Dual battery question: wiring inverter & accessories

[bwood]

There must be threads out there covering this, but I can't seem to find what I need (and I have little to no electrical experience, so bear with me). Just finished wiring a second battery in my 100 series cruiser, using the T-max kit and 2awg cable (used this as a guide).

So now I'm getting to wiring the accessories. I've got a winch wired to my starter battery, and am planning on running led tent/hatch lights, a few rear 12v plugs, an arb fridge, and an inverter off of the aux battery. I had planned on using a Blue Sea 6-circuit fuse block in the rear of the vehicle, and wiring everything to it, but with the addition of an inverter (600w xantrex), I'm wondering what the best way to wire everything is. Should the inverter be wired directly to the aux battery, separate from the fuse block? Ideally I'd like to run as few cables as possible. And what gauge cable should I be using?

 

[Mwilliamshs]

600w inverter can pull 60 amps at 12 volts and 6 AWG cable is good for that load at lengths upto 10'.

The fuse box u linked is good upto 100 amps total, 30 amp max on a single circuit. That'll need at least a 4 AWG cable upto 10'

Since the inverter exceeds the fuse box's rating, it'll need to be wired separately.

 

[patoz]

Also, your winch should be wired to the Aux battery and not the starter battery.

If you are making a water crossing and the engine stalls, the winch may get you out but what good is that if your starting battery is dead once you get back on dry land. Basically, nothing should be connected to the starting battery that is not OEM equipment, unless it's something very minor like a CB radio or small items you can plug into the cigarette lighter plugs, etc. Something like a hard wired air compressor would be OK provided you start the engine before using it.

Anything that has a large amp draw such as a winch, off-road lights, refrigerator, inverter, etc. that may be needed when the engine is not, or can not be started, should be connected to the Aux battery. If you drain it down, you will still be able to start your vehicle and recharge the Aux battery. If you plan on camping in one spot more than a day or two, solar panels connected to the Aux battery would help also.

Good luck and happy camping!

 

[ViperNL]

Also, your winch should be wired to the Aux battery and not the starter battery.

The other day I read the opposite. The person argued to hook the winch up to the starter battery as it has a direct link to the alternator and will deliver more power to the winch.

 

[RichJacot]

The other day I read the opposite. The person argued to hook the winch up to the starter battery as it has a direct link to the alternator and will deliver more power to the winch.

x2

 

[patoz]

The other day I read the opposite. The person argued to hook the winch up to the starter battery as it has a direct link to the alternator and will deliver more power to the winch.

That's a good point, however it will depend on what type of electronic battery isolator (diode type), combiner, solenoid, or ACR system you're using and how good of a job you did installing it. Any dual battery system I have ever built or installed used much heaver cables, connectors and ground points than the vehicle's OEM stuff. It also depends on how the system is designed. Are you just combining batteries, or using a A/B/Both/Off manual switch, which allows you to select which battery you want to use, and also connects the alternator directly to that battery.

If you're using a simple Batt 1/Batt 2 combiner system, you're probably better off connecting the winch to the start battery as long as you have the capability of self jumping the start battery via the solenoid from the cab, such as with the Blue Sea ACR 7622.

If the vehicle stalls, the alternator is no longer supplying anything, and now you're just winching directly off the battery. Personally, I would rather kill the Aux battery and leave the start battery alone.

Also, a lot of people will use a deep cycle battery or Hybrid Marine battery as the Aux battery. Both of these will give you much more winching time with a stalled or flooded engine, than the start battery.

 

[dwh]

The other day I read the opposite. The person argued to hook the winch up to the starter battery as it has a direct link to the alternator and will deliver more power to the winch.

That might've been me. But it is contextual and does depend on the type of isolator.

For instance a Blue Sea ACR disconnects the batteries when voltage drops, which it will when the winch is engaged. If you rigged the winch to the aux battery and the isolator disconnected the batteries, then you'd get no help from the alternator.

But some of the Blue Sea units can be forced to keep the batteries connected so then it's six of one, half dozen of the other.


But also there are power flows to consider. Say you hook the winch to the starting battery. Say a 200a draw, with a 130a alternator.

The first 130a of the 200a load will come from the alternator, because it has a lower resistance than the batteries. The other 70a will come from the starter battery, because it has a lower resistance than the deep cycle.

If and when the alternator gets hot enough and its output drops, and the cranking battery gets depleted enough, then the deep cycle will come into play to make up the difference.

Doesn't matter if you hooked the winch to the aux battery, the power is still going to flow like that (unless the wiring between the batteries is inadequate to start with). So you might as well just connect the winch to the cranking battery.


As for winching off a cranking battery vs. a deep cycle. If the engine is off, but both batteries are tied together during winching, the power will flow from the lower resistance cranking battery first, and the deep cycle will supply enough to make up the difference. Again, doesn't matter which battery you connect the winch to, that's how the power will flow.

If using only one battery with no help from the alternator, do you need to do short fast heavy pulls where the high amps output capacity of the cranking battery would matter, or long slow pulls where the lower amp but longer time of the deep cycle is going to make a difference?

I've also seen at least one isolator that was designed in such a way that you had to hook the winch to the main battery - no choice.

