Lithium batteries on an AGM budget?

[Ronnie]

Originally Posted by RobOfYork

If I buy 5 cells so I have a spare, how would the extra cell need to be stored?

Charged to 50% or so.



I would not buy an extra cell unless I was making several batteries, and was going to be making more batteries later. Just not worth it.

[RobOfYork]

Originally Posted by Ronnie

Charged to 50% or so.



I would not buy an extra cell unless I was making several batteries, and was going to be making more batteries later. Just not worth it.

The reasoning behind the extra cell is if one goes bad. I don't want to be without electric for 4 to 6 weeks waiting on a cell to come in.

[Mountain Gnome]

Just out of curiosity, what do y'all say about rotating the "spare" battery into/out of the pack every week, or some other timeframe? Then every battery gets to be a spare for a week at a time.

[kazetsukai]

Originally Posted by RobOfYork

If I buy 5 cells so I have a spare, how would the extra cell need to be stored?

Attached is the spec sheet for the EVE 280Ah cells, it has all of the technical information including storage SoC / temps. Let me know if you need any clarification, but honestly this is the document I'm going to be referring to.
lf280-3.2v-280ah-product-specificationversion-e-2019.7.5.pdf

[RobOfYork]

Originally Posted by kazetsukai

Attached is the spec sheet for the EVE 280Ah cells, it has all of the technical information including storage SoC / temps. Let me know if you need any clarification, but honestly this is the document I'm going to be referring to.
Attachment 55561

Thank you for the technical sheet. I just ordered 5 cells about 30 minutes ago.

[RobOfYork]

Originally Posted by Mountain Gnome

Just out of curiosity, what do y'all say about rotating the "spare" battery into/out of the pack every week, or some other timeframe? Then every battery gets to be a spare for a week at a time.

Now that's an interesting idea. Hopefully someone has done this and will chime in.

[jofred99]

Originally Posted by Mountain Gnome

Just out of curiosity, what do y'all say about rotating the "spare" battery into/out of the pack every week, or some other timeframe? Then every battery gets to be a spare for a week at a time.

Most of the lifepo4 batteries that I've seen are rated for a minimum of 2500 cycles from 100% down to 0% charge, which is a long life time. That 2500 cycles is a rate when the batteries will be at 80% capacity. Depending on how you are using your bus, that is a lot of usage.

I would save the coins from the extra battery for something else on the bus.

Just my .02 considering that I've just converted from lead acid batteries to lifepo4 and a little new to the game.

[bridg73988]

Originally Posted by RobOfYork

If I buy 5 cells so I have a spare, how would the extra cell need to be stored?

Store at its nominal voltage, secured so terminals won't touch anything, and somewhere that it won't be exposed to extreme temps especially freezing. A spare isn't an ideal situation since it more than likely won't be introduced to the other batteries until they have had a significant number of cycles on them, thus potentially causing charging problems or at least not optimal charging and discharging of the pack as a whole.

[bridg73988]

Rotating the spare would solve that problem but I think it would be an aggravating PITA after a while.

[BeNimble]

I just today am swapping out a 4-cell 12v pack that has one bad cell with a spare cell, as I bought 10 cells, and made two 4-cell 12v (40ah) packs I use in my Prius.
The bad one sat in the prius for months and drained it to 0v, which killed one cell.
It would now big useless if I did not have the spare, as you can't buy these cells anymore.

That said, these were not that expensive. I also have Six 160ah cells, because that is all they had left in the clearance sale at Balqon. Can't replace one now, and the cost to do so is now almost more than 4 more new ones. And battery prices will continue to go down in the future and chemistry may change, so a spare is ok, but when its not cheap (like those 280ah), i'd just go with 4.

Another thought would be to run 5 as a 12v pack and just keep them under charged.
Most 12v stuff will work with 16v inputs. A bit risky..

[BeNimble]

Oh btw, if you watched Wills video on these 280ah cells, you should have noticed they are raw cells, they have no enclosure. They need to be put inside something that prevents them from bloating. Best not made from wood below. A 3d printer comes in handy here..just 3d printed a repair part for a too-lightweight tripod. awesome.

[RobOfYork]

Originally Posted by bridg73988

Rotating the spare would solve that problem but I think it would be an aggravating PITA after a while.

I wonder if the cells where rotated once per month? Would that keep them all about equal?

Or maybe every other month?

[bridg73988]

Originally Posted by RobOfYork

I wonder if the cells where rotated once per month? Would that keep them all about equal?

Or maybe every other month?

It's more the number of cycles than time.

