All About the Deep-Cycle-Marine-BatteryAll About the Deep-Cycle-Marine-Battery Service loads require a battery that can withstand cycles of long continuous discharge, and repeated recharging. This deep cycling requires the use of the suitably named deep cycle battery. These are available in all battery chemistry types. What is a deep cycle load? Deep cycle, service or house power loads are those loads that draw current over long time periods. Equipment in this category includes the cabin lights, refrigeration, electronic instruments, radios, radar, autopilots, inverters, and entertainment systems. The deep cycle battery is normally used to supply these applications. Calculations are based on the maximum power consumption over the expected longest period between battery recharging. Where high current equipment i.e. thruster motor, can cause system disturbances such as large load surges and voltage droops, consideration should be given to installing a separate battery bank with the required characteristics to power the equipment. How is the Deep Cycle battery constructed? The lead acid deep cycle battery is typified by the use of thick, high-density flat-pasted plates, or a combination of flat and tubular. The plate materials may also contain small proportions of antimony to help stiffen them. Porous, insulating separators are used between the plates and glass matting is used to assist in retaining active material on the plates that may break away as plates expand and contract during charge and recharge cycles. If material accumulates at the cell base, a cell short circuit may occur, although this is less common in modern batteries. If material is lost the plates will have reduced capacity or insufficient active material to sustain the chemical reaction with resultant cell failure. Much development has gone into developing stronger and more efficient plates, and Rolls have their Rezistox positive plates. The grid design has fewer heavier sections to hold the high density active material. This is due to the dynamic forces that normally cause expansion and contraction with subsequent warping and cracking. Separator design has also evolved and Rolls use double insulated thick glass woven ones that totally encase the positive plate along with a microporous polyethylene envelope. This retains any material shed from the plates than cause cell short circuiting. All about the deep-cycle-marine-battery and more How many deep cycles are available? The number of available deep cycles varies between the different battery makes and models. Typically it is within the range of 800-1500 cycles of discharge to 50% of nominal capacity and then complete recharging. Battery life is a function of the number of cycles and the depth of cycling. Batteries discharged to only 70% of capacity will last much longer than batteries that are discharged to 40% of capacity. In practice, plan your system so that discharge is limited to 50% of battery capacity. The typical life of batteries where batteries are properly recharged and cycle capabilities maximised can be 5 –10 years. How is a deep-cycle-marine-battery selected? Many boat electrical power problems are caused by improperly selected batteries. Many battery bank capacities are either seriously under-rated which causes power shortages. If batteries are over-rated the charging system cannot properly recharge them, and sulfation of the plates can occur with premature failure. All the electrical equipment on the boat must be listed along with the power consumption ratings. Converting power to current. The ratings can be found on the equipment nameplates or in equipment manuals. The ratings are given in Amps (A) or Watts (W). It is recommended that where Watts are used this rating is converted to current in Amps. To do this, divide the power rating in Watts by the operating voltage, 12 or 24 volts. About battery capacity requirements. As the consumption rate on a smaller boat is typically based on a 6-hour period, a battery bank that is similarly rated at the 10-hour rate is required. In practice you will not match the precise required capacity; therefore you should go to the next battery size up. If you choose a battery that has 240 amp-hours at the 20 hour rate in effect you will actually be installing a battery that in the calculated service has 10-15% more capacity than that stated on the label. All about the deep-cycle-marine-battery and more
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