4 Types of Solar Battery Backup

Let’s say that recently you have started to experience short outages, or maybe you experienced a long outage due to a Hurricane or Tropical Storm. Your goal is grid reliability and outage resilience. There are a couple options that might fit your needs - commonly home backup generators or solar coupled with PV batteries.

Even once you’ve identified which general path you want to take there are lots of different options to consider - What type of batteries?  What capacity do you need? There are many factors to consider in identifying the right setup, and we strongly recommend talking to a professional to determine what setup will best fit your needs.

This is Part 1 of our Solar Battery Backup Series.


Here’s a short summary of the main battery options are and when you’d want to use them:

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AGM Lead Acid / Nano Carbon

These are go-to batteries for moderate cycling applications (how frequently you are charging and discharging your battery). They offer great flexibility in where and how they are used, and are reasonably affordable. Most commonly used in grid-tied backup systems.

For backup applications you can expect a good 10 years out of these batteries.  

If you are cycling the batteries daily, you would expect most AGM lead acid batteries to last 4-5 years. Nano Carbon batteries would last longer, with an expected lifespan of 6-7 years.

If you know that you want to use your batteries heavily every day, you would want to be using a Flooded Lead Acid setup (see below).

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Flooded Lead Acid

These are heavy-duty batteries for situations where you have heavy cycling and high-consumption needs. They are not too heavily strained by heavy use, so situations like Off-Grid or daily point-of-use applications are a great fit for these batteries.  

That said, they have a naturally short life cycle when they are not cycling, and hence are not ideal for backup-power situations.  

You do expect to have to maintain the batteries periodically to get the most out of them. In a later post, we’ll go over what a maintenance visit entails for this type of battery.

These batteries are especially sensitive to temperature.

These have lower up front costs than other battery types, though they require more frequent replacement.

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Gel Batteries

Gel batteries are the polar opposite of Flooded Lead Acid, as they excel in situations where they are very infrequently cycled. They also generally perform better in colder environments than the other battery types.

For backup applications, these can last up to 15 years. If you heavily cycle, you can expect that lifetime to shrink to 2-3 years, so it is very important to use these in power reserve applications only.   

These batteries are generally more expensive, reflecting the longer expected lifetime.

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Lithium

This is generally considered the premium battery for most grid-tied cycling or backup applications. You can fully utilize the battery in ways that you cannot for the other chemistries, which effectively lets you use a smaller battery bank for the same amount of power demand.  You also have a long expected lifetime even with heavy cycling applications and great flexibility in how quickly you can both charge and discharge.

Despite all these advantages, the Lithium battery is not suited for every situation. They are more costly than the other types, and have a narrower temperature range where they perform well.  

These are most commonly found in setups that maximize your self-consumption of solar power, that may or may not also provide limited backup (known more commonly as power-cycling applications).  


The effectiveness and longevity of batteries heavily depends on how suitable they are and how gentle you are with them. If you are fully discharging and charging regularly, or if their environmental temperatures are particularly hot or cold you will damage the battery and need to replace more frequently. Stay tuned for Part 2 of our Batteries Series where we’ll talk about how to size your system for backup batteries.

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