I am thinking of installing a second battery on my '85 F250 351W 4X4. I have a 8000 lb. Warn winch on the front it. When I use the winch I know it put a strain on the one battery. When I use the winch I leave the truck idling but it still pulls the battery down hard. What I would appreciate you gentlemen's input on is how to wire them. If I understand right I need some sort of automatic selector switch but I am not sure. I BELIEVE with the correct switch it allows you to operate off of one battery till it gets drawn down to a certain point then the switch automatically switches to the fully charged battery. But the switch, some how, also allows for the charge in both batteries to be maintained. As I said before I really don't know about all this that's why I am posting this thread so your input would be greatly appreciated.

 

I'm usually in the dent section. You can go about this a few ways.
1) A high amp alternator and your battery. This may handle the load, then again....
2) Adding a second deep cycle battery with an isolator post(usually 100 amp service). The isolator post is designed to charge the battery while your engine is running and isolate the battery when the engine is off. Another, easier method is to use a continuous duty solenoid(mine is 80 amp service). This looks like the starter solenoid.
3) A combination of 1 and 2.

As for wiring, you will usually need a 12v trigger that only comes on when the engine is running. This will prevent the 2nd battery from losing a charge, if you have the key in the ACC position.

 

Thank you 84 I appreciate your input. I may look into the "combination of 1 and 2", I wouldn't mind a high amp alternator but I would like to have the switch also. I wired up dual batteries with out the switch in a truck I use to own and it worked good......for about I week till I started burning up electrical parts LOL. Can you please tell me more about this isolator post (usually a 100 amp service). Do most auto parts stores carry them? If I walk in to buy one do I just ask for an isolator post? In your opinion do they come with wiring instructions? What is the continuous duty solenoid, how does it work? What would I ask for in order to purchase one of these? Again how would I wire it if I go this route? Sorry for all the questions but when it comes to this I am dumb as a stump LOL. Thanks again for your input.

 

Please see comments in red

 

First you need to ask yourself a question. Is the second battery going to be auxiliary only or in use all the time?

If auxiliary then you can set it up to drain down the second battery and still have the main to start the truck. However your still left with only one battery to run the winch(unless you add a third). Auxiliary setups work well if you want to operate things when the truck is off. For this install a large deep cycle battery and a battery isolator to charge it.

However I think you are better off with a full time dual battery setup. No fancy wiring or batteries are needed and both batteries are available to both start the truck faster and power the winch. In this instance all you'd need is some stock parts from the diesel version of your truck. They run two batteries in parallel stock. Specifically the second battery tray and the positive battery cable that ties the two together. The second ground cable is generic. Biggest complication is that the two batteries need to be identical and low resistance AGM batteries like Optimas should be avoided, or if used a solenoid added.

I personally use two 34/78 DT Red Top Optimas and a 500 amp continuous duty solenoid.

All this aside what you need more then anything is a fast idle solenoid on a switch to bump up idle speed when using the winch. This would greatly increase the output of your alternator.

 

Thank you gentlemen I appreciate your input. My fear is being out in the boon docks winching out of the mud alone, which I am usually alone when I am stuck in the mud LOL, and draining everything down to where the truck dies with out enough juice to restart it. Currently I have a thin piece of metal I use to idle up the engine but the fast idle solenoid sounds like a wonderful addition.


I once wired two batteries in parallel on a truck I use to own and it didn't take long before I started burning up electrical parts. I suppose I was hitting them with to many amps. I replaced 2 starter switches, the one mounted on the steering column, in about 2 weeks time. Both times I was stranded up a creek with no switch so to speak. I removed the extra battery and never burned up the starter switch again.


What I am "thinking" of doing and the reason for the switch, and the reason I am posting this is: install a second battery, wire in a switch, start and run my truck off of one battery but wire the switch (which ever switch is needed) so that the alternator keeps both batteries fully charged. When I use the winch I would like to be able to drain one battery down and once that battery reaches a point the switch does it's job and I start draining the other battery all the while having a higher output alternator turning at a high idle putting back some of the juice I am using.


