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Solar Batteries: A Beginner’s Guide

Last edited: 18/02/21

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Solar Batteries: A Beginner’s Guide

Last edited: 18/02/21

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Typically, batteries for energy storage are made of lithium-ion or lead-acid. When choosing the best battery for your solar panel system, it’s important to understand the distinction between what’s a deep cycle battery versus lithium, sealed lead-acid, and lead-acid batteries before making up your mind. Here are certain differences between lithium-ion versus lead-acid batteries:

Flooded lead-acid batteries

FLA (or flooded lead-acid) batteries have been used for the last 15 decades and are one of the most common batteries for off-grid solar setups. These solar batteries are 99% recyclable, inexpensive, and easy to get rid of at the end of their lifespan.

If you’re in search of an affordable option, these are the best batteries:

  • FLA batteries are designed to deal with daily charge cycling. Since they emit gas as a by-product, their proper ventilation must be ensured.
  • If you’re someone who likes to be hands-on with your system, FLA batteries will be perfect for you. While they’re the most affordable option, they need occasional upkeep to keep them functioning properly.
  • These batteries require regular maintenance. The plats of all cells in the battery must be submerged in water to function appropriately (hence the name ‘flooded batteries’). You’ll need to add water between 1-3 months to ensure that the plates remain submerged. Ideally, you’d want to check them once a month.

Sealed lead-acid batteries

If you’re unable to perform checks regularly, a sealed lead-acid battery is best for your solar panels. It offers the following advantages:

  • These batteries are non-hazardous and spill-proof. There are two kinds of sealed lead-acid batteries with characteristics that are quite similar: gel and absorbent glass mat (or AGM).
  • Sealed batteries are a self-contained system. Like flooded batteries, they don’t need to be refilled with water. Due to this reason, they work well at properties that are not occupied fulltime, like an off-grid vacation cabin you visit once a year.
  • Sealed batteries handle temperature better. Even if they sit idle for extended periods while you’re away, these batteries won’t self-discharge.

Sealed lead-acid batteries

If you’re unable to perform checks regularly, a sealed lead-acid battery is best for your solar panels. It offers the following advantages:

  • These batteries are non-hazardous and spill-proof. There are two kinds of sealed lead-acid batteries with characteristics that are quite similar: gel and absorbent glass mat (or AGM).
  • Sealed batteries are a self-contained system. Like flooded batteries, they don’t need to be refilled with water. Due to this reason, they work well at properties that are not occupied fulltime, like an off-grid vacation cabin you visit once a year.
  • Sealed batteries handle temperature better. Even if they sit idle for extended periods while you’re away, these batteries won’t self-discharge.

Lithium batteries

Lithium batteries are a novel technology that hit the market during the 1970s. They’re quite common in mobile phones and laptops. However, they’ve become more popular in the renewable energy space. While lithium batteries cost comparatively more, there are several benefits to justify the higher price tag:

  • Longer lifespan
  • More efficient power utilisation
  • More usable storage capacity (deeper discharges)
  • No maintenance
  • No ventilation/off-gassing

How to compare solar batteries

While going through your solar battery options, you’ll want to compare every type of battery based on its battery life, round trip efficiency, depth of discharge, and capacity to find the best batteries for solar based on your system’s requirements. Ensure to check the following:

  • Capacity: It’s the total amount of electricity that a solar battery can store. This power is measured in kilowatt-hours (kWh).
  • Depth of discharge: This indicates the amount of battery that’s used. The higher the depth of discharge, the more usage you’ll get from the battery’s capacity. Generally, your depth of discharge should at least be 40% or higher.
  • Round-trip efficiency: It’s the difference between the available amount of energy and the amount of energy used to charge. Generally, higher round-trip efficiency is more economical. You should aim for around 80% round-trip efficiency.
  • Warranty and battery life: Since battery performance decreases as time passes, a warranty guarantees good performance for cycles or years, further ensuring that the battery maintains a certain capacity.
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