H3 dual battery install

Both 34 (34/78) and 35 series batteries will fit in the H3. I chose 34/78 series, but the install process is basically the same.
The starting point is a bit of the chicken or the egg. Where do you start, battery or tray? I'll start with the batteries.


Sneek peek at what you will need:



Any two batteries will work, but it is best if they are the same type, brand and close build dates. Optima is a standard for aftermarket, so I chose them. No matter which manufacture you pick, the steps will be the same. There are three different types of Optima batteries:


RedTop:
Use this for normal engine starting where an alternator immediately monitors the state of charge and provides energy to the battery whenever it is needed. This would describe most stock vehicles.


Automotive and RV under-hood starting
Heavy equipment where starting is the primary function
Diesel powered vehicles with no aftermarket electronics




YellowTop:
Use this when electrical loads are higher than average, or when the discharge cycle is more than typical engine starting, such as vehicles without alternators. This also includes vehicles with significant electrical loads that may exceed the average alternator output (for example aftermarket audio system, GPS, chargers, winch, snowplow, inverters, drag cars). This can also include vehicles that have a lot of electronics from the factory, such as a minivan with power sliding doors and a DVD player, especially if the DVD player is used when the engine isn’t running.


Racing vehicles without a charging system (alternator or generator)
Dedicated drag racing vehicles
Diesel powered vehicles with aftermarket electronics
Car audio/video applications exceeding 250 watts over the OE system
Vehicles or heavy equipment with inverters, hydraulics, winches or other accessories
Electric vehicles




BlueTop:
The BlueTop starting battery (dark gray case) is to be used when a dedicated starting battery is required and it should never be used for cycling duty.


The dual purpose BlueTop (light gray case) can be used for both starting and deep cycling; it is a true deep cycle battery with extremely high cranking power.


Trolling motors, marine applications with heavy electrical accessories and RVs should use a dual purpose BlueTop (which is both a starting and deep cycle battery)
Use a BlueTop starting battery for marine applications and RVs when the battery’s only function is engine starting




Note: The difference between BlueTop and YellowTop deep cycle batteries is that BlueTop batteries have both automotive (SAE) posts and threaded posts, while YellowTops (other than D31T) only have SAE posts.


If you ever get confused on the color tops just remember: if it has a dark gray case then it is a starting battery; if it has a light gray case then it is a deep cycle (dual purpose) battery.


Reason for the size difference between the 34 and the 35 is that the 34 has more cranking amps.


YellowTop Specs
26
OPTIMA YELLOWTOP DUAL PURPOSE (STARTING & DEEP CYCLE) BATTERIES


MODEL NUMBER D34/78 D75/25 D34 D35 D51 & D51R D27F DS46B24R


PERFORMANCE
Voltage 12v 12v 12v 12v 12v 12v 12v


Cold Cranking Amps @ 0F
750 620 750 620 450 830 450


Cranking Amps @ 32F
870 770 870 770 575 1025 575


Reserve Capacity 120 100 120 100 66 140 66


Capacity (C/20 Rate)
55 48 55 48 38 66 38


Internal Resistance (ohms)
0.0028 0.003 0.0028 0.003 0.0046 0.0025 .0046


PHYSICAL SPECS
Length 10" 9 5/16" 10" 9 5/16" 9 5/16" 12 3/16" 9 5/16


Width 6 7/8" 6 13/16" 6 7/8" 6 13/16" 5 1/16" 6 13/16" 5 1/16


Height 7 13/16" 7 5/8" 7 13/16" 7 5/8" 8 15/16" 8 3/4" 8 15/16


Minimum Weight (lbs)
43.5 37.8 42.9 36.4 26 53.2


Type Post/Terminal
Dual SAE & GM Dual SAE & GM SAE Post SAE Post SAE Post SAE Post SAE Post


BCI Group 34/78 75/25 34 35 51 & 51R 27F S46B24R


Optima yellow top 34/78 batteries:



Since I chose Optima 34/78 batteries, these tray's are designed for Optmia 34/78 series batteries (red, yellow or blue). It is believed that they will fit 34 series as well. If not, they can be trimmed to fit the 34's if an issue occurs.


Plasmathought = 13.75 x 9.75 x 7.75. Made from 16 gauge steel.


Bluetourch = 16 x 10.25 x 7 made from 1/8 steel


Ballistic = 14.4 (16.902 with top bolt lips) x 11.1 x 7 made from 1/8 steel


Ruff stuff = 15 x 10 1/8 x 7 made from 12 gauge steel


ArTech = 15 x 10 x 8 made with 10 gauge steel


While I try to support our sponsors and friends of our site, I am also aware that not all of our members have endless funds. There are many great dual battery trays out there, including the powder coated H3 topped ArTech version. As of this time, the ArTech costs $137.99 +S&H, is a direct bolt in, comes with hardware and no additional work or prep is needed.


