R.H. NEWNHAM AND W.G.A., ADVANCED MANAGEMENT STRATEGIES FOR REMOTE AREA POWER-SUPPLY SYSTEMS, 10TH ASIAN BATTERY CONFERENCE, BANGKOK, THAILAND, SEPTEMBER 3-5, 2003
Abstract: An operating strategy based on partial-state-of-charge (PSoC) operation has been developed for a remote-area power-supply (RAPS) system in Peru. The facility will power an entire village and comprises a photovoltaic array, a bank of gel valve-regulated lead-acid (VRLA) batteries, a diesel generator, and a sophisticated control system. The PSoC schedule involves operation below a full state-of-charge (SoC) for 28 days, followed by an equalization charge. The schedule has been evaluated by operating a 24-V battery band under simulated RAPS conditions in the laboratory. It is found that operation between 58 to 83% SoC causes the negative-plate potentials to move to significantly more negative values during charging as the PSoC duty progresses. This behavior is undesirable, because it can lead to the activation of a preset limit and a subsequent reduction in system efficiency. Lowering the PSoC window to 47-72% SoC or 40-65% SoC during the 28-day cycle is found to stabilize the negative-plate potentials. The behavior of the negative-plates in gel batteries is very similar to that observed for absorptive glass mat (AGM) designs of VRLA batteries operated in hybrid electric vehicles.