Dual Battery Setups! Let's see them! Multiple Batteries Thread!

Battery charge voltage requirements vary not only due to battery type but also battery temperature. Even if you use the exact same battery in both locations, the temperature will likely be at least 10 F different, which is enough to really need a different charge voltage (if you want them to really last). These things are fixed by using a battery to battery charger with a temp sensor.

 

Doesn’t really give me a good idea of space. Any pics of the whole engine bay?

 

He's got that extra doohickey in that spot next to the airbox which would prevent a battery from fitting there. My truck doesn't have that.

 

Here ya go, from three angles, left/center/right:

 

Its the ABS module thing.

 

So I didn't see if anyone mentioned if the alternator in tow-package equipped TRD models (mine is a 2019 Sport) automagically adjusts the charging voltage for different battery types? For example, if I switched my OEM lead-acid battery for an AGM would the ECU notice and adjust the output voltage by an additional 0.6 volts? Asking since I can't do the cheap fuse/diode trick and wondered if Toyota built in a little magic...

 

No, it will charge like the ecu is programmed for a standard battery and is not fully charging your AGM.

 

Thanks for that. I'm very frustrated that there seems to only be two manufacturers of 3rd Gen side-by-side dual battery trays and both require drilling my new truck and also require using AGM batteries. This means my costs go from a simple hundred dollar tray to about six hundred because of DC2DC charger control, etc, etc.
/sad

 

An option may be to use a DC/DC charger like the CTEK D250 as it charges the house battery at 20amps and because the incoming amperage is higher but at a lower voltage, it can manipulate it to the correct AGM voltage. That doesn't solve the problem on the starting battery but a simple solution might be to change the position of the batteries, swap the house for the starting every other oil change. Then at least they both would be getting the full charge on an irregular basis. I'm not even sure this would work but I've got a contact at Odyssey/Enersys and I'll pitch this idea and get a response.

 

I think you would be able to use a flooded cell and an agm with the CTEK and not have to buy two new AGM batteries, which would save some money.

 

Absolutely. If pairing two like batteries is not an issue, then a flooded starting battery makes perfect sense and let the charger deal with the AGM house battery.

 

Something that I sat down and worked on the other day was an actual project cost spreadsheet. I wanted to find out what this project really costs and then evaluate the actual value of doing it. I needed a new starting battery when I did this so there are two Odyssey AGMs, two battery boxes, a CTEK DC/DC charger, cables, tools for making cables, two Blue Sea 15 amp 12 VDC outlets and miscellaneous stuff to hook it all up...$1551 is the total.

There are a lot of options one can consider for that price tag, the simplest being a a good AGM starting battery and a good jump battery like a

$100 NOCO GB40 : 1000A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack, Portable Jump Box, Power Bank & Jumper Cables - for 6.0L Gas and 3.0L Diesel Engines

NOCO GB40 for roughly $100 to bail you out of trouble.

If you want to get really serious, a Goal Zero Yeti lithium with a nice solar panel setup is <$1000 plus a jump battery and you're still ahead and it's all portable from one vehicle to another.

In the upcoming issue of TRAILS, I actually have to defend the decision to do a dual battery setup in our Point/Counterpoint article. Truthfully, I'm not sure I would do it again since we actually have the Yeti setup and have used it for over a year and I carry a NOCO jump battery all the time. Time and use will tell if this was a good decision.

I'd like to hear the rationale on both sides of the argument. What say the crowd?

 

I spent $1500 for 2 group 27 agm batteries, 2 100 watt solar panels, a mppt solar charge controller, an aux battery tray, and a smart isolator. Probably another 1-2 hundred if you tack on the extra stuff like wire and fuses.

You could get away with a LOT less if you wanted to do a single battery setup. If you just ran 1 agm in the stock location and 1 solar panel to keep it topped off, you're looking at around $600 for one group 27 agm battery, 1 100 watt solar panel, and a mppt controller. Could be even less if you got a cheaper battery. The one's I got were high end pricey ones.

 

Still leaves me with the original problem of how to fit a second battery under the hood. :-(

 

If it must be under the hood, then the first thing to grapple with is compromise. I would move the airbox out of the way and use a different air filter/air intake hose/filter location to begin with. That will create the space needed. It's what I had to do because I made some choices I was firm about. I was not going to move the power steering reservoir nor the ABS module on the passenger side fender of my 2nd Gen. I did choose to use a new intake hose since the ultimate location completely blocked the air intake from the inner fender. Doubling up on the batteries wasn't an option because I had previously chosen a larger starting battery that I didn't want to make smaller.

Second option is not under the hood at all. An AGM can be placed in multiple locations and in unique orientations. Assuming the exhaust still goes down the passenger side on the later models, I would contemplate attaching to the driver's side frame rail below the bed and add some weather and object protection. I'd also look at putting it in the bed itself. Some high amperage disconnects could make the entire package portable and usable in more than one vehicle. You could also look at a smaller AGM or multiple smaller AGMs in a "package" underneath the truck.

The final piece is answering the question "is it really necessary?" Perhaps a larger starting battery, a solar input, a portable setup like Goal Zero or any combination of these would make more sense.

Honestly, I spent hours just staring at the truck looking for a sign to send me the right direction. I ruled out a lot of options because of convenience of use, maintenance, my fabrication skillset, and a pandemic limitation on what parts I could get in time to meet my editorial deadline. Ultimately I ended up where I am.

 

Are there *any* vendors of dual (side by side) battery trays for the 3rd gen Tacomas any more? Off road engineering seems to only have one that fits the 2nd Gen (plus their website has SSL certificate problems and bad links) and columbia overland seems to no longer even be in business. The first post in this thread should be updated IMO.

 

Genesis offroad is still doing them. I was about to buy one but then saw some posts on here (will look for link) about peoples oil fill neck falling off due to the fact that it is glued on (yes...) and can contact the dual battery unit crammed up front. I also saw some posts about people having some cracking in the metal due to all of the weight there. It's a shame because their system seems really fantastic as far as how it functions. It just seems less than ideal when coupled with our gen 3 "features"

*updated with link*

https://www.tacomaworld.com/threads/genesis-dual-battery.539279/page-2#post-21070915

 

I just found this one, sent message asking when they will get more in stock: https://www.moleoverland.com/product/gen-3-tacoma-side-by-side-battery-tray/ and they also sell a smaller replacement aluminum oil filler neck for that reason.

 

Interesting. I’d still be a bit worried about the battery weight on the metal there especially with off road use.

the oil fill neck seems like a good idea. I wonder how those bolts would mount to our truck considering the factory neck is glued on.

 

Yeah, its a well known issue that the core supports on these trucks are weak if you do any amount of wheeling. Especially with the weight of 2 batteries