Dual Battery wiring Q's

[stevezero]

I'm putting together my parts list for my dual battery system, and I have a couple of quick questions about my dual battery setup I'm working on.

97 LX450. Battery #2 will be going in USPS battery tray (thanks Dan). Washer bottle has been reloacted (with minimal bloodshed).

What guage wire to use between batteries? I'll be running the surepower 1315-100 amp battery seperator. http://www.surepower.com/pdf/separatorinterconnect.pdf

With this setup, you do not have to alter any of the existing wiring on the primary battery. The seperator closes when the main battery is at 13.2 volts. It seperates below that voltage. Basically, you take a lead from your starting battery, a lead to your second battery, and a ground wire. You can also wire up a switch to manually combine both batteries (self jump). I guess their self jump feature on such a small seperator works by paralleling the batteries, and letting the good one dump some current into the weak one, rather than dumping all of the current to run the starter.(dont know exactly).

I'm debating on 4 gauge or 2 guage between the surepower seperator and the batteries. I'm going to install a 100 amp marine circuit breaker (since the seperator is 100 amp, and the alternator puts about 90 amps). These leads "should" not see more than the 100 amps.

I'll pull 2 gauge (+ and ground) to the rear of the truck to a bus block. That will be on a 150 amp(or larger) marine circuit breaker. Individual circuits will be fused appropriately off the bus block. If more capacity is needed, I can go with a larger fuse(in place of the breaker), or pull an additional circuit.

I'll pull a 4 gauge (+ and ground) to a bus block under the dash for accessories. That will be on a 50 or 100 amp breaker. Individual circuits will be fused appropriately from the bus block.

Grounds from battery 2 will be to the body and the engine block. Grounds from the feeds to the back will tie directly to the battery.

I'm using everstart maxx- 1N batteries (both top posts and side posts). They are made by exide, available from wally world. free 3 year replacement, prorated after that. 1000 CCA and 200 min reserve. I'd like to use the side posts for the surepower feeds, and the top posts for the existing wiring (on battery 1) and accessories (battery 2). I think the side posts should be able to handle that current (since they are used for connections on side post cars).

Crude schematic below.

Suggestions are greatly appreciated.

 

[Beowulf]

I used 00 between the 2 batteries.

-B-

 

[Hants]

What are you running in the back that requires 150A? Most fuse blocks I've seen are limited to 100A or less, aggregate.

I plan to use 2/0 (00) between the batteries. This is due to the Warn Winch that I'll be adding at the same time (up to 475A peak draw with some models).

If you're not running a Winch or Inverter, planning on 100A between the batteries is probably sufficient. Remember, though, that your primary battery can output > 100A into the secondary if the secondary is severely discharged. Think: camping for multiple days without running the truck, then fire it up to head home and fuse(s) blow.

EDIT: IIRC, the Surepower uses PWM (pulse-width-modulation) to limit the load going through it, so the above may not apply.

Planning (and fusing) for 60A to each of your fuse blocks may be sufficient (add up the loads, and bump for future expansion).

 

[stevezero]

150 might be overkill. I figured if I pull a big enough feed back there, I wont have to pull again. The bus could feed everything. Looking to run an air compressor, fridge, inverter, and whatever else might end up back there. Home theater system, margarita mixer....Even a ceramic heater if it gets cold ..

The circuit breakers I'm looking at wont reset if there's a fault. I like that idea instead of fuses. By the time you order a fuse block, and spare fuses, youre almost at the cost of a breaker. I figure the 100 amp breaker prior to the seperator should mitigate the risk of too much current and grenading it.

If I do ever end up with a winch, then I'll do a 2/0 feed (through a rotary switch) dedicated for winching. Break the connection between the seperator and the batts, and join through the big copper...But that's a long way off...

 

[tech_dog]

You're running about 6 feet of wire. Just run the fattest pipe you can fit. That will keep your options open going forward and will minimize power loss.

I went with 0 gauge for that reason. I didn't think anything fatter would fit in the OEM raceway across the radiator.

T.

 

[jamisobe]

I used 2/0 from the big battery to the seperator and then to the inverter which is about 6 feet away. I also used 2/0 to ground the inverter. Everywhere else I used 2 guage though I have been considering another piece of 2/0 (1.5 ft) to ground the big battery to the engine where the inverter is grounded.

 

[619TOY]

A few observations:

1. The isolator is rated at continuous current, the circuit breaker is rated for transient current. If your primary battery were to die, you may trip the breaker trying to start the car. I would probably use a 250A breaker myself, if at all.

2. Don't forget that if the wire between the two batteries does short out, you will have a fire to deal with as you haven't protected the cable with a breaker at the secondary battery. In this situation, prevention is definately better than the cure

3. I don't want to try to tell you how to wire your setup but I wouldn't worry about protecting the 1315 as much as I'd worry about protecting the cable (either with two breakers or by making sure there is no possible way for the wire to get shorted ever . I've never seen a 1315 damaged by overcurrent.

 

[stevezero]

Thanks guys. Thats why i threw this out there for discussion. The dual batt FAQ can get overwhelming and confusing because of all the options. So far, the only part ive bought is the 1315. everything else is still up for grabs. I can do fuses on both ends of the cable, but thought the cb idea was pretty good.