For the members that are on a tight budget, I found a low cost option. I found a one man shop that is making single trays that can be bolted together. http://www.plasmathought.com I was able to pick a set up for $37.79 +S&H from him on ebay. It is a simple set up where he sells you two single battery trays that bolt back to back to form a single dual tray.


Here's what you get:



I would advise if you get one to either tack weld the bottoms together or bolt them where they won't rub the casing sides. While trying to mount them it is almost impossible to keep the bottoms together.


Bolts at the top, nothing at the bottom:



They just want to seat themselves as single trays, leaving a small gap at the bottom. This will cause alignment issues at the top if you leave them this way. As part of the prep process, I would use weld through primer on them, bolt them together at the top, then just put a tack on each side at the bottom. Then bed line them. If you tack them at the bottom, the install will go much faster. They come unfinished and without the 1/4 20 hardware.


I etch primed and bed lined them:



With advise from other members, I modified the driver side tray. After studying the pictures of other members installs it was clear that the lid mounting point on the drivers side was hard to get to. I flattened the tab on the body of the tray and bent the lip of the lid upward. It will make it much easier to tighten the lid down and get the battery in and out.


Before:



After:



Side view:



Installed:



After I was done (it was a struggle to get the bolts in from behind, but a breeze to tighten them), I thought about using a standard auto type slip nut and running the bolt in from the front. I'm talking about the type that have the nut on a spring clip that slides over a piece of metal and holds itself in place. No doubt some type of locked in place threads after bending the tab would have made the install easier.


Stock 2006 battery:



Cover and cables removed:



Battery removed:



Bottom tray removed:



Spot welds drilled out, post cut off, bare metal painted in prep of install:

Front harness needs to be tucked out of the way:

Remove the two positive wires, tuck the harness in and reinstall the wires:



Tray installed, I used sheet metal screws. They could be drilled and bolted, but you would have to pull the inter fender well:



Batteries in place:



When hooking batteries together in parallel they should be of identical make, model and of similar age.Most any type of battery separator or solenoid can be used with an OPTIMA. Solenoid with home made brackets. Simple strap steel, bent, drilled, bed lined and mounted:



The important thing to remember is that the charging voltage must be within the limits suggested by OPTIMA Batteries. If you are using an OPTIMA and a conventional battery, your system must charge each battery independently. Remember, some isolators cause a voltage drop, so make sure your charging voltage AT THE BATTERY is sufficient. Continued undercharging of a battery will lead to premature failure and a drop in capacity.There are many ways to connect the batteries. All involve hooking them in parallel (positive to positive, negative to negative. This doubles the current (Amps) and leaves the voltage at 12 volts. You can separate the batteries for use, but not for charging (unless you run dual separate alternators).

Cabling:

Separating them for use allows for self jump starts (if needed after winching) and removes accessory drain from the main battery (large stereo amps, compressors, inverters, etc...).

The need for separating the batteries depends on what you are trying to do. If you just want more amps and battery run time, then there is no need for one. Just wire them in parallel. Both batteries would be used all the time. They will charge at the same time and discharge at the same rate. If you want to control when and how you use the second battery, than you need at least a switch. The switch and soleniod will allow you to seperate the batteries when they are not being charged. You would do this in order to have the second battery in reserve in case there was an issue with the first (jump start yourself) or you can run all of your high draw accessories off the second battery without ever effecting the first. It could go dead, but you could still start the truck from the first battery. The process of switching would be manual. You would have to remember to switch it back and forth. The controller adds automation to the process, but can be used in manual mode like the switch. It offers the added bonus of dual voltage gauges along with the switching function.


Another shot of the complete supplies required:



You will need a separator or solenoid, 2 gauge wire (battery cable, red and black), some type of switch or controller and smaller gauge wiring (16 or 18 gauge) to wire in the switch. You can assemble the control parts or buy a kit. The controller provides a degree of automation to the process. With a switch, it is up to you to set it correctly. There are also controllers out there that include dual voltage gauges. I chose a Tmax controller to go along with my install.


Tmax controller:



The wiring is very basic. You will need to drill a hole in your firewall to pass the wires through:



There are four wires on this kit. Red (primary positive), Black (primary ground), Blue (secondary positive) and green (soleniod triger).





The idea of a controller is that while the truck is running, both batteries are being charged. When the truck is off, the batteries are stand alone and can not draw from each other. The controller has a button to link the two batteries manually. This would allow for either a self jump start or make extra current available when needed. The winch should always be connected to the main top posts (not side posts) of the primary battery. The winch requires that the engine be running and the truck be in neutral for use. This makes both batteries and the alternator current available while winching. All other accessories (compressor, inverter, stereo amp, etc...) are run off the secondary battery.


The H3 was never intended for this type of install. This is a shoe horn install. It can't get any tighter putting two Optima 34/78's in a Hummer H3. There is little room to spare.

