Dual Battery: National Luna or IBS kit?

[lcgeek]

Very little design needed. Really, this is easy.
1-Mount the ACR somewhere convenient. The back of the #2 battery box is a good spot for a 7610, or on the firewall
2-Connect the grounds of both batteries together. #2 Cable works perfectly
3-Connect + terminal of one battery to the big terminal of the ACR Again, #2 cable
4-Connect the + terminal of the second battery to the other big terminal of the ACR #2 cable
5-Connect the ACR negative terminal with small fused wire to ground of #1 battery
6-Go have a nice microbrew

Note: you will want to fuse your + cables at the battery. I like the MRBF form Blue Sea, or ANL fuses in a quality holder. With 2 gauge wire, 150 amp fuses will be about right.

I have ACRs on 3 trucks, all working perfectly. Can't say enough good things. If you come through Sac, I'd be happy to help you make up cables-I have a mondo crimper for large cables that doesn't get enough use.

Thanks @Cruiserdrew for this. I had a National Luna that kept draining both my batteries so I installed a Blue Sea 7610. One question, I am electrical idiot, why do I need to fuse the negative back to battery 1? What size fuse would you recommend?

Thanks!

 

[Cruiserdrew]

Thanks @Cruiserdrew for this. I had a National Luna that kept draining both my batteries so I installed a Blue Sea 7610. One question, I am electrical idiot, why do I need to fuse the negative back to battery 1? What size fuse would you recommend?

Thanks!

So one of the terminals (the small spade connectors) is a ground that serves as the ground reference for the ACR to work. The fuse is in case something bad goes wrong inside the ACR it can't become a ground path a start a fire. I used a 10 amp fuse. I think the instructions have a recommended fuse size. It normally doesn't carry any current, so even a tiny fuse like 3 or 5 amps would be fine.

 

[lcgeek]

Got it, thanks. She is all hooked up and I will fuse the ground wire tomorrow.

 

[Jorgito]

My opinion have had the national Luna hated it for the following reason.
My deep cycle battery is normally much larger than my starter battery it never charges to full capacity. Thus my battery does not last all night for my fridge. My fridge cut off is set to 11.2v.

The National Luna battery monitor I find inaccurate.

I only run DC to DC systems and my battery gets charged fully.
I use a ctek d250s and my battery all charges fully. Also has solar input.

Rather put your own voltage monitor in.
DATEL DC Voltmeters

I must agree that ctek d250 is the best in charging the AMG deep cycle batteries. I will be getting one soon.

Jorge

 

[SmokingRocks]

Honestly I like my Tmax Dual battery system. I used 0 gauge wire in place of the 6 gauge they sent, but otherwise its perfect. Everything -save the winch- is run off of the house (main) battery, and the reserve battery is there to self jump in the morning.

One battery to run accessories and the other to self jump. What else do you need?

 

[Dave 2000]

I fitted the Blue Seas unit around 5 years ago, expensive but good, do it once and do it right! I did fit the NL battery monitor though, I leave the LED's on all the time, a quick glance when you jump in the car will give you a good indication as to your battery condition, neat and simple, again fitted around 5 years back with the Blue Seas unit.

My LC 80 thread.

regards

Dave

 

[mct75]

Why not two identical group 31 deep cycle batteries permanently connected? This gives you twice the deep-cycle capacity, more cranking amps than a single SLI (unless your starting battery is a beefy AGM) and avoids all of the switches, relays, solenoids, fuses etc. If you're really paranoid about draining your batteries I'm sure they make relays that lock out all your accessories at 11.8 volts or something. With two deep cycle 31's I bet you could run the fridge and a radio for days. Twice the utility with less complexity.

If you're driving 500 miles alone into the woods you should already have a backup jump starter (Lithium ones are cheap, work in the cold, and fit in a glovebox) or generator.

 

[Dave 2000]

Why not two identical group 31 deep cycle batteries permanently connected? This gives you twice the deep-cycle capacity, more cranking amps than a single SLI (unless your starting battery is a beefy AGM) and avoids all of the switches, relays, solenoids, fuses etc. If you're really paranoid about draining your batteries I'm sure they make relays that lock out all your accessories at 11.8 volts or something. With two deep cycle 31's I bet you could run the fridge and a radio for days. Twice the utility with less complexity.

