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The most common type of battery in a renewable energy system are lead acid. These come in two main types.

Flooded Lead Acid batteries are what you will find under the bonnet of almost every car. They are constructed with lead plates and an electrolyte solution of liquid sulfuric acid . The typical Flooded Lead Acid battery would have a flat positive and negative plate with a plastic separator between the plates. Some deep cycle batteries have a tubular positive plate which gives a greater life but are more expensive.

Sealed Lead Acid or SLA batteries have a similar construction to a Flooded Lead Acid type with the exception of the electrolyte. The electrolyte is either turned into a Gel (Gel type battery) or is absorbed into a Boron Silicate glass matt (AGM type battery). Both Gel and AGM are non spillable and never require any additional liquid. They have a Valve to vent any excess pressure that may build up, but generally over 99% of the oxygen and hydrogen produce from use is recombined to replenish it self.

Deep Cycle Batteries are available in both Flooded and Sealed types. The construction of the plates have a slightly different chemical composition to non deep cycle batteries and the plates and separators are thicker which increases their ability to withstand many more discharges to lower depths over a non Deep Cycle battery.

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