I am going to check the links you posted/provided and see what I can do. I really appreciate you gentlemen taking the time to help me with this, thank you.

 

I can't imagine a reason why two batteries wired in parallel would burn up ignition switches.

This drain one then the other thing won't work out the way you want and is very bad for the batteries. It defeats the purpose of having the batteries wired separately as it still leaves you without a charged battery to start the truck. It's also bad for the batteries, what kills a battery is being drained. Better to drain 2 batteries down 25% then one 50%.


One battery for the winch, one for the starter is a fine and common way to go about it. All it takes in addition to the second battery is a battery isolator.

 

Maybe you wired them in series, instead of parallel.

 

I wonder if it would be possible to operate the truck off of one battery but operate the winch off of both batteries but wiring them in such a way that the alternator keeps both batteries charged.


This is certainly a possibility, especially with my memory from 30 years ago. I do know I worked on dozers back then and they had a 24 volt system and the batteries were wired in series so if I remembered correctly I made sure mine were wired positive to positive and negative to negative. I am certainly not trying to be a smart a$$ here so please don't take it that way, but that is parallel correct?


Again gentlemen I really do appreciate your input and ideas and I appreciate each of you taking the time to share your knowledge with me.

 

Of course it's possible, and only slightly more complicated. But there is little point to it. It would drain both batteries when winching thus could kill both and leave you no way to restart the truck if it dies. And it removes the ability to use both batteries to start the truck.

That is correct, though you don't actually need to connect the two negative posts together. As long as each is connected to a good ground that is all that is required.

 

Brute those are excellent point and in my ignorance never even considered the points you brought up, thank you sir. It appears that your suggestion of running the truck on one battery and the winch on another battery is my best choice. Naturally wiring the winch to the extra battery is very simple but I don't know how I will keep it charged. I suppose I should say how do I wire it so the truck's alternator will recharge it after I use it. If I go this route will I be back to killing one battery by draining it with the winch? Man this is harder to do/figure out than I imagined LOL. Again Brute I really appreciate your input, ideas, advice, and the knowledge you are willing to share with me.....Thank You. I am going to go back and reread this whole thread and re-analyze the options.

 

Your welcome,

Wiring to charge the second battery without draining the other is very simple. They make a product just for that purpose, they are very common. It's called a battery isolator, it's simply a couple diodes, diodes are one way valves for electricity. You simply remove the wire from the alternator to the stock battery and connect it to the isolator then connect each battery to the separate posts on the isolator. The isolator then divides the charging amps between the two batteries.



Here's a diagram and example I found in a very quick amazon search.





Isolators like this(lower amps though) are so common you often find them in wrecking yards, old RVs, etc. If you looked odds are you can find one for free, but for $40 at first glance this looks like a decent one.

 

Thanks a million Brute I really appreciate the help. I really appreciate the diagram, heck even a dummy like me can follow that wiring diagram. Now that you mention it I bet I know where I can get everything I need for free. A couple of months ago I bought an old RV, for some spare parts, that has 3 batteries in it. I may have to hunt around on it a little to find what I want/need but I bet it's all there. Thank you again for your help and being willing to share your knowledge with me.

 

Again you're very welcome, that's what FTE is for and why it and Ford owners are the best.

Two small bits of added information.

I see no need for the circuit breaker in the diagram. Fuses, disconnects, etc. are always a good idea but not necessarily needed as they add both cost and complication.

In the RV world the auxiliary battery(s) are often referred to as the house battery(s). So if you come across an isolator or other diagrams you may find them labeled that way. In your case the winch battery is the same as the house battery.

 

You are absolutely correct about FTE and Ford owners sir, this is a great site to learn on and realize others need help just like I do. It's a blessing when others share their knowledge so freely with those that need it.


I am looking forward to snooping around that old RV to see what all I can find for my project.