Bronco Forum - Full Size Ford Bronco Forum banner

1 - 20 of 20 Posts

·
Registered
Joined
·
35 Posts
Discussion Starter #1
I am wanting to run a dual battery set up with a power inverter so when im camping i can leave one battery on and then when it is drained i can flip a switch and use the backup batter to start my truck and get home. I know i need a relay switch but i have found most are to run 1 batter with auxiliary things on itthen the other is the main. I want something selectable. Does anyone know how to go about wiring this and what kind of relay i need to have the switch to turn the other battery on and off. I hope you guys understand what i am asking. Im not wanti ng to pay 200 for an isolator switch. This is where i found most of my information on this but he doesnt say the specific type of switch it is. But same setup basically http://youtu.be/zP-dB4lBftc
 

·
Banned
Joined
·
7,158 Posts
This diagram & its caption show how Ford designed that circuit in the early 80s, and how to easily & inexpensively modify it to do what you're describing:
http://www.supermotors.net/registry/media/905321
Follow the links in the caption for more info, but you need a place to mount the aux.batt., heavy cables to connect it, a continuous-duty relay, and some small wire to build the stock circuit. To make it selectable, you also need a small fuseholder and an SPDT center-off (or SP3T) switch. The 2-color diode & its resistor are optional.

Once you have the 2nd battery installed & working, the first logical step is to add a fuse panel to it for connecting your camping circuits.
 

·
Erik
Joined
·
1,847 Posts
I used a cheap battery selector switch from perko that I would normally use on a boat. Got one with a key too so I can lock it when I turn the batteries off. Not the most sophisticated way but simple and effective. I normally alternate using only one of the batteries and only need both together when winching.
 

·
Super Moderator
Joined
·
9,700 Posts
I have been thinking about this too. Where have yall put the extra battery?

I put one of these Perko switches on my boat and I dont see why it wouldnt work just as good on my truck.

 

·
Registered
Joined
·
35 Posts
Discussion Starter #6
On the perko switch is one battery is completely dead would it feed off the charged battery or does it cut off power to the newly drained battery?
 

·
Registered
Joined
·
34 Posts
You are probably aware of this, but to be clear, you are going to want a deep cycle battery for your secondary battery. This is absolutely essential, since cranking batteries aren't designed to drain all the way, and you'll kill them pretty quickly if you use them like this.

That said, there are some deviations to this, but the general gist of what you want to do is to keep your cranking set of batteries hooked up to your alternator 100% of the time, and your deep cycle hooked up to your inverter 100% of the time. You then would bridge the two when your engine is running and separate when the engine is off, thus charging your deep cycles but not draining your cranking set. You can do this pretty easily with a solenoid (heavy duty relay) wired up to your engine-on key position. It might not hurt to have a manual override to separate or bridge the two when you want.

I'd look for a 150-250a solenoid (under $20). You'll also want to use pretty thick gauge wire. I'd recommend 0 gu. You will need to bridge your ground as well with equal gauge wire.
 

·
Registered
Joined
·
35 Posts
Discussion Starter #9
Ok thanks alot guys. I think when it is said and done i want tohave a winch and lights on the auxiliary battery and then my invrtertoo becaus i probably wont be winching and using the inverter. So just the selonoid is all i will need to switch from auxilary to my starting battery. So doesthis mean why i am camping with say a radio pluged in i want my starti ng battery inthe off position so it isnt drained?
 

·
Registered
Joined
·
34 Posts
Steve83, In practice, you are probably right that for the OP's purposes 0 guage would be overkill. I use it because I find that it's about the same price as thinner stuff, and, well, I have a 6kw inverter. :D

But since we are in a bit of a theory conversation, anyway: Your 1000 watt inverter should have a max draw of 83 amps, and if you are going over a 10 ft cable to it you will have about a ~0.66v drop, or 12v -> 11.34v. A 0 gu wire would do that run with a 0.16v drop, or 12v -> 11.84v. This means two things. The first is that that voltage drop is indicative of lost energy that is being converted to heat, and thus wasted. The second is that you will hit your minimum operating voltage on your inverter that much faster, and it will stop working while a thicker cable would let it continue. Although, this is pretty dependent on the length of your cable, so if the inverter is mounted right next to your battery with a 1ft cable, you wouldn't have as much of a drop.

Either way, I still prefer to overguage, for less drop.
 

