Dual battery install: DONE! - Uh, Sort of...

Martinjmpr

Wiffleball Batter
So after several months of thinking and planning and pestering other board members (Thanks, Jelorian!) my dual battery install is done. Well, SORT OF done. Done in the sense that the 2nd battery is installed and seems to be charging. I still need to "clean up" the engine compartment (no, I'm not driving it with all these wires all over the place, I have a separate DD!) I also have to get a power source to the interior of the truck and then put in my dedicated 12v power outlet for the fridge, and will probably run another power wire for my 2m HAM radio.
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Anyway, I thought some of you with GMT-800 vehicles might like to see my writeup, so here it is. Nothing too fancy, I basically copied Jelorian's but I did just a few things differently.
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On some dual battery setups, the hard part is figuring out where you're going to shoehorn in a 2nd battery in an already crowded engine compartment. But, since the GMT-800 trucks had an option for a 2nd battery on the passenger side near the firewall, that part is easy: You just get the factory battery tray and replace the brace on the fender with the battery tray. It's a straight bolt on.
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As you can see from the photo, I put the crescent-shaped hood brace back on because I wasn't putting the battery in right away (I got the tray back in June or July.) In order to put the battery on, though, that brace has to come off.
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Next I had to figure out where and how to mount the isolator. I went with the same 200a "Stinger" isolator that Jelorian used. I was nervous about drilling into the firewall (because I wasn't sure what was behind it - didn't want to hit a heater line or something) but it was no big deal. Instead of using sheet metal screws (which I was worried would loosen), I went with "jack nuts." For those who have never used jack nuts, they're pretty cool. Basically it's similar to the idea of a molly bolt, you drill a hole, then put the jack nut into the hole, then use a special tool to expand the back of the jack nut which then grips the sheet metal. In essence, it puts a nut on the "blind" side of a piece of sheet metal that you can then put an actual screw or bolt into.
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Located where I wanted the holes and drilled for the jack nuts:
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db1_zpsb3k9fdyf.jpg

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Jack nuts in place:
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Once the jack nuts were in, I bolted in the isolator using machine screws, washers and lock washers.
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Once that was done I turned to my cables. I got 20' of 2AWG welding cable from a local welding shop and some large ring terminal ends. I don't have shrink wrap, a soldering gun or any fancy crimping tools...but I DO have a bench vise!!
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I'll bet I use the vise more than any other tool I have! It's awesome for having a 'second set of hand' to hold onto things while I work on them. Got the ends crimped on...
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Then sealed with electrical tape...
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I know some of you use shrink wrap but for me the "redneck" style tape will work.
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My biggest expense (and the one thing that kept me from getting this done months ago) was sourcing the battery. I went with this from the local Batteries + Bulbs outlet.
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db7_zpsnx2svztv.jpg

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It's a group 34/78 (i.e. it has both side AND top terminals) deep cycle AGM, rated at 68ah. That's quite a bit more than my starter battery (also an AGM) which is rated at 55ah. It was very expensive (about $280 OTD) and while I was sorely tempted to go with a cheaper battery just to get this done, I thought, "No, I only want to do this ONCE." The battery fit perfectly in the tray.
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On the "starter battery" side instead of using a quick-release (as Jelorian did) to get enough extension to reach the positive side terminal (it's kind of buried in there!) I used a marine terminal on the top terminal of my 34/78 starter battery.
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db8_zpstzlw9tbm.jpg

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The reason I went with this was simple: Because I already had the marine terminal adapter. The only 'downside' of this is that I did have to remove the metal rod brace that runs diagonally across the top of the battery (GMT - 800 owners will know what I'm talking about.) I don't really know that the brace is even necessary. If I decide to use an extended side terminal adapter as Jelorian did, I can put the brace back but for now I think this works.
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You can also see that I wrapped the positive cable in red wire loom. Not really "needed" as the 2awg wire has a very thick insulator, but I wanted to be able to tell + from - at a glance and since the cables were all black, this was the best way to do it. It also lessens wear and tear on the cable.
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Hookups on the "house battery" side. The Stinger has 2 large posts that are for the positive connections to each battery and two small posts. One of the small posts goes to ground and the other goes to a powered circuit, to open and close the switch. It doesn't matter which one of the small terminals is used for ground and which one for the switch, they're interchangeable. In this photo I've connected the + cables but not the - or the switch to the Stinger. As you can see I used the Blue Sea side terminal fuse holder, just like Jelorian. I used 150a fuses on both ends.
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db9_zpspfigixzu.jpg

