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Gamble63

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Hey guys

Divided up the new cells I got into 14 packs. With the pack I was given some 6p Nickel which lead me to organise them like I have. The plan is to spot weld the nickel on each side to connect all the cells in parallel, with pos and neg top and bottom. Then connect them in series for the 14s.

This nickel goes well with these cells but can anyone see any concerns with this method? I will need to attach a bus bar of some form, and a balance lead etc.

Thanks
 

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OffGridInTheCity

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Suggest cell level fusing if it's a powerwall application.

These nickel fuse (spot-weld) strips are available from Battery Hookup if you're in the US - https://batteryhookup.com/products/...uous-roll-by-the-foot-18650-cell-level-fusing. See ~10:55 in this youtube by one of this site's founders for actual spot-welding example...
View: https://youtu.be/PenPYwa00CA

Or.. take look at this youtube spot-welding fuse wire with plain nickel strips.
View: https://youtu.be/THVMnyE4yAw

You can also solder, but since you're spot welding....
 
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Korishan

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Divided up the new cells I got into 14 packs
"New" as in, brand spanking new, basically new from BatteryHookup or similar site, or from reclaimed battery packs that have low cycle count?

If the cells are used with unknown cycle count, cell level fusing is recommended, as OffGridInTheCity mentions. If they are basically or are brand new cells, then you can do batch fusing. For example, if the pack is 100p, then you could take 10 cells, bond them together, then fuse that 10p to a common buss with the other 10p packs. Lithium Solar did this with some of his newer packs.
However this really should only be done with cells that basically know how many cycles were done and all cells are basically within the same life cycle count, AND are of the same cell type. Don't mix/match cells if this is the method used. Put each brand/type cells in their own packs/strings.
 

Gamble63

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"New" as in, brand spanking new, basically new from BatteryHookup or similar site, or from reclaimed battery packs that have low cycle count?

If the cells are used with unknown cycle count, cell level fusing is recommended, as OffGridInTheCity mentions. If they are basically or are brand new cells, then you can do batch fusing. For example, if the pack is 100p, then you could take 10 cells, bond them together, then fuse that 10p to a common buss with the other 10p packs. Lithium Solar did this with some of his newer packs.
However this really should only be done with cells that basically know how many cycles were done and all cells are basically within the same life cycle count, AND are of the same cell type. Don't mix/match cells if this is the method used. Put each brand/type cells in their own packs/strings.
The cells are brand new Samsung cells and haven't been cycled, all new. They had been tested and put into much larger packs

Didn't realise each cell could and should be fused, kinda makes this role of nickel pretty useless in this configuration. Looks like I should run a busbar on an empty cell holder and fuse them to that like in the video
 

OffGridInTheCity

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The cells are brand new Samsung cells and haven't been cycled, all new. They had been tested and put into much larger packs
At the risk of TMI...

The purpose of fusing cells is so that when an individual cell goes bad in a way that it becomes a dead-short, the overall pack amperage will short thru it, burning thru the fuse wire and short 'gone'. Otherwise the entire pack could continue to short all the way down, hi amps, hi heat, maybe fire. Tesla does this and is where the idea came from (I think) / lends credibility.

But batteries have different characteristics....

An ebike pack that's used here and there and running outside and not so many cells is not as big a deal. A powerwall on the other hand, if it's like mine, charges/discharges almost every day - year after year - e.g. I'm up to 1,274 cycles on my oldest 14s120p battery now in it's 4th year of operation. Who knows if one or 2 of the 1,680 cells in that battery might deteriorate 'fast' and short out! This is similar to a 10yr life span on a Tesla battery - e.g. day after day, long term battery.

You say you have new cells, but after a year of powerwall operation you'll have at least 1 yr old, 365 cycled 'used cells'. And after 2 or 3 or 4 years, I wouldn't want to go back and add cell level fusing. New cells don't stay new in the big picture.

I say all this because I'm in year 4 of my solar/powerwall power production - and the years have gone fast. As the years mount up, the cell level fusing *may* save me trouble and gives me comfort.

But of course my purpose is only to share info for consideration - not make judgements :)
 
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Korishan

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OffGridInTheCity has good points, valid points. And I do agree.

One big difference between with Gamble's configuration is that he's using all brand new cells. This makes a huge difference in how the cells will handle later in life. The chances of a cell going rogue, short circuit, it a lot less. Especially if they are taken care of from day one. IE, don't over charge-discharge them, don't over-current them, and don't float charge them on a regular basis.
These things are what causes the breakdown in the cells, which leads to short circuits.

Using the cells within their designed spec range, or narrow the range slightly, will drastically make the cells safer, and decrease the risk of runaways.

