What battery should I upgrade to?

I did a test fit of the Noco group 27 box in the photo below, and it looks like it should fit fine & will hold a Trojan T-1275 150AH battery using the wood block method to fill the old frame & bolting on a new frame at an angle like you did, @ScottG.  This battery is available from a local golf cart shop for around $200 and should satisfy our occasional need for more power without hookups.  An AGM battery would be nice to have, but unfortunately won't easily fit our situation.  I may add solar at some point for extended power, but right now just trying to prepare for a trip in a couple months.


I wonder if there would be more usable space by moving the battery switch to where the gas regulator is, and moving the regulator to the left corner.  Even one inch could give more options.

Thanks for pointing out that clever glove box mounting, @Sharon_is_SAM.  That could solve one storage issue caused by the new battery box.  Still have to find a spot for a couple of sewer hose connectors, but I think there may be room left in some corners.

Well, I finally got this battery mod done..
I could not find a 12 Volt Trojan Plus battery locally, so I bought the slightly taller model T-1275 with 150AH for about $216 at a local golf cart store.  It would have been $45 cheaper if I had an old battery core to turn in, but had to pay the "deposit".  I will just keep the year-old stock battery & bring it along for an extra 75 AH of emergency backup.  I could put in in the rear storage when not charging to offset some tongue weight.  And speaking of that, I weighed our tongue after removing the old battery and it was 178 lbs with spare tire, before adding the new 85-lb battery, so we'll still be under 265 lbs, which should be fine.


After removing old battery


An 11-inch long piece of treated 2x8" lumber had the perfect 7-1/2" width to fit the old frame, with a thickness that was about 1/4" taller than the larger piece of metal framing, so perfect for keeping a new battery frame supported above the old one.


I made a template from a piece of scrap matboard used for framing photos, to match the 7-1/2 x 13-1/2" footprint of the Group 27 battery box, and used that to layout the locations of where to drill holes for bolts that would go through the old frame, wood block, and new frame.  I used 1-1/4" steel angle iron to make the new battery frame shown above after drilling & welding at a local welding shop, before sanding & painting with rustoleum.


I had to add an extra small block of wood for one of the 1/4 x 2-1/2" stainless bolts.  For the locking battery strap (from the old battery - the new box came with a less convenient buckle), I was able to easily pass the strap under one side of the new frame, but for the other one I chiseled out a 3/16" deep slot into the surface of the wood block.


Also added a piece of 1/4" outdoor grade of plywood which allowed the box to sit level over the unevenly placed bolts & framing.


The box has a good pair of handles, and fortunately I was able to lift it with the 85-lb battery into the tub without injury.  We have a healthy 28 y/o son who was on standby if needed, so hope he'll still be available 7 or 8 years from now.  The battery voltage read 12.25 before hooking it up & good water levels, so was in ok condition.  The dealer said they get shipments every two weeks directly from Trojan, so they don't need to charge them routinely.


The new battery has hooks for lifting, so I made this simple carrying strap using a piece of rope, pvc pipe, & S-hooks.  Worked great for lifting it into the box.


Finished mod, with no room to spare so measure carefully if you do this!  The box lid would only snap closed on one side, due to battery height being about a half inch too tall (which is why I had wanted the shorter "Plus" model), so the other locking tab sat up about a half inch too tall to snap shut, but it still fit inside the provided slot so the strap holds it all snugly in place inside the frame.

Next I'll try to find a place for hose connectors & gloves, and then I'll start thinking about solar panels.

Thanks, @jkjenn!  I wasn't even trying for "freat"  but glad you like it.

Now we need to figure out a plan for a test trip to get a feel for what we can & can't do and for how long.  Will have to wait until A/C season is done & maybe wait until we might want to use the Alde.  We've actually never gone off-grid with our T@B, so have never even tried using the Alde or frig on propane, or had to depend on the fresh water tank for that matter.  I guess we probably should have at least tested the gas appliances before the warranty expired. 

I’ve got a surplus Eaton PWHR12280W4FR - basically a G24 80AH but extreme stability and high current capacity.  $55 locally surplus from UPS lease.

Its self discharge rates are insanely low.

Eaton has 115# ones that were like 140Ah?

It’s going in my TAB after running off my portable solar for camping.

@elbereth, I'd love to put your setup in our new 2018 T@B 320 CS-S -- (yahoo!) --  but I'm worried that the tongue weight would be way over the 200# spec of my very-similar-to-yours 4-cyl 2013 Subaru Outback.  How do you deal with that weight?

