Making The Grade With Lithium Solar Batteries

When a longtime client needed to replace the flooded lead acid (FLA) solar batteries in his off grid solar system, he asked us about upgrading to lithium iron phosphate batteries (also called LiFePO4, or LFP). LFP batteries are excellent for living off the grid, as they require no maintenance, provide more usable power, and have a longer life expectancy than batteries traditionally used for off-grid solar, like FLA.

But they’re not cheap.

Despite the upfront cost, however, we know that over the life of the battery system, lithium batteries are a better value. Nevertheless, our customer had some sticker shock and went to do some more research. (And we always encourage our customers to do their due diligence!)

A few weeks later he asked us about a brand of LiFePO4 batteries he found online that were less expensive than what we recommended. It was a brand we hadn’t heard of, but given the number of lithium solar batteries on the market it wasn’t surprising. Because we’re dedicated to finding and providing the best products for our clients– we gave this brand a look–and we’re glad we did. Because there’s a reason some brands are cheap–and it’s not good.

In this article, we’re going to discuss how different lithium batteries are graded, and why choosing the Grade A option is the best deal–even if it comes with a higher cost up front.

When it Come To Lithium Batteries, Grades Matter

Because it’s impossible to make a 100% perfect product all the time, manufacturers and regulators often use a grading system as a way to measure and communicate the quality, performance and even cosmetics of products. And just like many other products, lithium cells are given letter grades where “A” is the best. Understanding exactly what the grade means is helpful when you’re shopping for the best lithium solar battery.

• Grade A Lithium Cells. Lithium cells that meet a manufacturer’s highest standards are given an A grade. These high quality cells will be uniform in their capacity, internal resistance, how they hold a charge, and in their appearance. These will be the highest priced cells–and, spoiler alert–these are the only ones we at Fire Mountain Solar will recommend to our customers.
• Grade B Lithium Cells. Lithium cells that don’t meet the high standards to be graded A are classified as B grade cells. B grade cells have failed one or more of the manufacturer’s standards for A grade cells. This could simply be a cosmetic flaw, but usually the difference is more significant, such a higher self-discharge rate. These cells will be less expensive than grade A cells, sometimes up to 30-40%, but are often less reliable (and, in our opinion, not worth the risk).

• Grade C Lithium Cells. Grade B cells also have minimum performance standards, and cells that don’t meet those are classified as C grade cells. Not all manufacturers have a C grade for cells, possibly because they can only be used for limited applications that have very slow charge and discharge rates, and they have a lower expected battery life. Some cells that don’t meet B grade standards are such poor quality they can’t even be sold. 

Now, we don’t know for sure that the much less expensive lithium solar batteries our client asked about have B grade cells, but the battery industry experts we spoke with assured us that corners had to be cut somewhere in order for anyone to sell a lithium solar battery at such low price. And B grade cells are the most likely way.

READ: Why ProductReliability is Critical When You Live Off the Grid

Who Sets the Standards?

For many products there is a regulating agency that sets standards for different grades of the item. Unfortunately when it comes to lithium batteries we have some bad news: There is no industry standard grading system for lithium cells. Each cell manufacturer sets their own standards, which means that what might be a grade A cell to one manufacturer, could potentially be a grade B or C cell to another. (Source: Battery Manufacturing and Battery Cell Grades, Dan Hagopian) 

This means that though the lithium cell grading system allows battery manufacturers and consumers to compare batteries from the same cell manufacturer, it isn’t possible to compare the same grade of cell between manufacturers. 

Choosing the Best Lithium Solar Battery

With all of this in mind, you might be wondering how you can be sure the lithium solar batteries you purchase are the high-quality product you want? Here at Fire Mountain Solar, we work with companies that we trust and recommend brands with proven quality over many years of use.

But as you’re doing your own research, here are some considerations as you look at all of the different lithium solar batteries on the market:

• Grading. Request the grading criteria for the cells that were used in the batteries you want to compare. But realize that the battery manufacturer is unlikely to be the cell manufacturer, so that information may be difficult to get. 
• Testing. One way to be 100% sure of the result is to test each lithium battery cell yourself to see if the capacity, internal resistance and self discharging rate of each cell in each battery is the same between brands. However, keep in mind that you’d probably have to buy them and testing equipment all to be able to do this.
• Price. Buy based on cost only. While a substantially low price is a good indicator that something about the battery is lower quality, there is nothing to stop an unscrupulous manufacturer from selling poor quality batteries for a price close to market pricing on high quality lithium batteries. There are good deals on lithium solar batteries to be had, but they won’t be ones that make you wonder if the too good to be true deal actually is.
• Reputation. Purchase a battery brand from a manufacturer with a reputation in the industry for quality and a proven track record of backing up their products and warranty, in the event there is an issue at some point. As with most products, this is usually the most reliable way to make sure you get a battery you can depend on. 

Browse Lithium Solar Batteries

Rely on the Experts at Fire Mountain Solar For Help

When you’re in the market for Lithium Ion Phosphate Batteries, there are a lot of options, as well as a lot of things to be wary of. We always recommend that customers check online reviews of products and talk with sellers who also have a strong reputation for integrity and really know the products they sell–like our team at Fire Mountain Solar.

It’s true, you might save a few dollars by buying from a click and ship reseller, but rarely do they have the knowledge and experience to answer technical and practical questions, and get you the details you need to make the best decision for you. This might lead you to buying a battery with lower quality Grade B cells without knowing it, and the result could be your batteries end up letting you down when you need them most.

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