Typically when we size a renewable energy system, because of the higher cost of larger wire, we usually will allow and account for a 2% line drop loss. Although, we don’t really follow this rule when it comes to battery cables. Oversize your battery cable and shoot for a 0% loss. American Wire Gauge (AWG) #4/0 is the minimum wire size we suggest for typical battery banks, but 500 MCM sounds good too. All right I’m kidding, 500 MCM is far too difficult to work with. We generally use X-Flex #4/0 cable, similar to welding cable with its fine strands and flexibility. Flexible cable is a lot more cooperative and can make your short battery-to-battery connections and longer runs much easier to deal with. You’ll find that Trace inverters don’t give us much room to work with so flexible leads are pretty important although Outback Power Systems has done a super job of making this much less of an issue with their well designed system components. The point is, in low voltage systems we need all the current carrying capacity we can get. We don’t want our cable size to strangle our batteries and we don’t want any high resistance connections interfering with our flow. A big pipeline will reduce resistance and give us a greater load surge capacity.

You also have to be aware of the chemical dangers involved when working with batteries. Lead acid batteries contain sulfuric acid, which can do a lot more than just eat holes in your favorite pair of jeans. Batteries are flammable and explosive so always work on and store batteries in a ventilated area. Have plenty of baking soda or other neutralizer readily available in case of a spill. Wear protective clothing, rubber gloves and eye protection and have fresh water available in case the electrolyte splashes on your skin or in your eyes. Wash your hands thoroughly and frequently. You probably don’t want to earn a new nickname like “Sparky” or “French Fry” so please keep open flames and sparks away from batteries. In order to avoid common sparks and arcs, I like to make my final connections at the buss bar or inverter. Also, discharge any body static electricity before working with battery terminals and generally refrain from smoking around batteries.