If you're driving 500 miles alone into the woods you should already have a backup jump starter (Lithium ones are cheap, work in the cold, and fit in a glovebox) or generator.

There is a problem with one faulty battery in parallel with a healthy one is that they will both be flattened.

Also two batteries cannot be tested without disconnecting them from each other.

You cannot monitor individual batteries when in parallel.

There are devices that prevent the batteries getting too low however, they go between the battery and the vehicle systems, they cannot distinguish between a battery going bad or two healthy batteries going flat.

The jump start packs tend to either be forgotten and left at home, or they are put in a dark place and forgotten until they are needed, and then you find they are flat.

Absolutely agree there is the added complexity, but if you purchase decent gear and install correctly then problems are rare.

regards

Dave

 

[mct75]

You raise valid points, but I would counter that two identical batteries should have similar lifespans, and are easy to test individually as part of a PM. Just remove one terminal and load test each one. Paralleled batteries are very common in other industries with no ill effects.

If you're going on an expedition alone, checking gear is part of the prep. For day-to-day driving I can leverage calling friends or getting a jump from another vehicle like anyone else.

Both ideas have their merits. To me the extra "usable capacity" of dual deep-cycles outweighs the advantage of a separate, isolated deep cycle and SLI battery. If you leave your headlights on accidentally and run the fridge for 2 days, your battery isolation system will not save you from the wolves. So, you still need a jump starter as emergency gear. And if you need a jump starter, you might as well have two big beefy batteries with less stuff to fail. Just thinking out loud here.

 

[SmokingRocks]

I run two Batteries Plus AGM Deep Cycle X2Power Group 31M Marine and Boat batteries and they work great. If you are adding a dual batt system I highly suggest that you buy two of the same batteries instead of running one new and one old.

The T-max system will show you battery voltage of each unit when not charging (engine off), obviously you can 'check' the voltage with the engine on but both batteries will read the same.

 

[Dave 2000]

You raise valid points, but I would counter that two identical batteries should have similar lifespans, and are easy to test individually as part of a PM. Just remove one terminal and load test each one. Paralleled batteries are very common in other industries with no ill effects.

If you're going on an expedition alone, checking gear is part of the prep. For day-to-day driving I can leverage calling friends or getting a jump from another vehicle like anyone else.

Both ideas have their merits. To me the extra "usable capacity" of dual deep-cycles outweighs the advantage of a separate, isolated deep cycle and SLI battery. If you leave your headlights on accidentally and run the fridge for 2 days, your battery isolation system will not save you from the wolves. So, you still need a jump starter as emergency gear. And if you need a jump starter, you might as well have two big beefy batteries with less stuff to fail. Just thinking out loud here.

I agree to 'similar' lifespans but therein is the problem, they are unlikely to fail at the same time. But how many strip off the terminals and check their batteries? IME a load test can bring an ageing battery nearer to failure but NOT necessarily at the time of the test. I do use two marine batteries of the same capacity, they are dual purpose start and deep cycle, my last set lasted about four years.

On a positive note, drawing from two batteries at the same time during cranking for example would extend their lives, given the load is shared, so that is a good thing, as you said there are merits.

If my car is parked overnight then in the morning even though the alarm is set, the batteries are still in parallel, so I start the engine with two anyway. If I leave it three or four days then the VSR splits the batteries, the alarm draw dropping the voltage on the auxiliary battery. If I thought about it enough I would press the parallel button and start the engine from both batteries but I do not, if I forgot and the button was left in the parallel position, then the scenario of two flat batteries could occur. I am a 'fit and forget' person, I leave the override in auto and forget about it. If I enter the car after say a week I can glance at the battery monitor and know whether or not the batteries are holding their own.

A fridge is 100% essential for me, I normally take a solar panel or two depending where I am going, this keeps both batteries charged, so TBH I reckon I cover the bases anyway.

regards

Dave

 

[DanMedeiros]

Hi Guys,

Bought two group 34 odyssey 15000. Will be using a blue seas acr to link them together. i keep going back and forth about which battery to wire my accessory loads to. Seems the standard route is off the nona-starting battery. However in camp I might be drawing down the start battery (stereo, interior lights, ect) and then also drawing down the 2nd battery with may fridge. Wouldn't this create the scenario where both batteries could get killed?

