Solar Batteries Guide

Solar Batteries

In this article, you are going to learn all about Solar Batteries.

You will understand what the differences are between the types of solar batteries, how they fit into a Solar System, how many you’ll need and more.

Here’s the breakdown:

Let’s get started.

What Are Solar Batteries

Solar Battery - Level Of Discharge

A solar battery is used to  store energy to use when there is no grid or solar power supply .

For a system we need to:

  • Charge the battery via the inverter during the day using solar power or grid supply.
  • Use power from the battery during the evening or during load shedding.
  • Then recharge again, repeating the process thousands of times over.

Deep-Cycle

You will hear the term “Deep-Cycle”, what this refers to is the  Depth Of Discharge . Deep-Cycle Solar Batteries are  specifically designed to regularly discharge until it has used most of its capacity .

The depth of discharge will depend on the type of battery you choose (we will go into this more in-depth below).

A typical  Lead-Acid option you will go to 50% DOD (Depth Of Charge) . Whereas with the  Lithium-ion Solar Batteries you will go to between 80-100% , this is important to understand when calculating your solar battery needs.

What Kinds Are Best For Solar Power?

In short, there are 2 main types of Solar Batteries, Lead Acid and Lithium-ion

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 short lifespan (depending on the brand) and are expensive for what you are getting.

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.

New AGM batteries cannot be connected in series to existing, older batteries as this will damage the newest addition.

Pros

  •  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
  • Lower initial cost

Cons

  • Lifespan from around 3-5 years (depending on brand)
  • Need to replace more frequently
  • Only 50% depth of discharge is recommended

Lithium-ion

Lithium-ion Battery

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 Lead Acid batteries and are perfect for setups that have space restrictions.

Easy, versitile Installation

Lithium-ion batteries come in a number of sizes and are easily installed. Should you need to add new batteries later, you’d simply need to add them to your existing battery pack.

Furthermore, you are able to choose how and where you’d like to install them. Lithium-ion batteries are available in wall-mounted, floor-mounted and rack-mounted options which give you the freedom of choice. For rack-mounted batteries, you also have the choice of a cabinet.

Pros

  •  Maintenance free 
  • Lighter and smaller
  • Don’t have to be mounted upright
  •  Produce more cycles (6000 – 10000) 
  • Can produce 100% of the stored energy
  • Lifespan from around 10-20 years
  • High charging and discharging efficiency,  more than 95% 

Cons

  •  Highest cost 

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:

PylonTech

Pylon Technologies, Co. Ltd founded in 2009 is regarded as the pioneer for LFP (lithium iron phosphate) battery deployed in ESS (energy storage system).

Pylontech’s battery products and solutions have been used for high-end vehicles, cloud computing systems and telecom power backups, new energy storage systems and electric vehicles.

Top features:

  • Innovative
  • High Quality
  • Specialise in Lithium technology
  • Used by companies such as Apple
  • Award-winning
  • Great value for money

View PylonTech website

Dyness

Dyness Energy StorageA relatively new player in the market Dyness have made an impressive start by rivaling the mightly PylonTech by creating similar spec lithium-ion batteries.

They have a sophisticated team of Lithium-ion experts with specialist R&D team.

Also used in various sectors the Dyness range suits Solar applications like a glove, their Power Box module is a big hit due to it’s athetically pleasing design at a fantastic price point.

Top features:

  • Innovative
  • High Quality
  • Specialise in Lithium technology
  • Well designed Wall Units
  • 10-Year Warranty
  • Great value for money

View Dyness website

Fusion Solar

BlueNova EnergyFusion Solar’s creators have seen the demand in South Africa for more choice when it comes to Solar Batteries. Passion for the South African Solar Industry has seen them answer this demand by finding excellent batteries that were not available in South Africa before.

Additionally, the batteries were specifically chosen for their price point and size to be able to cope with long periods of no grid supply and compatibility with quality inverters.

Their batteries have been popular thanks to their reliability and stylish design.

Top features:

  • Stylish
  • Functional
  • Realiable
  • High Quality
  • 10-Year Warranty

View Fusion Solar website

AlphaESS

Founded in 2012, AlphaESS is one of the leading energy storage manufacturers in the world.

Their passion for green energy is evident in their excellent product range. AlphaESS offer a variety of residential and commertial storage solutions in over 60 countries world wide.

Additionally, AlphaESS ranked fifth as one of the top suppliers of Residential Storage Systems for 2020, accounting for 15% of the global market share.

Top features:

  • Good reputation
  • Long life-span
  • Excellent quality
  • Great support

View AlphaESS website

How Many Batteries Do You Need For A Solar System

Working out how much storage you need isn't as difficult as you might think.

Here's what you need to do:

  1. Start with looking at your electricity bills
  2. Take the last 12 months and add the kWh together
  3. Divide the total kWh by 12 to get your daily average
  4. From that average, figure out what portion you use during day and night
  5. Nighttime 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).

For 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.

Note:  Be aware that you need to double up for Lead Acid batteries .

Here is an example of sizing a Lead Acid battery:

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

If you find this complicated and aren't sure about the right battery for your system, consider purchasing a Hybrid or Off-Grid Solar Power Kit that will include the correct battery size and type.

How Much Do 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 option, they start from around R20k plus depending on how much you need

Overall Review

[wp-review id="11307"]

Ask A Question About Solar Batteries

If you have a question feel free to add a comment below or contact us directly.

3 comments

  1. Anonymous

    Visitor Rating: 4 Stars

  2. Visitor Rating: 5 Stars

  3. Hi. A cycle on the lithium batteries. How’s the cycle calculated? For example, if the battery was 20% discharged, then charged again, is that a cycle or not?
    Thx

    1. Hi, if the battery is 80% DOD and it goes from 100% to 20% that would be 1 cycle, if it went to half that then that would be half a cycle.

      Hope that answers your question.

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