When running dual batteries,

[CyberSniper]

Get an ANL fuse rated for the short circuit current rating of the wire, or 200% more than what you think you will ever run through it. You don't want a voltage drop across it but you also want to prevent unintentional welding. Spartan Systems sells a nice gold plated one with a nice fuse holder and a nice 1' lead for $20.

Grounds are easy to screw up. It is easy to end up with a floating ground. The best way to avoid it is to ensure the grounds are always substantial in size and have high quality terminations. Positive side is easier to troubleshoot. I try to have a 2/0 wire to the frame and from that same spot on the frame a 2/0 cable to the engine somewhere (I like to use the alternator bracket). Then 2/0 from the body (ideally, the cab) to that same spot on the frame. However, it is not always convenient to do that. And you can still end up with weird crap happening (ever notice GM always puts grounds to the core support so the headlights work).

Yandina makes several nice battery combiners at a decent price. It is basically relays/solenoids inside with a little bit of logic. It works great for charging the second battery or light loads (read: not winching). It is about twice the cost of a ColeHeresy 200 amp continuous duty solenoid. I used to use diode-based isolators but I don't anymore.

I started using BlueSeaSystems switches. They make a nice one that allows you to run off one battery, combine two, or turn it off altogether for about $25.

 

[Moody Bricker]

Ok,,thanks for the info. But,,but what about 4 battery, ,2 for the truck and 2 for the camper chalet?

 

[CyberSniper]

It depends on how you want to use them. I would keep the "camper" batteries separate except when you want them to be connected for charging. I assume you have a "converter" of some kind for charging house batteries. You can use that to charge the ones in the truck also, but I would not leave them always connected. Deep Cycle batteries have a different discharge behavior and it won't work out that great unless you are using all batteries of the same vintage and model/type.

Cole Hersee 24213 works pretty nice for isolating/combining batteries if you want a remote option. It is what I am using (several of these) in a 1978 GMC Royale for different things. Blue Sea Systems 6011 works well for combining batteries manually.

 

[anwat]

Don't know if this will get seen, since I'm trying to revive a 2010 thread here, but it definitely seems like the place to go with my question. I'm running a dual battery setup, no isolator. I just went out and purchased two new Odyssey Extreme PC1500s to the tune of $600. Before I put them in, I decided to do a check on my wiring and make sure everything was tight, corrosion free, and had good insulation on it. I thought we were good, but i did have a question about whether or not it was "proper" to use ring terminals at the battery or if I should be running a post with a traditional cable end. Then I read this thread, and now I think I may have my grounds amiss.

So, first question: I'm running a 0ga cable as my primary cable off the passenger's side. It goes all of 3" to a solenoid, then to the starter via another 0ga. Your typical Ford starter setup. The only other wire to that battery is the 10 ga charging wire, with a fusible link, that runs to the bus bar then on to the 200 amp alternator, and the 0 ga that connects it to the driver's side battery.
The driver's side has an 8 ga to the FItech ECM, plus a 10 ga charging wire from the other (+) terminal, which I now think is redundant...with the 0ga already connecting the two batteries, that 10 ga is useless, right? The batteries are actually acting as one, neither one will charge above the other, correct?

All the power for everything comes from the bus bar, the oem and aux fuse block, the compressor, lights, fans etc. The charge wire and the sense wire from the alternator both run there also.

I think I'm OK so far, but after reading about the grounds here, I may have a problem. In other trucks, I've had hard to find electrical problems more often than not turn out to be related to poor grounding. So, I'm a big believer in grounding. If it's important, I try to run a ground cable to it that's at least as big as the power cable supplying it. So, I've got a 0ga to the passenger's side frame rail from the pass. battery. I've also got a 2ga from that spot on the frame rail to the block, as well as a 2 ga from the battery to the pass. side body. Because my compressor and fuel pump are grounding to the frame in the rear, I also ran a 2 ga from the battery to the pass frame rail just over the rear axle, and ran the ground cables from both to that same spot. The driver's side battery is grounded to the driver's side frame rail via a 0 ga, to the driver's side body via a 2ga, and to the block via a 2ga. I also ran a 2ga from that battery directly to the aux fuse block, since I'm connecting a lot of my grounds to there (radio, lights etc. ).
Should I run a cable from ground to ground on the batteries? Is it OK the way it is? I've had no issues with anything electrical, but i also know that doesn't mean it's right.
The entire system seems to be running correctly, it will idle at about 13.7 v measured at the batteries and the bus bar; with everything on except the winch, it's still at about 13.7v at the batteries. At the bus bar it's about 14v.

I'm no electrician, nor do I play one on TV. So I know this sketch isn't electrically correct, but it does the job for me...maybe it will make it easier to understand for you also.

 

[Wes Harden]

Your grounds are good, both Og and both to frame and body.
Nothing wrong with ring terminals. Less maintenance in mind than lead clamps.
Your diagram makes sense to me. My only question is the ecm power lead, Doesn't that need to be switched ?
Depending on routing and exposure to damage, I might consider a fuse in the cable between the 2 batteries.

 

[rampage]

Just at a quick glance at your schematic, yes the 10 gauge coming off your alt is redundant and you can eliminate it. I’ll take a better look when I have more time.

 

[anwat]

Good news so far, then. As far as the ECM switching, I misrepresented a bit. The connection runs to the six pin connector, which then distributes it to the ECM, it goes from there to the fan relays, the fuel pump, so I think there's an internal switch there...the instructions said to wire it directly to the battery. While I don't always follow instructions, I try to when it comes to electricity that I don't completely understand. Possibly because the fuel pump is directly wired to the ECM because it uses PWM, so no relay. Kind of a poor design in my opinion, since it's like a 12 ga wire that goes all the way to the back of the truck, plus I installed a inertia switch in the line, so that adds even more resistance.
As far as a fuse between the batteries, what amperage would you think? I have one of those fancy ANL maxi fuse holders I ordered by accident, that would work on the O ga cable...I'd imagine I'd need a pretty high amperage fuse though. I've got a 150 amp circuit breaker just before the bus bar, never tripped it, but the starter wouldn't go through that.

 

[Wes Harden]

I am thinking 2x the current of the conductor.

 

[Blue85]

Your typical Ford starter setup.

Typically, they're done wrong because a Chevy starter is not a Ford starter. Running through 2 solenoids like you're doing is not ideal, but usually still works better than the factory setup.

So, I've got a 0ga to the passenger's side frame rail from the pass. battery. I've also got a 2ga from that spot on the frame rail to the block, as well as a 2 ga from the battery to the pass. side body.

The #1 ground current path on every vehicle is from the BLOCK to the battery, because the #1 current return is from the starter motor. That's why factory battery cables go from the battery to the block directly, with a smaller connection to the frame/body. Sure, electrical gremlins can pop up from poor body grounds, but a weak connection to the block can light the car on fire.