How to make a cheap isolated dual-battery setup for $50

[Jelorian]

When I did mine, I used 2AWG from EWCS on amazon.com.

Made in USA and great customer service. I had an issue with my first order. They shipped me 2/0 AWG instead of 2 AWG. Not their fault, it was Amazon's, but they told me to keep it and they immediately sent out the right sized cable, no more questions asked. I had no use for 2/0 AWG so I told them to send me UPS label and I'll send it back. I will buy more from them when I install a 3rd battery to my rig.

 

[archipeep]

Forgive me if anybody posted this, but I've scrolled through and didn't see it. Why are there two fuses between the batteries? Wouldn't 1 be enough? My build has the batteries within two feet of each other with an isolator/relay between; I'd think if I were running the battery to the back of a truck, sure, so close I'm thinking it's overkill. I, however, am not a master at this stuff and am looking for some advise.

Thank you

 

[IdaSHO]

Purpose of the fuse(s) is to kill power to the hot lead in the event of an overload or a short.

When you have two banks, BOTH are sources of power, so you need two fuses, one at each end of the conductor.

 

[randy h]

My build has the batteries within two feet of each other with an isolator/relay between

With that short of a run, even if you wanted to fuse near each battery, there might not be room for it without your run nearly being all fuse holder. However, Blue Sea Systems 5191 Fuse Block Terminals fit right to the battery terminal. I wish I had seen these before I built my system. I had to add stupid looking loops in my run to fuse the way I wanted. Here they are at Amazon:
Amazon Link

 

[Nd4SpdSe]

For the solenoids, I run a PAC-200, and picked it up for C$75, but that was with a military discount, but regularly sold for C$99...so around the same price as the 80A, but way more amperage (can handle my 165amp alternator), and a plastic housing which helps much against rust, especially those of us who experience winters and road salt

 

[Hillbilly Heaven]

I went with what most might consider overboard but used 500 amp relays in my triple battery setup. Reasoning was because of heavy cranking and winching loads.
Compared the PAC500, IB500, and the BIR500. They all appear the same just a different label. Went with the IB500.
http://www.sonicelectronix.com/item_28365_The-Install-Bay-IB500.html?from=701

 

[dlichterman]

For the solenoids, I run a PAC-200, and picked it up for C$75, but that was with a military discount, but regularly sold for C$99...so around the same price as the 80A, but way more amperage (can handle my 165amp alternator), and a plastic housing which helps much against rust, especially those of us who experience winters and road salt

I also have that same solenoid and it has been working great for 3 years.

 

[Altide8]

What would be the highest gauge wire for a simple setup? that is safe to use?

 

[murrayargo]

This is dependant on expected loads upon your system.

Right now I just plan to use it for a small inverter in the back. Basically just to charge laptops, phones, run some lights on occasion


Sent from my iPhone using Tapatalk

 

[Hillbilly Heaven]

I would mount the inverter as close to the battery as possible. The electrical losses are greater with DC are higher than AC.

 

[cgregs32]

I just finished installing my setup yesterday. I have a Trimetric, and it was pretty cool to see the system working. My setup uses a solenoid that I have wired to an On/off switch. I did not connect the solenoid to an ignition wire. My question is when is the best time to connect and isolate the two batteries? For example: Connect two batteries before or after vehicle ignition? Isolate Batteries before or after the engine is turned off? I don't want to damage anything, and I remember someone mentioning about this in the thread but I cant seem to find it. Can I Isolate the batteries while my Aux battery is being charged? Thanks!

 

[DiploStrat]

In simplest Terms ...

You combine the batteries when either battery is being charged and disconnect them when neither is being charged. Period It really is that simple.

You can leave them connected when cranking the engine, assuming that your wiring is of the proper gauge.

You are actually making a good case for a key controlled system, assuming that you have no charger other than the vehicle's alternator or an automatic relay if you have a charge source (e.g. solar, shore) connected to your camper battery. I am a great fan of making this as fool proof as possible.

 

[Hillbilly Heaven]

The 3 position switch makes it about as foolproof without going to an automatic system. I am not a fan of the automatic systems as I want the freedom to do what I want when I want. First position connects the two batteries only when engine is running. 2nd or middle position isolates both batteries all the time. Third position connects both batteries all the time. Third position comes in handy if the main battery fails and you can then self jump start yourself. Never ever leave the two batteries connected for an extended period of time. Time being more than a day or two. Reason not to leave connected is if one battery fails with a shorted cell or some additional power drain it will drain the other as well leaving you stranded. I generally leave mine either off or in the first position making it worry free.

 

[dlichterman]

The 3 position switch makes it about as foolproof without going to an automatic system. I am not a fan of the automatic systems as I want the freedom to do what I want when I want. First position connects the two batteries only when engine is running. 2nd or middle position isolates both batteries all the time. Third position connects both batteries all the time. Third position comes in handy if the main battery fails and you can then self jump start yourself. Never ever leave the two batteries connected for an extended period of time. Time being more than a day or two. Reason not to leave connected is if one battery fails with a shorted cell or some additional power drain it will drain the other as well leaving you stranded. I generally leave mine either off or in the first position making it worry free.

This is what I've got and I like it.

 

[dwh]

The 3 position switch makes it about as foolproof without going to an automatic system. I am not a fan of the automatic systems as I want the freedom to do what I want want.

It's trivial to add a switch to the cheap solenoid setup to force/on force/off the solenoid, while still having it ignition controlled automatic when you want it.

Simpler and easier than the marine battery switch, and does exactly the same thing.