How do I know what battery bank I need?

How to Choose the Right Battery Bank for Your Solar Power System in South Africa

When South Africans think about solar power systems, the first thing that often comes to mind is solar panels. But the real powerhouse behind any reliable system is the battery bank. Without it, you won’t have stored energy to use during load shedding or when the sun isn’t shining.

At Solar Power Space RSA, we’ve been designing and installing solar and battery backup solutions for nearly 20 years. Here’s everything you need to know before investing in the right battery bank for your home or business.

What Is a Battery Bank?

Much like ordinary batteries power your TV remote or torch, a battery bank stores the solar energy captured by your solar panels. When Eskom cuts the power, your battery bank supplies electricity to keep essentials like your Wi-Fi router, TV, laptop, and lights running.

Because batteries are the most expensive component of a solar power system, it’s crucial to size them correctly from the start.

Types of Batteries for Solar Power Systems in South Africa

There are several options when it comes to solar batteries. Here are the most common choices:

Lead Acid Batteries

The cheapest option (often called “flooded” or “wet” batteries).
Short lifespan: 1 to 3 years.
Usually come with only a 12-month warranty.

AGM Batteries (Absorption Glass Mat)

More efficient than standard lead acid.
Easy to charge, reliable, and last 4 to 10 years with proper care.
Still generally sold with a 12-month warranty.

Gel Batteries

Use silica to turn acid into a gel-like consistency.
Good depth of discharge but very sensitive to incorrect charging.
One mistake can permanently damage them.

AGM + Gel Batteries

Combine the strengths of both technologies.
Longer design life: 8 to 12 years.
Great for renewable energy systems.

Lithium Batteries (Best Long-Term Choice)

Light, powerful, and durable.
Can be discharged up to 80% (vs. only 50% for most other batteries).
Perform well in extreme hot or cold conditions.
Longer warranties: 3–10 years.
Higher upfront cost, but cheaper in the long run due to longevity and efficiency.

How to Calculate the Battery Bank You Need

Designing the perfect system should always be done by a professional, but here’s a simplified way to estimate your battery bank size.

Step 1: Add up your load

Example equipment to run during load shedding:

10 x LED Lights = 100W
1 x Smart TV = 100W
2 x Smartphones = 60W
1 x Router = 20W
1 x Laptop = 65W
Total = 345W

Step 2: Multiply by backup time

Load shedding can last up to 5 hours:
345W x 5 hours = 1.725kWh

Step 3: Select your system voltage

12V → best for small setups (under 2kWh).
24V / 48V → better for larger systems and future expansion.

In this case, a 24V system is suitable.

Step 4: Convert to Amp Hours (Ah)

Formula: Watt Hours ÷ Volts = Amp Hours
1,725Wh ÷ 24V = 71.88Ah

Since most batteries can only be used to 50% depth of discharge, double it:
71.88Ah x 2 = 143.76Ah

A 150Ah 24V battery bank would cover this load.

Battery Bank Care & Maintenance Tips

To protect your investment and extend the life of your battery bank:

Keep batteries elevated off the ground in a cabinet or box.
Store them in a dry, ventilated area with space between each battery.
Connect inverter and charger cables across the full bank (not just one battery).
Always match your charger voltage to your battery bank (24V charger for a 24V bank).
Avoid adding new loads without recalculating capacity.
Install a battery monitor to track usage and prevent damage.
Don’t store batteries unused for longer than 3 months—recharge them monthly.

Key Things to Remember Before Buying Solar Batteries

Check the C-Rating (charging/discharging speed).
Compare cycles (number of times a battery can charge/discharge).
You get what you pay for—cheap batteries won’t last.
Always buy from reputable solar providers in South Africa with technical expertise.

Final Thoughts

Choosing the right battery bank is just as important as choosing your solar panels. It’s the heart of your system and ensures your home or business keeps running smoothly during load shedding.

At Solar Power Space RSA, we’ve been designing custom solar battery banks for South Africans for nearly two decades. Whether you want a small backup system or a complete off-grid solar power solution, we’ll help you find the right setup at the best value.