Which battery type is best for solar with home energy storage?

Adding batteries to solar is hardly a new concept. For decades, people seeking to back up their home with clean power have coupled batteries to their solar PV systems. But it hasn’t always been pretty.

In recent years, home energy storage has grown increasingly attractive, spurred by key advancements in battery technology resulting in simpler and more efficient designs.

That simplicity is key: solar with battery backup was a mess until very recently, consuming tons of floor and wall space and usually requiring ongoing maintenance. Lithium ion changes that, and now homes can couple their solar PV systems to “smart batteries” that can be fully discharged without damaging and which use slim, lightweight electronics in space-conservative designs. These lithium ion batteries also require no maintenance, removing a key barrier to adoption for many would-be customers of ‘solar-plus-storage’ systems.

So, does that mean lithium ion is always the best battery chemistry for tying to solar?

Not necessarily.

The answer all depends on the intended use of the battery. Conventional deep-cycle batteries are not designed to be used for many, many charge and discharge cycles for years on end. They’ll usually need to be replaced after a few years if they are charged and discharged daily. In applications that call for this amount of charge and discharge cycling, such as using a battery for daily electricity cost management, lithium ion is by far the preferred option, as they can be cycled thousands of times. In fact, lithium ion batteries are designed to be charged and discharged regularly, and they risk degrading in performance if they sit idly for too long.

That brings us to backup power, the common application of using batteries as an alternative to a gas generator for solar-fed buildings. In this scenario, lithium ion batteries can do an excellent job of providing instantaneous clean power in the event of a grid blackout, but if that blackout only occurs a few times per year, the lithium battery will mostly sit unused in a state of waiting for a backup event.

This is where conventional deep cycle batteries can be a good choice. While they don’t offer the high cycle counts you can get from lithium ion batteries, maintenance-free deep cycle batteries (commonly known as AGM, or ‘absorbed glass mat’ batteries) are a great choice for backup power because they won’t incur damage if they sit unused for months on end, awaiting a grid blackout that triggers a backup power event.

In short, both conventional (AGM) and modern (lithium) battery chemistries have their place in the new home energy storage market, and each has strengths aligned with the most common applications for batteries coupled to solar.

Pika Energy offers the Harbor Smart Battery™ series for customers seeking lithium ion performance, ideal for self-supply, rate arbitrage and intermittent backup power. For applications where backup power is the primary purpose and the batteries won’t be cycled daily, Pika Energy offers the Coral Smart Battery™ series, which takes advantage of conventional deep cycle batteries to provide backup power during grid blackouts.

Source: pika-energy