Batteries

Batteries


General:

Batteries are the heart of all solar systems. Batteries are used to store energy that can be re-used when the sun is no longer shining or when external power is down.

Batteries are available in various voltage sizes and the most common is 12V as used in cars.

Battery energy is normally specified in terms of Amp hours (Ah) and gives an indication of the current available over a 20hour period from a fully charged battery.

Battery selection and maintenance:

Battery

Selection:

  • All calculations for solar systems must be based on energy required or energy used.
  • As previously mentioned, batteries are normally specified by an Amp Hour (Ah) rating.
  • Battery selection is done by first measuring the energy required for the application.
  • Energy is measured in Watt over a period of say 1 hour , giving you Watt-hour
  • Perhaps you run a hairdryer for 15 min or ¼ hour. The hairdryer's label says it is a 960Watt hair dryer.
  • The energy used in 15 min is then : 0.25 hour x 960W = 240Wh
  • A 12V system will then require 240Wh/12V = 20Ah
  • Normally a battery is not allowed discharge more than 50%
  • Then for the above a battery of 40Ah will provide the energy to run the hairdryer for 15 min

Maintenance

There are so-called “maintenance free” batteries on the market, however, for solar systems it is preferred to use deep cycle maintainable batteries.

Batteries should not be allowed to discharge by more than 50%, and should be fully charged at least once a week, depending on the application.

In order to monitor battery health, a battery monitor can be installed that will provide the Ah status of the battery as well as alarms for low voltage or high voltage conditions.

Discover Batteries are commonly used in solar systems where long life and deep cycle characteristics are required.

Battery Internal Diagram
Discover batteries are engineered to last longer, and are proven to outperform its competitors.  The following construction and chemistry features will help you understand how Discover batteries can provide you with the optimal battery solutions.
  • Super pure grid alloys which incorporate proprietary additives that increase the surface area of the plate which ultimately helps to retard corrosion and extend the life of the grid
  • Using thicker grids (>3.5mm) achieves more corrosion resistance than thinner grids
  • Discover® VRLA batteries are protected against deep discharge because they are acid-starved, and in the case of the Discover® 700 Series and the Discover® EV Traction Dry Cell types extremely acid starved. This means that the battery uses the power in the acid before it uses the power in the plates. Therefore, the plates are never subjected to destructive ultra-deep discharges. More technically speaking, the quantity of electrolyte must be tightly controlled in such a way that the battery attains the expected design life (under normal operating conditions), taking into account the rate of recombination and the corrosion of the positive electrode.
  • Discover® uses more active material per amp hour of battery capacity which ultimately results in a more acid starved reaction meaning, that even when the battery is discharged deeply (the sulphuric acid in the electrolyte is used up and absorbed by the active material in the process of discharge) the active material utilization is kept to a minimum. More technically speaking, the active material is over dimensioned to ensure that all of active material is never completely charged or discharged in the discharge and charge cycle Depending upon the part number, Discover® 700 Series Dry Cell and EV Traction Dry Cell Batteries contain as much as
  • 77% more active material than Flooded Deep Cycle batteries, and
  • 33% more active material than competitive VRLA deep cycle batteries.
  • Discover® GEL batteries contain ultra-premium poly, ribbed glass-mat, dual-insulating separators which will not break down in service. The glass mat embeds itself into the plate, which retards life-shortening shedding.
  • Discover® High quality Dry Cell batteries contain glass separators at the ideal compression and ideal saturation to achieve the best balance between capacity utilization and recombination efficiency. The dual insulating separators also help to prevent separator misalignment and treeing or shorting at the bottom and sides of the plates. The glass embeds itself into the plate, which retards shedding.

About Post Author

With more than 30 years experience in engineering and project management, Steph Van Jaarsveld a registered Pr.Eng, decided to start SA Solar Systems. With a passion for high quality products, fitting your pocket and loving the concept of free energy from nature! ”It’s amazing how we have the technology to turn the sun rays into usable electricity! It’s like a miracle from nature.”