[RobOfYork]

Originally Posted by BeNimble

Oh btw, if you watched Wills video on these 280ah cells, you should have noticed they are raw cells, they have no enclosure. They need to be put inside something that prevents them from bloating. Best not made from wood below. A 3d printer comes in handy here..just 3d printed a repair part for a too-lightweight tripod. awesome.

I have watched a lot of how-to videos for building batteries with raw cells. Also have read so may websites about building batteries. I have not seen anyone create an enclosure like that. Have only seen battery boxes with a little room in them.

Do you have any links that are recommending building a tight frame around the cells to prevent bloating?

I'm still in learning mode and would appreciate it big time.

[BeNimble]

The battery manufacturer say to do it. The Winston/CALB/xxx cells use rigid plastic that leaves some airgap. That is how i'd do these EVE cells, use some open plastic between them.

Another more important tip is to use a flexible interconnect between the cells.
In the picture, the straps have an arch/bend to the so they can slightly move without stressing the terminals and eventually leaking and killing the cells.

[joeblack5]

Benimble, I am pulling the lishen 272 together with 4 rods . In between each cell I have roofing rubber pieces as extra insulator incase the blue plastic film gets damaged. Some of these style cells have some kind of electrical contact between the casing and the internal cells.
The rubber also allows some, very minimal expansion.

I agree that for mobile applications it seems not good to have solid busbars from one cell to the next. I use flat woven grounding strap. Also feel that the connection to the battery poles is better with all the individual wires pressing down, of course washer on top to keep the pressure even..

Johan

[joeblack5]

Double post
Johan

[kazetsukai]

Originally Posted by BeNimble

Oh btw, if you watched Wills video on these 280ah cells, you should have noticed they are raw cells, they have no enclosure. They need to be put inside something that prevents them from bloating.

Originally Posted by RobOfYork

Do you have any links that are recommending building a tight frame around the cells to prevent bloating?

Originally Posted by BeNimble

The battery manufacturer say to do it.

The manufacturer says you'll get around 2500 full cycles without, 3500 cycles with doing it. I'm on the fence about it, really.

Originally Posted by joeblack5

Benimble, I am pulling the lishen 272 together with 4 rods . In between each cell I have roofing rubber pieces as extra insulator incase the blue plastic film gets damaged. Some of these style cells have some kind of electrical contact between the casing and the internal cells.
The rubber also allows some, very minimal expansion.

I agree that for mobile applications it seems not good to have solid busbars from one cell to the next. I use flat woven grounding strap. Also feel that the connection to the battery poles is better with all the individual wires pressing down, of course washer on top to keep the pressure even..

Johan

Thank you for these ideas. Where did you get the grounding strap?

If I was going to compress, I'd cut sheet metal to the size of each cell's largest side, use your roofing rubber + sheet metal in a sandwich:

Sheet - Rubber - Cell - Rubber - Sheet - Rubber - Cell ....

And small sections of strut on each end so I could use threaded rod to keep it all together.

What I'd really like to do is compress each 3-cell group individually, so I could connect them in series via 250A winch connectors. I collect long term data on my pack at a cell level, so I'd notice if one was dipping before the others.

I did buy 4 extra cells, Given they're all good I'll probably play around with them in a 12V configuration but for the OP's use case I'd recommend storing them in a cool dry place at nominal voltage, checking on them every few months.

[RobOfYork]

Originally Posted by BeNimble

The battery manufacturer say to do it. The Winston/CALB/xxx cells use rigid plastic that leaves some airgap. That is how i'd do these EVE cells, use some open plastic between them.

Another more important tip is to use a flexible interconnect between the cells.
In the picture, the straps have an arch/bend to the so they can slightly move without stressing the terminals and eventually leaking and killing the cells.

I'm really surprised that I have not seen any build your own battery videos that even mention this then. Hmmm...

What keeps going through my mind is if you prevent a battery cell from swelling out it's sides, it is still going to find the path of least resistance. That would possibly be the top of the cell or bottom.

This really interests me and I wish I could find more info on it.

[RobOfYork]

Originally Posted by kazetsukai

250A
https://www.amazon.com/DALY-LiFePO4-.../dp/B08KD66M54

Make sure you get a BMS designed for LiFePo4 or "LFP". "Lithium" or "Lipo" tends to mean a different Lithium chemistry with different voltage ranges. Electrodacus is configurable for any kind of chemistry.

Here is what I have so far.

600watts of solar panels
4 EVE Lifepo4 280Ah cells
Building a 12v system
Want to run a 2000 watt inverter

Would the DALY BMS 4S 12V 250A LiFePO4 Battery Protection Module You mentioned be a good choice to go with?