barngal6

I'm wiring my 98 12v with a 7pin receiver, for my horse trailer.
2 questions (so far)

1) How do I wire this battery saver?

I have a 3 post "doodad" that I want to use to prevent the trailer battery from discharging the truck battery when the truck is turned off but the trailer is still connected.

can't remember the name of the doodad, and don't have any instructions,
but I installed one a long time ago and it worked great.

On doodad--there are 3 posts--one on each side, and one in the middle
1 2 3


Im guessing that (1) is attached to the truck battery, (3) is attached to the
plug (and thereby the trailer battery)

What is the middle terminal? this terminal post is smaller in diameter than the other two...Something I guess that goes off when truck is turned off...

QUESTION 2
where should a fuse be placed in the above circuit to prevent shorts to the truck battery?
And is a 30 or 40 amp the right size fuse?

Thanks...I'm sittin here hoping I can go finish this!

GreyTD

it's called battery isolator, batteries are attached to outside posts while your alternator is connected to the centre. If you look at the truck battery(ies) there are two wires (typically) going the postive, one heavier guage than the other, the smaller of the two is the alternator wire. That's the one that should be remove from battery and connected to center on battery isolator. Same guage or better then goes from isolator back to battery. Other side of isolator then goes to trailer connector(battery), clear as mud right?

barngal6

OK, almost there..

On the center terminal for the alternator...

Can I just run a line from alternator terminal to the center terminal of brake terminal, and not divert the current alternator line?

sorry if I'm head banging on this...

and where should I put a fuse to prevent damaging truck battery in this circuit?

thanks a bunch

GreyTD

close, but in order for it to work properly you need to disconnect alternator wire from battery. Here is a diagram that may help better http://www.bcae1.com/battiso.htm, ignore the fuses, but you should put a fuse in the line going to the trailer 30A should be fine.

GreyTD

here's more info for you. http://www.newmartelecom.com/pdf/Man...0Isolators.pdf

barngal6

Yikes--I need to back up.

My plan was to run the trailer battery lead from the Secondary battery...

the alternator lead is attached to the Primary battery.

Also, the alternator lead is really complicated (sorry, but I was hoping I could do this myself ).

There are two leads going to the alternator, one I think is a ground, but the
other looks like a battery terminal itself.
I couldn't possibly connect that large thing to the battery isolator terminal.

I will study the info you sent to me--thanks very much for the diagram
If I still have questions, I'll be back!

Thanks again

jaypry

Sorry to muddy up the water but our pickup's 2 batterys are both hooked up like they are one big battery. what you need to do is buy a simple 30 or 40 amp relay (like for fog lites), and wire this to turn on with your key, in either on, or acc. use a 30 amp fuse after the relay. then hook it to your trailer that way when your driving it's charging the trailer. If you use a battery isolater you lose about 1 volt going thru it to your main batteries and your trailer battery. Plus these relays are much cheaper than an isolater.

Joe

Oilguy

I just hooked in to the trailer connector to the one that says + on it.... If I ran two batt's I would use an isolator though.... I have been running for 2 years this way and had 0 problems.... If your looking for a shortcut... there you go...


Or are you saying that you don't have a 7 pin plug and you are installing one so that you CAN charge a trailer battery through it??

If that is the case then I agree with jaypry and using a relay with a 30Amp inline fuse so if you get a weak battery in the trailer >>> It won't suck down the truck batteries. I wouldn't think you would need anything bigger than 10ga wire unless you are going to be taxing the trailer battery and drawing a lot of amperage from the truck... But then I am not a electrician or mechanic...

barngal6

Man, I didn't know anything about the inline fuse protecting the truck battery from a low trailer battery...

Here's what I had in mind...I finally found it.
the diagram you gave me GreyTD was more complicated than I was hoping I needed.

Here's how I had it connected on my old truck, I finally found a diagram

http://www.rverscorner.com/wiring/solenoid.jpg

My truck has 2 batteries; I'm running a 10g wire from the secondary battery
(+) to the solenoid.

I ran a 10g wire from the other post of the solenoid to the trailer receiver at the back of the truck.

The middle post of the solenoid goes to the ignition.

So when the trailer is hooked up to the truck, while youre driving the truck is recharging the marine battery in the trailer.
When you turn the truck off, the trailer no longer draws on the truck battery.

Seems simple enough...why wont this work? (I had a solenoid in the garage for a truck it never got installed in, so I thought I could use it here..)

The trailer is only for exterior lighting, which I only use occassionally, so the trailer battery usually has some juice in it...