested in setting up a dual battery system that can expand to accept a solar charger at some point in the future. I have been researching many different dual battery setups and I'm wondering is anyone has real world experience with different systems, the benefits of each and the problems I might expect to encounter. I've heard good and bad things about Optima batteries and I'm also wondering what options are available for a solid reliable battery (or two).
 

Dana Ramos

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I have a 2017 Tacoma Off Road and I'm interested in setting up a dual battery system that can expand to accept a solar charger at some point in the future. I have been researching many different dual battery setups and I'm wondering is anyone has real world experience with different systems, the benefits of each and the problems I might expect to encounter. I've heard good and bad things about Optima batteries and I'm also wondering what options are available for a solid reliable battery (or two).
Ha, I've been down a pretty deep rabbit hole researching dual batteries for my 3rd gen.

In your case, this thread is a good place to start. But, a lot of that info is more specific to the second gen trucks.

As you're researching, the big thing to keep in mind with the 3rd gens, is that the truck's ECU controls the alternator voltage and limits it to ~13.5v. AGM batteries need around ~14.8v to charge completely. On the 3rd gens, unlike the 2nd gens, there is no workaround for that. That being the case, you're best off just leaving your stock battery alone so the alternator can charge it completely. If you replace the stock battery w/an AGM, you'll need to purchase a battery charger and connect it to shore power on occasion to fully charge. And/or, you'd need a solar panel/charge controller, either mounted on board, or connected at camp, to fully recharge while away from home since the alternator won't get you completely there.

One option that I think makes the most sense:

Adding a aux AGM battery + tray for the passenger side to distribute the weight evenly, and wiring in a Redarc BCDC1225. Your starting battery will be charged as usual by the alternator. The Redarc will then charge your secondary AGM to 100%. The Redarc also accepts solar input and can charge even charge LiFePO4 batteries if you wanted to go that route. Add an aux fuse panel to that battery and connect your accessories to it. Done.

The Redarc is the same price just about anywhere (~$380).

Multiple options exist for a second battery tray, many are covered in the thread lined above. The aux battery trays from Off-Grid Engineering or MOLE Overland (~$220) both have brackets to relocate the fuel resistor to. Otherwise, you'll probably have to get creative with that part. It seems like Group 35 batteries are generally suggested for that location but I've seen multiple people running with a 34 or 27F on those trays linked above. It mostly comes down to cost vs Ah, and how much weight you want on that spot.

Again, multiple options for batteries too, but Optima, Odyssey, and Northstar are probably the most popular. It seems that Optima not so much these days. Batteries+ sells re-branded Northstar batteries labeled X2 Power (~$300). These come with a longer warranty and for less money after coupon codes and rebates.

The Redarc, and probably a fuse panel, will also have to be mounted somewhere. If your'e handy or creative, you could probably figure something out on your own. Power Trays (~$85) has several products that could work and are affordable. MOLE offer something similar that costs a bit more. Off-Grid has an entire replacement tray for your starting battery, with a mount for the BCDC on the front, and that costs the same as the bracket from MOLE (~$110) .

In addition, you'll need some 8 gauge, terminals, loom, fuses, solder, tools, time, etc. (~$100)

On the high end of this setup, you're looking at ~$1100 to source all the components and do it yourself. You could probably save a few bucks buy keeping your battery in the camper, or shopping around and fabbing some stuff yourself. Off-Grid sells a kit with everything you need besides the battery for $900. They'll even pre-wire the Redarc w/labeled terminal connectors for an additional $100.

There are other ways to go about it, but all of those will require you to plug your truck in to the wall (or a solar panel) to keep the battery fully charged. Some of them will even require you to purchase multiple matching AGMs that need to be manually charged.

Alternatively, and if your power needs aren't that great, you could just replace the starting battery w/an AGM for ~$300, install a solar panel and charge controller for ~$300-400, and buy a smart charger to maintain it once in a while for ~$100. At that point you're most of the way to a dual battery system which eliminates the manual charging.

Any way you go, definitely keep a charged jump pack in the vehicle.

Happy rabbit holing!

D
 
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