- 2,052
- 57
- 48
- Location
- Milford / Michigan
I wanted to post this thread showing how I fabricated up an auxillary battery box for my 12 volt system on my Deuce. I have a Delco 10SI alternator mounted above my factory 24 volt alternator to run 12 volt accessories. My design was to have a dedicated 12 volt system separate of the 24 volt system so I could operate lights on the truck while the engine is off and not worry about draining my start batteries. This would be handy in camping situations where I can power an inverter, power a radio in the truck (which I do not currently have because I don’t have that part engineered as to where I would put one in a location that looks good), or operate 12 volt lights on the truck (Currently I have two side “wing” lights under the front of the box that shine forward and two lights in the back that act as backup lights. I would like to add something in the front also, but am concerned on the appearance and do not want it to look like the lights are supposed to be there and not an add on).
Before I started building, I had some specifications I wanted to follow:
The project turned out very well and am pleased with the location of the batteries. When I put power to the excitation wire of the alternator the voltage was 14.2VDC in all batteries (because they are wired in parallel). I wish I had more pictures, but these are the only ones I can get at the moment. It gives you a good idea of how I did it and how it looks after it is done.
Before I started building, I had some specifications I wanted to follow:
- Quality workmanship/design, appearance, safety, form fit and function. That pretty much explains it.
- My one 6TL battery died, so I ended up finding two group 31 batteries to replace them with. I was not able to put them into my current plastic battery box because I was lacking about a quarter inch. I located another plastic battery box that must have been made by another military vendor that was just a little different that allowed me to get the extra hair of room that I needed. As many of you know, there is more than one company the military contracts to make parts. This current battery box looks a little bit better built than my previous plastic box. I’m sorry, I don’t know if there was a cage code or not on the box. I noticed this current battery box had a tighter radius on the corners than my previous battery box. Anyway, with the extra space in my battery box, I had the room to put a deep cycle battery in there. It worked well because I everything fit nice and tight. I had to lengthen my battery hold down bolts because I put a piece of wood under the batteries so I did not have to modify the original battery box (box was made to support two square batteries, not 3 rectangle ones). I also made my own battery hold down bar out of 3/8” rod.
- Charging and Battery Capacity. Deep cycle batteries like a nice slow charge and a nice slow discharge to maintain maximum battery life. This poses a problem if I operate my 12 volt generator that converts 12vdc to 120vac at 1600 watts. It draws a lot of power. I’m sure I would not use it often but it would be nice to engineer my system to help support that. To support the heavier load, I would need more deep cycle batteries and/or a higher capacity alternator. Another concern if I had one battery and a high capacity alternator is charging the battery too fast that would limit the life of the battery in some way. My current Delco 10SI alternator is a 63 amp. That seems like a lot to be thrown at one deep cycle batter. The only logical option is to add more deep cycle batteries to my system. This would allow my alternator to still charge my batteries and support a fair electrical load and also distribute the charge between three batteries instead of just one. That way each battery would receive about 21 amps of charge instead of one getting 63 amps.
- Where to put the extra deep cycle batteries? After lots of thought I decided to put them in the area above my fuel tank. This would give me a total of 3 deep cycle batteries. I carefully placed a battery on top of the fuel tank to see how much room I have and where I would mount it. Long story short there is more room between the floor braces of the box and I mounted the batteries between the braces for maximum clearance. I build a battery tray out of 1.5” angle iron and mounted the rear of the battery tray to the front edge of the cargo box and the rear mud flap. I designed it to be bolted in and not permanently welded in to be minimally invasive. It also provided me with a hinge effect that allowed the front of the battery tray to tip down for easier installation of the batteries given it was a tight space. Then I placed a 3/8” stud to come down in front of the tray that connected the cargo box to the battery tray. This gives me three mounting points to support the battery tray under my cargo box.
- Going back to my first specification on this list is quality workmanship/quality and appearance. There is plenty of room between the tops of the batteries and the box that they should never short out and plenty of space between the battery tray and fuel tank for allow the truck to flex off road. I can’t see any problem there at all. Everything is mounted very well and very sturdy. I then built a sheet metal cover to mount on the battery tray to cover up the batteries for appearance and protection. I love when I get done building something and to me, it looks like it was supposed to be there right from the military. This cover that built then incorporated it into my 3 color camo scheme was the icing on the cake for me.
- I connected the batteries with 4 gauge cable wrapped in split wire loom (the wire loom found on many production cars) and then cable tied to prevent chafing. Don’t forget, the front edge of the cargo box could lift up from the frame when flexing off road, so consideration was taken when I ran the wires.
The project turned out very well and am pleased with the location of the batteries. When I put power to the excitation wire of the alternator the voltage was 14.2VDC in all batteries (because they are wired in parallel). I wish I had more pictures, but these are the only ones I can get at the moment. It gives you a good idea of how I did it and how it looks after it is done.
Last edited:
