How to make a cheap isolated dual-battery setup for $50
- Thread starter evldave
- Start date
FLHummer
New member
Finally got around to installing my dual battery setup today based on evldave's initial design on page one. I am wondering if I have a bad solenoid because I am getting continuity between the two posts for the positive from the batteries even when the 12V trigger isn't hooked to anything. Shouldn't get any continuity right, only when the 12V trigger is initialized?
dwh
Tail-End Charlie
Shouldn't get continuity when the solenoid is de-energized AND the batteries are disconnected from the solenoid.
With the batteries connected, you have continuity from the post on one side of the solenoid, though that battery to ground, through the ground to the other battery, through the other battery and to the post on the other side of the solenoid. Backdoor continuity.
Open the circuit somewhere - disconnect the ground cable from the aux battery - and try it again.
Nice clean work BTW.
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Finished mine up this evening. The Tundra didn't have a bunch of space, but I was able to fit 2 Optima Yellow top's on their side facing in. in the original battery location. Everything is mounted, wired and I ran the truck and checked all connections for shorting and such. Not sure this ended up a ton cheaper, but I am confident in how it is wired and what I am doing with it.
Thanks for the writeup!
Thanks for the writeup!
RichardT
Adventurer
FLHummer
New member
Have to agree. Not a huge savings in the long run but I ended up with better components than you get with the kits and it's all fused.
Thanks, very happy with how it turned out. Couldn't have done it without evldave's original posts as well as all the responses from everyone else.
dwh
Tail-End Charlie
You don't. The alternator charges the starting batteries. The solenoid isolator ties in the auxiliary battery so it gets charged at the same time.
Did mine this way... came out a few bucks cheaper by not buying beer.
And I had 50 feet of brand new 4awg welding cable that I got with my portable welder... the previous owner had a 2awg stinger and a 4awg ground cable on it... not sure what the logic was there. I upgraded both to 1awg, so Ive got a nice supply of heavy wire for power projects.
Just an Fyi... A good budget way to crimp battery lugs is to take a small worn out cold chisel and grind the end flat so you've essentially got a rectangular punch. Then pinch a pair of vice grips on the sides of the crimp section, place on an anvil/vise/concrete floor, and give the punch a few good whacks with a hammer. The vice grips keep the crimp from squashing out flat. Works much better than smashing the crimp with a hammer or squishing it in a vice. Not as good as a proper crimper, but it does work quite Well.
And I had 50 feet of brand new 4awg welding cable that I got with my portable welder... the previous owner had a 2awg stinger and a 4awg ground cable on it... not sure what the logic was there. I upgraded both to 1awg, so Ive got a nice supply of heavy wire for power projects.
Just an Fyi... A good budget way to crimp battery lugs is to take a small worn out cold chisel and grind the end flat so you've essentially got a rectangular punch. Then pinch a pair of vice grips on the sides of the crimp section, place on an anvil/vise/concrete floor, and give the punch a few good whacks with a hammer. The vice grips keep the crimp from squashing out flat. Works much better than smashing the crimp with a hammer or squishing it in a vice. Not as good as a proper crimper, but it does work quite Well.
dlichterman
Explorer
Every time it comes up I can't recommend this crimper enough. I've used it for almost all the wiring on my truck and it makes crimping large lugs really easy.
http://www.harborfreight.com/hydraulic-wire-crimping-tool-66150.html
dlichterman
Explorer
Yeah I went with HF because I assumed I'd use it once, but I've used it for almost every wiring job on the truck, and I've got another one in progress right now.
Is this possible? The two batteries are NOT connected, but must be charged by the alternator. i.e. can the alternator isolate the two?
Been out on a work trip...let's get some updates going!
Here's an updated basic diagram, with the fuses for the solar array (buy two panels, then start calling it your solar array, people will think you are either really cool or some diabolical madman bent on world domination)
Now some additional comments...
Using an 80A isolator when trying to automagically jumpstart your car
While you may be able to jumpstart your car by using the smaller current isolator, there is a real chance you will 'burn up' the isolator. This happens when the charge between your starting battery and your house battery is great...ie your starting battery is at 8V and house battery is at 12V. When that differential happens, it's like water flowing down a steep hill instead of a shallow hill - more faster! More current! More cowbell!
Why is this a problem? When isolators 'fail' or 'burn up' - they don't always show it! In fact, the most common failure mode for an isolator being exposed to excessive current is to 'fuse' the contacts inside, with no evidence showing on the outside! OUCH that sounds bad! What does all that fancy language mean? The isolator will always be on, your batteries will always be connected, and you'll be draining both at the same time. Fine in town, not so great when you've been hanging out in the Nevada desert after the apocalypse and the zombie hordes are coming your way...and your truck won't start because you've drained both batteries drinking mail-order beer out of your cheapo fridge.
Wiring in two separate batteries, with one or two isolators
If you don't need your two house batteries separate from each other - you want a big battery bank...just wire the two batteries in parallel after the solenoid.
If you want your starting battery isolated from your house batteries and you want your house batteries isolated, you need to isolators. Just hook them both up the same way...sorry I got lazy making pictures, so you'll need to visualize it
Hooking up fully isolated, fully automatic, with manual bypass starting, house, and trailer batteries (whew!)
This is only for the most experienc...meh, that's a load of crap...this is really easy!!!!! I have basically this same setup in my truck and I did the whole thing drunk!
This diagram is really not that complicated. A few things to remember:
- I've upgraded the 'jump start' solenoid to 200A. This gives us plenty of extra capacity to flow current if we want to use the solenoid to jump start our truck instead of using jump cables (lazy bastard). Better yet, order the way good isolator and get 500A!
- I also upgraded the fuses to 200A. You know, because if I didn't do that I might blow a fuse or two (depending on the voltage difference of the batteries, you were paying attention earlier, right?)
- I also upgraded my wiring to 2GA. Remember, always overcompensate for the size of your...wire! We could have probably survived with 4GA, but what if we want to put in a winch later? hmmm, 2GA would likely run the winch, 4GA would definitely NOT run a winch. hmmm...500A isolator...2GA wire...winch, 2 fully engaged batteries...this might need it's very own 'how to wire up your winch really cheap' addendum...
- I put 'in dash' switches for each isolator. This is a little complicated...each switch needs 'power' from somewhere in your cab. I'm sure you can find it. Just wire the switches with power from within your cab and then run the wire to the solenoids. By doing this you can 'turn on' your solenoids without having to start the truck!
- The trailer circuit is 80A. This is likely the most you will ever need. Remember overkill!
The fastest way to figure out where to run your wire to the fuse box is a 12V detector thingamajig. Turn your key to 'ON' (don't start truck) and then start probing empty holes in her fusebox. At some point your thingamajig will light up. Write down all her locations that lit up your thingamajig and turn her OFF. Then start probing those same empty holes in her fusebox that lit up your thingamajig again. Find any empty hole in her fusebox that lit up your thingamajig when she was turned ON but got no light from your thingamajig when she was turned OFF - that's the circuit you want to use (ALL THE TIME, if you get what I'm sayin