Add Dual Batt on 86 gmc
 

Ive got a 86 Gmc sierra classic, basically everythings stock but anyways, i hit a deer screwed up my front end abouyt 6 months ago, perfect chance to add some stuff and customize. I would like to know how to make my current system a dual battery system. i am going to use all new wireing harnesses(painless wireing) fuse block all that. and i was wondering how to go about that since there is only one batt tray under the hood?

thanks

I've seen Chevy Duty, www.chevyduty.com, offering a driver's side battery tray just like what came from the factory. I've been thinking about this for my Suburban, as well.
I would just run a large gauge wire between the two batteries. I am thinking double ought gauge (00). I had another truck and had an isolator from a boat, which was really cool, but I never used it. You could run one and charge the other, run both, completely turn them off so no one could start (steal) the truck, etc. I would definitely use Optima red tops--they are the best: no doubt about it. you can even mount those bad boys upside down, no venting, spillage and they're tough as leather.
Good luck with your project!

I think you need a regualtor or something between them. I'm no guru on this but I remember reading that you needed something between them. Maybe Arveetek our diesel guru can help out since they run 2 batteries.

GM diesels don't use a battery isolator. They just have the batteries wired in parallel. For a diesel with the stock wiring, you have to keep your batteries exactly the same, ie when one goes bad, you replace them both. The only purpose they serve in a diesel is to give the current the starter on the diesel needs to spin the engine over fast enough to get it to run. With a battery isolator between your two batteries, the second battery can be kept in reserve, ie if you leave your lights on or play your radio too long without running your truck, the isolator won't let the second battery get used until the key is in the start position, keeping you from getting stranded. Also, if one battery is weaker than the other, it won't become a drain on the stronger one.

I added the second battery tray to my '84 gas burner.

I knew diesels took two batteries so I also knew that General had to make a battery tray for the other side.

In I went to the my local dealer and plopped down $65 for the second tray and bolted it up.
I also second the Optima post above.....I have three of them now.

Anyone want pics of the second tray?.......let me know.

yea mike if you dont mind id like to see the second tray

Here you go.....this is on the drivers side

thanks for the pic that gives me an idea of how its goin fit in there

is there a benefit in performance, i dont have any other problem with that

Performance with what?
The avalible amps in the battery system? Yes
Net power at the rear wheel? No
Considering the ineffcient nature of all batteries, wire, and everything else hooked to charging system it actually hurts power as you have to offset the weight of the second battery and wire.
To see how much this would be just take a car battery on a jog around the block. If you carry it by hand you see how much power it takes.
When you add that you have to turn the alternator to charge that second battery the loss of power becomes more apparent.
A good little test of this is to unhook the belt on your alternator and switch something 12v on while trying to turn the pulley with your hand.
This is something I have shown many people that want to add a electric fan to replace the stock one.
It still takes power to turn the electric one. In fact....it usually takes more power to turn the electric fan than to turn the stock one.

Simply put, this might make sense, but with everything taken into account, it probably doesn't. If you use a temperature activated switch for your electric fans, they will be more efficient then even a thermostatically clutched mechanical fan. This will be most true when you are driving down the road at about 30 mph or more. At the faster speeds, the air moving through the radiator just from the truck moving is more than what the fans move, and the fans can shut off.

If you never drive above 30 mph, mechanical fans will be more efficient assuming you have a good fan shroud and the fan is properly placed. This is because you don't have to convert rotational energy to electrical and back to rotational with each conversion having some inefficiencies.

As far as two batteries, if you don't need them, the second one really is just extra weight and extra cost.

But, and a big one at that is this, an electric fan setup will very, very, seldom come on. Only time mine ever comes on is when I sit at a stop light for a few minutes, or maybe in a drive thru window. Normal driving, it never runs. Unless you've ever had electric fans, you'd be amazed at how little we actually need a fan. So, as long as we are moving, this is no drag on the alternator, at all. So how can this rob power? Answer, it can't.

It's a no brainer to me.

I don't know who Mike (edit: Swervin) was responding to, but that's pretty much what I was trying to say since I think everyone drives above 30 mph. (Probably as much above 30 mph as they can get away with!)

Joe, you and I must have been replying at the same time. I was replying to Mike. :)

Very true Guys......
I agree that if one has a good radiator (Alu.) and a thermostat hooked up to the fan, it would not run much as compared to a mech. one.
What I was referring to in my post was the people that did not want to wire in a thermostat. Ie;they just want to take off the mech. fan and add a electric one thinking this will cure all.

It won't fix a crappy radiator of give you a instant 50 horsepower.
The only good point to a stock fan setup is they don't have electric motors to burn out.
Mike

Mike how right you are on this point.

My radiator is just a factory 3 core, which was bought new to replace the old one, but not by me. When I got the truck, the guy told me he installed a new radiator. I pretty soon found out why he had to. The owner before him never knew what changing antifreeze meant. Anyway, when I replaced the 305, I had the radiator rodded out to like new condition.

I run a Stewart Components Stage 2 aluminum water pump. This is all the upgrading I've done to my cooling system, besides my dual 14" Spal fans. Of course I have a wired in temp switch that kicks my fans on at 210, and off at 180. But, they will only come on, like I said after running at idle for a few minutes. I have never had them come on while driving.