Tips When Choosing a Solar Battery

A solar-plus-storage system consists of 3 key elements:

? PV arrays absorbing and converting solar energy into direct current electricity

? Batteries storing the unused power for later usage when solar electricity cannot be generated

? Inverters converting direct current into alternating current suitable for home usage

? A major part of modern storage solutions includes intelligent technologies like wi-fi and applications for monitoring a battery state of charge and performance

Solar energy storage products can be categorized into full storage systems (with DC/AC inverters incorporated) and batteries alone (requiring inverters separately). Besides, storage products can be grouped into utility-scale systems (as a rule, with a capacity exceeding 100kWh) and small ESSs for home use. 

The Key Points to Pay Attention to While Choosing a Solar Battery:

1. Usable capacity. Battery capacity is how much energy (commonly expressed in kilowatt-hours) can be stored in a battery. A battery must never be totally discharged, so it is important not to confuse the parameters ‘total’ and ‘usable’ capacity. For example, Powerwall 2 has a total capacity of 14 kilowatt-hours, while the capacity that can be used is 13.5 kilowatt-hours. It cannot be completely discharged, otherwise the cells would be damaged.

2. Warrantied cycles. One battery cycle consists of full discharging and full charging. However, a battery never gets 100% discharged. In case it discharges 50% and then recharges 50%, it is half of a full cycle. Check the number of cycles a battery manufacturer warranties. This way, you can calculate the amount of energy the batt is supposed to provide during its cycle life.

3. Chemistry. The key types of solar batteries are lead-acid and lithium. The former is much cheaper but not as efficient and long-lasting as the latter. That is why, most modern solar batts are made of either Li-ion or LFP, in spite of expensiveness of the material. Lithium-based batteries are long-living and provide much more energy during lifespan. Consequently, their lifetime cost is cheaper compared to lead-acid products.

4. Power output. There are batteries that cannot discharge more than 800 watts of power, while a small domestic appliance like electric kettles requires 2 kilowatts to power. Or in case your solar panel produces 4 kilowatts of power and a battery can store only 3 kilowatts, this would mean 1 kilowatt is wasted by injecting to the power grid. Make sure you have chosen the battery with a proper charge and discharge power to avoid buying much power from the electric grid in spite of having a battery.

5. Price per kilowatt-hour. Prices of different ESSs vary considerably, so it is reasonable to calculate the price per 1kWh of a battery capacity. It is up to you to choose the proper capacity for your home. Keep it in mind that the more energy is stored the less you pay for the electricity, as this allows you to charge at cheaper rate hours and sell back to the power grid during the time of higher rates.

6. Powercut cover. The majority of solar batteries are intended for storing the energy only. But there are storage solutions that can provide backup power in case of outages. If you’d like a battery with a powercut backup, take into account the following two points. Some devices may need removing from the backed-up circuit, otherwise either a device or a battery can be damaged. It would be wise to think of a larger battery that can store more energy in reserve.

7. Type of coupling. DC batteries are connected to photovoltaic modules directly, while an electric meter is required for connecting AC batts. Consequently, you install direct current batteries simultaneously with PV modules, and alternating current batteries are optimal for retrofitting the existing solar array. AC-coupled batts require separate inverters for converting direct current into alternating suitable for domestic usage and back into DC for battery storage. An AC-coupled system is more flexible in terms of location, since the battery can be installed indoors, while inverter requiring a cool temperature can be placed outside the house. However, DC-coupled ESS transfers power more efficiently by 1-3% and the installation is cheaper because only one inverter is needed.

Some More Things to Consider

Necessary Maintenance 

No solar batteries can be just installed and left. In order to provide optimal efficiency and safety, they require to be regularly monitored and maintained. You should keep the battery state of charge optimal, make it ‘power-boosted’ and gassed regularly, and make sure you store it at required temperatures and weather-protected.

Spare Parts

A solar batt is not as long-living as a PV module. The lifespan of modern qualitative batteries ranges from 10 up to 15 years, depending on the way they are used and maintained. Keep it in mind that solar batteries are a considerable expense.

Still Grid-Reliant

Though modern technologies are shifting toward fully autonomous self-sufficient energy solutions, solar batteries do not currently allow disconnecting from the power grid entirely. No battery is secured against a fault, every product has a limited lifespan and other limitations. That is why, for the time being, it is reasonable to be optionally backed-up by the grid. 

Solar Batteries and PV Arrays

One does not necessarily need solar modules installed to get a solar battery. You can use a battery as an independent backup solution for the case of an outage. Besides, this can be a money-saving option, if you charge the battery in low-rate hours and use the energy stored when electricity rate is higher. Or one can earn money by selling the electricity accumulated by the battery to the grid.

 Quote from https://list.solar/storage/best-solar-storage/