jakew009
Well-known member
You are better off using bus bars like these that have some flex in them to eliminate that problem
15 year old lithium battery
- Thread starter geem
- Start date
You are better off using bus bars like these that have some flex in them to eliminate that problem
GHA
Well-known member
jakew009
Well-known member
What sort of a response is that
if it helps my business imports lithium batteries (for non leisure usage) and I have followed the development of them like a hawk over the past 10 years, which you tend to do when you depend on it for your livelihood.I'll leave you to it...
Neeves
Well-known member
I'd be surprised considering the amount of copper, the thickness of the bars, that they accept much flex at all. If the cells are not held rigid under, some, compression I'd expect any movement to be absorbed by the cells moving slightly and the nuts slackening. The bus bars illustrated might be useful to absorb expansion from heat - but then they should not get hot.
I recall that some battery makers, and or their appointed distributers, who supply cells also supply bus bars - but they are simply flat blades of copper. But my memory may be jaded.
However the concept sounds good - so why not? I cannot see any downside (except maybe cost)
I had a quick search EEL BATTERY|Lifepo4 Battery Cells|DIY Battery Pack|Battery Storage System
Jonathan
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Neeves
Well-known member
What sort of a response is that
I'll leave you to it...
Many of the applications on your website are for leisure applications.
Not that I understand why the application makes any difference.
But don't be upset to be questioned - its a forum, we are here to learn (or offer advice). There is considerable value in having people with different backgrounds and its also valuable if options and comments have some form of 'peer' review. You would accept questions in your chosen career - why not here.
Jonathan
Neeves
Well-known member
A thought
If the cells need to be insulated from each other then printers blanket might be a good product. They are thin, around a millimetre in thickness, and are a canvas, or fabric backed, with a 1mm layer of rubber bonded on top. They come in standard sizes to match all the common printing presses. If you know a printer used blankets might do - but will be a bit grotty - the blankets should be available from any retailer/distributor servicing the printing industry (for example Pressroom Consumables. Fast, Reliable Service from Intuprint - I don't know them, just came up on a google search). For the threaded rods used to constrain the collection of cells (or for compression) then the heat shrink tubing used for rope might be ideal. It comes in a variety of sizes and when shrunk thickens up (I buy mine for rope from Aliexpress/Temu etc)
Jonathan
If the cells need to be insulated from each other then printers blanket might be a good product. They are thin, around a millimetre in thickness, and are a canvas, or fabric backed, with a 1mm layer of rubber bonded on top. They come in standard sizes to match all the common printing presses. If you know a printer used blankets might do - but will be a bit grotty - the blankets should be available from any retailer/distributor servicing the printing industry (for example Pressroom Consumables. Fast, Reliable Service from Intuprint - I don't know them, just came up on a google search). For the threaded rods used to constrain the collection of cells (or for compression) then the heat shrink tubing used for rope might be ideal. It comes in a variety of sizes and when shrunk thickens up (I buy mine for rope from Aliexpress/Temu etc)
Jonathan
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jakew009
Well-known member
The way the flexible bus bars are made us by taking lots of copper sheets then ultrasonically welding them together at the ends (ultrasonic welding is awesome).
The reality is though there are millions of cells out there that don't use flexible bus bars and they are absolutely fine. Most premade batteries have the bus bars laser welded on like this and then just strapping tape around them with some sheets of fr4 between them.
Sorry I didn't explain well, EEL battery is just some random website I found I have nothing to do with them. We have batteries made for us by a different company in China but they are used predominantly for highway monitoring applications (hence the non leisure comment). Of course they could be used for leisure but it's not a market we're in.
Lots of premade packs have an FR4 (basically PCB material without the copper layers) sheet about 0.5mm thick between them. That obviously provides a good amount of insulation. However the important bit is that the cells are just absolutely locked together so they cannot move relative to one another.
I think it's probably fair to say there is probably different requirements bundling 4 cells together compared to say 8 or 16 or even more. My comments refer to a pack of 4 cells which would be standard in a lead acid drop in replacement, I don't have any experience of bigger parallel packs. The expansion problem gets worse the more cells you have in a line.
jakew009
Well-known member
I always think this is an interesting video
EVE manufacturing packs for electric vehicles. Notice how they stack a bunch of cells next to each other in a steel case and then laser weld the case up.
The argument is that for cells used in EVs, they are going to be discharged at high C rates so more likely to puff slightly hence the steel case to hold them in shape. In typical leisure applications where they are running at tiny C rates it's far less of an issue.
EVE manufacturing packs for electric vehicles. Notice how they stack a bunch of cells next to each other in a steel case and then laser weld the case up.
The argument is that for cells used in EVs, they are going to be discharged at high C rates so more likely to puff slightly hence the steel case to hold them in shape. In typical leisure applications where they are running at tiny C rates it's far less of an issue.
GHA
Well-known member
Seems reasonable enough to ask for any test data or published papers for statments on a web forum which say the opposite of the manufacturers (though the language could have been less "in yer face"..What sort of a response is that
)Catl datasheet states cycle life figures are with compression, a quick look at EVE they specify compression used to for testing capacity.
With no evidence to the contrary & no real downside imho seems logical to stick with what the manufacturers datasheets say
edit- EVE actually state a 40% increase in cycle life with compression >
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jakew009
Well-known member
Seems reasonable enough to ask for any test data or published papers for statments on a web forum which say the opposite of the manufacturers (though the language could have been less "in yer face"..
