What is a Battery?
A battery, in concept, can be any device that stores energy for later use. In a stand-alone power system, the energy stored in batteries can be used when energy is needed. Battery does not generate electricity, its an electrical storage device for later use like we store data on our computer, laptop or smartphone devices for later use may this is bad example but water tank storing water for later use is better and best example to depict battery. For battery life expectancy there are so many variables, such as depth of discharge, maintenance, temperature, how often and how deep cycled, etc.Types of Batteries in Solar Power System. Three Types of Batteries used in Solar Systems:
- Flooded lead acid
- Have longest track record in solar usage
- Longest lifespan
- Least cost per amp hour
- High maintenance
- Absorbed Glass Mat Sealed Lead Acid
- Ideal for grid tied solar w/ battery back-up
- Also called as “starved electrolyte” or “dry”
- Low to no maintenance because fiberglass mat is only 95% saturated with Sulfuric acid and there is no excess liquid.
- Becoming more affordable
- Gelled Electrolyte Sealed Lead Acid
- Predates AGM batteries but are losing market share
- Must be charged at a lower voltage (2/10th’s less) than flooded or AGM batteries
- In hot climates, water loss can be enough over 2-4 years to cause premature battery death.
- Current must be limited to the manufacturers specifications.
Some of their key features and differences between lithium-ion and lead-acid batteries are
Batteries for Backup Power
Our focus for this discussion is mainly on solution for power storage bank or battery bank for backup power. These aren’t the kind of batteries you put in a flashlight. Instead, we’re talking about 12-volt deep-cycle lead-acid batteries similar to the battery in your car. “Deep-cycle” means that they can be almost completely discharged without losing their ability to produce their specified output. Remember batteries give output in DC and most of our home/small office equipment works on AC power. Now once decision taken to put solar power backup system for power then first thing come in mind to look for answer for question ”What is needed off-grid or on grid solution”, as requirement for battery is ideally different in both.
Deep Cycle Batteries
- Deep cycle batteries can be repeatedly discharged to 80% and recharged without damaging them
- Recommended for use with solar
- A true deep cycle battery and difference with others is that the plates are SOLID Lead plates – not sponge
- Deep-cycle includes solar electric (PV), backup power, traction, RV and boat “house” batteries.
Shallow Cycle Batteries
- Occurs when the top 20% or less of the batteries energy is discharged and then recharged
- Shallow cycle batteries not recommended for solar use
Generally for on-grid solution Lithium-ion batteries type are recommended and suggested. For off-grid type “deep cycling lead-acid” batteries are better option. Batteries in solar applications have to meet the demands of unstable grid energy, heavy cycling (charging and discharging) and irregular full recharging. There’s a variety of battery types fitted for these unique requirements. Considerations for choosing a battery include cost, cycle life and installation and maintenance. Batteries are not 100% efficient – some energy is lost as heat and chemical reactions when charging and discharging. If its uses for 1000 watts from a battery, it might take 1050 or 1250 watts or more to fully recharge it.
Battery Backup Time
Total backup time of the battery may vary depending on the age and condition of the battery, and the power demand being placed on it by the equipment being operated by the inverter. 500 Watt and larger Inverters: recommend to use deep cycle (marine or RV) batteries which will give several hundred complete charge/discharge cycles. The main decision to make is whether to get sealed or unsealed battery. Sealed batteries are often called “maintenance free” because don’t have to periodically top them off with distilled water, which makes life much easier.
Physical Size of Battery
The greater the battery capacity, the greater the battery size and weight. Typical domestic systems vary from being the size of a small computer to the size of a washing machine. Batteries and battery systems can vary considerably in shape, size and weight.
Battery storage systems are often provided with a power rating in Kilowatts (kW). Storage batteries for a grid connected solar PV storage system are typically around 1kW to 7kW. This is the capability of the battery to provide power. A battery’s stated electricity capacity, as expressed in kilowatt-hours is generally larger than the battery’s actual useable capacity, because most batteries are not designed to get drained / discharged in full routinely as this phenomena can reduce battery life. Some have deeper discharge capability than others. All batteries lose some energy in charging and discharging, though some have better ‘charge-discharge efficiency’ than others.
Choosing the Correct Battery
Battery sizing is essential but often overlooked by users and installers. Batteries in PV systems are routinely undersized due to cost or because the system loads were underestimated. It’s important to know the power needs and correctly plan.
Battery Performance & Care
- The charging and discharging of the batteries is governed by temperature and charge/discharge current
- The colder the temp. the slower the reactions, and the warmer the faster the reactions
- Optimum temp. for a lead acid battery is 77 degrees F (Highly recommended , its a suggestion and a best practice)
- Battery voltage should be kept at or above 50% state of charge at all times for maximum battery life
- Use only distilled water to fill batteries, never use tap water or boiled water etc
- Keep batteries electrolyte level at the marked full level
Also check for beautiful and easy to move inverter, UPS battery trolleys. As heavy batteries are not easy to move and cause great damage if mishandled. Should opt for trolleys which are spacious, safe and made from tough long lasting material which does not get destroyed by spillage from batteries.