With a diode-type isolator, the batteries never help each other. So the most you get is one battery + alternator. For that, I'd hook to the cranking battery which can do quick high amp bursts, but will also recharge faster off the alternator. Just don't run the winch non-stop for 20 minutes at a time.


Which is another important point. Winches have duty cycles. Use it a bit, then stop and let it cool off a while. If you are doing that - and you should be - and the engine is running, then the burst amps and quick recharge of the cranking battery is the winner. Especially if it's backed up by the heavy reserves of the deep cycle.

 

[MagicMtnDan]

There's a lot of information related to this subject on this forum.

Here's a wiring diagram that might help:

Link to above: http://www.expeditionportal.com/for...ear-storage-area-(behind-the-rear-seats/page2

Here's a really good thread to review: http://www.expeditionportal.com/for...ke-a-cheap-isolated-dual-battery-setup-for-50

 

[patoz]

For instance a Blue Sea ACR disconnects the batteries when voltage drops, which it will when the winch is engaged. If you rigged the winch to the aux battery and the isolator disconnected the batteries, then you'd get no help from the alternator.

But some of the Blue Sea units can be forced to keep the batteries connected so then it's six of one, half dozen of the other.

Thanks dwh, I just learned something I didn't know about the Blue Sea ACR. That does change things considerably.

 

[bwood]

Thanks for the tips. I had decided to wire the winch to the starter battery for the same reasons others mentioned above.

As for wiring the accessories to the aux battery: since the blue sea 6-circuit fuse block won't support the addition of a 600watt inverter, would something like the Blue Sea Safety Hub 150 be a better choice? As Mwilliamshs mentioned, I could run 4awg cable to the 6-circuit fuse block, which would power a fridge, some LED hatch lights, and 12v outlets, then wire the inverter separately direct to the battery, but I'm hoping to cut down on the number of cables that need to be run through the firewall. So, if I can get away with running cable (I've got a bunch of 2awg left over) from the aux battery to a single point (safety hub 150) in the rear of the vehicle, and wire everything to that, it seems like it'd be easier. And if I went that route, do I need to run negative cable back up to the aux battery? or ground to the chassis somewhere near the fuse block?

 

[umpqua]

^^ This.

The other day I read the opposite. The person argued to hook the winch up to the starter battery as it has a direct link to the alternator and will deliver more power to the winch.

 

[patoz]

Thanks for the tips. I had decided to wire the winch to the starter battery for the same reasons others mentioned above.

As for wiring the accessories to the aux battery: since the blue sea 6-circuit fuse block won't support the addition of a 600watt inverter, would something like the Blue Sea Safety Hub 150 be a better choice? As Mwilliamshs mentioned, I could run 4awg cable to the 6-circuit fuse block, which would power a fridge, some LED hatch lights, and 12v outlets, then wire the inverter separately direct to the battery, but I'm hoping to cut down on the number of cables that need to be run through the firewall. So, if I can get away with running cable (I've got a bunch of 2awg left over) from the aux battery to a single point (safety hub 150) in the rear of the vehicle, and wire everything to that, it seems like it'd be easier. And if I went that route, do I need to run negative cable back up to the aux battery? or ground to the chassis somewhere near the fuse block?

IMO, you should use the frame or frame/body combination, since either of these are better conductors than one single 2 AWG cable. However, I will present this and let you make your own decision.

https://www.w8ji.com/negative_lead_to_battery.htm

 

[WSS]

I run two batts with a ford 200amp solenoid to combine and a noco isolator to handle the charging and maintaining of both batts. Power is supplied by a custom built 110amp alternator with a 4awg cable from alt to noco isolator, from isolator to batts it's 6awg. BAtts to starter, winch is 2awg, 4awg to starter. All welding cable (fine strand, abrasion and heat resistant)

I use anderson connectors on the system to make it easy to connect to make 24vdc for my readywelder. I use the same connectors on my jumper cables I have a connector out the front and a short section of jumper cable to connect to battery while it is out of the vehicle, this way it can be carried to a vehicle that cannot be reached by my vehicle.

cables from alt. to isolator and batts:

 

[bwood]

Ok, so hopefully this is the last question before getting this done. I installed the Blue Sea safetyhub 150 in the rear cargo area, running a 2awg cable from the aux battery + back to it (fused near the battery). Then ran another 2awg cable from the negative bus of the safetyhub as a ground to the chassis nearby. Got lights, fridge, and 12v outlets wired to the safetyhub and all are working. Last on the list is wiring a samlex 600w inverter; I ran 6awg cable from both + and - terminals on the inverter to the safetyhub. However, there's another earth ground lug on the inverter that I'm not exactly sure what to do with. Should this be separately grounded to the chassis as well? Or since the - terminal is actually running through the chassis via the safetyhub, is it necessary?

 

[dwh]

It's a safety ground. In case the thing shorts out internally, it will carry current to ground to blow a fuse instead of sitting there like a booby trap waiting for a boob to come along and get shocked.

In the manual, page 39 section 8.6 tells you to connect it to frame ground using #8 wire. (Bigger than #8 is fine, smaller is not.)