Maximum recommended cell size.

[GILow]

I’ve just been chatting to a fellow yachtie whose wisdom and experience I’ve always respected.

We were discussing my lithium battery plans and I mentioned that I was considering building my own batteries from EVE 280 AH cells. He liked the idea but recalled that at one time 100AH per cell on boats was considered the sensible limit due to the physical construction of the cells and how they were strained by boat movement. He wasn’t sure if this was still an issue.

Can anybody shed some light on this?

Matt

[sailorboy1]

Well I don't know at all. But I believe the oldest reported on installation here is mainesails and it is 400ah cells and over 10 years old.

In my research I never have seen an issue of cell size far as being able to secure them. That seems completely up to the builder

[Avionics_Joe]

Not all Lithium iron phosphate cells are created equal, some of them were junk. The ones you are talking about look like they are a high quality product but do make a strong container to secure them.
I used 16 CALB 180ah cells for my bank 3 years ago and have been REALY happy with them.

[rabbi]

For the EVE LF280K the manufacturer recommends a pressure of 300kgf on the flat sides of the batteries.
So just build a case that can handle this and nothing will ever move.

[GILow]

Originally Posted by rabbi

For the EVE LF280K the manufacturer recommends a pressure of 300kgf on the flat sides of the batteries.

So just build a case that can handle this and nothing will ever move.

Yes, the whole case thing is far from clear to me yet.

Some builders are leaving gaps between cells, others put in foam padding. Some just wrap the cells in tape, others build steel frames.

A lot more for me to learn, thankfully I’m a long way from needing batteries.

[rabbi]

Any case with gaps, foam, tension belts, etc cant produce the pressure required

Eve is fairly clear on this. Cells should be pressed or they will only reach half their cycles. So it's 6000 with and 3000 without a suitable case. 300kgf is a lot and the only solution i found to achieve this for every state of charge is heavy duty springs.


But then many people argue that 3000 cycles is more than they need anyway and just keep it simple. The cells have a limited lifespan so i tend to agree.

[wholybee]

I don't think current wisdom holds to that requirement. The concern was that physically smaller cells would hold the plates/spiral more securely than a single large cell, so would last better when subjected to vibration and motion on a boat. Similar wisdom also said not to use aluminum case cells, and only use plastic case cells.

Of course, the main market for these cells is automotive, which has similar vibration and motion. I've heard it suggested that those rules were put forth by the larger manufactures that at the time only made 100Ah plastic case cells. Cell manufactures specify a frame with some compression to prevent movement. That should take care of any concerns.

I used 100Ah Calb cells, but looked at others. My decision was based on the height of the cells. Nothing bigger would fit the space.

[GILow]

Originally Posted by rabbi

Any case with gaps, foam, tension belts, etc cant produce the pressure required



Eve is fairly clear on this. Cells should be pressed or they will only reach half their cycles. So it's 6000 with and 3000 without a suitable case. 300kgf is a lot and the only solution i found to achieve this for every state of charge is heavy duty springs.





But then many people argue that 3000 cycles is more than they need anyway and just keep it simple. The cells have a limited lifespan so i tend to agree.

I’m looking into this. Apparently those instructions are not included with all their cell sizes. I’ve lost track of which cells do and don’t, and maybe it was an accidental omission anyway.

[GILow]

Originally Posted by wholybee

I don't think current wisdom holds to that requirement. The concern was that physically smaller cells would hold the plates/spiral more securely than a single large cell, so would last better when subjected to vibration and motion on a boat. Similar wisdom also said not to use aluminum case cells, and only use plastic case cells.

Of course, the main market for these cells is automotive, which has similar vibration and motion. I've heard it suggested that those rules were put forth by the larger manufactures that at the time only made 100Ah plastic case cells. Cell manufactures specify a frame with some compression to prevent movement. That should take care of any concerns.

I used 100Ah Calb cells, but looked at others. My decision was based on the height of the cells. Nothing bigger would fit the space.

Hmmm… I also figure the loads in a car would far exceed any encountered on any boat I sail.

[rabbi]

Please find attached the product spec sheets for the current EVE LF280K cells, the ones with the double screw terminals. It's clear the 6000 cylce promise is only valid with 300kgf applied.


Its fairly hard to get genuine A Grade cells, most suppliers sell either fake, old, used, B-grade, or all together. NGE seems to be a genuine source in China and NKON in Europe.
At least I got fresh A cells from NKON including EVE test reports for each cell, and I heard the same for NGE.

[PaulCrawhorn]

Lots of reports that even 400Ah are OK at sea.

But yes, Eve are not top tier there are huge differences.

Personally I'd stick to ~200 Ah

more cells can allow for greater flexibility in reconfiguring / redundancy when things go wrong out in primitive locales

[GILow]

Originally Posted by PaulCrawhorn

Lots of reports that even 400Ah are OK at sea.

But yes, Eve are not top tier there are huge differences.

Personally I'd stick to ~200 Ah

more cells can allow for greater flexibility in reconfiguring / redundancy when things go wrong out in primitive locales

I've been pondering this issue of redundancy in case of cell failure. It's true, batteries made of smaller cells would give me more options. But, they'd also increase the probability of failure plus increase the complexity of the construction.

No clear preference to my mind at this point.

Now, you say EVE are not top teir. That surprised me, I thought they were up there with the good stuff. Who else would you use?

[s/v Jedi]

Best is Thundersky Winston. Just choose between 200, 300, 400, 700 or 1,000Ah and buy 4 cells for 12V, 8 for 24V etc., connect in series and your batteries is there. No parallel cells.

I don’t think I’ve heard of cells better than Winston, but I think my 2nd battery will be CALB.

[wholybee]

I think the top tier would be Winston, Calb, and Sinopoly. Eve might be the top of the cheaper cells that share the same 280Ah form factor. I would consider EVE 280Ah cells, but prefer one of the top tier. I wouldn't consider any other brand of 280Ah cells.

I agree with Jedi, 4 cells in series at the capacity you need is the preferred route. Not always possible, but that would be the ideal.

[GILow]

Thanks guys, I'll see if the budget can extend to those brands.