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A guide to storage batteries

On a dark and gloomy day, how effective are solar panels? That’s typically the question on everyone’s mind when considering a purchase. Thankfully, we are now being introduced to the world of storage batteries, which can be charged during the day to fully kick in when your solar panels are less effective, giving you a back-up source for when the sun is hidden away. Thanks to this storage, we could see more homes opting for a solar-powered future as well as across-the-board savings on energy bills.

What is a storage battery and how does it work?

Your typical everyday battery consists of several cells and connectors to power various everyday devices, going from your phone to your watch. Just like any other battery, storage batteries consist of three parts, an anode (-), a cathode (+), and the electrolyte. The chemicals inside batteries cause a build-up of electrons at the anode once connected to an electrical circuit. In a rechargeable battery, they produce current in the same way, however, this time the negative-to-positive flow of electrons is reversed to restore charge.

Solar storage batteries rely on solar panels, which contain solar cells on the surface to collect energy from the sun. These photovoltaic (PV) panels convert the sun’s energy by springing electrons into life using photons from sunlight. The same energy is passed through an inverter and converted into power that can be used directly for your home or stored. Storage batteries work by storing excess solar-produced power for use at night or darker days, which is a cost-effective solution as opposed of selling it back to the power grid. In order to decide on a solar-based storage battery, you should take into consideration their useable capacity, cycles and power output.

Choosing a storage battery

To get you on your way to choosing the right storage battery for you, we have listed the key elements below so you know what to look out for:

  • Useable capacity – This refers to the amount of energy (measured in kWh) that the battery can store. You will normally find that some batteries are advertised as being 6kWh when their useable capacity really is closer to 5.5kWh. The reason for this is that none of these batteries should drain to zero, thus reducing the risk of damage.
  • Cycles – One complete discharge and one complete charge is called a cycle. You will find some manufacturers advertise how many times their batteries can be charged, and typically this will be in the thousands. For example, if your phone has an advertised lifetime of 1200 cycles and you fully charge your phone in the morning and use it all day till the following morning, you should expect the battery to last approximately 3 years before it loses its effectiveness.
  • Power output – It’s incredibly important to remember that the power output has to be up to scratch to be able to power even the smallest of devices through to your whole household. If you consider the number of devices and appliances in a typical home, you may be better off going for a larger solar battery to cater to this demand.
 Tesla Powerwall IIPowervaultSonnenbatterie
Storage capacity14 kWh2-6 kWh2-16 kWh
Warranty10 years3,5 or 10 years10 years
Price£5,400£2,000 – £2,800£3,800 – £14,500

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