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-   -   Dual Battery Install W/ Voltage Sensing Relay (http://www.risingsun4x4club.org/forum2/showthread.php?t=11009)

rover67 10-06-2009 08:55 PM

Dual Battery Install W/ Voltage Sensing Relay
5 Attachment(s)
After a bunch of reading and some stupid questions I decided to do the dual battery install using a marine voltage sensing relay, or VSR. I liked this option because the thing is rated at 300amps continuous and something like 1500 for less than 10 seconds. It also won't join both batteries untill the main battery voltage comes up, and has a manual connect/disconnet switch on it. I was able to find one on ebay from a marine supply company in florida for $150

I figured i'd write it up since I haven't seen a write up on one of these before.


I also am using a National Luna Dual Battery Monitor to monitor both batteries. I figured it'd be nice to know how low they were both getting and I liked the idea of being able to monitor charging voltages. I got the recessed one from Paul at Equipt since I figured i'd install it in the fuse box cover to keep it out of the way and to keep clutter down. $75 for this little gem.


For the wiring, I kinda over did it by accident. I was going to buy 1ga cable from a marine store, get all the nice ends and shrink wrap and do them up myself, but when I looked at the total for that it was close to what I could buy them made for.

I had bumped into these folks online and thought that their cables looked nice, and I am always stoked to get something professionally done in the mail for about what I coulda done it for.


They had a kit that came with a new fusible link (spare for the tool box) REEEAAALY beefy 1/0 main cables, Mil spec battery terminal clamps, and all cables to replace the grounds on the truck. I called them and told them what extras I needed and they put it together for me in no time.

Their standard FJ60 Cable kit with fusable link and battery clamps
Additional 84" 1/0 gauge cable with red shrink wrap and 3/8" lugs on both ends (Driver Batt to VSR)
Additional 16" 1/0 gauge cable with red shrink wrap and 3/8" lugs on both ends (Aux Batt to VSR)
Additional 36" 4 gauge cable with red shrink wrap and one 1/4" lug and one 3/8" lug (Alternator)
Additional 11" 1/0 gauge cable with black shring wrap and 3/8" lugs on both ends (Driver Batt Gnd)
Additional set of battery post clamps

They charged me about 150 bucks for these additional parts, and I got their FJ60 kit. When I got the cables I realized that 1/0 was almost retarded big. Part of me didn't really mind since I had a few kinda long runs that could be loaded while winching. If I were to do it again i'd really skip down on the main cable gauge. When I worked it all out, the $330 I paid for cables was probably 60 bucks more than what i would have paid to do it myself.

Battery Trays were from the stainless trays place.


The layout was kind of non standard i'd say. One of the things I did not want to change was all of the cable routing I had already previously set up. Basically everything went to the passender side before. All the Auxilliary stuff like the Winch, fridge, CB, HAM, Subwoofer Amp, and stereo was wired over there as well as the trucks main wiring. I really did not want to extend those cables and wires. Sooo I decided to put the Auxilliary battery over there and hook all of those Aux items up to it. This made it so none of those cables or wires had to change. The main battery had to move to the other side though. So What I did was run the main positive cable from it to the VSR and hook all of the "lifeline" stuff from the truck, and the starter cable up to it. I essentially used that main post on the VSR as the main post for the truck. It got crowded but it all fit, and even though all of this crap was hooked up really far from the main battery, it was through a 1/0 cable.. so i figured it was fine.

Tho other side of the VSR just hooked up to the aux battery with the big 1/0 cable again.

So here's a bunch of pictures. This first one is my schematic. I am at home, so I drew it up on a peice of paper and took a pic of it. pretty cheap, but all I could do.

1. Schematic
2. Old battery (it's 10 years old)
3. New cables
4. New cables
5. New tray, relocated overflow tank

rover67 10-06-2009 09:03 PM

5 Attachment(s)
More pictures...

First few are my bracket for the VSR. My aluminum welding is not so great.. been toooo long.

Last few are the VSR. It has wiring to allow for remote control for emergency starts. Basically it manually closes the relay even if there's no charging voltage present. I didn't wire this up because I figured it'd not be too hard to hop out and flip the switch that it has on it. For winching the engine will be running and the solenoid will be engaged.

rover67 10-06-2009 09:06 PM

5 Attachment(s)
More Pictures..

The VSR with the wires hooked up to it, and both batteries in and wired up. Tight squeeze in there now, but it all fits.

Uncle Ben 10-06-2009 09:10 PM

Great setup! Essentially the same as the National Luna complete system. Thats the system I have and I like it for the most part. The only time it doesn't work flawlessly is when my big group 31 aux batt is heavily discharged it will drop out of combined charge too early. With the NL monitor it's easy to spot the shortfall at a glance and manually over ride the "brain" so both batts are again linked and charging. Good choice, obviously based on research! :thumb::thumb:

rover67 10-06-2009 09:15 PM

2 Attachment(s)
Last pics..

Picture of the 4ga cable to the alternator, and the Dual Battery monitor.

I really like the way it turned out, but the cables again are kinda overboard I think. I also don't really want ot add it all up. Definitley more than the $375 for the NL kit from Paul, but it will handle winching, and has beefy cables. I feel like I never have to worry about it.

I did make a few compromises.. It has no fuses (god help me if there is a bad front end collision that severs cables), and the radiator overflow bottle and VSR are just mounted to the support braces for the battery trays. Not ideal, but it works, and they are pretty stout. We'll see if they crack.

So, the truck starts REALLY fast now, and the fuel pump runs faster and quieter. the fans also run a little faster. I'm thinking that the ground cables were in seriously bad shape.

Now I never have to worry about the battery going down at camp, or worry about my 10 year old optima giving up the ghost.

Anyways, hope ya'll enjoyed the tour.


MDH33 10-07-2009 10:01 AM

Great Job Marco! :thumb:

I still need to come up with a better solution for the relocated overflow bottle in my 60. want to weld me up a mount?? :beer:

rover67 10-07-2009 10:05 AM

Sure, just let me know what you are thinking. I ditched my headlight washer bottle and there is ton of space over there. Either that or if your headlight washer bottle is in good shape convert it to an overflow bottle...

MDH33 10-07-2009 10:12 AM


Originally Posted by rover67 (Post 121175)
Sure, just let me know what you are thinking. I ditched my headlight washer bottle and there is ton of space over there. Either that or if your headlight washer bottle is in good shape convert it to an overflow bottle...

Yeah, I pulled out the headlight washer too, but I still have all the smog stuff in the way on that side. Right now I have it over on the PS fender via a booty fab bracket which isn't ideal.

rover67 10-07-2009 10:17 AM

snap a pic of it, i'll make a little bracket if you want. Mine's pretty busy on the passenger side, but I might be able to mock it up

Jacket 10-07-2009 10:43 AM

Sweet. Now you can hook up that electric blanket that Mead has always wanted....

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