Lithium-ion vs Lead-acid Batteries For Your Solar Grid

When choosing an energy storage option for your private solar grid, you come across several types of batteries to choose from. However, the choice almost always boils down to Lithium-ion or Lead-acid.

Today we are going to compare two of the most common battery options for solar installations in order to help make an informed choice.

Solar panels

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Cost

Affordability is usually the consideration on everyone’s minds when deciding the feasibility of a project. However, the question of cost effectiveness has no simple answer as it dependents on the needs of your project. We all know that some expensive components of a project may have long term benefits that outweigh their cost.

Lithium-ion vs Lead-acid Batteries For Your Solar Grid

Lead acid batteries are popular due to their cost-effectiveness. A lead acid battery storage system generally costs much less than a similarly-sized lithium-ion setup. This makes Lead-acid batteries a great choice for projects where space is abundant and the budget is low.

Though lead acid battery system has lower purchase and installation costs compared to lithium-ion equivalent, in the long term the lifetime value of a lithium-ion battery evens the costs.

Energy density

A Lithium ion battery has an energy density of 125-600 Wh/L against 50-90 Wh/L for lead acid batteries. This means that the lead acid battery could take up to 10 times the volume that the lithium ion would for the same capacity. On top of that, it would be heavier.


Charging

Lithium ion batteries can accept current at a faster rate than Lead-acid batteries, which means they charge quicker.

Lithium-ion vs Lead-acid Batteries For Your Solar Grid

Lead-acid batteries have a lower charge rate, mainly because:

  • they will overheat if you charge them too quickly.
  • the charge rate gets significantly decreased as you approach full capacity.

Depth of Discharge

Depth of discharge refers to how much overall capacity is available for use before recharging the battery. For example, if you use a quarter of your battery’s capacity before recharging it, the depth of discharge would be 25%.

We usually consider depth of discharge a very useful parameter when comparing batteries because batteries don’t discharge fully when you use them. Every battery had a recommended depth of discharge which guides you on how much of its capacity you can be use before recharging it.

Lead-acid batteries have about 50% depth of discharge. Any use beyond that point can negatively affect their lifespan.

Lithium-ion batteries have a depth of discharge of 80% or more, which means they have a higher usable capacity.

Efficiency

Efficiency is a measurement of the ratio of output energy to input energy.

Lead-acid batteries are on average 80-85% efficient, which means if you have a solar panel supplying 1,000 watts of electrical power charging the battery, only 800-850 watts will be available for you from the battery.

Lithium-ion batteries are more than 95% efficient, which means for the above scenario you’d have over 950 watts of power available from the battery.

Conclusion

As you can see, there is no one-size-fits-all approach to batteries.

  • Lead-acid batteries cost less initially, but have a shorter lifespan and regularly require maintenance to keep them running properly.
  • Though Lithium-ion batteries are very expensive, they are virtually maintenance-free and have a longer lifespan to even their higher price tag.

So the choice is now up to you to either choose Lead-acid which costs less, but requires regular maintenance and doesn’t last as long. Or to choose Lithium-ion which has a longer lifespan and higher efficiency, but expensive.


Sydney Chako

Mathematics, Chemistry and Physics teacher at Sytech Learning Academy. From Junior Secondary School to Tertiary Level Engineering Mathematics and Engineering Science.

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