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.

Chapter 1

What Are Solar Batteries

Lets start at the beginning

Solar batteries are a part of a solar power kit that contains an inverter, solar panels, switches, mounting and cabling.

They also fit into a kit that does not contain Solar Panels. These kits are lovingly known as Load Shedding Kits.

Solar batteries store the overproduced solar power during the day to provide you with usable solar power in the evenings and during grid failure.

In Load Shedding Kits, they are charged using grid power.

The more solar power you store and use during downtimes will help you use less grid supply, saving you money on your electricity bill.

Solar Battery - Level Of Discharge
Chapter 2

Fundamentals

Solar lingo explained

Understanding the terms used in this guide is very important as they'll help you understand what to look out for when sizing your own battery bank. If you know the basics, skip to Chapter 3.

What does Deep-Cycle mean?

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.

DOD

DOD (Depth of Discharge) refers to how much of the battery can be used.
A typical  Lead-Acid Battery will have a DOD of 50%  . Whereas with the  Lithium-ion Solar Batteries have a DOD of between 80-100% , this is important to understand when calculating your solar battery needs.

Chapter 3

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

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.

AGM Lead Acid

Pros

  •  Completely sealed so no 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

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, versatile 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.

Lithium-ion Battery
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 
Chapter 4

How to Size a Battery Bank

In 3 easy steps

To begin, it's a good idea to check the power ratings of your appliances. You have to make sure you have a large enough battery to accommodate your needs.

Let's Start

Now to work out what size solar battery bank you’ll need, you’ll need to work out what you want to run off your battery and for how long you need to run these appliances.

There are three main questions you need to answer:

  1. What appliances need to run off the battery bank?
  2. For how long do these appliances need to run off the battery bank?
  3. Will your battery be used during load shedding, evenings, nights and mornings?

Whatever your answer is, you’ll be able to work out your kWh needs by following the steps in this section.

I’ll refer to load shedding, evenings, nights and mornings as ‘downtime(s)’ as this is the period you’ll not be producing solar power.

Step 1

Add the power ratings of all the appliances you’d like to run off your solar battery bank.
As I have said, it is a good idea to  check each of your appliances for their ratings  to get an exact idea of your usage.

Step 2

Next, we’ll need to  work out the amount of time you typically use these appliances .

You’ll use your appliances for varying amounts of time throughout the down phases. Like a TV might be on for 4 hours while your microwave is only on for 3 minutes.

This section is entirely reliant on your usage.

Step 3

 How will you use your solar battery ? Load shedding? Non-production time? Both?

Non-Production Time Guidelines

Below are some guidelines for figuring out how many hours you'd like to run your appliances off your battery bank.

Load Shedding Usage

In some areas, they can expect  2.5 hours of load shedding , and in other areas, they can have up to 4 hours of load shedding. It’s essential to consider these times.

Evening Usage

The average evening usage is around 4 hours for appliances that we use when we’re awake from when we come home from work till the time we go to bed. We’ll work from 18:00 to 22:00.

Nighttime Usage

Say you’re getting in a good night sleep at the recommended 8 hours a night. Most of us still run a few essential appliances like fridges, alarms etc.

Morning Usage

We use a lot of power in the mornings because we use appliances like kettles, toasters, microwaves and hairdryers. All of these appliances pull large amounts of power.

Usually, between 06:00 and 10:00, we don’t produce enough solar power to supplement our load. Therefore, it is beneficial to have a big enough battery to cover as much of our usage in the morning as possible.

As a rule of thumb, we suggest being mindful of what you are running off your battery bank, but mornings are different because who wants to start their day de-caffeinated with a severe case of bedhead?

In the next section, we'll take a look at a case study of my home to show you exactly how to work out your battery needs.
Chapter 5

Adding Up All The Data

Now we get to the fun part: working out our usage!

Below, I’ll give you an example based on my home and the appliances we own with their ratings, how many times we use them, and how long we use them in 16 hours.