Catl datasheet states cycle life figures are with compression, a quick look at EVE they specify compression used to for testing capacity.
View attachment 176840
With no evidence to the contrary & no real downside imho seems logical to stick with what the manufacturers datasheets say
If you read back through my posts in this thread you'll see I have never actually disagreed with you.
My original post was
"Even if you were not to bother with compression, and if you ran the cells up to 14.4V every day, and ran them back down to 0% every night, they would still last such a long time it’s not even worth thinking about.
I bet there have been more cells damaged from over compressing than under compressing them."
My point was that these cells are far more robust than people think. I evidenced that by showing that the vast majority of factory made batteries with prismatic cells inside them do not have containment / compression
I also maintain that there have been more damage done to cells by people attempting to 'compress' them, rather than just strapping them together as tightly as possible. Normally either by people tightening them up too much and literally crushing their cells, to contraptions with springs that don't actually contain the cells at all and still put pressure on the terminals when they expand.
GHA
Well-known member
deleted, not constructive to the thread
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vas
Well-known member
fully agree with that, on my boat with a 304Ah@24V lifepo4 bank and 600W solar I charge at typically 0.05C (unless I get generator or engine - v.rare where I go up to 0.25C)
and max I can manage to discharge with watermaker and other things running is 0.3C.
Things are rather soft for lifepo4 onboard and even more so with ppl running BMSs that limit I/O even further...
OTOH, wouldn't leave my cells in a contraption that wouldn't let me even move them or secure them from things dropping on them.
jakew009
Well-known member
We use mostly EVE 280 / 300Ah cells in remote monitoring applications. The batteries get abused, charged to 100% and discharged to 0%. They often sit at 0% waiting to be swapped for extended periods. They do have relatively low discharge rates.
Over many thousands of batteries (and the oldest batteries are now 5+ years old) it's hard to see any noticeable loss of capacity as a result of our usage (and we have extensive monitoring via the JBD serial protocol which is all logged).
Unless the cells are in an electrical vehicle or similar, they will die of calendar aging way before anything else.
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Sea Change
Well-known member
I think quite a few of us are running close to 1C with large inverters for electric cooking etc- I certainly was with my initial installation, 271Ah battery and 3kva inverter.
GHA
Well-known member
15 years & still full capacity for Rod Collins charging to 13.8V, maybe not....
jakew009
Well-known member
Sure, but again there is a big difference between cooking on it for a few hours a week vs an electric bus driving around Shenzhen 24/7. Which is of course the primary use for these cells.
vas
Well-known member
SC, you are right in that the 12V guys do run close to 1C on 300Ah packs while cooking, which granted is the most demanding task (almost even worse than watermaking).
Hoever, even so you'll see real 1C whilst cooking for a few mins (imho) as inductive cookers are on pwm (or whatever) mode most of the time unless you're on boost mode for a few mins to boil whatever and eventually demand much less than that over time... Not cooking on induction yet, so would like to know a day's meal vs an hour of watermaking "cost" in Ah.
Another advantage of having a 24V setup (would be even better at 48V on home installations
)B27
Well-known member
A statistical sample of 1.
gregcope
Well-known member
View attachment 176780
FWIW, this is mine (304Ah, now into its 3rd year):
two 20mm marine ply on the sides,
cut handles to help in carrying it - still lighter than a 200Ah 12V LA, and similar size...
8cells as it's 24V,
2mm thick rubber sheet between each cell (and cell to ply sides)
4X10mm rods,
two bottom ones closer to each other so that cells rest on them (rods have rubber hose over them so that they wont damage the cells)
busbars with black shrink on them to avoid nasty sorts,
(still not fitted rubber cups on the M6 nuts though)
perspex lid just in case, it's on a locker,
DIYBMS one pcb per cell to communicate state to BMS/passive balance to almost 1A, etc
on the locker above from left to right is power supply to the BMS, BMS (with lcd touch screen, - also wifi/bt), shunt and at the far right bluesea bistable relay,
Class T fuse not in this pic for some reason.
BMS linked to VenusOS raspberry pi which controls/communicates with BMS, MPPT controller (600W on hardtop) and Multiplus 3KVA inverter.
Main load is 1.8kW watermaker and usual crap onboard a 43ft mobo
Re tightening the assembly, I discharged batteries to circa 30% (iirc) and clamped it with a torque wrench at a reasonably low value (which I cannot recall, maybe @gregcope remembers - we discussed them in PMs back then)
Once a year I open the locker to see if they are still there
I do follow their performance via the Victron touch screen on board or remotely from victron VRM:
View attachment 176782
and or grafana dashboard:
View attachment 176781
boat currently on the hard, last three days charging is off due to having reached 99% SoC 4days ago and now on rest mode till SoC drops to 35% or so when it will start charging again. I've configured that, need to alter the top charging level but not had the time to deal with it yet. Ideally off season I'd like to have them cycle from 30-50% and just stay there with or without fridge running. I got a more or less permanent 1.3-1.5A @24V load from all the systems on board 24/7 (bms, n2k bus and devices, switch, 4G router, alarm, etc.)
V.
I cannot remember the exaxt details of those PMs.
I do remember researching how to achieve Eves claimed clamp force settings and never really landed on how much torque to apply to bolts to get to the right number.
I just clamped mine with clamps and wrapped with strong packing take (several turns) as shown here; Lithium 304Ah Build
They are tight. No idea by how much. The ends are now 2mm FR4. Several layers of that tape is very strong.