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Final setup of the house battery with all wires connected. If I was more picky I might have used black wire for the ground connection and red for the power connection, but I had a bunch of yellow so that's what I used. :sombrero:
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A few notes about this: I used an extended side terminal bolt on the negative side, that had another bolt on the end of it. Both the negative/ground battery connection and the negative wire to the Stinger are attached to the outer bolt. The negative battery cable is also a 2awg welding cable with a crimp-on ring, the only difference is I wrapped it in black wire loom rather than red. The yellow wire that runs from the negative terminal to the stinger uses ring connectors on both ends. The negative attaches to the small post closest to the front of the vehicle (closest to me in the photo) and the yellow wire that runs from the rear small post on the Stinger is the power wire for the switch that runs to the fuse block.
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You can see that I routed the large negative battery cable (black wire loom) underneath the Stinger....
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...and connected it to the same bolt as the chassis grounding strip behind the engine. The yellow wire is the power wire that goes to the fuse box.
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And here's the fuse box (sorry for the fuzzy photo, it was getting dark and my camera was having a hard time focusing.)
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I used an add-a-circuit and went into the same 10a ignition fuse slot that Jelorian used on his. Wire is routed underneath the fusebox.
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After I got everything buttoned up and bolted down, I started the truck. Measured 14.5 volts at the starter battery and about 14.25 at the house battery - I'm assuming that means the system is working as the house battery appears to be receiving a charge?
 

Martinjmpr

Wiffleball Batter
So Obviously I'm not "Done" done. I still need to "clean up" all my cables, put the power cable into a wire loom, zip tie everything together and if I can, I will try to "hang" the cables so they don't rest on the engine (I don't like the idea of electrical cables resting on the hot engine!)
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And then of course I need to figure out how to "use" the house battery. I need to pierce the firewall with a wire (I have some 10g electrical wire for that) and then put that wire into a place where I can put in the dedicated fridge outlet. But at least the difficult part (for me) is pretty much over.
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If anyone has any questions or wants to know what parts I used, reply to this or shoot me a PM.
 

02TahoeMD

Explorer
Nice writeup. I like the use of the jack-nuts. I trimmed off the leftover sheet metal fender bracket just to make it easier to move the battery in and out of the location.

Good job.
 

dwh

Tail-End Charlie
Now that you've got the cables cut to the right length, you could probably just take them to the welding supply shop and have them do proper crimped terminals if you wanted.

Nice job.
 

dwh

Tail-End Charlie
Most likely the engine battery was full and the surface charge zoomed to 14.5, while the new house battery was a bit low and needed to absorb a little to catch up.

I would just let it run a while, or drive it around for a couple days and see if the new house battery finally catches up.
 

rayra

Expedition Leader
Martin, it's a simple matter to chuck that battery connector back in your vise by the bolt end, aimed upward and apply heat to it with a propane torch and feed solder into that connection until it is full.

I just used some rubber insulated cable clamps along the top of the firewall to route and secure my battery cabling -
http://www.expeditionportal.com/for...ucture-seeking-inputs-on-my-inputs-and-ouputs

hmm dont' seem to have taken / posted a picture of that. They look like this -

514225.jpg
 

dwh

Tail-End Charlie
No doubt he measured across the battery terminals, so he saw the battery voltage of each battery.

The charging loop will be at battery voltage, and even though paralleled there are two different charging loops involved...

Alt -> start batt pos -> start batt neg -> ground -> alt

Alt -> start batt pos -> acr -> house batt pos -> house batt neg -> start batt neg -> ground -> alt

Each loop will be at the voltage of the relevant battery.

The start batt, being almost certainly at full charge quickly zoomed up to the voltage regulator's set point (alt max potential).

But the house batt, being fresh from the retailer and possibly having sat around a while was less than fully charged and needed to absorb a bit to catch up.

The slight difference in potential of .25v, combined with the high resistance of one fully charged battery and one nearly fully charged battery probably precludes any flow from one battery to the other.
 

Jelorian

Adventurer
Martin, glad you were able to get your dual battery set up.

With regards to the way your terminals are pressed into your cabling, I'm afraid I have to agree with what some of the other guys have suggested. I would either bring them to a shop and have them crimp it properly or solder the terminals on. While they will probably work in the state they are in now, they won't be as efficient in carrying the full load.

If you decide to go the solder route, I used solder slugs.