I have broken them down into three sections.

  • Mornings
  • Evenings
  • Nights

Mornings

Appliance Watts Number of uses Duration of usage Total Watts
Espresso Machine 1450W 2 10 minutes 484W
Toaster 850W 1 3 minutes 43W
Microwave 1200W 1 minute 20W
Hairdryer 1000W 1 10 minutes 166W
LED Lights x 10 @ 5W each 50W 1 3 hours 150W
TV x 2 @ 160W each 320W 1 2 hours 640W
Fridge Freezer 150W 1 4 hours 600W
Alarm 6W 1 1 hour 6W
Modem 10W 1 4 hours 40W
Heat Pump 1250W 1 1 hour 1250W
Total 3399W

Evenings

Appliance Watts Number of uses Duration of usage Total Watts
Toaster 850W 1 3 minutes 43W
Microwave 1200W 2 3 minutes 120W
LED Lights x 10 @ 5W each 50W 1 4 hours 200W
TV x 2 @ 160W each 320W 1 4 hours 1280W
Fridge Freezer 150W 1 4 hours 600W
Modem 10W 1 4 hours 40W
Heat Pump 1250W 1 1 hour 1250W
Total 3533W

Nights

Appliance Watts Number of uses Duration of usage Total Watts
Fridge Freezer 150W 1 8 hours 1200W
Modem 10W 1 8 hours 80W
Alarm 6W 1 8 hour 48W
Phone Chargers x 4 @ 20W each 40W 1 2 hours 80W
Laptop Chargers x 2 @ 45W each 90W 1 3 hours 270W
Total 1678W

Case Study Findings

Now that we have totals for each time frame, we can determine my family’s overall usage and battery needs to cover 100% of our load using our solar battery bank.

We’ll add all three totals together: 8610W or 8.61kW.

To choose a battery, I’ll need to consider the battery’s DOD (Depth of Discharge). If I choose a battery with 80% DOD, I’ll need to subtract 20% from the overall rating of the battery.

I could consider these options to cover my usage completely:

4 x PylonTech US2000C Batteries giving me 9.12kWh @ 95% DOD.
5 x Dyness 2.4kWh Batteries giving me 9.6kWh @ 80% DOD.
3 x PylonTech US3000C Batteries giving me 9.975kWh @ 95% DOD
3 x PylonTech US3000C Batteries giving me 8.645kWh @ 80% DOD
2 x Alpha ESS 5.8kWh Batteries giving me 10.44kWh @ 90% DOD.
Chapter 6

What Solar Battery Brands Are Best?

Here's a selection of brands which we recommend

As 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.

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 a specialist R&D team.

Also used in various sectors the Dyness range suits Solar applications like a glove, their PowerBox module is a big hit due to its aesthetically 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 commercial 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

Chapter 7

Solar Battery Prices

What you can expect to pay

We all know that the initial solar battery prices are pretty high. But if you’re cycling a battery bank once a day and have 6000 cycles, that gives you over 16 years of battery life.

Lithium-ion prices range from just under R12,000 for singular batteries and upwards of R53,000 for large battery banks with multiple batteries.

Solar product prices are also falling yearly. As a result, you’ll most likely find that solar battery prices will be far more affordable by the time you will need to replace your batteries than they are today.

This fact may put you off buying batteries now, but consider how much money you will still save on your electricity bill by using solar power.

You could even start small by only covering your evening usage and expand your battery bank as you go. One of the joys of Lithium-ion batteries is that you can add new batteries to older batteries without causing any damage to the new ones.

Depending on your budget, you have a couple of options:
Have a big enough solar battery bank and array to ensure you use as much solar power in the morning as possible.
Or
Supplement your load demands with grid and solar battery with a Hybrid Inverter Solar Power Kit.

Either way, you will still be saving money every month on your electricity bill.

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

  4. 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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