Each 2 volt battery will have specified discharge rate known as the “C” Rating.
The “C” rating of a battery determines how much energy each battery has available over a given period.
“C10” rating means the battery is designed to discharge all of its energy in only 10 hours.
a “C100” rating means the battery is designed to discharge all of its energy in 100 hours,
Most modern sites should be calculated at the “C10” it is generally expected that the energy will be available over this period, commercial communications sites or UPS units will have slightly different C rating needs.
Amp hours is the amount of energy a battery has at a certain discharge rate, let use a “C10” rating. 48 volts multiplied by the amp hours of the batteries equals the stored capacity in watt hours over a 10 hour period. 2 volts x 1000 amp hours equals 2000 Watt hours. This means this battery system can deliver 2 kilowatt hours in 10 hours until it is completely discharged, remembering we need 24 batteries to achieve 48 volt nominal operating voltage so in total we would have 48Kwh if fully discharged.
The Depth of Discharge (DOD) of a battery is the percentage of energy which is allowable when calculating the life of the battery the greater the DOD the shorter the life of a battery..
Most battery manufacturers recommend a daily DOD of 30% and no greater than 50% to get a reasonable service life from your batteries the amount of DOD determines the cycles.
The amount of cycles a battery has is used to determine the estimated life of a battery. A complete cycle consists of charge-discharge-charge this is not full discharge and recharge this is partial discharge and recharge constitutes one cycle. Typical cycle life of a quality battery is 5,000 to 6,000 cycles if you were to partially discharge and charge the battery 3 times each day on average this would allow for 2,000 days divided by 365 days each year gives the expected life of the batteries as 5.47 years.
Charge and discharge inside the cells of a battery are affected by temperature. A higher temperature will allow for a more rapid discharge but a significant reduction in expected battery life, generally batteries nominated operating temperature is 25 Degrees.
Battery Charging, typical gel batteries or more traditional batteries used in off grid power solutions take 8 hours to charge to 80% and a further 8 hours to reach full state of charge, as result batteries need a regular super boost to get them to 100% state of charge if this isn’t achieved the battery life will also be reduced and may not be covered under warranty.
Each battery and its location and its placement inside or outside will determine the cabinet design, no matter what the technology, batteries should be protected from the elements, good clean, dry, moderate temperature with good cross flow ventilation, in some cases a small fan may be needed inside the housing that is controlled by a temperature thermostat or in extreme cases a cooling system may be considered.