How-To Battery Upgrade from Group 27 to two GC2 6 Volt

JeepCherokeeTABman

Hey fellow Tab owners as I started to boondock it was really clear the supplied group 27 battery wasn't up to the task. The original interstate battery had 88ah and would get me through 2 days max and that is with good solar. The upgrade raised me to 210ah which should allow me to boondock for ~5 days before the batteries start to get beat down below the 40%-50% range and maybe a bit more with my solar on some sunny days.

Here is a parts list of what I bought:

Costco GC2 6 Volt Batteries (Interstate) @ $79 each

Camco Heavy Duty Double Battery Box with Straps and Hardware - Group GC2

Stromberg Carlson 2020-Jr Bottle Rack for 20 Lp Tank

Cable for 6 volt to 6 volt connection

SNUG Fasteners for connections

Here are the steps I went through to make the change: 

The process was to first remove the existing box and cut the LP Bottle Rack out of the storage area

Because the fit is so tight with not much more than 1/2 of extra space you will need to trim down the battery box including the plastic handles on the ends and cutting down the lid. I used a cut off wheel which made the cutting fast and easy.

Route the straps and attach the battery box. I used the original self tapping screws from the group 27 box. 

 

Next I attached the new LP hold down which is far more compact than the original one and sadly they welded the original one so I had to cut it out anyway. 

And the finished product all strapped in! I hope you all find this useful and please share other ideas you might have as I am always looking for a new project LOL

pthomas745

That is certainly a nice setup.  One thing that seems to be missing:  what are you using to monitor your battery?  How did you determine that the previous battery was not working for you even with solar?

rh5555

One comment for others looking to follow this mod:  The Costco golf-cart batteries are wet-cell batteries, whereas the golf-cart batteries installed in our TAB400 are AGM batteries.  There are several advantages to AGM batteries that may make you think they are worth the extra cost:

1. They require no maintenance (no acid levels to check)
2. They require no ventilation (not a problem in this install)
3. They can be discharged by 80% before recharging with very little loss of overall capacity, so you can boondock longer before needing to recharge.  Usable capacity 180Ah vs 105Ah.
   
4. They can be recharged much, much faster (with an appropriate charger) so you can recharge them from a generator in a couple of hours
   

ontheroad

@JeepCherokeeTABman...we did the same mod..we had a local welder cut out the propane brackets and reweld them in the same spot as yours... NuCamp really needs to relocate that bracket...we gained so much extra room for storing some pads that we use under the stabilizers...hubby has also made a lightweight removable shelf over the dual battery box...

JeepCherokeeTABman

Regarding monitoring batteries I am using the Victron Energy Shunt bluetooth monitor. I am looking for as little compromise as possible on running TV, Laptop on 300watt inverter, and a secondary 30 quart fridge.  The 88ah battery was a 2 day max with the battery following below 11 volts on 2nd day. 

JeepCherokeeTABman

AGM's are a great upgrade and I thought about that but at this point the cost is more than I wanted to absorb. These are the ones I considered if I was going that route VMAX XTR6-235 6Volt 235ah Golf Cart Battery AGM GC-2

 Home built Lithium looks to be the best next step for me though. Although the fast charging of AGM and your comment about generator charging speed is super cool. 

pthomas745

@JeepCherokeeTABman the reason I asked about  your monitoring is that only 2 days with your 88AH battery (which means 44 usable amp hours) just sounded a bit off.  Your laptop will use about 4 amps per hour, and the TV only about 1 an hour.  How many watts does your extra fridge use? 

JeepCherokeeTABman

I believe my supplemental is taking about 3.5 an hour but I do get your point. I know there are some good articles on here that outline the amp hours on items such as the heater and fantastic fan. I based my upgrade on what I experienced when boondocking and the battery meter showing me voltage that was in the 10volt range. I likely have a lot to learn about these but I think any way you cut it more amp hours is better   

4ncar

@JeepCherokeeTABman: I think your well on your way. Sometimes overthinking only makes it worse.  I made the upgrade for this season, and though I have measured & made a spreadsheet calculating expected use & draw, have a BMS...real world application is always, imho, is the true litmus test.