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Gary... I've been considering adding a winch to my rig as well... and when you get it completed... the Aux Battery installation/mod sounds like a valuable addendum to your "cool web site" ... replete with lots of pics, x's and o's, arrows, circles, parts, diagram, schems, logic, reasoning, schedule, lunch menu... since you have so much free time on your hands
Looking around, it seems the hardest part to find is the darn LH battery tray! I'm thinking of constructing my own out of aluminum... something to accommodate the larger battery dimension. Thx for all the info so far... great post.
Happy to help. But, if you are serious about the winch you might want to check with 4wheelparts.com immediately. I bought my Smittybilt 12k winch with synthetic line (#98412) for $523 yesterday, and that includes a cover. The winch lists for $650 and the cover for $25, so that a $152 savings.
I also bought another Odyssey Extreme 31M-PC2150 for $346. So, now when I get the time I can start on the installation. However, we have some family things in the near future that will preclude working on trucks.
And, I'll be sure to add info about the winch, aux battery, and the wiring to my web site. I'll probably add a page or a tab to the page on Big Blue and show it all there.
But I did have another thought about the warning light on the dash. The CH battery isolator provides an output to power an indicator that shows when the batteries are paralleled. I used it on the boat to drive a green LED, and it gives me peace of mind knowing that both batteries are getting charged. So, using the far left window of the warning lights for a label that says "Battery" and installing a green LED behind it would do the same on the truck. If the batteries are paralleled then you know the alternator is charging or the primary battery wouldn't have come up to bring in the relay. But, if the LED were a red/green unit and it stayed red when they weren't paralleled then it would get the driver's attention if it were to come on while cruising.
Smittybuilt sounds like a good deal... I'll check it out
re the change status light... the more system feedback the better, I always say.
just fyi... the far left light well on my cluster is for "Emissions" (haven't dove into the source of that sender yet) and "4x4" on the right... Do you have an "empty" well to use?
I'm thinking that a dual-color red/green LED could be rigged up to give:
Green when the batteries are paralleled, meaning the system is charging and the primary battery is above 13.2v
Yellow, meaning both red and green, when the batteries are paralleled by the switch. And, this would also bring the warning buzzer in as I wouldn't want the switch to be left on all the time.
Red when the batteries aren't paralleled, meaning in startup and if there's a sudden loss of charging, which would drop the primary battery's voltage below 12.7v.
My only minor concern is the roughly 2 minutes after startup when red would be showing. But, that's a small price to pay for having an indication of what is going on, and especially the red that would come on if the alternator fails.
Well, it has almost been two weeks since I posted the above about having an indicator on the dash to show the situation on how the batteries are/aren't paralleled and no one has commented. So, I'm gonna guess you either don't think I can figure out how to do it or don't think it needs to be done. However, I have figured out how to do it, so those naysayers lose the bet. As for the rest of you, just wait and see.
Anyway, I'm in the shop scoping out what I need in the way of marine wire, terminals, etc in order to make all-new battery cables and have some questions:
Size:
Primary Battery: I'm planning to go with 2/0 cables for both the positive cable to the starter as well as the ground cable to the block. However, that's probably overkill to say the least.
Alternator: I'm going to go to a 3G, so will use #2 which is good for 210 amps, from the alternator to the Megafuse, and from it to the primary battery. (Yes, that's overkill, but since I'll be using #2 on the aux battery I'll have it available and this way I'll not have to order a different size wire.)
Aux Battery Positive: The stock setup runs a 10 ga wire from the shunt, which has to go since it can't handle the 3G alternator, into the cab to the fuse box, and then on to the Aux Battery Relay, as shown below. That size wire is only good for 60 amps (or maybe up to 12% less if that's a #10 SAE rather than AWG), so it isn't up to handling the output of the 3G, and it will have to when I'm running the winch off the aux battery. So I'm planning to use a #2 from the primary battery across the top of the radiator to the battery isolation relay, and then to the aux battery. That'll give 210 amp capability for the aux battery to support the primary battery during cranking if I need it.
Aux Battery Negative: The EVTM shows that the gas engine's aux battery grounded to the fender, but that the diesel's left-hand battery grounded to the block. I think I'll ground to the block as well and will use #2 to do it.
Connections: Both of the batteries I'm using (Odyssey Extreme 31M-PC2150's) have the studs, so I'm thinking of using ring-tongue terminals and connecting to them instead of using the post-style terminals.
The 1986 EVTM doesn't have the wiring diagram for the aux battery relay anywhere, although the relay itself is depicted on Page 14. The 1981 does have the wiring diagram, which is where those pages came from, as do the 1984 and 1985 EVTM's. But, not the '86. Go figure.
. It is capable of 200 amps, which fits with the wire I've chosen that is good for 210 amps, and even a hopped-up 3G that might be good for 160 amps. Here are the features:
Doesn't parallel the batteries until one is at 13.2 volts, meaning the alternator is working and has the primary battery almost fully charged.
Disconnects the batteries when they get to 12.7 volts, so if the winch pulls the aux battery down a smidgen it'll protect the primary battery.
Has a "force-parallel" feature where you flip a switch and it pulls in to parallel them. That way I can continue having the 3G charge the aux battery while winching. But I'll have to watch the aux battery's voltmeter (there will be two voltmeters, one for each battery) to ensure I don't let things get too low or the engine will die. I guess I could use a 555 timer to monitor the voltage and open the force-parallel switch circuit at a preset voltage, like maybe 10?
And, as previously explained, I plan to use a red/green LED in the Emissions window, the one to the far left, with a new label that reads something like Parallel, to show:
Red: Batteries not paralleled. This will be the case for about 2 minutes each time the engine is started and then, assuming the battery is charged, it'll go green. But, if you are cruising down the road and lose the alternator it'll come on RED.
Green: Batteries paralleled in normal mode. This means that the alternator is working properly.
Yellow: Batteries force-paralleled via the switch, at which time the headlight-on buzzer will also be alerting the driver that this ain't right - I don't want anyone leaving the switch on and the batteries always paralleled.
... makes sense.
I have a light socket/connector in the emissions spot (the connector is red ) but no bulb... not that thats a big deal. I mean to track that wire down... I'm curious
On mine nothing lights the light. But presumably the trucks with computers have a connection to that light, although I haven't found it in the EVTM.
Anyway, it isn't used in Big Blue as he didn't come with much in the way of emissions controls, and certainly no 'puter.
No, not the oxygen sensor, but a timer that makes the thing come on every ~50,000 miles or so, it's located behind the dash near the wiper **** and has a hidden RESET button... I had elaborate pictures of that device out here at one time....
... replete with lots of pics, x's and o's, arrows, circles, parts, diagram, schems, logic, reasoning, schedule, lunch menu... since you have so much free time on your hands 
) but no bulb... not that thats a big deal. I mean to track that wire down... I'm curious 
