Grade A Versus Grade B Lithium Deep Cycle Batteries

Grade A Versus Grade B Lithium Deep Cycle Batteries

The consumer market for lithium deep cycle batteries is flooded with inexpensive batteries that are less than half the price of the established name brands in the industry. These batteries are made with lower quality lithium cells or Grade B cells.  In this blog post, I will explain to you the difference between Grade A and Grade B, why that matters, and which type is right for you.

Before we get started, a Grade B battery is a fine product in its own right.  It is just different from a Grade A battery.  And, in order to make an informed purchase decision, you need to know what you are purchasing.  So the problem isn't the Grade B batteries themselves, but that some of these companies are either not telling anyone that they are Grade B and letting people assume or, worse yet, telling people they are Grade A when they are clearly not.



Every individual lithium (Ion, NMC, LFP, etc.) cell that is manufactured is tested and graded before being sold. This is a lengthy process that can take a month to complete and involves numerous tests. The manufacturer compares the results of the tests to the ideal specifications for the cells and looks for anything that is a deviation or outside of a tight tolerance. There are 6 main categories that each cell is graded for: Appearance, Capacity, Capacity Recovery, Internal Resistance, Size & Weight, and Rate of Self Discharge.

If a cell is within the tolerances of each of those 6 categories it is a Grade A cell. (There are actually A+, A, and A- minus ratings, too, but for this article we will keep it simple)  If the cell is slightly out of spec it is Grade B and if it is way out of spec it is Grade C. Grade C cells are usually not used for making battery packs so we will ignore those for the purposes of this article.  Grade B are sold at auction for pennies on the dollar compared to Grade A cells (typically less than 1/3 of the price).  



When a company makes a lithium deep cycle battery, which consists of numerous cells that are connected to each other, they can make them with Grade A cells or Grade B. The Grade A cells inside a Grade A battery will stay the same voltage, slowly self discharge at the same rate, charge at the same rate, and provide the same amount of energy storage or capacity. This allows the Battery Management System (BMS) to do its job easily, which is to charge and monitor all of the cells. The Grade B cells inside a Grade B battery may have slight variations in cell voltage, may self-discharge at different rates, may charge at different rates, and may not all have a uniform energy capacity. This makes the BMS in the Grade B battery work harder as it has to compensate for these differences and variations.

In the short term, the BMS can compensate just fine, so a Grade B battery will perform well and usually cannot be distinguished from a Grade A battery. But the cell tolerances get looser and drift apart over time and the BMS has to work harder and harder to keep all of the cells in line with each other. This can cause a premature BMS failure, cause the battery to take longer to charge, and/or result in a decreased battery capacity in the medium to long term. And finally, on a longer timeline the BMS will fail to be able to get all of the cells to fully charge and get to the same voltages and capacities and the entire battery will fail or have greatly decreased performance capabilities.



When will a Grade B battery fail? Who knows. It is a roll of the dice. Most lithium iron phosphate (LFP or LiFePO4) deep cycle battery companies are comfortable enough with warrantying a Grade B battery (that is being openly marketed as such) for about 1,200 cycles and between 5 and 10 years if they have a really good BMS inside that can handle the extra duty. But part of that confidence is in knowing that the overwhelming majority of customers will not discharge the battery every day and, thus, only a handful of customers will ever fully use up the life expectancy of the cells inside.  There are many reputable, high quality sellers with Grade B batteries that put out a great product and package their Grade B batteries with a high quality BMS that can handle the extra abuse.  In the 12V 100Ah size market, these will typically be about $500.  But there are many that are popping up between $299 and $400 on Ebay and Amazon.  And you can be sure it those batteries utilize a very cheap BMS that will not last anywhere near 1,200 cycles.

Can't someone just test the battery and leave a review and warn people?  Not without an immense amount of effort and a lot of luck.  These dishonest companies know that you cannot tell the quality of the cells from an assembled battery, even if you cut the case open and look inside.  Someone would have to completely disassemble their battery, test all of the cells individually in those 6 grading criteria, and then compare that data to the original cell manufacturer's specs. And that is IF the tester could get their hands on the original cell manufacturer's technical specifications.  So, unfortunately, no one does that. The best I have seen anyone do on Youtube or other sites is to test the cells for capacity and voltage. But they aren't comparing those results to the original cell manufacturer's technical specifications.  They are merely comparing the cells to each other.  And, even if those cells were perfectly within spec on voltage and capacity, they could still fail to be within spec on the 4 other criteria and thus be a Grade B cell (or worse).  So the dishonesty is almost impossible to prove except by looking at the price or asking the manufacturer for cell grading test results.



Which should you buy? That is up to you. There is nothing wrong with buying a Grade B battery. They still perform better in many ways than an AGM lead acid battery. Some consumers may make the decision based on cost, since a Grade B battery will cost half or less compared to a Grade A battery.  But if you can afford to buy both, in my opinion you should base the decision on how often you will use the battery.  If you intend to buy the battery for your fishing boat and you go out 30 weekends a year, I would lean toward a Grade B battery.  As long as the BMS holds up, a Grade B battery could last you 40 years with that usage.  Look for a company that puts a top quality BMS in their Grade B batteries, such as MillerTech.

But if you are buying a battery that you are going to use every day, especially if it is a critical use like a well pump or a refrigerator, I would lean toward a Grade A battery.  Because even fully discharging a lithium deep cycle battery every single day you could still get over 8 years out of it, as opposed to about 3 years for a top shelf Grade B option.



I normally work with consumers buying batteries for recreational uses in boats, RVs, golf carts, and electric bikes.  But, the flood of low cost, low quality batteries by dishonest companies has even made it into industrial applications.  My friend, Maxim Khabur, is the Marketing Director for OneCharge Lithium Batteries ( in Garden Grove, CA.  OneCharge manufactures lithium batteries for forklifts.  I pinged him to get his thoughts on this issue and he stated:

"As lithium solutions grow in popularity on the USA market of forklift batteries, there are more brands launching new products, often offering a suspiciously low price. The suspicions are very much grounded. Material handling equipment is used in applications associated with vibration, extreme temperatures, long operation hours, and exposure to other elements at industrial sites. Forklift batteries require specific engineering know-how and special grade of components to guarantee stable performance. Unfortunately, some customers fall prey to the false promises of these cheap battery brands and have to pay double in the end."

Obviously, Max and I have a bias toward our products and a vested financial interest in their success.  But we are also consumers, too.  I personally have a dozen deep cycle batteries in my personal collection, many of which are used in off grid solar power systems around my house.  So I can put myself in the shoes of the consumer and feel bad for someone making an uninformed decision that may end up being a big waste of money. 

The last point here is that there may be no recourse if someone is wronged or has a problem after the sale.  Some of these companies have figured out that they can enter the American market from overseas, undercut the competition and sell a bunch of batteries, and then exit the market as their bad reputation and lack of customer support starts to catch up with them.  Max agreed with this:

"Some new lithium forklift battery brands often win customers with a low price. But some buyers often discover the downside of such deals. New players do not invest in the development of service and support networks, neither they are integrated with established OEMs or MHE dealer companies. So when a battery malfunctions, these buyers simply have no support. And the product quality of cheap brands is not the best to start with."



In my opinion and the reason this situation is frustrating, the consumer should know if the battery they are buying is made with Grade B cells. The problem is, many lithium battery companies are hiding it and banking on consumer ignorance and the extreme difficulty that someone would have to go to in order to prove them a fraud. But the price won't lie.  Look for a company with a reputation to uphold, that has telephone support during US business hours.  And don't be afraid to ask the seller tough questions.

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