Lets just end it with a couple shots of the completed install:

Even buying on the cheap and looking for deals this one really adds up. When everything is all said and done the cheapest I could gather everything that I wanted to use for was still over $500 (ballpark). If I went top end and full price it is easily over $1000. If you have some of the parts or can pick some up used, you may be able to get the cost down lower.


The batteries are the biggest cost. Used are useless. That only leaves new. Places like Pepboys, Auto Zone or even Walmart seem to be less then online and no shipping. Most will price match to online and if you search, there are printable coupons online for percentage discounts off large items. If you know someone that works there, their employee discounts are great and in most cases larger then any other discount you can find. Bring an old core with you and save that charge. I believe the best you will find Optima yellow top 34/78 with all this discounting is still in the $130 range each.


I showed you the cheapest ($38) dual tray out there that will fit in an H3. You could look to have it made local, but I doubt someone could do it much cheaper. You could look used...


You could skip the controller and add it later. Hunner just runs them directly connected in parallel. This works to give you double the current, but you don't get much protection.


I found that searching the web turned up some pretty good deals on switch and controller kits. The Tmax was the cheapest I could find, even cheaper then plan switches. Here is a couple links to a Tmax controller kit that has everything needed to finish off the install. I've watched the prices go both up and down over the last six months.


It is currently listed for a little more then I sent at $115 and I had free S&H.


http://autoplicity.com/products/381...ntent=38168NOFITMENT&utm_campaign=GSNOFITMENT


Here's one with free S&H at $124:


http://www.autoanything.com/car-batteries/69A6229A0A0.aspx


I upgraded much of the kits pieces as I was only looking for the solenoid and controller out of it, but you could get buy with what is included in it. I wanted 2 gauge red and black wire, the kit came with a roll of black 4 gauge wire, that type of thing.


Let's see, cheapest dual configuration, just wired in parallel
1 - Optima yellow top 34/78 at $130
1 - Optima yellow top 34/78 at $130
1 - eBay dual battery tray at $38
1 - Red positive cable $10
1 - Black negative cable $10


Total $318, so I did get it cheaper.


Now remove the cables and add a kit...


1 - Optima yellow top 34/78 at $130
1 - Optima yellow top 34/78 at $130
1 - eBay dual battery tray at $38
1 - Tmax controller kit $124


Total $422 sounds about right.


Upgrades:
1 - Positive battery terminals $15
1 - Positive battery terminals $15
1 - Negative battery terminals $15
1 - Negative battery terminals $15
1 - Red battery cable $10
1 - Red battery cable $10
1 - Black battery cable $10
Cable end lugs and other supplies were another $30.


Total upgrades $120
Grand total (ballpark) $542.


Right back where we started, not a cheep upgrade, but what on a Hummer is. The only other trick that does not bring the cost down, but spreads it out is piece mealing this together over time (and pay checks).

I got the clamp covers from here:
https://www.vtewarehouse.com/

Another place is here:
http://www.remybattery.com/Battery-Terminal-Protectors-C1654.aspx



I changed terminal clamps after I already ordered them and they did not fit the new ones, so I cut them down, hit them with a heat gun to take shape and zip tied them in place. I've had them off and on now a couple of times. I just slide the zip tie off and lift them. I reverse the process to put them back on.

we are lucky out here as the brakes are on the other side and can install a second battery behind the original

Yea, it is a very tight install on the left hand drive H3's. Not much room to spare, but they do fit.

One of the best tech writeups we've had - great job! Really impressed with the detail, pics, etc. Thank you.

Great writeup.....this is one of the mods that i wanna do in the near future.......:thumbs:

Thanks for the awesome write up helped me out bigtime!!!

That is a good write up.

The reason I left mine simple and run together most of the time is for simplicity and less cable runs and connections. I like the added amperage for winching and accessories, of which I have many. When I off road to remote places I simply remove a cable between the two. Then when I hit the pavement I re-connect. One of the great things about AGM batteries is the ability to retain a charge for longer periods of time, especially the deep cycle ones. I manually manage mine.
I build more involved marine systems and use isolation charging devices and multiple battery switches. I run as many as 5 batteries in three banks on my sailboat since I don't run the engine anymore than needed to bring the batteries up. I have my sensitive electronics isolated from the designated cranking battery, which is also deep cycle and has more amps than a plain cranking battery.
There is an inherent drain on multiple batteries setups anyway and I prefer less cabling when possible.

great writeup!

Price isnt too bad and I dont think its off par with other vehicles. Most of these parts would be needed by any other vehicle. I would love to do this one day with a high output alternator too.

Looks like I know what my next mod is going to be.

Great write up!!!! Thanks!

Just a minor update... I was asked about the ground wire in the back of the tray area. I did not move it. It sat between the installed trays and did not require any action on my part. Look at thread #2, third picture down, you can see it there.

Great write up. I've reviewed it before but going over it again to make sure I have all the parts needed. Going to try and convince the wife that I need 4 more arb 7 in lights attached to my Gobi Ranger. The Gobi looks so lonely......lol