What's the deal with the 277/280 Ah cells?

[wholybee]

New member, and reading a lot about the 277/280Ah cells from several mfgrs and suppliers. They seem too good to be true.

I have a space 15l" x 13"w x 10"h to fill for a 12V bank. I can fill it with 12 100Ah Winston cells, or 8 280Ah cells. The 280Ah cells would provide nearly twice the capacity, in the same volume of space, and would weigh only slightly more. What is it about the chemistry or physics of these cells that allows so much more energy density by both volume and weight? Also, I have seen some 240Ah cells that are the exact dimensions and weight as the 280Ah cells. Odd. Are these 280Ah cells going to have the longevity as other cells, or is the mfgr (or a distributor) squeezing more into them than they should?

My application is a boat. Durability is very important. They will be subject to vibration, sometimes intense. Also, occasionally in rough seas I might be "knocked down" which can be very violent, almost like a car accident. They will be shaken and tips on their side. I can mount them securely so they won't break loose and wont' physically break their casing, but I need a cell that is sturdy internally. Assuming solid mounting, would the 280Ah cells hold up?

I will be sailing remote locations, where it simply will not be possible to obtain parts or replacement. Carrying an extra cell or 2, and an extra BMS is reasonable. But primary concern is that they don't fail. I had been looking at expensive drop-ins (battleborn) but I am hoping to get at least 300Ah in my space, and 300Ah of drop-in won't fit.

 

[Bob B]

It has yet to be determined how well the 280AH cells hold up in mobile and extreme vibration over the long term .... They will be more susceptible to failure than the smaller cells, but the data is just not there.

If you have some VERY rough conditions, it might be possible to build a shock absorbing mount for them ... but, the Winston cells have a proven track record in RV's ... but even there the degree of vibration is not as intense as you are describing.

 

[wholybee]

Perhaps this thread can be moved? Sorry about that...

 

[Dzl]

New member, and reading a lot about the 277/280Ah cells from several mfgrs and suppliers. They seem too good to be true.

I have a space 15l" x 13"w x 10"h to fill for a 12V bank. I can fill it with 12 100Ah Winston cells, or 8 280Ah cells. The 280Ah cells would provide nearly twice the capacity, in the same volume of space, and would weigh only slightly more. What is it about the chemistry or physics of these cells that allows so much more energy density by both volume and weight?

I'm not sure about the chemistry or physics of it, some of it is just design tradeoffs (the nylon cased cells are constructed to be much more robust, the aluminum cased cells are constructed to be much more energy dense but not nearly as physically robust), and iteration/incremental improvements (the newest generation of Aluminum cased cells are pushing beyond the 270-280Ah bunch in terms of both energy density and capacity, but these aren't widely available on the grey market yet).

Also, I have seen some 240Ah cells that are the exact dimensions and weight as the 280Ah cells. Odd. Are these 280Ah cells going to have the longevity as other cells, or is the mfgr (or a distributor) squeezing more into them than they should

There are two questions embedded in your question. (1) are energy-dense large form factor prismatic cells going to have the same longevity as other cells (for your application), (2) if they do, will the cheap ones popular here which are in many cases the ones that did not pass QA hold up as well as the Grade A cells from the manufacturers.

My application is a boat. Durability is very important. They will be subject to vibration, sometimes intense. Also, occasionally in rough seas I might be "knocked down" which can be very violent, almost like a car accident. They will be shaken and tips on their side. I can mount them securely so they won't break loose and wont' physically break their casing, but I need a cell that is sturdy internally. Assuming solid mounting, would the 280Ah cells hold up?

I will be sailing remote locations, where it simply will not be possible to obtain parts or replacement. Carrying an extra cell or 2, and an extra BMS is reasonable. But primary concern is that they don't fail. I had been looking at expensive drop-ins (battleborn) but I am hoping to get at least 300Ah in my space, and 300Ah of drop-in won't fit.

Based on the above two paragraphs, I think the grey market 280Ah cells are not your best option. I suggest you read the link in my signature 'Nordkyn Design', its a series of articles geared precisely to your usage (and is one of the best comprehensive introductions to LiFePO4 out there).

A couple points, for marine applications the best practice is <200Ah cells, the nylon cased cells (like CALB, Winston, Sinopoly) are in many respects better suited to harsh environments, and more physically robust, but the tradeoff is lower energy density and sometimes higher cost. An aluminum cased cell can be protected and designed around, but it takes more work/care and external mitigations. If you want the energy density benefits of aluminum cased cells, Frey (marketed as 'Fortune' in the US) is worth looking into.

The cheap and popular 270-280Ah cells (manufacturer cheat sheet: 271Ah = CATL, 272Ah = Lishen, 277Ah = ETC, 280Ah = EVE) are what are referred to as 'grey market cells.' While there are many reasons cells can be sold through grey market sellers, most share in common that for one reason or another the manufacturer was not comfortable selling them through official retail or wholesale channels. In many cases this is because they did not pass one or more parts of the QA process (AKA grade B cells), in other cases they may be old stock, or cosmetically or mechanically damaged. Once they are on the grey market, its really not easy to differentiate. Many (most) of these cells probably fall into the rough category of usable but not retail quality. Beyond this, the other factor leading to the low price is that these are usually unmatched cells, for many applications this is un-ideal but not a big deal, for other applications matching is more important. It can lead to slightly diminished capacity and uneven wear (or that is what I have read).

With the above in mind, these cells can still be a remarkably good deal if the risks and caveats are not dealbreakers for you. Many here are building hobby systems, or occasional use UPS backups, and even the people using them for off-grid residential or RV builds, do not have nearly as critical a use-case as off-shore or RTW marine. I'm not saying these cells (or other grey market cells) would be especially risky if well tested and stressed before being put into real world use, but what I am saying is I don't know, and I don't think anyone else does either, at least not for another 5 years or so when we can start assessing longer term trends (this applies to both larger aluminum cased cells in general, and grey market cells in particular).

If it were me, If I were in your shoe's, buying for your use-case, I would take the less risky but more expensive route and buy smaller cells, from a reputable manufacturer, through a known and reputable sales channel. CALB, Winston, Sinopoly and I believe Frey, all have authorized sales channels and distributors you can buy from, In the case of Frey you can buy directly from the manufacturer for a decent price and there are a couple of US based resellers with good reputations. GBS is another company that you can buy from directly.

 

[Dzl]

Perhaps this thread can be moved? Sorry about that...

where would you like it to be moved?

 

[wholybee]

where would you like it to be moved?

The DIY Lifepo4 section would make more sense than the solar section.