The humble battery powers our laptops, starts our cars, powers a beam of light through the darkness of night.
The purpose of any battery is simple: store energy until needed. Direct current is the form of electricity that can be stored and in today’s world that form can be inverted into alternating current for use in our homes.
This technical ability is what gives the battery storage device two more job descriptions on its already impressive resume.
Batteries in an off-grid setting store the power generated by the photovoltaic panels and wind turbines. In a grid-tie setting, batteries play a central role in backup systems.
This allows for the operation of vital functions in the event of the grid going down.
Smaller backup systems would power furnace, fridge and lighting for a day or two; larger backup systems would power the complete home for an indefinite period.
The most common type of battery, and the oldest version, is the lead acid battery.
It is available in voltages ranging from two to 24 volt and amp hour capacity to 3426 amp hours.
Amp hours are the amount of current that the battery can provide over a period of time, technically one amp of electrical flow for one hour.
For example, a 3,426-amp-hour lead acid battery will provide 34.35 amps for 100 hours.
If the amperage draw goes up, then the amount of time it will be able to supply that current draw will go down. If the current draw went to 121.5 amps, the battery bank would only be able to provide that amperage draw for 20 hours.
Lead acid has the advantage of a lot of power for a relatively low price. The cost per amp hour is approximately 38 cents, compared to an AGM (absorbent glass matt) battery’s cost of 93 cents per amp hour.
Lead acid batteries drawbacks are they require fluid level maintenance, they can only be positioned upright, and they need to be equalized regularly.
AGM batteries and gel cells use recombinant technology to recombine the hydrogen and oxygen produced when any lead acid battery is recharged.
They are categorized as VRLA (valve regulated lead acid), this allows them to be completely sealed, protected by a safety relief valve should they be charged at a higher rate than which the hydrogen and oxygen can be recombined.
The AGM and gel cell require no maintenance of fluid level, can be mounted in almost any position, and have high rate of power cycling characteristics.
The AGM batteries have more power by size when compared to lead acid and tolerate low temperatures better.
The electrolyte in the AGM battery is absorbed into a glass fibre mat positioned between plates.
The electrolyte in the gel cell, as the name implies, is actually a gelled form of sulphuric acid.
Capacity and cost are the major drawbacks for both types.
Battery technology is advancing rapidly, in the future look for lower cost and more enhanced storage abilities.
Lorne Oja is an energy consultant, power engineer and a partner in a company that installs solar panels, wind turbines and energy control products in Central Alberta.
He built his first off-grid home in 2003 and is in the planning stage for his second.
His column appears every second Friday in the Advocate. Oja, who lives in west Central Alberta, can be contacted at lorne@solartechnical.ca