Dual Battery Wiring Help (1 Viewer)

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Rea1994

Rea1994

Joined
Feb 17, 2015
Threads
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111
Location
Northridge, CA
Hello Everyone,

First off I have to say thank you to @NLXTACY for all of the help with this already, but I would like to know what you guys think, and what suggestions you have as well.

I want to add a dual battery to my truck, and I would like the ability to self jump. I know there is the IBS system and NL, but those are quite expensive. I was looking at the blue sea 7622, but wanted to know if the 4/0 awg wiring like they recommended is necessary, or I can use smaller wiring? Also, what size fuses would I need between the ACR and each battery? If you guys have any other suggestions for other systems that have the capabilities of the blue sea please feel free to share them.

I know there is a FAQ on the dual battery setups, but I didn't see a lot of info on wiring and other things of that sort.

Thank you everyone in advance!
 
Lots of options out there. Lots of beautiful installs as well. It also depends on what you want to accomplish with your system. The Blue Sea ML-ACR that you mention looks really nice I think for the price in my opinion. When it was all done and said, I think I spent around $1K, but that included Photomans alt bracket, used Sequoia 130A alternator, and a 1500 W inverter I installed in the rear. IIRC, just the 1/0 ga wire, lugs, 175 fuses/holders and heat shrink cost close to $150-$200. I went with a simple isolator system, and two Blue Sea switches. One to join the two batteries, and one to provide power to my winch. Comparatively speaking, the cost for the just the isolator and one switch was probably around $120, but I got the isolator on sale for $60. BTW, fuses should be based on current carrying capacity of wire type / gage being used which in part will be determined by the length of wire aside from the power required by the load. My advice is to do it right, and spend the money on quality wires, lugs/ terminals, etc. You do not want to save a few $$$ on circuitry that can potentially be carrying hundreds of amps.

Here a link to my system for comparison.

https://forum.ih8mud.com/threads/canmans-dual-battery-and-inverter-install.448921/

Here is a nice wire gage chart as well.
image.jpg
 
I used a Blue Sea 7622 and I went with 1/0 welding wire. I didn't use any fuses. Note the in cab switch has 2 bright red LEDs that are always on so be strategic where you place it.
 
canman said:
Lots of options out there. Lots of beautiful installs as well. It also depends on what you want to accomplish with your system. The Blue Sea ML-ACR that you mention looks really nice I think for the price in my opinion. When it was all done and said, I think I spent around $1K, but that included Photomans alt bracket, used Sequoia 130A alternator, and a 1500 W inverter I installed in the rear. IIRC, just the 1/0 ga wire, lugs, 175 fuses/holders and heat shrink cost close to $150-$200. I went with a simple isolator system, and two Blue Sea switches. One to join the two batteries, and one to provide power to my winch. Comparatively speaking, the cost for the just the isolator and one switch was probably around $120, but I got the isolator on sale for $60. BTW, fuses should be based on current carrying capacity of wire type / gage being used which in part will be determined by the length of wire aside from the power required by the load. My advice is to do it right, and spend the money on quality wires, lugs/ terminals, etc. You do not want to save a few $$$ on circuitry that can potentially be carrying hundreds of amps.

Here a link to my system for comparison.

https://forum.ih8mud.com/threads/canmans-dual-battery-and-inverter-install.448921/

Here is a nice wire gage chart as well.
View attachment 1085232
Click to expand...

Nice chart and from the US Coast Guard
thumb.gif
 
You actually can spend much less, with a much easier install using a Blue Sea 7610. You loose the ability to self jump with the inside switch, but you can carry jumper cables for the 1 time you will actually need to do this. Then you can down size your wiring to 2 ga and everything is neater and more compact. The 80 series alternator only makes 90 amps and so you can size the ACR to that.

Even combined the flows between batteries rarely exceed 20 or 30 amps. A discharged battery is still at 11 volts or so so the delta between the voltages is only 2 or 3 volts, which means the current flow will not be the huge inrush currents everyone fears. Likely worst case 50 amps, which the ACR can easily handle. In fact it's rated by Blue Sea for 200 amps for 5 minutes or 120 amps continuously.