Put the terminal lug in the vise, put the slug in the terminal, heat up the terminal lug till the slug melts, then slowly insert the cable while still applying heat to the terminal.

I know it will be a pain to take everything apart, but I think it's worth it in the end.

Also, I remember you asked how I mounted the cables coming from my 2nd battery to the starter battery. I just remember that I used zip tie anchors like this.. However, the adhesive that comes with it is not strong enough so I use 3M double sided trim/moulding tape.

If you wanted to use screws you could use this product.

Good luck finishing it up.
 
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Martinjmpr

Wiffleball Batter
The start batt, being almost certainly at full charge quickly zoomed up to the voltage regulator's set point (alt max potential).
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But the house batt, being fresh from the retailer and possibly having sat around a while was less than fully charged and needed to absorb a bit to catch up.
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That seems the likely reason. Before anyone gets too worked up about the difference, understand that it was getting dark and I was in the process of putting everything away. I just pulled out the volt meter as an after thought and very quickly checked both batteries by putting the volt meter probes on the exposed battery terminals. This whole thing took place in about 30 seconds and this was after I had started the engine maybe a minute (or less) before.
 

Martinjmpr

Wiffleball Batter
Martin, it's a simple matter to chuck that battery connector back in your vise by the bolt end, aimed upward and apply heat to it with a propane torch and feed solder into that connection until it is full.

I just used some rubber insulated cable clamps along the top of the firewall to route and secure my battery cabling -
http://www.expeditionportal.com/for...ucture-seeking-inputs-on-my-inputs-and-ouputs

hmm dont' seem to have taken / posted a picture of that. They look like this -

514225.jpg

Where did you get those? That's pretty much what I want to keep my cables out of the way.
 

Martinjmpr

Wiffleball Batter
If you want to make those cables right let me know, I have a couple of good crimpers (actual FTZ, calibrated for the terminal color codes and everything), adhesive shrink and a heat gun.

I can't stress enough that you really should crimp (or solder if no other option) those connectors on right. There's more to it than just mashing them flat.

See this post:
http://www.risingsun4x4club.org/forum2/showpost.php?p=285862&postcount=9

FWIW, the terminals you used are the flared/starter type. The FTZ chart listed the dies for those, too.

PM sent. ;)
 

Jelorian

Adventurer
If you want to make those cables right let me know, I have a couple of good crimpers (actual FTZ, calibrated for the terminal color codes and everything), adhesive shrink and a heat gun.

I can't stress enough that you really should crimp (or solder if no other option) those connectors on right. There's more to it than just mashing them flat.

See this post:
http://www.risingsun4x4club.org/forum2/showpost.php?p=285862&postcount=9

FWIW, the terminals you used are the flared/starter type. The FTZ chart listed the dies for those, too.

Thanks for that link. Since I soldered mine originally, I will probably swap my cables out for crimped terminals in the future. In a vehicle that is subject to lots of vibration, I can see where a mechanical crimp would be superior to a soldered one.

Cheers!

Jel
 

rayra

Expedition Leader
Where did you get those? That's pretty much what I want to keep my cables out of the way.

Electrical section of Home Depot / Lowes has them, multiple sizes. I used self-tapping sheet metal screws into the firewall bulkhead ETA - I used such for the solenoid mount itself - , actually the cowl just below the rubber seal. IN one spot IIRC I used a stud on the firewall where an engine grounding strap was attached. I'll take a couple pictures and post them here shortly.


eta - I actually used two existing studs on the firewall to mount my cable clamps. My clamps are ~1/2" dia, as I used 1/0 cabling. It's a good close fit with enough room to slide another pair of small gauge wires for the solenoid as well.


auxbatt058%20cable%20clamp1_zpsaxpebjha.jpg
auxbatt059%20cable%20clamp2_zpsz4du4way.jpg



Also, for IT nerds, there's a type of cable organizing zip tie which has a screw eyelet built right into it, so you can readily anchor a bundled bunch of cables to anything with the appropriate screw.
 
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Jelorian

Adventurer
When this happens the resistance starts to creep higher, which on high current paths creates heat. If allowed to continue long enough the connection resistance can increase enough that under heavy loads (starting, winching, jump starting, very high current situations) the temperature can rise enough to reflow the solder and allow the cable to fall out of the terminal.

I do have the Ancor Marine grade heat shrink on all my connectors so at least I have some mechanical connection if the temps get high enough for a solder reflow.

Should hold me over till I get my terminals crimped.
 

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