I've seen a few systems now where all the loads come off the start battery. The 2nd battery is strictly to start the car in an emergency (or for winching). Interested in everyone's opinion on how they did their system and why.

 

[Cruiserdrew]

The reality is you don't draw down your start battery. You don't even use it, and it's hugely convenient to pull your loads like fridge and camp lighting off your #2. Is there a theoretical chance that you might one day take both down? I suppose, but it's and extremely rare theoretical balanced against the every day goodness of pulling your loads of your #2 battery. Plus, no matter what, there will likely be enough charge in #2 to jump a dead #1.

And if you really want to preserve one battery at all costs, you could just use a hellroaring system which does this exact thing.

If you're a worrier, get one of those tiny lithium jump packs for that one in 100,000 times that both batteries fail at the same time.

It really is better to separate battery duties. I have had both and having a dedicated "house battery" is way better.

 

[Dave 2000]

I too went with the starter battery being reserved for exactly that....starting. I also chose the one nearest the starter for minimum voltage drop, but then I am a bit OCD, my 'aux' battery does everything else.

regards

Dave

 

[DanMedeiros]

One more question that I can't seem to figure out. I am rigging up a battery disconnect switch and running all of my grounds to a blue seas bus bar. I bought a 600 amp continuous duty bus bar but would prefer not to use it. It's massive. Would a 250amp version work? The main grounds from the engine will be connected here as well as a aux fuse block (max capacity 100amps)

 

[Blondie]

I used one of these dual voltmeters for my acr install in my 4Runner, it's designed to fit perfect in that vehicle but could be retrofitted for use in the 80's. They're wired up to two mini rockers so I can watch my batt voltages on demand and not have parasitic draw.

Dual Battery Volt Meter Toyota Prado 120, FJ Cruiser, Landcruiser 100, 79 Series, Hilux and More - Solid Kit

I also highly recommend a crimping tool like this one with interchangeable dies, and a hydraulic crimper for larger cable connections:

TRIcrimp, the best crimping tool for Powerpole for 15, 30 and 45 amp contacts | Powerwerx
Hydraulic Wire Crimping Tool

So far my acr has been great, I love its simplicity, robustness, and manual override. Combined with dual voltmeters it offers straightforward operation.

 

[Blondie]

I used one of these dual voltmeters for my acr install in my 4Runner, it's designed to fit perfect in that vehicle but could be retrofitted for use in the 80's. They're wired up to two mini rockers so I can watch my batt voltages on demand and not have parasitic draw.

Dual Battery Volt Meter Toyota Prado 120, FJ Cruiser, Landcruiser 100, 79 Series, Hilux and More - Solid Kit

I also highly recommend a crimping tool like this one with interchangeable dies, and a hydraulic crimper for larger cable connections:

TRIcrimp, the best crimping tool for Powerpole for 15, 30 and 45 amp contacts | Powerwerx

Hydraulic Wire Crimping Tool

So far my acr has been great, I love its simplicity, robustness, and manual override. Combined with dual voltmeters it offers straightforward operation.

Here's the voltmeter with the switches I made.

 

[Dave 2000]

One more question that I can't seem to figure out. I am rigging up a battery disconnect switch and running all of my grounds to a blue seas bus bar. I bought a 600 amp continuous duty bus bar but would prefer not to use it. It's massive. Would a 250amp version work? The main grounds from the engine will be connected here as well as a aux fuse block (max capacity 100amps)

Your single biggest draw will be when cranking the engine, I would earth engine block to batteries, then batteries to body/bus bar. All the other 'stuff' can then go to the lighter duty bus bar, the 600 amp bus bar will be fine for an anchor if you own a boat.


regards

Dave

 

[Sharky1528]

View attachment 1382852

Here's the voltmeter with the switches I made.

That's a sweet set up and love the voltmeter !!!

 

[Dave 2000]

View attachment 1382852

Here's the voltmeter with the switches I made.

Nice and neat, I like it.

regards

Dave