@ckjs - tongue weight is still only about 185 despite the battery being much heavier than the original.  I don’t remember all the specifics, but I think in the end it only added about 30
pounds to the tongue weight - has to do with the geometry of the distance of the load from the axle.

rfuss928 said:

I have had very good results with Optima Blue Top batteries.  I fit a D31M in the original group 27 box with no trouble. 

Optima blue top batteries (spiral AGM construction) are know for higher power density, extreme vibration resistance, significantly longer life and zero maintenance compared to flooded lead acid batteries.  They are a premium battery with a premium price but in the long run are less expensive to own because of their long life.  These were the batteries of choice in industrial/commercial power back up systems I worked on.

I am on my fifth camping season with two D31M batteries and they continue to perform as new.  I have not even seen them since I screwed the cases shut in 2011.

I also put in an Optima Blue top 31 a few years ago, and it has been really problem free. I have the 12V fridge, and have no problems with it staying charged while driving. I also have a power mover which is a bit of a battery hog, and the battery has never failed me when I need to move the camper around. (I don't boondock, so always have Shore Power at my destination, and have a 30 Amp plug at home.)

@ChanW, it is a super tight fit.  I’m not seeing any marks on anything, so I think it’s so tight there isn’t much movement and it all kinda moves as a unit.  The strap just wraps around the old frame with plywood in it - it’s actually not even super cinched down, so I really think it’s the friction of everything wedged in there.
We haven’t done hundreds of miles of washboard or anything, but have been on dirt forest service roads as well as at highway speeds on the, well, highway, and everything stayed comfortably in place.

We recently installed a Battle Born 12V 100 AH LiFePO4 battery in our 2018 T@G Outback. It came with a Group 24 75 AH battery which was not adequate for our boondocking requirements despite a 120 watt Zamp solar siutcase. The install was simple. The battery fits into a Group 27 box in the front of the Outback, works nicely with the solar panels and can be charged (albeit not fully) with the WCFO converter if we happen to be plugged in (rarely for us). I also purchased a separate Progressive Dynamic 9130 LV battery charger for when we are at home and a Victron 700 BMS battery monitor to assess the state of charge and amp/hour consumption on the road. The battery weighs only 29 lbs. As stated earlier in the thread, LiFePO4s allow you to utilize 98-99% of the battery’s capacity before requiring a full charge and are touted to have 3000+ charge cycles over the life of the battery. IMO our other option was a two 6V golf cart battery (200-235 AH) system which would have required some modifications of the front tub and likely down-sizing the propane tank. Also, the additional weight of the two batteries (50-65 lbs each) would seriously have increased our tongue weight. Hence the rationale for going with the lithium choice. Attached are some pictures following the install.The cost of the battery was $949, the Victron 700 $147, and the battery charger $201. 

@WilliamA On a solar RV site there is a guy who put a Tesla battery in his unit! Apparently those and packs from other electric cars are being used and so you aren't far from reality! Right now I am debating the merits of trying to order a 400 with a pair of the Battle Born Batteries! If they could be swapped in at the factory, I belive the cost difference may be about $1200-1500? Of course that is also going to require a different charging system for optimal life, haha.

SweetlyHome said:

@scottg and @willA I have given this some thought as well.  IMHO it has to do with voltage drop in the TV charge line and the relative voltage of the battery as the battery and TV are parallel.  I applied the current squared times resistance calculation and got roughly a 1 volt drop in 15 feet of 10 gage wire at 10 amps.  The 13 volt alternator output is 12 volts at the battery and fridge at 10 amps draw. I stand corrected if I messed up the math.  The battery discharges trying to hold the voltage up, losing the ability to do so as it discharges.  Is there sense my thinking?

I'm a little late here, but I checked your math for ya, @SweetlyHome..
I used the online calculator.. 
https://www.calculator.net/voltage-drop-calculator.html
..and checked theirs too by looking up the resistance of copper cable, which conveniently is one ohm per 1000 ft of 10AWG cable.  So 15ft is 0.015 ohms, and plugging into Ohm's law, V=IxR:
V=10A x .015Ω = 0.15V
x 2 conductors = 0.30 V drop or 12.7V
at the battery.
Your idea seems like it could be a contributor to a lack of charging from the TV, but I'd say not a very significant one (2.3% loss).