What are solar batteries and how do they work?

Solar batteries are used to store the solar electricity power generated from a solar array. This power can then be stored and used during times when the array is not producing power, for example in the evening or in the event of a power failure.

Solar batteries are constructed from lead plates and a water and acid mix liquid reserve, which can withstand deep depths of discharge, a measurement used to asses a battery’s state of charge. As a load is placed on the battery the acid is drawn from the water mix and absorbed into its lead plates, and the charge levels begin to drop. When a charger is placed on the battery the acid is slowly released back into the water and the specific gravity and charge levels are raised.

How are solar batteries rated?

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All batteries are given an Amp hour (Ah) rating, with the 100-hour rate, an index to measure and compare batteries of different sizes and types, most often used in solar applications. The 100 hour rate is the amount of Amp hours the battery will deliver, drawing 1 Amp per hour, during a 100-hour discharge. How long can a battery operate once fully charged?

Charge levels and times vary depending on a solar battery’s Ah rating and the load placed on the battery. For example, if a 12 volt battery rated at 100 Ah was used to run a 12 volt 5-Amp light for 10 hours around 50 Amps would be used and the battery would be discharged to approximately 50 per cent depth of discharge. If the same 5-Amp light was used with a 200 Ah battery for 10 hours, 50 Amps would still be used but the battery will be discharged to approximately 25 per cent depth of discharge.

It is recommended that a solar battery is never discharged past 80 per cent depth of discharge, and when sizing a battery, 30 to 50 per cent depth of discharge should be aimed for in order to help gain maximum cycle life. What sort of voltage do solar batteries have?

Solar battery voltages vary from 12 to 120 Ah and sometimes higher depending on the size of the application and the required load or run times. Most purpose-built solar houses will have low current devices installed to reduce the load on the batteries, and ideally the batteries should be selected to allow minimum depth of discharge.

What are the main chemical components of solar batteries? Why are these substances most suitable to this application? Conventional lead batteries are still common and have good cycling capability; however, they require frequent water filling particularly towards the end of their life, due to antimony migration between the plates. Batteries with lead-calcium alloys usually made for dual-purpose starting and cycling applications require far less watering, but tend to have poor cycle life capacities.

The highest quality solar batteries are constructed with lead-selenium alloys which are low-antimony types and have the addition of selenium as a hardening agent. These alloys promote good cycling capability while maintaining a constant and low level of water consumption.

What are solar batteries generally used for?

Solar batteries can be used for many different applications, including small camping set-ups, stand alone house power, back-up house power, street lighting systems, remote water pumps, telecommunications back-up and any application that requires off grid power or grid-connected back-up power. What are the benefits of using solar batteries?

When grid power is not available, using solar batteries for remote applications can help reduce long term costs, when compared to a generator or diesel fuel.

A good quality solar battery can provide10 to 20 years of service. Solar batteries produce clean energy and are approximately 98 per cent recyclable, making them a clean and environmentally friendly energy solution.