My Dual Battery Install

[taugust]

Well, I spent hours typing up the install, only to loose it all when I tried to upload some photos. Starting over...

During last week's net on dual batteries and fridges/coolers, Dave, K6DTK, asked me to post my dual battery install.

My system is similar to his, using dual Odyssey batteries and a Hellroaring Battery Isolator/Combiner. I have a 2003 Toyota Tacoma XtraCab, V6.

The batteries installed. The main battery is on the left.

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For me, there were several key factors to consider in a dual battery system for my truck. First was size. I needed to be able to install the batteries in the engine compartment, in the stock battery location. Not enough room elsewhere in the engine compartment. I didn't want it in the bed, as I used the entire bed occaisionally and having an exposed or boxed battery did not appeal to me. While I could have mounted a second battery under the bed, the long cable run needed wasn't appealing either, and exposure and accessibility was a factor. After doing some measurements with the stock battery removed, I found that I could fit two Odyssey 1200's in the stock location with some modifications. I also wanted the batteries to be the same make, model, and size for compatibility reasons. When I bought them, the batteries (PC-1200 MJT cost $160 each. Now the same units from the same sourch are about $222. Ouch. They have "standard" terminal configuration and a metal jacket around the case. The terminals are brass and come with top bolts. Very well made units.

For the isolator system, I wanted to remotely control it from the driver's seat. I looked at several styles and systems. I did not want a heavy duty switch in the cab, as the bulk and heavy cable run into the cab would not be a tidy solution. I looked at the advantages and disadvantages of several systems and settled on the Hellroaring BIC95300B Battery Isolator/Combiner. It is designed to run all loads off the main battery, and to keep the secondary battery as a backup only. It is rated at 150 amps continuous and 300A for 20 seconds. There is another model that is more suited to use in an auxiliary load situation, where all auxiliary loads are run from the secondary battery and the main battery is used for vehicle starting and systems. An option is the small remote control switch box that can be easily mounted in the cab to control the system. System price was a factor as well, since the Hellroaring unit is less expensive than other options.

There are advantages and disadvantages to both setups. For me, the most secure was always having the backup battery as a reserve, made the most sense. Most of my loads currently are not high, so the drain on the main battery is also not high. Now that I have a high output alternator, loads on the battery during driving are no longer a factor. If the fridge, radio or lights kill the battery, I can always self jump start the truck. I have been known to leave interior lights on and killed several batteries this way, as well as other ways. Even though the Toyota has a timer to shut off all lights and loads if not used for 30 minutes (with the key off), I still killed the stock battery by leaving the key and interior lights on. I like the security of a backup battery. With always-on loads connected to the secondary battery, one could conceivably kill both batteries, leaving no backup.

Another advantage detailed in the Hellroaring website that I had not thought of, but like, is that the backup battery is always charged and never used, keeping it, in effect, new. When the main battery eventually dies, swap the secondary to the main position, and buy a new secondary. This way, the backup battery is always the best battery in the system. You don't have to replace the main battery when it still has useful life due to a lack of confidence in its reliability, as you might in a single battery system.

The Hellroaring website (http://www.hellroaring.com) is a wealth of information on dual battery systems. There are lots of pages and the organization needs work, but click on all the links to learn a great deal. The info is understandable and represents some interesting viewpoints. Mike, the tech guy there (and maybe the owner?), is very knowledgable and helpful. He often answers the phone. When I was having a problem with charging, I called for help during the day, but didn't have the truck with me. He gave me his cell number to call him after hours when I got home and walked me through some tests for an hour to determine the source of the problem. Now THAT is what I call customer service.

I fabricated the battery tray and the hold-down strap to fit in the stock battery location, with some modifications. The batteries are oriented longitudinally (along the truck axis) , where the stock battery is oriented laterally (across the truck axis). After removing the stock battery, I had to relocate the radiator reservoir forward as much as possible so that the batteries would fit. The reservoir has a locating pin on the bottom that slides into a hole in the sheet metal. This hole had to be opened up forward to allow the tank to shift forward about 3/4". I didn't want to move the stock fuse block, since it bolts to the inner fender well. With the room for the batteries, I fabricated a battery tray out of 1" x 1" x 1/8" angle stock around the perimeter of the two batteries nearly touching. I used 1" x 1/8" bar stock to fabricated two cross members and welded across the short side of the tray. I drilled and used countersunk bolts through theses cross bars to bolt the tray to the flat battery support platform in front of the inner fender.

The battery hold-down was more 1" x 1/8" flat stock, with a couple contact braces welded on the bottom. The Odyssey batteries have a raised cover in the middle of the top of the case, that covers the vents. You cannot apply hold down pressure on this plastic cover. The contact braces apply the hold down pressure on the edges of the battery where the case is stronger. The inboard end is drilled and the stock battery J bolt is used to connect the hold-down to the tray. The other end of the hold-down is tech screwed into the inner fender sheet metal. This is not the strongest location, but it seems to work.

The J bolt and part of the hold-down bracket

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The battery isolator/combiner was then installed on the firewall, next to the brake booster. This puts it out of the way, so that inadvertant contact and shorting are prevented. Using tech screws, I screwed it to the flat sheet metal.

The Battery Isolator / Combiner

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Heavy cables were routed from the BIC to the starter and the backup battery. I used 2 guage battery cable for these longer high current runs, although the instructions indicate that 4 guage is sufficient. I routed across the firewall to the starter (connected to the main battery with the stock starter cable), using nylon cable clamps. The backup battery was connected with 2 guage cable routed along the inner fender on the drivers side. I bought ring terminals in the appropriate sizes from West Marine, since they had a good selection of cable and ring sizes and they are intended for marine applications. They are probably alot more expensive than others, but I didn't know of a source for cheaper terminals. I bought brass battery terminals and the cable from http://www.wiringproducts.com. All connections were soldered and shrink wrapped. I had a hard time finding good battery terminal covers that would cover the terminals and the extra load connections as well. I finally settled on some from West Marine.

The remote control box is simply a three position locking switch and an LED that connects to the BIC with three control wires and a ground. I mounted it on the right side of the frame around the gear shift. The wires were routed under the dash and through the firewall to the BIC. The remote is visible and accessible from the drivers seat, but out of the way. Dave had mentioned on his post that he mounted his in the guage cluster on the dash and had said during the net that the LED was very bright at night. The way he has it oriented, it shines right in the driver's eyes. With my mounting position, the LED is visible, but does not shine directly at the driver. It is only in the peripheral vision so is not a nuisance at night.

The remote switch and LED

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The Isolator/Combiner works by charging both batteries while the engine is running, but keeping them isolated from each other. The system is normally left in the center position. To combine the batteries for self jump starting or extra power when winching, move the switch toward the LED. The batteries are now combined. To disconnect the batteries, move the switch away from the LED. The backup battery is completely disconnected from the system, including charging. The LED lights while the engine is running to show that the alternator is supplying charge voltage. It also lights when the batteries are combined.

That is about it. I have attached several photos to show my configuration. Unfortunately, I don't really have any install photos or ones of the battery tray without the batteries in it. Sorry.

[DaveK]

Tim:


What a great post. The attention to detail that you have given to your installation is outstanding. Anyone looking to install dual batteries needs to read this. Thanks!!!!