Performance evaluation of lead acid batteries for use with solar panels

This paper discusses the preliminary results of a long term evaluation of the charging of sealed lead acid batteries with unregulated solar panels. The US Coast Guard (USCG) uses unregulated solar panels to recharge batteries that power night navigational aids. The USCG is examining the benefit of replacing the current maintenance free lead acid batteries with sealed batteries. The test will determine the useful life and failure mode of batteries exposed to unprotected outdoor environments. Preliminary results of the test found that the batteries were being exposed to charge voltages of between 12.5 and 16.0 volts, which are well outside the designed charging voltages for sealed lead acid batteries of 13.5 to 14.2 volts. Charging at these voltages (both overcharging and undercharging) accelerates the decay of sealed lead acid battery positive plates and greatly reduces the expected service life. Preliminary results of fielded batteries found that the maintenance free batteries lasted approximately 60% longer then sealed lead acid batteries