Lets assume you have an appliance that is rated at 120 watts & you want to power it for five hours a day.
You would take the Watts (120) & multiply that number by the hours of use -
(5 x 120) W x H = 600Wh.
So we will need at least six hundred watt hours of battery time per day.
You would also want to have some additional standby power to allow for those days that are cloudy or when no solar is being generated.
A three day window is a good starting point, which means you can safely use your appliance during over cast days.
We now take our 600Wh figure and multiply it by three. We now know we require a battery that is capable of producing 1,800 watt hours daily.
A typical 12v 100 amp hour battery is rated to deliver (12v x 100) = 1200 watt hours.
However flooded lead acid batteries can only provide 50% of their capacity!
So a 100 amp hour lead acid battery can only supply a maximum of 600 watt hours.
This is where Lifepo4 batteries come into their own.
A lithium battery can provide 100% of their capacity, so a 100 Amp Hour LifePO4 battery will supply a full 1,200 watt hours.
In order to supply our 1800 watt hour power needs, we would need either 1 X 24v 100Ah battery , 2 x 12v 100Ah lifepo4 batteries or 4 x 12v 100Ah lead acid batteries.
This gives us a total of 2400Wh of usable battery capacity. 2 x 1200Wh = 2400Wh
If you are planning on using a 24v battery, either a single 24v or 2 X 12v in series be sure to choose a 24 Volt Inverter of sufficient wattage to meet your needs.
Server Rack Batteries are becoming the new go-to option for residential off grid power demands. They are easily expandable and a very cost effective power system.
If you can afford the initial cost of buying a Lifepo4 battery system I suggest you buy them over lead acid batteries.
Lifepo4 batteries will out perform & out live lead acid batteries.
Lead acid may seem a less expensive option, but you need to think in terms of years.
You will need to replace lead acid batteries frequently as they will degrade much quicker than Lifepo4.
Find Lifepo4 & Lead Acid Batteries on the Batteries page.
Clicking the image will take you to Amazon UK were you can find the current price on this twelve volt 3500W inverter, which i have used without issues or you can click here to buy from eBay (Usually Cheaper)