Need for Battery Banks for Solar Power Plants

Battery banks give a constant level of electrical power and stores energy produced from the system during the day and power appliances at night.

For solar systems, we need batteries with long, reliable life and low cost of ownership. Today’s batteries are better than ever before and they definitely have improved performance characteristics.

Batteries for off-grid solar systems or those meant for back-up in grid-tied PV systems should be able to support the PV system in case of an emergency. For this, the rating and the make of the battery plays a key role.

Types of Batteries Ideal for Solar Power Systems

A high-capacity solar battery with deep-cycle storage capability is ideal for solar systems. Deep cycle, lead acid batteries are the most commonly used batteries for solar applications. A deep cycle battery is designed to be capable of discharging up to 80% of its total battery capacity and thus ensures that it delivers a large volume of electricity when needed.

Types of deep cycle batteries used:

  • Flooded lead acid batteries: These are the most commonly used batteries for solar systems. They have the longest life and the lowest cost in comparison to the other batteries, hence is extremely popular. Their only drawback is that they require regular maintenance.
  • Gelled Electrolyte Sealed Lead Acid: These batteries contain a silica type gel in which the electrolyte is suspended. The advantage of these batteries is that they wouldn’t spill and in effect require very little maintenance. They are a little more costly than the other options available today and also have lesser power capacity when compared to other options. Recharging this type of batteries is however a bit tricky. Hence not many would opt for these kind of batteries.
  • Absorbed Glass Mat Batteries: In this type of battery, the electrolyte is suspended in a very fine fibre boron-silicate glass mat instead of a gel. Like gelled batteries, they will not leak acid even they are broken, hence are safer to handle than the flooded lead acid batteries. They’ve better features than an average flooded battery like a lower self-discharge rate and more tolerance to temperature variations. But these typically cost about 2 to 3 times of a standard flooded lead acid battery of the same rating.

Types Other than Deep Cycle Lead Acid Batteries

Apart from the deep cycle lead acid batteries, there are other types of batteries such as the Lithium-Ion, Nickel-Cadmium and Nickel-Iron batteries. These are not as common as the deep cycle lead acid batteries, though use of types such as Lithium-ion battery is on the increase, thanks to efforts by companies such as Tesla. Some of the disadvantages for these batteries are:

  • High cost – this is the biggest drawback for most non lead acid batteries.
  • Lower efficiencies when compared to lead acid batteries
  • Higher rate of self-discharge
  • Some of these are more susceptible to temperature changes than lead acid batteries.

Good quality, standard deep cycle batteries have a life of about 5 years. From a review of the current market, it appears that for the next few years at least, lead-acid batteries would be the dominant battery type for solar PV power plants worldwide.

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