daking Posted November 3, 2014 Share Posted November 3, 2014 I just finished the mount for my rear under bed battery. The mount is supper strong, can't budge it, so It'll support the battery no problem. I had to weld extra supports to stiffen side and forward. I move the battery to rear on most of my off-road trucks. Better weight distribution, Cleaner engine bay. I'll be running 0/1 Welding cable to the front. Welding cable has a high copper content, un like auto grade cable. There will be a rear emergency cut off switch too, I'll put a distribution block up front for the power. Main input from battery, large gauge out to wench, 8AWG to starter, 8AWG to factory fuse-block, and 8AWG to custom fused relay center. And a fused 8AWG cable from the rear battery, popped up to the rear behind the seat for audio. Image Not Found Image Not Found Link to comment Share on other sites More sharing options...
dscowell Posted November 3, 2014 Share Posted November 3, 2014 Interesting! I like the idea but what about mud or water getting up there? Link to comment Share on other sites More sharing options...
yellaheep Posted November 3, 2014 Share Posted November 3, 2014 Wondering about operating a winch with the battery mounted that far away with such big cables....... Wouldn't the battery work harder and the draws be increased when winching? Link to comment Share on other sites More sharing options...
Jeep Driver Posted November 3, 2014 Share Posted November 3, 2014 Wondering about operating a winch with the battery mounted that far away with such big cables....... Wouldn't the battery work harder and the draws be increased when winching? I mounted my battery in the trunk of my Camaro many years ago and used the same cable as he did........never a problem. And this is common practice among hot rodders. OP- since you went to all that trouble.........I'd have gone to a large deep cycle battery. Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 3, 2014 Share Posted November 3, 2014 Interesting! I like the idea but what about mud or water getting up there? Yeah, I think I would have mounted it in an "enclosed" enclosure, like an aftermarket battery box, something like the Chevy SSR and other trucks do it to keep it out of the weather. Also would have used a non-venting battery like the Optima. Link to comment Share on other sites More sharing options...
Incommando Posted November 3, 2014 Share Posted November 3, 2014 Wondering about operating a winch with the battery mounted that far away with such big cables....... Wouldn't the battery work harder and the draws be increased when winching? I mounted my battery in the trunk of my Camaro many years ago and used the same cable as he did........never a problem. And this is common practice among hot rodders. OP- since you went to all that trouble.........I'd have gone to a large deep cycle battery. And did you then run a winch off of the front of your Camarrow? :) It is used in drag racing for better weight distribution and may help add a little weight to the too-light rear of the MJ. I don't think I would do it that way in the terrain that I wheel in but we do not all live in the same climates. At minimum I would have to use a battery box as mentioned above to protect against exposure to mud and other hazards around here like snow,ice, and road salt. But I, too, would wonder about the effects on a winch. Link to comment Share on other sites More sharing options...
yellaheep Posted November 3, 2014 Share Posted November 3, 2014 Yeah, nothing similar about the Camaro battery install and an off road truck with a winch. The camaro relies on the battery for a quick turn of the starter. I'm talking about sustained pulls to un-stuck one's MJ. I've run hard core trails and been massively stuck and I was able to get an Optima smoking and melted the led terminals..... and the battery was in the stock location with stock gauge cables. I can only imagine the loss in performance and taxation of the power having to power a winch through 20' of large gauge welding cable. This required A LOT of winching....... using my Warn 9500....... and two other winches from above me...... :nuts: Hot winches and batteries make ..... "unique"....... smells...... :yes: Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 3, 2014 Share Posted November 3, 2014 The larger the cable diameter, the less resistance. And the longer the cable, the more resistance per foot. So if you know the manufacturers ohms per-foot resistance of the welding cable you are using, the total length, and the load of the winch, it's pretty easy to calculate. Link to comment Share on other sites More sharing options...
Jeep Driver Posted November 3, 2014 Share Posted November 3, 2014 The larger the cable diameter, the less resistance. And the longer the cable, the more resistance per foot. So if you know the manufacturers ohms per-foot resistance of the welding cable you are using, the total length, and the load of the winch, it's pretty easy to calculate. That's correct. Also- Welding cable may have 50-60 strands of fine wire wound to make up the cable, whereas the 4g cable that everyone uses for automotive may have 5-6 strands of heavier wire wound to make up the cable. The 10-11ft required to run from the battery to the firewall may actually have LESS amp draw loss than the 3ft of 4g cable. These guys are concerned for nothing. Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 3, 2014 Share Posted November 3, 2014 Also correct. That's one reason (besides flexibility) that using wending cable for mains cables is always a good idea. Link to comment Share on other sites More sharing options...
