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.
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
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
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)
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!)
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.