Which Battery is Best for Solar?

The best solar battery is a lithium battery. It has the longest lifespan and has more energy capacity than other solar batteries.

Lithium isn’t necessarily the best solar battery in every case. Sometimes it’s better to go with the other options. This post looks at how to compare solar batteries and choose the one that fits your needs.

How do I compare solar batteries?

Solar batteries have unique characteristics. Knowing these characteristics and how they influence the performance of your solar system will help you find the right battery.

What are your options?

You can get lithium, flooded lead acid, AGM and gel batteries anywhere in Zimbabwe. You can compare solar batteries based on:

  1. How much energy they can supply (battery capacity)
  2. How long they last (battery lifespan)
  3. How efficient they are (battery efficiency)
  4. How much upkeep they need (battery maintenance)
  5. How many appliances you can run on them (load capability)
  6. How much they cost (price)

These are the most important specifications. Let’s compare the types of batteries for solar systems using these specifications.

Lithium batteries

Lithium batteries have the longest lifespan lasting up to 15 years. A depth-of-discharge of 80% gives them a greater capacity than other batteries. They also have a better efficiency (85%) which allows them to charge quicker than other batteries.

Lithium can handle a large load and doesn’t require maintenance. The only drawback with lithium batteries is that they’re the most expensive solar battery costing up to three times as much as a flooded lead acid battery.

Check out this guide for a detailed look at lithium batteries.

AGM batteries

AGM has a depth-of-discharge of 50%. They can be discharged to 80% but manufacturers recommend you discharge them to 50% to maintain the batteries capacity for longer. AGM has a lifespan of 4 years.

They have lower efficiency (80%) than lithium so they charge slower. AGM can handle higher loads, doesn’t require maintenance and is cheaper than lithium.

Check out this guide for a detailed look at AGM batteries.

Gel batteries

Gel batteries are like AGM. They have a depth of discharge of 50% and have the same efficiency and charge rate. They also don’t need maintenance and cost less than lithium.

The difference with gel batteries is they don’t handle higher loads as well. Although they can be more expensive than AGM they do however have a longer lifespan of 6 years.

Check out this guide for more on gel batteries.

Flooded lead acid batteries

Like gel and AGM, flooded lead acid batteries have a depth of discharge of 50%. They also have the same efficiency and have a lifespan of 4 years.

The biggest drawback of flooded lead acid is they require maintenance and they charge the slowest compared to other batteries. They are, however, the cheapest solar battery.

Check out this guide for more on flooded lead acid batteries.

Lithium batteryGel batteryAGM batteryFlooded lead acid battery
Depth of discharge80%50%50%50%
Lifespan in years10644
Efficiency85%80%80%80%
MaintenanceNoNoNoYes
Quick comparison of solar batteries.

How do I choose a solar battery?

Which battery specification should you pay the most attention to? Capacity, efficiency, price? While it depends on your needs, here are some general guidelines.

Deciding which battery specs matter for your needs

These are a few common situations and what specifications you should look out for.  

You need a lot of energy

If you need more power at once look for batteries with a higher power rating. If you want to power energy-intensive appliances like pumps, compressors and machinery, get a battery with a high instant power rating.

Power rating is how much power a battery provides. It tells you how many and which appliances you can power. A power rating can be given in kilowatts or amps.

Batteries have a continuous power rating and an instantaneous (5-minute) power rating. The instantaneous power rating is important if you want to run appliances that need a high current to start before they run on lower power. Pumps are one such appliance.

Off-grid home

For off-grid homes, you need batteries with a high capacity, efficiency and load capability. You’re relying solely on your batteries, so you want to get the most out of it. You also might consider the lifespan of the batteries.

Battery as backup

If you’re using batteries just for backup when there is load shedding, you don’t have to worry as much about capacity or efficiency. The critical factors here would be how much maintenance you’re comfortable doing and what load capacity you need.  

Conclusion

That in short is how you can select the right battery. Ultimately, it comes down to how you will use them and your budget. That’s why you need to know how they perform. If you haven’t already, read the guides to batteries I’ve linked to get a detailed understanding of each battery.

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