GEL CELL BATTERY A key factor to consider with a Gel Cell Battery is the deeper the battery gets discharged on a daily basis, the less cycles it will achieve through its expected lifespan. How to eliminate this concern and ensure you are getting the maximum number of cycles and efficiency from the battery is to size the battery system so that your average daily demand never takes the discharge below 50%. Where you are using a gel cell Battery on a grid inverter system, the inverter will ensure the discharge rate is maintained not to drop below this threshold. Gel cell remains the most cost effective as the capital investment is considerably cheaper than an alternative battery. LITHIUM ION BATTERY The main benefit to Lithium Ion Batteries is their ability to discharge up to 100% of the stated capacity which makes them a better option for those who have a high or fast energy usage and the battery are likely to be discharged quickly. An additional benefit is they are very low maintenance compared to an alternative battery; however, the additional upfront capital cost is higher. A Lithium Ion battery is lighter with less space required for housing. As with most forms of technology, one size does not fit all and in the case of a battery system, where they are being used and most importantly the rate of expected discharge are the most important factors to consider when selecting the best battery for your installation. BATTERY SIZING A battery has two main specifications: voltage and capacity. Multiplying these two values will calculate the watt-hours of energy storage. Adding cells in series will allow you to build up to 12, 24, 48, 120 or any voltage. Capacity is measured in Amp hours (Ah). A string of 800Ah cells makes a 800Ah battery. More amp hours can be gained by connecting more strings in parallel. Your system designer will apply these basic principles when designing your off-grid system. CHOOSING YOUR BATTERY There are typically two main types of battery that are used on renewable energy off grid systems – Lead Acid Battery (Gel Cell) and Lithium Ion Battery. Alternative new designs are reaching the market and SD advises that all specifications should be considered depending on your location, KEY FACTORS There are various approaches to what has been described as the ‘black art’ of battery selection, sizing and design, although, there are some key considerations:   Is the battery fit for purpose and rated for its duties?  Does it have an adequate storage capacity and cycle life?  Is a sealed or vented battery more appropriate for the particular installation?  Will the battery be made up of series cells or parallel banks? All of these elements will be considered by your system designer dependent on the needs of your application, 24 BATTERY SIZING & SELECTION