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

  1. #1
    Join Date
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    Default How to make a cheap isolated dual-battery setup for $50

    So there are a lot of kits you can buy to have truly isolated dual-battery setups. Those are VERY NICE kits. They are also very expensive. I try and replicate those kits without spending as much money, while still having a similar level of quality and/or reliability. There are constantly posts on this forums about 'How to do dual-battery setups' and most are from people who don't want to spend the $$ on the kits. I didn't want to spend the money either, so came up with a simple list people need to buy to get a reliable and safe dual-battery setup.

    Step #1 - Get a beer, this will take awhile

    Step #2 - Look at the diagram - study it in detail as this is an incredibly complicated setup that will take years to learn properly. Plus, there will be a test at the end.



    Step #3 - Have another beer, that was a rough diagram and you deserve a reward

    Step #4 - Source your parts!

    Get your own batteries - I won't go into batteries, which are best, etc. I have 2 DieHard Platinum batteries in my truck and a cheap Wal-mart battery in my trailer. Some like Odyssey, some like Optima, some like Trojans

    Get your cables ($14)...for a simple setup you can go w/8 or 6 gauge, but I've found that 4 gauge battery cables with the ends cut off work well, because they are cheap and carry a decent amount of current.

    http://www.handhelditems.com/20$$-gu...e-p-47794.html

    You'll also need some 12 gauge wire. If you don't have 12 gauge wire laying around, you probably shouldn't be wiring your own dual-battery setup. Or borrow some from a friend. If you don't have any friends, turn off your computer and get a life!

    Get your connectors ($7)...you know, to connect your cables to your batteries and stuff

    http://www.amazon.com/IMPERIAL-71861...ref=pd_cp_hi_3

    Get your fuses!!!! ($13) ... you need one fuse for each battery, trust me on this one

    Go here are order part number ANB740N0N02, they are 80A ANL fuses + the fuse blocks

    https://www.vtewarehouse.com/content...nl/anlfuse.php

    Note: If you are wondering why 2 fuses, it's because each battery has power and could blow up your truck, so it's best to fuse both batteries. Put the fuses as close to the battery as is practical.

    Get your solenoid ($16) ... this is what keeps one battery from draining the other battery, or something similar to that (mostly it keeps them 'isolated' from each other so you can still start your truck to make a beer run)

    Cheap -->http://www.amazon.com/Continuous-Dut...sim_sbs_auto_1
    Good -->http://www.amazon.com/Cole-Hersee-24.../dp/B001FQL43U
    Way good -->http://www.amazon.com/gp/product/B00...ls_o00_s00_i00

    Step #5 - While you're online, order some good beer from the great Pacific Northwest (they ship everywhere!)

    http://www.northwestliquidgold.com/

    Step #6 - Wiring everything up

    Follow the picture above


    • Find somewhere to put everything in your engine compartment (or truck bed, or wherever your 2nd battery might end up...unless it's one of those fancy sealed-up battery things, don't put it inside your rig or it might leak hydrogen gas and Hindenburg your *****, so just don't do that, okay? ).
    • Make a short 4GA wire from your main starting battery POS (short for positive, not for piece of $hit)to your fuse block.
    • Make another 4GA wire from your fuse block to the isolator
    • Make another 4GA wire from the other side of your isolator to the other fuse block
    • Make a short 4GA wire from the other fuse block to your other battery POS
    • Make a single 4GA wire from the NEG on your starting battery to the NEG on your other battery
    • Connect a 12GA wire from pin on the isolator to a fuse in your fuse box that is only 'hot' when the key is in the 'ON' position (aka the truck is running)


    Note: You can use fancy heat shrink on your wire connections, and that will work very well. Or you can take a roll of electrical tape (UL Listed, please) and wrap each connector-wire connection in electrical tape. It's about 80% as effective at about 10% of the cost or effort.

    TOTAL COST - $50 (cheap) $59 (good)


    • Cables - $14
    • Connectors - $7
    • Fuses - $13
    • Solenoid - $16/$25



    Note: Cole-Hersee solenoid will be much more reliable, so spend $9 less on beer and upgrade to the nice solenoid
    Note #2: Don't try and jump-start your truck using your other battery using just this setup (ie through the solenoid). Instead, pull out your jumper cables (you DO have jumper cables, right? you didn't just cut up the pair you keep IN THE EVENT OF EMERGENCIES, right? right?) and jump from your backup to your starting battery using the jumper cables
    Note #3: The big difference between this and the fancy setups (other than the cool battery gauge things) is those will usually use a voltage-sensing time-delayed-opening solenoid-type dohickey that allows your starting battery to charge first, before charging up your other battery. If that means anything to you, it might be worth spending the $200 more to get one of those sets. If you have no idea what that means, get in line, I don't really understand it either, but apparently it's worth $200

    Final Step - Have a beer, enjoy how cool you are, and now go build a cheap $100 awning with the money you just saved.

