The whole idea of a battery is to store energy to use on demand, the concept is exactly the same when dealing with Solar Power but there are some fundamental differences between the typical battery we use every day to a Solar Battery.
For Solar Power we need to:
Charge the battery during the day using the sun
Use power from the battery during the evening when there is no sun
Then recharge again the next day, repeating the process over and over again
What Kind Of Batteries Are Best For Solar Power
In short, there are 2 main types of Solar Batteries, here they are.
Flooded Lead Acid
For solar applications the Lead Acid battery works perfectly, they’ve been used for solar since the very beginning. Recommended for those on a budget these batteries are cheap but require regular maintenance.
How do they work?
Lead Acid Battery
Typically referred to as flooded or wet cell batteries, they have cells submerged in a sulphuric acid solution.
The maintenance consists of adding distilled water every month, ventilation for the gasses to escape. With FLA model batteries the acid solution reacts with the lead plates, which gives off hydrogen and oxygen.
Cheap, ideal for starting out
Lifespan around 5-7 years (depending on brand)
Require regular maintenance
Ventilation is required
Sealed Lead Acid
AGM Lead Acid
An upgrade to the flooded version, Sealed Lead Acid eliminates the maintenance required compared to its counter partner.
It’s not without its drawbacks, however, a shorter lifespan (depending on the brand) and higher price they can make a difference if you require a large amount of storage.
How does it work?
AGM (Absorbent Glass Mat) are capable of handling higher temperatures with a lower self-discharge when they are idle. The cells have a lower resistance compared to conventional cells, they don’t leak and they don’t need to be in an upright position.
Completely sealed so the risk of acid leaks
No maintenance is required
Don’t have to be mounted upright
Charge quicker with a lower voltage
Lifespan from around 3-5 years (depending on brand)
The most efficient battery on the market Lithium-ion technology is the future of solar storage. They waste significantly less power when charging and discharging. The cycle is deeper using more of their capacity with a long lifespan.
Completely maintenance free they are lighter, smaller and they don’t produce as much heat as other Lead Acid batteries which are perfect for setups that have space restrictions.
Lighter and smaller
Don’t have to be mounted upright
Produce more cycles (5000 – 7000)
Can produce 100% of the stored energy
Lifespan from around 10-20 years
High charging and discharging efficiency, more than 95%
What Solar Batteries Brands Are Best
As like with the other components the brand of the battery is closely related to the quality of the product, Solar Batteries are no different in this regard.
Here’s a selection of brands which we recommend:
HOPPECKE has been making batteries since 1927!
The group is the largest producer of batteries in Europe, their headquarters are in Brilon-Hoppecke. They have subsidiaries, offices, partners, distributors, production and assembly facilities worldwide. They have almost 2000 employees with a €400 million turnover.
A huge producer of electronic equipment LG Chem is part of the LG group. Established in 1947 this Korean company leads the way in the chemical industry. With almost 30,000 employees this giant produces batteries for almost every industry.
Their flagship Lithium-ion batteries are high quality perfect for home or business.
A division of Sinetech, OmniTech have been in the PV solar industry since 1995, Sinetech is a South African brand that has gained a solid reputation for Solar Batteries and other Solar Energy products for over 20 years.
Working out how many batteries isn’t as difficult as you might think.
What you need to start with is looking at your electricity bills, get the last 12 months and add the kWh together, and work out a daily average. From that average, figure out what portion of the average you use during day and night. Night time usage is required to be cycled through the use of batteries.
Say it is 5kwh required for night and you wish to use lead acid batteries, using the formula “watts = volts x amps” this is what the equation will look like:
5000 watts = 12 volts / (?) Amps
5000 / 12 = 416.66 Amps
Now because with lead acid you can only use 50% of the battery to not damage it, you would have double the amps to have 5000 watts of available power. Therefore 12v 833.33 Amps gives you 5000w of usable power.
Changing the voltage of the battery bank:
If you were to use a 24 volt battery bank (2 x 12v in series) you would require a 24 volt 416 Amp battery bank, and so on. This is where you choose the required battery for your needs.
You commonly get 100A or 200A batteries, so you would require 4 x 12v 200A batteries to get a 24v 400A battery bank (2 in series and 2 in parallel), if it was a 48v bank, would be 4 in series, so 48v 200A bank. All of these give the same amount of usable power, just configured differently.
Add the result of this into the calculator below to get your battery size in kWh.
The next step is to decide how much backup you need, if you are going Off-Grid you will need to consider how many days you want power for.
To do this you will need to add the result by the number of days you want.
Sizing Your Battery Bank
Depending on which battery type you will be using you will need to do some further math to work out the actual amount, this is because the batteries are not 100% what they output, there are variables which affect the overall result.
Be aware that you need to double up for Lead Acid batteries.
Here is an example of sizing a Lead Acid battery:
10kWh x 2 (for 50% depth of discharge) x 1.2 (inefficiency factor) = 24 kWh
Here is an example of sizing a Lithium battery:
10kWh x 1.2 (for 80% depth of discharge) x 1.05 (inefficiency factor) = 12.6 kWh
How Much Do Solar Batteries Cost
This all depends on the type you choose (Lithium or Lead Acid) and how much storage you need.
The cheapest Lead Acid battery starts as little as R1600 and up to R500k plus.
For the Lithium-ion batteries, they start from around R20k plus depending on how much you need.
Here’s a list of external resources that will help you learn more about Solar Batteries:
Overall Solar Batteries are only important if you need backup storage if are looking for a Hybrid or Grid-Tied system you can rely on the grid to provide electricity when the sun goes down.
If you opt for the low end of the battery range it can be a maintenance nightmare, if you invest Lithium however it will save you a lot hassle with the added benefit of being cleaner and longer lasting.
This doesn’t come without a high cost though, just make sure that you are utilising the backup power on a regular basis to make it worthwhile.