If that's all you're wanting to do, simply wiring in a $25.00 solenoid as suggested above will work fine. Both batteries will charge while you drive, they will be disconnected until your ignition is hot, and should require only minimal service. I can't really see why you would need any more elaborate system off the top of my head. Tie your winch to the second battery and leave the key off when you use it.

 

Well, I am going to poke a hole in, and deflate this whole thread and say it would be easier, cheaper, and more useful for you to buy one of those battery jump boxes. They cost just as much as a regular car battery, and boy are they handy. If your dune buggy is down over the hill with a dead battery, just carry this thing down over to it, and jump it off. And of course it will jump the truck off also. They will recharge through the cigarette lighter if you need to on the way there. But it won't help with the winch.

 

It's a little bit of learning as well. I have seen the set up before and never understood how the circuit was set up. I have an old '77 chevy 3/4 ton that has a shot motor. Someone stole the dead battery out of it and I found the isolator block in it and wondered the hows & why's. I constantly have 4 or 5 small projects like this that come out of my curiousity.

 

+1 on what Franklin said. If you killed your battery from using the winch, you can use the jump box to get it going again.

 

Hi Franklin.

I would never dispute the value of a battery pack, I have carried one on my service truck for years, but have a couple of thoughts. Having a second battery on board meaning never having to say "oops, I forgot to recharge my power pack" and if you go with a battery pack, don't go cheap. You really do get what you pay for.

Steve

Steve

 

I'll still probably go with the 2 batteries, but what are the better jump boxes to get? I'll buy hammers and toold I'll use once from harbor freight, but never anything electronic. Most car part stores have their own brand of them, but no idea who the makers are.

 

By adding a second starter solenoid, it will only engage the extra battery when the ignition it turned all the way to start, just like a normal starter. How does the alternator charge it ones the key is left in the on position? It seems like it would open the circuit? Do you then run the alternator to the isolator?Or do you add a second lead off of the alternator as well?

 

you send power to the solenoid w/ key in run position

 

So it's powered all the time the key is in run, and that's why you can't use a regular solenoid, you have to get a large relay or solenoid that is rated for "continuous duty".

 

I see now. I was thinking it only came on in the key "start" position. Thats what a couple mentioned with a switch, but you have to remember to use it. You want to keep the batteries in parallel, other wise you'd need a 24V starter in series?

Two batteries in parallel with a constant load solenoid wired to the ON position in between the batteries. When running things like a winch, lights or radio, the truck would need to be in the accessories position or run the winch directly off the main battery. With the key In Acessory position, the other battery is out of the circuit.

 

I've been using the continuous duty style isolator system for quite some years in my work trucks & for the thread starters purpose that system standing alone will be fine. But an interesting issue created by this system is if you use your AUX bat to power anything, in my case gps base station, diesel pumps & or fridge ect. Is that once you run down your AUX then flip the ignition on to start the truck your AUX bat which is dead flat is now connected directly to your primary which drags the @ss out of the primary cranking voltage & the truck cranks like the battery is 1/2 flat.

There are many ways to avoid this issue one is the diode packs, but what we have been doing is when we wire up the AUX solenoid we install an oil pressure switch or AC HI/Lo pressure switch which switches at around 30/40psi. Now during that initial cranking the 2 batteries still remain separate till oil pressure reaches 30/40 psi. By then the motors already fired. Just a push button like a starter button can be used as an override if you leave your lights on or something & flatten the primary but still have a fully charged AUX & would like to use it to start the truck.

 

That problem can be avoided by running smaller wire and a circuit breaker from the charge relay to the aux battery. After all, it's just a charge wire, and should charge the battery slowly. Wire this aux battery using a very large charge wire, and yes, it will kill the starting battery, and that area of the wiring is going to get a little warm also, since the one battery is trying to charge the other battery all at once. Bad for both batteries also. The factory only used a 10 gauge wire for this.

This is not the way to do it. Like I said in the above paragraph, only run a small charge wire between the two batteries with the continuous charge solenoid or the isolator. Then hook your very large heavy wiring for the winch and any other loads directly to the aux battery only. You leave the keyswitch off. That way you can kill the aux battery(which should be a deep cycle type) and not affect the starting battery.

There never should be the need to use the aux battery for starting the truck, but if that rare situation ever occurred, I would have a set of jumper cables to jump the aux battery to the starting battery, or have the batteries close together so the cables can be swapped. This will avoid the problems fordsgofaster was talking about.

 

Very informative, do you mind if I pick your brain for a second ?

I have never seen factory aux wiring system. Nearly all aftermarket aux bat systems I see here that run continuous duty solenoids for switching use 13mm (what would that be in the US ........6 gauge....is that right) leads as insurance against burning anything up if you get a back feed while cranking.

When I first started wiring up our work trucks from the very first system I put together I've only used 6mm (would be equivalent to the 10 gauge you mention) charge wiring. The advise I got was 6mm wire was good for about 80amps max so I purchased a relay in excess of that & a 80amp circuit breaker to put in the system. Relay was switched directly from an ign source. It kept burning up the 80amp circuit breakers .......... I wasn't game to install a higher rated breaker but also notice that whenever one of the trucks got caught in the field with this I just get them to pull the lead off the 2nd pole & put it with the other one on the first pole. This means there's effectively zero breaker/fusing of any kind on that main circuit, yet not once did any of them burn up the charge wire before I got to hold of the vehicle again (could be a month or more).
Still not game to fit circuit breakers with a higher rating than the wire I came up with the oil pressure switching system which was just a tweak on a dead man system I'd seen on stock cars that run electric fuel pumps to cut the fuel pressure in the event of a stack with a stalled engine but ign still on. Zero problems at all since.

But its the fact you mention the factory systems using circuit breakers that's got me curious as to where I went wrong originally

The biggest problem with the circuit breaker seemed to be on the diesels, it seems to be that while their running the glow plugs it starts a current flow & then when they start cranking it overloads the circuit breaker badly.

Obviously if the factory systems are using circuit breakers reliably I've got something screwed up in my layout. Is there anything obvious you can see I've missed ?
Alternatively I have been wondering for some time if I created this issue by fitting deepcycle aux batteries that are a higher cca than the trucks primary battery .........not to mention my own truck runs two aux batteries both with a higher rating than the primary bat.

P.S. our f350 runs a tray mounted winch (flatbed mounted) its the one that has 13mm (6g) leads & before the pressure switching thing it was the one that would crank slow when you run down the winch bat. The override on it is actually used for when the winch just can't quite make it on its own bat you can very easily help it the last bit by flipping the override which connects in the main battery before the very last resort of starting it. Alt also has 13mm charge lead because it inevitably goes to max output if the winch is running & is higher output than stock.
Anyway as a side effect the override is also very convenient if you flatten the primary but the aux is still charged.

 

When I stated the factory wired it this way, I meant the 10 gauge wire. They usually used fusible links, which are very tough when it comes to overloads.

The beauty of the 10 gauge wire is the resistance it provides when the current gets high. For extreme cases, the 10 gauge as you mentioned, is too small. This creates a voltage drop in the wire, which keeps things in check. The wire is going to get a little warm, but if it's not wrapped tightly with other wires it should be ok. From the problems you are experiencing, it sounds like making the 10 gauge charge wire a little bit longer may help you out. Even though you may only need to run a short distance, experiment with the length of this wire, making it twice, three times, etc. the length it needs to be, and this will control the current between the two batteries. The wire becomes a "resistor".

 

Per factory Aux battery wiring, it uses a 14 gauge fuse link.

That is dead on with what Franklin states. A 14 gauge fuse link is meant to protect a 10 gauge wire.