I recently upgraded my old dual battery setup to a new high-tech installation using two Hawker Odyssey Drycell Batteries and a Hellroaring Technologies Isolator/Combiner. I also took the opportunity to replace all my battery terminals and distribution blocks with high grade components from Darvex

My old setup, while more than adequate for most situations, didn't give me the confidence I was looking for. I had a regular SLI battery and a deep cycle AUX battery charging through a SurePower Isolator. I still had the potential for killing both batteries, leaving me stranded. In addition, both batteries showed leakage after any off-road excursions. 

As usual, I researched the options thoroughly and was finally impressed and inspired by Mike Peter's dual Odyssey setup using a Hellroaring Isolator. The Odyssey batteries are tiny compared to standard lead acid units and the isolator is very compact and super efficient. Hellroaring's concept for a backup battery setup is to connect everything to the main battery, leaving a fully charged backup at all times. I couldn't disagree with that.

I knew with a little persuading, I could get two Odyssey 1200 batteries in place of one regular battery. I achieved this by removing the front right wing and cutting out the inner wing with a Sawzall to allow the second battery to extend into the inner wing about an inch. Unfortunately I didn't photograph this procedure. The batteries are cased in steel, so I had no safety concerns with this modification. Once I got the batteries located, the next challenge was deciding on a location for the isolator and the other connecting blocks I had chosen. The only logical place on my 93 Range Rover was under the expansion tank. Once I removed the tank, everything started to fall into place.


I had read the excellent documentation from Hellroaring several times and knew exactly what needed to be done. I disconnected all the existing battery cables and ground wires and moved them out of the way. I located the isolator, a distribution block and a T block all within close proximity of the battery box. Next I cut the cable from the starter to the right length to pass through the T block and reach the distribution block. I stripped the insulation away where the cable passed through the T block. This would be the power connection from the main battery, and the most direct route to the starter.


Next I wired the other end of the distribution block to the center 'B' terminal of the Hellroaring 85300 Isolator using some of the remaining starter cable and the supplied connector. At this time I connected the Sense Resistor and the optional TVS (Transient Voltage Suppressor) to the 'B' terminal and to the sense terminal and isolator ground terminal respectively. Everything is clearly marked and color coded. Hellroaring's attention to detail is incredible.


Next I located the optional remote switch on the right side of the center console and routed the wires through the fire wall to the isolator location. Sorry, no pics. of that procedure. I trimmed the color coded wires to length and connected them to the remote terminals on the isolator. The power and the ground wire required inline fuses to be installed. I reconnected all the ground wires at this point and installed a jumper on the isolator between the 'A' and 'C' terminals.


Next I reconnected the hot wires to the distribution block. These were previously connected to the old positive battery terminal. I also connected the hot wire from my 600 watt inverter to the distribution block at this time. I then proceeded to stare at my work for several minutes, double checking all the connections. Now the fun part.


Actually it was all fun, but this was really fun! I dropped the Odyssey batteries back into place and began connecting. I had chosen the battery terminals based on what I knew I would need to connect to them. The main positive terminal is bigger than the other three, being the main source of power for the whole rig. I made up a positive cable using 0 gauge power cable (the yellow one) and connected it to the T block. I connected the winch directly to the positive terminal at this time.


Another decision I made early on was to use two mirror image batteries. One has a right side positive terminal and the other a left. This made the final connections simple and very neat. I jumpered the two ground terminals together and connected the main ground from the frame, the winch ground and the inverter ground. I didn't have any more red cable so I made up the backup positive cable using a spare piece of black wire and connected that to the 'A' terminal of the isolator.


Almost done! In the left picture above you can see the two hoses in position to receive the expansion tank. I tie wrapped all the cables, making sure nothing could touch anything it shouldn't. I also took the opportunity to replace the old expansion tank with the new improved version (less prone to exploding) and finally everything is back in position. I now have a very reliable, leak-proof dual backup battery setup. The batteries can be combined by the remote switch for winching, giving an unbelievable 2400 amps (5 secs.). For cold starting, they'll put out a combined 1100 CCA and 1450 CA. When switched to 'auto' I will always have a fully charged backup battery whenever I may need one.

I have since added an Odyssey PC1700 and a second Hellroaring isolator in the rear of the truck for auxiliary stuff like the Engel fridge/freezer and an 1800 watt inverter.