How does battery storage work?
How does it work?
Battery storage systems operate similarly to conventional batteries commonly found in everyday devices such as torches or TV remotes. Whether charged by solar panels or the grid, they provide autonomous home power and significant cost savings.
For homes with solar panels, any surplus electricity is typically sold back to the grid. If you require electricity when your solar panels are not actively generating power, you will then typically need to purchase it from the grid. However, by integrating a solar battery storage solution, you gain the ability to store any excess energy generated by your solar panels. This stored energy can be used at your convenience without incurring additional costs.
No solar panels? No problem. Home battery storage solutions extend their advantages to every home, regardless of whether solar panels are installed. During off-peak hours when energy costs are at their lowest, your battery quietly charges up. When electricity rates spike during peak hours, you can seamlessly switch to using the stored energy, effectively avoiding costly peak-hour charges. This technology empowers you to manage your energy consumption, save significantly on your bills, all while making a positive contribution to the environment.
Understanding the lingo...
“Battery Cycle”
A battery cycle is one full charge and discharge of a battery.
One full cycle could be through lots of smaller charges that all add up to 100%. Most batteries don’t fully discharge and recharge; they often discharge and recharge partially, like 33%, which is 1/3 of a cycle.
It’s important to check your battery’s warranty for the number of cycles it covers. The batteries we install typically come with a minimum warranty of 6,000 cycles, but we also offer batteries with unlimited cycle warranties. In typical usage, you’ll charge and discharge the battery once a day. So, with a 10,000-cycle warranty, your battery is covered for approximately 27 years.
“Charge” and “Discharge”
Charge Power (Charging): Charge power is the speed at which energy from sources like solar panels or the grid refills the battery. The charge power depends on the battery’s capacity and the inverter’s capabilities (we recommend a minimum 3.0kW inverter).
Discharge Power (Discharging): Discharge power is how quickly energy flows from the battery to power household devices. The battery’s discharge capacity and the inverter’s capabilities determine discharge power, affecting how rapidly the battery supplies electricity to the home.
“Kilowatt (kW)” and “Kilowatt Hours (kWh)”
Understanding kW and kWh is vital for monitoring electricity costs.
Kilowatt (kW)
- kW measures an appliance’s energy consumption rate, equivalent to 1,000 watts (W).
- Convert watts (W) to kW by dividing by 1,000.
Kilowatt-hour (kWh)
- kWh quantifies the total energy an appliance uses over time.
- For example, a 2,000W (2kW) washing machine running for 2 hours consumes 4kWh. In 30 minutes (0.5h), it uses 1kWh.
In summary, kW reflects the rate of electricity you use, and kWh indicates the amount of electricity you use.
“Capacity” and “Useable Capacity”
Capacity is the size of the battery (i.e. 5.8kWh or 8.2kWh) and represents the volume of energy or amount of electricity in kilowatt-hours (kWh or “units”) a battery can store.
Useable capacity is the amount of capacity that the manufacturer allows to be used out of the nominal capacity of a battery.
Inverters
Inverters convert electricity between AC and DC and accompany all battery installations. AC electricity is needed to power appliances in your home, while DC electricity is generated from solar panels and is needed to charge the batteries.
Adding a battery to an existing Solar PV system
If you are looking to add battery storage to an existing Solar PV system, you will need an ‘AC Coupled’ arrangement.
You will already have one inverter that converts DC electricity from your solar panels into household AC electricity.
When you add a battery to your system, you will need a second inverter installed that converts that AC electricity (plus any AC electricity from the grid) back into DC electricity to charge your battery.
Installing a new Solar PV and Battery system
With this arrangement you only need one inverter which will work seamlessly with you solar panels and battery.
The electricity generated from the solar panels flows into the inverter as DC. The hybrid inverter then either converts it into AC to be sent to the house or the grid, or the inverter keeps the current as DC to be sent to the battery to charge it.
This type of set-up can only be used for a new solar system being simultaneously fitted with a battery storage system.
Battery Types: Lithium-ion batteries
Lithium-ion batteries are very popular with domestic solar storage systems.
- More efficient
- Faster charging
- More capacity
- More expensive
- Smaller and lighter
- Lifespan of 10+ years
Most lithium-ion batteries are equipped with the capability to charge from the grid to top up the batteries when they cannot reach full charge during from the solar alone – this is common in winter when the days are shorter and there is less solar irradiance available for the solar panels to generate enough electricity to charge the batteries. Keeping the battery topped up is important because incomplete charging can have an effect on the lifespan of your battery.
Battery types: Lead-acid batteries
Lead-acid batteries are often used for energy independent properties, who live entirely off the grid, where more storage is needed.
- Considerably cheaper
- Less efficient
- Shorter lifespan (up to 7 years)
- Bigger and heavier
- More maintenance
The average solar PV system can last 25+ years, unfortunately, there aren’t any battery systems with that length of lifespan, so your battery system will need to be replaced within the lifetime of your solar system.