Dual battery tray/location for true deep cycle alongside regular starter - not twins like most seem to do

andrew61987

Observer
I'm wanting to add a house battery to my 08 Tacoma 4 cyl for worry-free engine-off lights and music in woods and am currently planning the wiring scheme. Something that's troubling me is the location. I see a lot of people running twins in the factory location rotated 90* using an aftermarket dual battery tray, but they all seem to be designed for identical batteries and most people seem to be running twin dual-purpose starting/deep cycle batts like a couple of Optima Yellows or similar. Is there a reason for this? Isn't a better option to run a regular starting battery and a true deep cycle with a solenoid that only closes with key-on? Is there a tray that will allow for the rotation of the factory battery to make room for a true deep cycle that is presumably a different size/mfg? Just curious how others are running this particular setup as I'm under the impression that a "dual purpose" battery is not ideal compared to a true deep cycle. I'm prepared to build my own tray just thought I'd ask.
 

DaveInDenver

Middle Income Semi-Redneck
Can't speak to other's logic but I run a pair of Odyssey batteries in the stock location. The reason I did this is redundancy and because my truck retains the old style vacuum booster and ABS module on the passenger side the obvious location by the firewall wasn't going to be a simple fitting. Perhaps some day I'll mount a smaller battery on the passenger side and go back to a single large on in the factory location, but I doubt it. If I do anything major it will be to move the battery(ies) completely from the front left to somewhere else.

The starter doesn't tax the battery very much so you actually don't need a big battery for that. In fact a single PC1200 such as I have will run the truck without an issue just fine and almost for as long as the group 27 it originally had. But things fail so I wanted a backup. Actually each PC1200 is still something like 75% as good as the single flooded one that was stock. Putting in a single large AGM would have been better but the pair of batteries I have are roughly 110 A-hr, so it's not bad.

Since it was convenient I went ahead and used the secondary battery to run the fridge wired as a house battery but I wouldn't suggest this as a be-all, end-all solution because as you note it's small (only 55 A-hr) and doesn't run it very long. I have a marine AGM that I use on longer trips that was mounted in the old truck but I haven't done anything about permanently mounting yet in the new truck.

The Odysseys I have are dual purpose, neither truly starting nor true deep cycle. This is pretty typical of AGM, which are rarely true deep cycle but rather starter types that tolerate long duration small loads better. Since I'm after redundancy and may parallel them in a worst case dead battery or winching situation I actually didn't want the aux battery to be a true deep cycle anyway.
 

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