I used gel cells when they came out for my sailboat to eliminate gassing while enclosed in a confined space. (remember the Hindenburg) hydrogen gas + sparks! I was impressed with their serviceability. So started using a pair of them in my Dodge Cummins and one in my 06 Hummer. I never got around to adding the second one in the Hummer until I got the 08 Alpha. I was going on more extended trips farther from home and help.
They were not tolerant to high voltage DC unregulated chargers. Cooked them. They did work well with a properly regulated alternator.
When regulated chargers got developed that could use the proper charging required these did ok.
Along came AGM absorbed glass mat with some of the same features and more. No gassing, no leaking acid, do not corrode terminals, deep cycle, faster charging rate, resistant to vibration and can withstand the submersion in water and not short out. All of the great features of these batteries are also good for a bouncing offroad vehicle.
They are also good for more cycles of deep discharge whereas a starting battery is designed for short discharge and continuous maintenance recharge in a vehicle. This would work well in case of a drowned or dead engine you should be able to winch to at least a dryer place to work.

I used the battery vent hose for the cable run from the winch. I really don't need to spray the batteries with crap thru that thing and I don't think the bugs and dust insulate it all that well inside that thin plastic box. I put a reflective coated neoprene pad on the side of the battery closest to the engine and it was long enough to cover the ends. It is still the same distance from that wiring harness the battery tray was. I did not push them over but did release them from the tray and removed the plastic tray. The battery is two inches closer to the engine than it was.
I decided to go "KISS" (keepitsimplestupid) on this for now. NO switch, but I can just remove a terminal or swap the main lead.
I want both charging all the time, more amperage for winching and can always disconnect one jumper to save one hot if I'm winching with the engine dead so I have a gauge on what to try next before reconnecting it. That eliminates extra cable and simplifies the setup.
I used the screw terminals for the jumpers between batteries and attached the winch to those. I used SS nuts, not the wing nuts. I have now updated those to 2 Gauge 7 1/2 inch instead of the 2/0 which allowed me to bend them in over the batteries. I used welding cable with heavier insulation and fine flexible wire. I used copper lugs that were tinned with closed ends and a special crimper with shrink wrap. I also have an open pos and neg terminal for my rear winch connections.

Exide Marine dual terminal deep cycle.
CCA 750 @0* CA/MCA 950 @32* more like Arkansas weather!
compared to AC Delco
CCA 590 no listing on the battery for CA/MCA

I replaced those OEM main terminals. I decided to just torque one past the point I consider safe to see if it would ever tighten enough that I could not move it. It begain to buckle underneath and actually loosened it. Snip!
I have now Hunnerized the new main lead terminals. Universal ones don't fit the negative tapered post. Those first ones I used in the proto-type are those "emergency" style you find everywhere. You will have an emergency if you depend on that crap. They do not even provide a tapered nut anymore, so it does dig into the lead before it gets tight! I drove the 60 miles to my Brother-in-laws electrical automotive shop. You think I'm pickey!!! He has a great selection of special fittings and several high tech crimpers. We used the hydraulic ones and they are CRIMPED completely and evenly all around the diameter. Not a screw that pierces the wire or pushes on a tiny plate. These gives the full current carrying capacity of the gauge of wire being used.
A secure physical connection insures a good electrical connection.
Looks like a candy store!





This was before the heat shrink was slid up flush and heated to show the crimp. It also shows the "emergency" type terminal that just are not right for this application.

We had to make some custom dies for the hydraulic crimper to keep from distorting the fittings. We did it in two stages with two dies. The one that came with it are for larger wire and terminals. Like for John Deere's. That of course required us to machine our own dies on a verticle milling machine. Another excuse to play with neat machines. He was busy so I got to use his special tools. I used lead coated copper fittings with closed ends and sealed them with shrink wrap lined with adhesive that when shrunk really seals things up. So I did not pursue the marine grade tinned wire.

This is the progress for now.

This is a detailed install and so was written for someone considering doing it. It is not "lite" reading.
Unique to these batteries is the two holes between cylinders that on top is capped off by the thickness of the blue top piece. The difficulty on the H3 using the existing base for the second battery, the position closer to the engine, has for some reason a large hole right where I needed to drill. Then the other hole would line up with a contour edge. I center punched and drilled that one. Then the problem is the bracket is formed down to the fender liner. That leaves a folded seam where these two come together and would not work to drill thru and install washers and nuts.
I went with "J" bolts found at any autoparts store except I made them "L" bolts by straightening the ends to a level position. Use at least 5/16 that was as big as I could find. Here comes the most "tecknackle" part. Caution this involves duct tape! I stuck them down in the two holes in the base and taped them so they would stay oriented with the L under the base plate. I just used spin on nuts, lock washers and locktite on the top to keep from turning them. I left the threaded part a little long. Im considering running a brace across the top of the batteries just for good measure. Hunnerized!
The battery closest to the fender I used a long bit clear down thru the fender liner. The liner is not against the fender so would not allow for tightening. I used a die grinder to make a hole for a socket to fit up in there to hold the nut. I use stainless for everything since I had most of it and it will allow for easy removal. I used 3/8 all-thread and put nylocs on the bottom end to hold that in place and was able to use them on the top while holding the bottom. It's a stretch to reach!
The base plate I had to bend down a tab with a hole in it for a wireloom connection to get it out of the way. I then added some neoprene on the slight edge since it is too short and strong to bend.
The SS ubolt in the middle was my first attempt to install a battery hold down strap, fail! Not enough room.




stay tuned a work in progress..................
Found a possible switch if anyone goes that way. It's inclosed so will be protected. I found another place that indicates those panels like you see in the top can be removed on any side to allow the wires to go in.

http://www.wholesalemarine.com/pc/S-...with+****.html

Here is another for a little more money but not as boxy.
http://www.westmarine.com/webapp/wcs...ial/20/0?N=377 710 1641&Ne=0&Ntt=Batteries &Ntx=mode matchallpartial&page=CategoryDisplayLevel1&isLToke nURL=true&storeNum=5002&subdeptNum=9&classNum=29

Link for terminals
Electrical Connectors & Terminals For A Variety of Projects - Waytek Wire

 

Thanks for posting! Now I'm trying to figure out how to get a good connection with what's available at autozone. My connections look like crap. Is there a place that will do it for me? Any repair shop or should I look for some placed specialized.