·
Registered
Joined
·
35 Posts
Discussion Starter #11
Okt thanks everyone i will put a deep cycle as my main and run all loads to it then use a cranking battery for my backup sense it should never be drained. I have found a few isolators for 40 bucks that have an overridethat puts the batteries in parallel so it will work as my jump batter. Ill try to do a write up once i do this to help out others. You guys are a huge help i am newhere and its a wealth of information.
 

·
Registered
Joined
·
136 Posts
I think you kind got that kinda backwards. The deep cycle should be used for auxiliary use and the cranking battery for starting. My dad tried using a deep cycle as the starting battery on a boat with a cranking battery for aux. The deep cycle didn't work for starting (That was only turning over a 2.3l ford!) They are meant to discharge slow and charge slow. Starting ones charge fast and discharge fast.
My experience anyway.
 

·
Registered
Joined
·
242 Posts
I used this...
http://www.amazon.com/PAC-PAC-500-500-Amp-Battery-Isolator/dp/B001YIPXR2/ref=sr_1_2?s=automotive&ie=UTF8&qid=1421003689&sr=1-2&keywords=pac+battery+isolator

It could be found around the 50 dollar range when on sale. It's a mechanical isolator/relay and is really heavy duty. It's wired to my switched power 12 volt ignition switch so that when closed my front battery is isolated from my rear aux battery.

Upon killing the primary, the power left in the primary is enough to open the isolator by turning the ignition switch to the run position. It starts the truck effortlessly and allows the 3G alternator to charge the dead primary battery, which recovers fairly quick as they are both Optima yellow top starting/deep cycle batteries

The wiring I used was 2/0 welding cable all around including the inverter that is connected to the aux battery only, for true isolation. A cheap battery box from Oreilly's
http://www.oreillyauto.com/site/c/detail/ATT0/90841/N0357.oap?ck=Search_battery+boxes+&+trays_-1_3044&keyword=battery+boxes+&+trays

behind the rear passenger seat made for a really accessible location to wire the inverter with a really short run of wire. It also makes a very easy spot to attach a small run of wiring that terminates with an Anderson power pole at the bumper for jump starting or heavy current 12 volt applications.




 

·
Registered
Joined
·
34 Posts
I agree with what everyone else has said about keeping the cranking battery for your main. Just move your stereo and anything you might want to run with the engine off over to your auxiliary system.

Steve:
My 12v examples were just designed to illustrate the voltage drop, I understand that batteries optimally put out more. It would start at around 13.2 when fully charged, and then drain down to around 11, or whenever your inverter cuts out. The voltage drop from the wire still means that your inverter will "see" a lower voltage than your battery puts out, thus triggering the voltage cut-out sooner. Meaning, if you have a .6v drop on your line, your inverter would cut out when your battery hits 11.6, instead of 11.

Reading the manual for your inverter, it looks like they recommend you "use a minimum No. 2 AWG for the DC input cable with a [...] maximum cable length of 1.5 meters (5 feet)"

http://www.xantrex.com/documents/Power-Inverters/Xantrex-Inverters-Hardwired/XPower 1000 Inverter Owners Guide (975-0557-01-01_Rev-B).pdf

Wire gauge scales exponentially, so 2x 12 gu wires is actually worse than a single 6 gauge. It's probably not going to burn up on you, especially since you are just using it for a winch, but that's not very optimal, and could be dangerous if your inverter ever gets fully used (or shorts out). I would certainly not recommend to someone else on a public forum they do the same. 2x 12g wire will give a 1.33v drop in my theoretical example above.
 

·
Registered
Joined
·
35 Posts
Discussion Starter #17
Ok now i understand what i should do. I was confused a little bit so thanks for clearing it up for me. I really appriciate all the info guys and i hope it will help others with same idea. I didnt k.ow a deep cycle wouldnt crankthe engine i just figured it cranks our boat engine but its very small compaired to any car engine. Thanks
 

·
imdabes
Joined
·
937 Posts
Little late,

My setup is this:

I have 2 group 65 batteries side by side in the stock spot, hammer the tray flat and they fit fine.

Main battery is connected in the stock configuration, with an additional 0ga wire doing to a 500 amp relay - pac-500 on amazon 30 bucks or so -

Second battery is only connected to the relay.

I have a switch panel in my cab whose main power source is connected to the aux battery so if my main dies my switches still have power.

The ignition wire is just ran to a switch in that panel.

When I flip the switch the relay opens to connect the two batteries, when its not flipped the second battery is isolated.

I usually always run with the switched flipped open so the aux stays charged.

I only drive every few days for a couple miles so I jump frequently lol. Flip the switch and start the truck
 
1 - 20 of 20 Posts
Top