  2. #2
    Join Date
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    Middle of Nowhere, Outer Skin of Space Ship Earth, 1 A.U. from Sol, Outskirts of Milky Way.
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    You da man!
    ...
    ...
    Current: 76 E-250, bubble-top, self-contained|couple of old Yamaha enduros
    Previous wheelers: 41 Willys|78 FJ40|78 Bronco|84 Bronco|74 Ramcharger|78 Ramcharger|79 D150 PowerWagon|77 D100|79 D400 dually, converted to 4WD, utility bed, 10' Lance|75 Westy|69 Scout, RHD|bunch of others|bunch of bikes|couple of boats|couple of motorhomes|blah blah|so what|not my idea|just doin' what I'm told|wank wank|this space for rent|candy is dandy|but liquor is quicker

  3. #3
    Join Date
    Jun 2010
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    Laguna Hills, CA
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    This is a great writeup - if I wanted to add solar to the "house battery" what would I need other then a controller and a panel - can the solar panel be charging the house battery at the same time the alternator is?

    thanks

    J

  4. #4
    Join Date
    Dec 2007
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    Somewhere west of north
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    Default How to add 60W Solar for Under $125

    Adding solar is fun and easy...first step, make sure you live somewhere other than THESE PLACES

    Step #7 - Get a solar panel ($80)

    I prefer to just use some tin foil and spare speaker wire, but if you want a real solar panel, you can't go wrong with Solarblvd

    60W on sale

    Step #8 - Get a beer

    Did I mention you can order beer off the internet? No, really...you don't even have to leave your chair! (except when the UPS guy comes)

    Step #9 - Order a 'Charge Controller' ($44)

    wtf is this, you ask? It's a complicated thingymajig that makes sure your solar panel (or tin foil) doesn't overcharge your battery, leaving you stranded somewhere warm and sunny but with a dead battery (which means no power for your cheap Edgestar fridge, and NO COLD BEER!)...luckily people way smarter than either you or I figured out how to make it also work with your normal alternator, so you don't have to keep unplugging it every time you start your truck.

    Apparently, tribes in the Amazon have a website that allow you to order this magical device delivered from the man in brown. Hopefully it survives the trip down the river and through the rainforest.

    Note: Hooking up a solar panel is really easy, check out the schematic for the above controller...a few squiggly lines and some funny arrow-things can't be that hard to do IRL, right?
    Note 2: Since like the crackhead you were in your youth, you'll jump right on any bandwagon driving by, make sure you get a larger charge controller now, so you can hook up more tin foil later, otherwise you'll have to re-buy another controller and then it won't fall under the 'cheap solar' category anymore, kapish?

    Step #10 - Hook it up like this picture




    Total cost - $124

    • Solar panel - $80
    • Controller - $44



    I'm sure there's more to it than this, right? right? I can't believe, if you have two batteries already, and you have $200, you aren't fully equipped for a solar-charged, isolated, dual-battery setup yet, right? I spent $200 in beer in MARCH! Get out your credit card and contribute to our economic recovery!!

  5. #5
    Join Date
    Mar 2012
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    California
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    Perhaps I'm not understanding your diagram correctly but I don't see how this is a true isolated dual battery system. You have one battery isolated but when you want to use it, it's run in parallel through the other. A true isolated dual battery setup would allow you to run solely on battery 1, solely on battery 2, both or neither.

  6. #6
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    Quote Originally Posted by lqdchkn View Post
    Perhaps I'm not understanding your diagram correctly but I don't see how this is a true isolated dual battery system. You have one battery isolated but when you want to use it, it's run in parallel through the other. A true isolated dual battery setup would allow you to run solely on battery 1, solely on battery 2, both or neither.
    Good point. Technically it is still 'isolated' from the starting battery, and so isn't affecting your starting ability, but it doesn't have the flexibility that many kits (that cost more) have - being able to switch around as you indicated. Adding those abilities would add significant cost and/or complexity, and let's be honest, for 80% of the people who want an isolated dual battery setup, this will work for them (plus jumper cables if they end up draining their starting battery).

  7. #7
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    Ahhh ok, "isolated" as in isolated from the starting battery. Makes sense now, thx

  8. #8
    Join Date
    Sep 2009
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    Quote Originally Posted by lqdchkn View Post
    Perhaps I'm not understanding your diagram correctly but I don't see how this is a true isolated dual battery system. You have one battery isolated but when you want to use it, it's run in parallel through the other. A true isolated dual battery setup would allow you to run solely on battery 1, solely on battery 2, both or neither.
    I'm no expert and still on step 1 of drinking beer ... but the solenoid only isolates the batteries... if you want more "features" like which one to use, etc.. cut off switches bells and whistles , etc... you would have to pay for it. A $ 60. solution to to the dual battery problem is pretty good

  9. #9
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    Cloudbreak, Arizona
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    I want to make sure I understand that you can jump the starting battery off the house
    battery .... just hook up the cables ....

    Best regards,

    Mike

  10. #10
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    Quote Originally Posted by mbuckner View Post
    I want to make sure I understand that you can jump the starting battery off the house
    battery .... just hook up the cables ....

    Best regards,

    Mike

    Yes...and really you only have to hook up the POS since NEG is already hooked up. When you turn over the key, it will engage the solenoid creating a circuit through the solenoid, but it can't handle the current draw of a starter (measured in hundreds of amps for a few seconds). By hooking up your set of jumper cables between the batteries directly, it creates a nice way for the current to flow and you can jump-start yourself. Just be aware don't do this too often, especially if (1) you use a deep cycle battery for your 'house' battery as they don't like these 'fast' current draws and it will wear out your house battery sooner than normal, and (2) you don't want to go blind.

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