2 batteries on the rig, need one more, isolated

[IdaSHO]

I need help understanding what I need to do to accomplish the following.

My truck already has a dual battery setup. No idea how it works, but it is a factory setup. 1996 F250 Powerstroke

I want to install an isolated battery for the camper. One that will be charged by the truck when running. When the truck is not running, the camper 12v will draw off the battery, while not effecting the trucks batteries.

What equipment do I need? This seems simple enough for a rig with only one factory installed battery, as you buy a "dual battery kit"

What do I need?

Or am I just making this way to complicated? :Wow1:


Thanks for any help.

 

[earthmuffin]

I was kinda hoping someone would chime in that had some experience with this as well. I have a diesel suburban with dual batteries that is screaming for a deep cycle in the back.
From the research that I have done, I think you can treat it like a single battery system and add the extra battery using a diode or solenoid style isolator, if your alternator is cabable of charging 3 batteries.

Factory dual batteries on diesels usually are set up in a parallel configuration to deliver more starting power and juice for glow plugs......which really means they just act like one big capacity battery.

I could be totally wrong here.......thats why I haven't done mine yet!

 

[ntsqd]

So far everything that I've read here is correct to my understanding. I push the VSR (Voltage Sensing Relay) or ACR (Automatic Charge Relay) option for charging remote/'house' batteries because they make the most sense to me. A relay that automatically senses when the starting batteries are re-charged before connecting the remote/'house' battery to the system to be re-charged, and then senses when the charging system has stopped and disconnects the remote/'house' battery from the charging system. All in roughly a 2" by 2" by 2" package. ACRs are available from West Marine and VSR's are available from Del City Wire. My VSR cost just at $70.

There are other options out there. I've some experience with the marine battery bank switches, but none with the National Luna or Hell Roaring systems.

With two batteries on-board do you need a third? Why not set up a system that separates the two existing batteries when the engine isn't running. Can wire the camping draws to one battery only, and then if desired set up a system to connect them when starting. This is what I did with the dual batteries that used to be on my Suburban. I used a marine switch to turn one battery off.

That use lead to my planned current configuration (once the engine swap is completed) of wiring the VSR across the battery terminals of the marine switch. That way one battery can be left out of the system, yet the VSR will make sure that it stays charged. Then, if needed, the marine switch will allow both batteries to be connected in parallel.

 

[earthmuffin]

I'm going to need to do a little more research on the VSR/ACR option, it seems like it would be ideal. As far as the "need" for a 3rd battery, for my application I would say yes.
Especially when the weather is cold, I feel like my 6.2 requires 2 fully charged batteries to bring life to the beast. I am working through some of the starting issues, but for now its all hands on deck when I push the go button! I would be concerned about running a bunch of camping goodies off of one of my batteries, especially a fridge which is at the top of my list.

Its just the joy of an older rig!

I wonder what the alternator output on my burb or on idaSHO's powerstroke is?

 

[ntsqd]

This is the VSR that I have:
http://www.bepmarine.com/125-Amp-Voltage-Sensitive-Relay-(VSR)-166-1468.html

This is the ACR that I was looking at prior to buying the BEP product. (Thanks to Whatcharterboat for pointing me at them.)
http://bluesea.com/category/2/productline/overview/387

Both companies offer "Add a battery" packages.
http://www.bepmarine.com/Single-Engine,-Two-Battery-Banks-180-1460.html

http://bluesea.com/category/2/productline/overview/329

 

[Travelmore]

Forget all the gadgets. All you need to do is find an outlet/wire that only gets power when the vehicle is on. Connect the battery to it. When the ignition is on it charges the battery. When the ignition is off the ignition isolates the battery from the primary batteries allowing you to run your radio or anything else you attach to it without draining your primary. And no the wire doesn't need to be thick 0 gauge wire to charge your battery.

 

[ntsqd]

You're right, it doesn't.

However the rate of charge from a tiny wire is going to be tiny. If the drive time is long enough then no problem. If the drive time not, then a problem. Should the remote/'house' battery be in a deep discharge state the voltage drop in a tiny wire is going to be large, which will prolong the charge time.

 

[earthmuffin]

Forget all the gadgets. All you need to do is find an outlet/wire that only gets power when the vehicle is on. Connect the battery to it. When the ignition is on it charges the battery. When the ignition is off the ignition isolates the battery from the primary batteries allowing you to run your radio or anything else you attach to it without draining your primary. And no the wire doesn't need to be thick 0 gauge wire to charge your battery.

I considered this as well, but with a twist....

What if a guy were to use that ignition on hot wire to power a continuos duty solenoid that would isolate the deep cycle when the ignition switch was off and allow charging when the ignition switch was on.

Would that work?

 

[ntsqd]

It would, and is what was used for years before the diode bridges (boo, hiss) came into prominence. The down side is the parasitic draw of the solenoid. It's not a lot, but it is there. A pitfall of the scheme is if you happen to select a wire that is live during cranking mode too. Then the solenoid connects the batteries together and tries to draw a large current through the charge wire, which frequently is too small for that job and the solenoid is definitely too smal for that job. Another pitfall is if you should happen to leave the ignition on for some reason.

 

[matt s]

Ignition wires may run to more than you realize. For instance on my (granted very old) blazer I had my 3rd battery (a large jump start unit) plugged into the cigarette lighter to charge. My lighter port is not hot unless the ignition is on. However when the ignition was off the 3rd battery still plugged into that port would power the dash and a few other gadgets on the same side of the ignition cutoff. No biggie, but if there is a parasitic draw from the dash, radio or other item then it kinda ruins the fun when you come back to the rig after a hike and find your accessory battery is dead.

That is all a very long way of saying you would be wise to have a cutoff (a marine switch is cheap and simple) from the system. Just using an ignition wire may not isolate you as much as you might think.

 

[earthmuffin]

What do you guys think of this?

http://www.colehersee.com/pdf/hot_feed/D-617_SmartBatteryIso.pdf

It has a boost button for connecting all batts for starting which is nice.

My only concern is that when the vehicle is shut off, the house load is drawn off both batts until both batts are down to 12.7V and then it isolates. I wonder if it could be tricked into isolating as soon as the vehicle is shut off?

Looks like you can get it for around $100 online.

 

[ntsqd]

Interesting, another variation on the VSR-ACR theme, only using a constant duty solenoid like those commonly used before the diode bridges came along instead of a solid state relay.