Tech Notes Battery Interconnects George Chase c. 1993 George Chase The wire interconnects of a battery bank in an alternative energy system have numerous possibilities for energy loss. After seeing the article in HP #30 on Home Power's neat installation of a new alkaline battery bank, I decided a new approach to my battery interconnect cables was due. The old system: wire interconnects Most of us cannot afford the an alkaline battery bank. We usually rely on six Volt lead acid golf cart batteries. My battery bank consists of eight 6 Volt batteries wired in series-parallel with cross-wiring. Cross-wiring helps maintain an even state of charge between the batteries in the pack by providing a parallel path for current. The eight battery bank has sixteen posts. Back in HP #7 were instructions for making your own battery cables. I followed Richard's advice and made my own also. The process took me a long time but when finished, I felt the cables would last the rest of my life. Today those cables are as good as the day I made them but I could tell by monitoring that all my batteries were not being treated equally. I got tired of trying to keep all those connections in good condition. New connections with copper bar In an effort to remove as much resistance as possible from the battery bank, I decided to try a solid bar system. I got some solid copper bar (1 inch by 1/4 inch by 12 feet) and made a battery interconnect system that cuts the resistance points to the lowest possible number. It also makes maintenance a snap, and it looks great! Here's what I did: 1. Place the batteries in proper position, (positive leads in straight line and negative leads in straight line.) See diagram. 2. Cut bar to proper length allowing room for connections of the PV array and backup charger on the positive and negative bars. 3. Measure distance between posts (center to center) and drill holes in bar. 4. For the offset connections I cut the short bars to size and soldered them to the long bar first. Then I measured and drilled the holes. See diagram. 5. Tin the side of the hole that will make contact with the lead post. 6. You need to protect the metal from accidental shorts from wrenches or other tools that might touch them. I priced "heat shrink" tubing but it proved too expensive. I bought liquid electrical tape at the hardware store in a can with a brush cap. You just paint it on where needed. This system has been in use for about six months now and is a pleasure to maintain. Once a month I remove the bar, polish connection points with steel wool, read and record the voltage of each battery, and replace the bar and add grease to all areas not rubber coated. All this takes about 5 to 10 minutes. Then I apply a 3 hour freshening charge to the bank with my backup charger. This gets a good bubbling action going to remove the sulfate from the plates. An equalizing charge should be applied if voltage varies by 0.05 Volts from 2 Volt cell to 2 Volt cell. Since on most 6 Volt batteries it is not possible to measure from cell to cell, an equalizing charge should be applied if voltage varies by 0.10 Volts from 6 Volt battery to 6 Volt battery. So far the voltage of each of my 6 Volt batteries has remained within 0.01 Volts of each of the others. It took me about 5 hours to make the system which cost about $60. The cost is a little more than making cables out of large wire but the ease of maintenance and equal power distribution should far offset that cost in longer battery life. The copper bar could be reused on future batteries or even different batteries by soldering in the holes and redrilling new holes if necessary. It works great! I'm more than satisfied. Access George Chase, 1183 Girl Scout Road, Arcadia, FL 33821