What Batteries Are Best For Off-Grid Solar?

Batteries are the most expensive component of an off-grid solar solution. Choosing the right battery chemistry is essential for optimizing cost, ensuring safety, and meeting your requirements.

While there are multiple vendors and brands in the battery market, there are only three viable chemistry choices: Lead-acid, lithium iron phosphate (LFP or LiFePO4), and lithium cobalt oxide (LiCoO2). One is a clear winner for off-grid solar in warm rural environments.

Let’s delve into the nuts and bolts.

First thing first… what is battery chemistry?

Battery chemistry is the materials and chemical reactions a battery uses to store and release electrical energy. It determines the battery’s voltage, capacity, lifespan, energy density, efficiency, and other performance characteristics. 

Different battery chemistries are suited to various applications based on these attributes. Besides the intrinsic characteristics mentioned above, we consider safety profile, maintenance effort, cost, and space constraint when choosing a chemistry for each tailored solution.

Let’s see how the three most common battery chemistries measure up.

Are lead-acid batteries good for off-grid solar?

The short answer is not anymore. This old-school chemistry has low energy density (i.e., stores less power in the same volume), so your battery bank will be heavier and larger than an LFP or LiCoO2 one. It has the lowest efficiency of all options (70 to 85%) and a shorter lifespan of 300-500 discharge cycles. It’s also often the most expensive option.

Moreover, you must limit the depth of discharge (DoD) to around 50% to ensure longevity (i.e., you should not drain the batteries at all!) The small range means reduced usable capacity—you must use more cells to achieve the desired power storage capability, increasing cost and space requirement.

But not all is lost if you have lead-acid batteries in your current installation! The key is to dial in the battery settings to accommodate the narrower depth of discharge range (hit us up if you need help with that) and flood them with deionized water regularly to prolong their lifespan.

Are lithium iron phosphate (LFP) batteries good for off-grid solar?

Yes. In general, we recommend LFP batteries for most of our clients. They have a higher density than lead-acid and the longest lifespan among popular options (2,000 to 5,000 discharge cycles). They also have high efficiency (around 95%) and take up much less space than lead-acid batteries for the same power storage capacity.

What we like most about LFP batteries is their safety profile. Plus, high-quality lithium batteries come with a protection circuitry (many LFP batteries on Amazon don’t have it). LFP is the most stable chemistry available on the market and least prone to thermal runaway, an important characteristic here in Caliente, where fire risks can be high.

LFP batteries are maintenance-free. You can regularly discharge them to 80 to 90% without significantly affecting their lifespan. However, freezing temperatures are detrimental to LFP batteries when they’re charging (but you can set the protection circuitry to prevent that from happening). Fortunately, prolonged cold temperatures aren’t a big issue in our area, and housing the batteries indoors will mitigate most of the risks.

We use mostly LFP batteries for our off-grid system. 

Are lithium cobalt oxide (LiCoO2) batteries good for off-grid solar?

It depends. “But the Tesla Power Wall uses it!” You may say. Many suburban installations use cobalt chemistry because it’s the most energy-dense option (i.e., lighter and takes up less space)—manufacturers can stuff the cells into fancy- and sleek-looking panels in space-saving designs and charge an arm and a leg for it.

LiCoO2 batteries have similar efficiency as LFP ones but a shorter lifespan (~500 to 1000 discharge cycles). They’re more prone to thermal runaway and less chemically stable than LFP batteries, therefore less suitable for fire-prone environments. You may discharge them to around 80%, but safety concerns often limit deeper discharges.

Another downside of these batteries is their environmental impact. Cobalt mining is very detrimental to the environment. Moreover, almost all of the Earth’s cobalt is concentrated in the Democratic Republic of the Congo (DRC). The mining operations raise ethical concerns, while the supply can become unstable due to geopolitical instability.

The best battery chemistry for off-grid solar solutions in rural environments

LFP batteries are our top pick for most clients due to their longevity and safety. They’re particularly suitable for the rural environment where space constraint is often a non-issue, and the low risk of thermal runaway is a big plus during fire season.

Learn more about our services for a modern, cost-effective approach to off-grid solar.