You need to size the fusing to the wire. So for 2ga, assuming good marine wire, 150 amp fuses provide good protection. I really like ANL fuses and the holders from Blue Sea but any of the appropriate size will work. Since the job of the fuse is to protect the wire from melting, you need it as close to the battery as possible-the Coast Guard says within 7 inches.

Not fusing a big wire is poor practice. You may get away with it, but if things go bad, your truck catches on fire. It is true the factory does not fuse the starter main, but they have real engineers designing the wire size and path. Most back yard mechanics don't have the same experience or knowledge.

In my view, the Blue Sea ACRs are a great value. They have a great and detailed website, great tech support and are water and vibration resistant-perfect for mounting in a Land Cruiser. Not to mention, the hook up is only 3 wires in the case of the 7610. I'll try and get some pictures of my install if you would like.


One last thing about wire. Not only is the size important, but so is the rated temperature of the insulation. For Marine grade wire, it will usually have a 105C rating, where as welding wire is 75C. The fuse sizing you need will vary a bit based on the temp the insulation melts on the wire. As an example, 2ga wire with the 105C rating could be fused with a 210 amp fuse max, where the same wire with 75C rating would need to be fused at 180amps max. Blue Sea has great ampacity charts on their website.
 
Thank you guys. That helps a lot. @iptman Thanks for that! If I end up going that route I'll have to keep that in mind!
 
@Cruiserdrew Thank you for that! That's the one thing I've been struggling with is that should I just give up the self jumping ability for the sake of making the system easy. I mean you're right though. How often are you going to need that? And it's not a big deal to carry jumpers.
 
Last edited:
4/0 seems pretty extreme. I used 2 gauge wire between the two batteries and the blue sea acr 7622. The highest load it will ever see for any appreciable time is during winching, and the winch I have is wired directly to the starting battery and only pulls max 350 amps total. So max amps from the house battery is probably in the area of 150, with maybe an 8 ft total circuit length from one battery to the other.
 
I have Blue Sea 7610, 2ga wire and 150amp mega fuses at each battery.
 
coax said:
4/0 seems pretty extreme. I used 2 gauge wire between the two batteries and the blue sea acr 7622. The highest load it will ever see for any appreciable time is during winching, and the winch I have is wired directly to the starting battery and only pulls max 350 amps total. So max amps from the house battery is probably in the area of 150, with maybe an 8 ft total circuit length from one battery to the other.
Click to expand...

I think he meant 4awg not 4/0
 
NLXTACY said:
I think he meant 4awg not 4/0
Click to expand...

No no I meant 4/0, because that is what blue sea's website says is required, but I know that it will never see that kind of power, which is why I was asking.
 
Haha that's like garden hose. I ran 1/0 (thinner) but still a pain in the ass to work with. 4/0?! Ugh.
 
Yeah exactly why I asked. I thought no way!
 
In the Blue Sea instructions it states that the 4/0 cable is only required if you have a 300A continuous load.
 
Rea1994 said:
@Cruiserdrew Thank you for that! That's the one thing I've been struggling with is that should I just give up the self jumping ability for the sake of making the system easy. I mean you're right though. How often are you going to need that? And it's not a big deal to carry jumpers.
Click to expand...

Yep, and you only need to jump the +12volt since the ground is already grounded. On one truck I have the ability to self jump and I've never used it.

LFD2037 said:
I have Blue Sea 7610, 2ga wire and 150amp mega fuses at each battery.
Click to expand...

My set up is basically this, except I used ANL fuses rather than MEGA fuses. Both will work fine. I like the Blue Sea fuse holders and so just used that.
 
I ran 1 gauge welding wire from my main batt, thru a bussman 150 amp circuit breaker. I ran that in loom tie wrapped up under the radiator support from drivers side to passenger side. Ive got a surepower 1315 100 amp bidirectional separator mounted behind the passenger tray that feeds the aux batt, and a defroster switch/relay to manually combine the batteries when i want to charge the aux. The nice thing, it requires sufficient charge voltage to combine, even with the switch turned on. so i "shouldnt" run my aux down. I can trip the bussman 150 amp breaker manually to force separation as well.

You can get 1ga welding wire pretty cheap, and its very fine strand and flexibile. That distance with 1ga, you should be just fine.
 
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