Battery Guide – LiFePO₄ vs AGM Solar Batteries | The Sun Pays

🔋 Battery Guide for Solar Systems: Why Lithium is the New Standard

Choosing the right battery for your solar system is critical. While lead-acid batteries (AGM/Gel) were common in the past, LiFePO₄ lithium batteries have become the preferred choice in modern solar installations — especially for off-grid and hybrid systems.


⚡ Lithium (LiFePO₄) Batteries – The Modern Standard

  • ✅ Longer lifespan – 10+ years or 3000–6000 cycles (80% DoD)
  • ✅ Higher usable capacity – up to 100% DoD on quality models
  • ✅ Lighter and more compact – high energy density
  • ✅ Low maintenance – built-in Battery Management System (BMS)
  • ✅ Safer chemistry – LiFePO₄ is one of the safest lithium types
  • 💰 Higher upfront cost — but lower long-term cost per cycle

Important Tip: Always choose a lithium battery with a built-in BMS to prevent overcharging, deep discharge, or overheating.


🔋 What About Lead-Acid (AGM/Gel) Batteries?

AGM and Gel batteries are older technologies that:

  • 👎 Last only 2–4 years (fewer than 1000 cycles)
  • 👎 Must not be discharged below 50% of their capacity
  • 👎 Are heavy and bulky
  • 👎 Require external battery balancers (not plug-and-play)

These may be suitable for very small, low-budget systems — but offer poor performance over time.


⚙️ How to Calculate the Energy Storage You Need

Energy (Wh) = Voltage (V) × Capacity (Ah)

Example:
A 48V, 100Ah lithium battery stores:
48V × 100Ah = 4800Wh or 4.8 kWh
With 80% usable capacity: 4.8 kWh × 0.8 = 3.84 kWh usable


⏳ How Long Will a Battery Last on Load?

Example: 1x 48V 100Ah LiFePO₄ battery @ 80% DoD

(Includes inverter losses and Peukert effect)

Load on Inverter Runtime Estimate
2500W ~1 hour
1270W ~2 hours
630W ~4 hours
410W ~6 hours
230W ~10 hours
150W ~14 hours
130W ~16 hours
90W ~20 hours

Add batteries in parallel to increase runtime.


🧠 Why We Recommend Lithium for Most Systems

  • 🔋 More usable power per Rand spent over time
  • 🔄 Faster charging and more charge/discharge cycles
  • 🧠 Built-in smart protection (BMS)
  • 🏡 Safer for indoor or outdoor installation
  • 📉 Lead-acid is being phased out in most quality solar systems

🔌 Smart Inverter Settings for Lithium Batteries

Many modern off-grid or hybrid inverters allow you to:

  • ⚙️ Limit charge and discharge rates to protect batteries
  • 🔋 Set battery protection thresholds (for longevity)
  • 🔁 Automatically switch to the grid or generator if needed

We also offer inverters that operate without batteries for solar-only or grid-tied applications.


✅ Need Help Choosing the Right Battery?

Our team will help you select the correct size, voltage, and configuration for your solar system — with safe, affordable, and long-lasting lithium solutions.

👉 Contact us at sales@thesunpays.co.za or browse our lithium batteries here.