Pete M Posted November 4, 2014 Share Posted November 4, 2014 while we're on the subject, if anyone might be wondering exactly why lots of little wires work better than fewer larger ones, electricity actually flows along the outside surface of a wire. the more tiny cables you have, the more surface area you have. :thumbsup: (this of course assumes I'm remembering that class correctly. :yes: ) Link to comment Share on other sites More sharing options...
daking Posted November 4, 2014 Author Share Posted November 4, 2014 Thanks everyone for your all's ideas and comments. I go through many design aspects when doing a project, such as a battery relocate. The 2 major concerns is battery mount and securing, and electrical. Battery Mounting: This includes location as well mounting. The further back the battery, the better for weight distribution. Lets say the battery weighs 50#. If you put the battery exactly over the rear axle, the effective weight is #50. The further back from the axle, the more the effective weight. For example, putting a 50# battery ~3ft behind the axle may net an effective weight of #65. So removing a 50# battery from the front and putting as far back, actually equates to losing more then #50 in the front, due to weight transfer. So finding a safe spot as rear word as possible is what I look for. I also tend to mount on the passenger side. The mount needs to be extremely solid, any vibration will cause failure in the future. So I opt to use cross braces as well as down hangers. Keeping the battery tight in the mount is important too. This install will have 2 methods of securing the battery to the tray. This way, If one fails, or something pop's there is a 2'nd secure mount. On the concept of moving weight to the rear, on this Comanche. A 4X4 will handle better if the front and rear have good weight. The Comanche truck is light overall due the uni-body. But the rear is very light, when compared to other trucks. AMC / Chrysler knew this, that's why the "brake proportion valve " is on the Comanche. It's not a nifty feature they put on for sales, its a safety device. It was added cause in testing, during hard braking, the light rear would cause issues. It was a solution to a problem. I'm relocating many parts to rear to help with balance. Including, Battery, Air tank, Air-compressor (s), Transmission cooler, spare tire, and some other little items. Electrical: When relocating a battery, there are many things to take into account for the electrical. Including loads, main cable safety, ground, and so on. First the loads, In order of power usage: 1.Winch 2.Starter 3. Alt (yes, you need to insure the alt as good connection with battery) 4.Fans 5. factory wiring (if you have a sound system, that would be ~1 to 3 in this list depending on amp's. In my case, I'm running a dedicated cable to the battery from behind the seats) Winch, this was a concern for me. A winch will suck some real power, and it'll heat up. Both the electrical cable and motor will heat up fast with usage. As a winch heats up, its power to work ratio gets worse. It'll take more electricity to run a hot winch then if it was cool. Picking of the main line cable was based on winch usage. Welding cable is made from near pure copper, and is made of very fine strands. So it conducts electricity extremely well. The size the cable I went with is about 5/8th thick. It's much larger then the cable that came on the winch. In my application I don't plan on pulling many people out. ( I didn't buy the winch for me, I got it for the others like Hummers that get stuck, come on man, Comanche don't get stuck :) ) If winching is going be used heavily then maybe keep a front battery. But, also keep in mind, many add a winch the the rear, so they are running on a long run. To be honest, I'm not sure of the long run effect yet. This is my first rear mount battery with a front mounted winch. But I feel really confident the cable and design will be fine. The starter is the normal front big load on a truck. The lines feeding the starter will all be larger then factory. The alternator is actually something many skip or don't think about. Well it's not taking a load off the main feed, it is dumping a load. It's important to insure proper cable size for distance. In this build, I'll run a larger cable from alt to a distribution block in the front. The distribution block will have the main cable, Alt, winch, factory fuse block. On another build I did, I had to run 4AWG from the ALT, directly back to the battery location. Due to the amount of juice the alt pumped, and for the kill switch. On that truck, cause I race it, it has a battery kill switch. But when testing, I found the Alt was making enough juce the keep the 600+HP HEMI breathing when the kill switch was engaged. So I had to run the alt line to the rear too. No plans to do this on the jeep. It just adds failure point's. Grounding is actually the one main thing people forget or don't focus on. If your positive cable is 3" thick, and your ground is some lame cable, barely bolted, you will have issues. This is very common in car audio installs. The installer will focus on positive power, thick cable, slick distribution blocks, pure copper fittings. Then they'll run some cheap ground cable to a bolt.. lame. I actually apply more effort to grounding then positive. In this build, there will be a large cable bolted the frame (uni-body) in the rear near the battery. And I'll be running a smaller ~4AWG cable to front the a block mounted on the body. Grounding cables will connect the body, engine and transmission, to insure a strong solid ground across the truck. Link to comment Share on other sites More sharing options...
benjy_26 Posted November 10, 2014 Share Posted November 10, 2014 Wait... I always thought that the smaller the gauge # signified a physically bigger (thicker) cable. I'm running 2AWG welding cable for all my major grounds and power leads (starter, alternator to battery, et al.) and it is some seriously big cable. Someone please enlighten me. Link to comment Share on other sites More sharing options...
Dando Posted November 10, 2014 Share Posted November 10, 2014 Yes the smaller the gauge number thearger the actual wire. Random google image to help explain. Link to comment Share on other sites More sharing options...
Pete M Posted November 10, 2014 Share Posted November 10, 2014 just to clarify, that chart applies to the overall size of the entire cable, not the individual strands. :thumbsup: Link to comment Share on other sites More sharing options...
benjy_26 Posted November 10, 2014 Share Posted November 10, 2014 Thanks guys! Link to comment Share on other sites More sharing options...
daking Posted November 11, 2014 Author Share Posted November 11, 2014 Here are some of the engine bay pictures. Main Distribution, relay center, fuses, circuit breaker. Image Not Found Image Not Found Image Not Found Link to comment Share on other sites More sharing options...
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