Could My NL Dual-Battery Setup Kill My Battery?

So after successfully replacing my timing belt, tensioner, idlers, alternator, cam seals, spark plugs, adjusting my valves, resetting my TPS and rebuilding my IAC, I was feeling super confident and installed the National Luna DIY Dual Battery Kit on my 2001 Tacoma, along with the Columbia Overland Dual Battery Tray. The kit had been sitting on a shelf for a few years and I decided now was the time. We had been using two Sears DieHard Platinum P-35 batteries, one under the hood in the stock setup as our starting battery and the other in the cab, connecting it to loads and charging it as necessary. This worked OK but we wanted to automate the charging and integrate our solar panel.

I ended up ditching the oddball sized wires/connector/fuses/terminals that came with the NL DIY kit and upgraded to marine-grade tinned copper wires and connectors, heavy duty military style battery terminals and Blue Sea MRBF terminal fuse blocks. The new alternator I installed is an LC Engineering unit with a claimed maximum output of 160A. I also replaced all the alternator and battery connections with #2 AWG. This was all tied into a Morningstar Sunsaver Duo PWM solar charge controller and a 100W solar panel. All this to support our ARB fridge, LED lights and to keep our electronics and jump-pack charged while extended camping.

After driving around town for a few days making sure everything was working as planned (it was), I decided to test it all on an easy 9-day trip to Toroweap to see how it all worked in the field. For 4 glorious days, the system worked great. The entire setup held fast during my blast over the wash-boarded 65-mile road to Toroweap. The NL solenoid and dual-battery controller appeared to be working perfectly and my batteries were being topped-up after only a few hours of sun light each morning.

Then, when I was taking a day trip back to the highway to meet some friends, I stopped to check something out. When I started the engine, the alarms sounded on the NL controller, showing almost no charge on my aux. battery. Looking under the hood, I could see that the 50A fuse between the aux. battery and the NL solenoid had blown. I decided to continue to the highway where I found I couldn't restart my engine from the main battery. It was showing good voltage across the terminals but would not turn over my engine, not even a click. I got a jump from another vehicle and chanced the trip all the way back to my camp, sincerely hoping I could fix it back there, since it's a $1500-$2000 tow back to the nearest town. During my trip back to camp, it got dark and I could see that my lights dimmed significantly at lower RPM and I could hear a faint high-pitched buzz that changed with RPM (alternator?).

The next day at camp, I removed all the dual-battery wiring, switched my aux. battery to the main location and the truck started up fine and got me home. There were no apparent shorts in the system or the wiring. Nothing seemed to be amiss save for the blown fuse and dead battery. I took the battery back to Sears, where they put it on a load tester and it showed like ZERO or negative amps if that's possible. Since it was less than 3-years old, they gave me a new one in return, no questions asked and no details volunteered. What troubles me is the question: Was it just a battery that had gone bad on its own, or did I kill it with my setup?

I'm hoping that one of the TW electrical gurus can give some ideas on what to check next before I kill another battery and that I included enough info in my (long-winded) post. I had seen on another sight (Expedition Portal - I think) where someone claimed that their NL Dual-Battery setup killed their battery, but it never got explained.

Thanks in advance for any insight, this forum is so helpful and I never could have done any of this work without all the great help here.

 

There are a number of possibilities that could of killed your car battery, but the most probable was an internal short between plates or deep discharge assuming the battery was healthy to begin with. Car (starting) batteries are designed for thousands of shallow (<5%) discharges. Deep cycle batteries are designed for deep discharges of 50% to 80%. The average life expectancy of a wet car battery in a hot climate like LA is 41 months, but drops to 30 months in extreme heat like the dessert due to accelerated grid corrosion. Flat plat AGM's should last 2X to 3X longer.

For more information, please see Section 2 and 7 in the Car and Deep Cycle Battery FAQ on www.batteryfaq.org.

 

Thanks for your post. Yes, I was aware of those battery facts. I was hoping that someone with a similar experience with battery isolators would chime in. I remember reading a post somewhere of a similar experience.