But as OffGridInTheCity says, "gives me comfort". This is the most important as long as all other safety measures are followed. If you feel more comfortable adding a few extra fuses now, then go for it.

If they were used cells, I would say fuse now, for you it will most likely save you trouble in the future.
 

Gamble63

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This information is golden, thank you guys.

I think considering the stage of design and build I'm at, it seems like the best idea is to incorporate cell level fusing. Wouldn't want to get further down the line and wish I had.

I will need to re jig the way I use the nickel and look at which fuse wire etc. Im thinking something like the "detailed schematic drawing" attached, with the green being the main busbar, removal of the centre nickel and the blue being fuse wire. Would the fuse wire need rating to 3 x cell current plus a bit?

edit** just looking at that again and that wouldn't work as all the cells are still connected via the vertical strips aren't they, Hummmm**

Exciting stuff!

Thanks again
 

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italianuser

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edit** just looking at that again and that wouldn't work as all the cells are still connected via the vertical strips aren't they, Hummmm**
Uhm, I don't think those nickel strips are convertible to a fused version. I have the same ones in 4P version but I put them aside and I'm at the phase "prepare 28 busbars" for the first 14s battery. After a lot of work and many plan changes I ended up with making the busbars and now I must cut them in half and weld them again WTHHH! LOL

My first version of busbars for 14s20p was: each busbar connects two 20p packs to make up series; a kind of "long" busbar crossing two packs:

busbar2.jpeg

I realized I couldn't test an individual single 1s20p pack if the busbar crossed two series, so now I'm cutting them in half to make individual busbars for each of the 14 series. And will connect a series with the next one using SC16-8 connectors (they arrived last week from AliExpress after 28 days).

busbar1.jpeg busbar3.jpeg

I would have liked to connect each pack to the next one using two copper segments but I choose going for one only (the orange line in the photo). It takes quite a bit to process each single busbar.

New goal: get everything ready for this summer otherwise my wife will put me, the batteries and the mining rig out of the door!
 
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Gamble63

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Ah great, are you going to join each cell to the busbar with fuse wire?

looks good, im not sure how i can weave round mine yet but i will have a better think about it, Thanks for the ideas
 

italianuser

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Ah great, are you going to join each cell to the busbar with fuse wire?
Yes, every cell will have a fuse wire on both positive and negative: I bought 5mt (16ft) of wire on Ebay, tinned copper wire 35SWG 0.2mm, should break over 5A.

There's a YT video from @daromer, at minute 4:00 you can see his good job with the spot welder and fuse wires:
View: https://youtu.be/H_b3OJuQpEE?t=240

After spot welding the fuse wire they'll be welded on the busbar with a drop of tin.
 

Gamble63

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Been playing around with ideas as I had plenty of this copper strip laying around. Thinking I'll spot weld the fuse wires on and then solder to the 3 busbars, then connect the 3 together to make the one cell.

3d printed this holder which will attach to the cell holders. I know this isn't needed and seen others go straight onto the wire.
 

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italianuser

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Been playing around with ideas as I had plenty of this copper strip laying around. Thinking I'll spot weld the fuse wires on and then solder to the 3 busbars, then connect the 3 together to make the one cell.

3d printed this holder which will attach to the cell holders. I know this isn't needed and seen others go straight onto the wire.
Looks very neat and clean. In my case I wanted to be able to easily change a cell in case of problems, easy maintenance is one of my goals.

With the kind of holder you're using (nice, indeed) swapping a cell out means to remove the holder and disconnect the fuses from the busbar, swap the cell, re-fuse cells. You could maybe make the holder in three pieces, attached one to the other like a puzzle or something; that way in the event of a cell swap you could reduce work by 2/3rd.

Or how many actually do, you could use a pack-level-maintanance. In case of problems on a cell you remove the whole block, put a new block in (with the same voltage as the other packs in the battery), and then do the maintenance with no hurry.
 

Gamble63

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Looks very neat and clean. In my case I wanted to be able to easily change a cell in case of problems, easy maintenance is one of my goals.

With the kind of holder you're using (nice, indeed) swapping a cell out means to remove the holder and disconnect the fuses from the busbar, swap the cell, re-fuse cells. You could maybe make the holder in three pieces, attached one to the other like a puzzle or something; that way in the event of a cell swap you could reduce work by 2/3rd.

Or how many actually do, you could use a pack-level-maintanance. In case of problems on a cell you remove the whole block, put a new block in (with the same voltage as the other packs in the battery), and then do the maintenance with no hurry.
Very good points on the maintenance if an individual cells goes wrong. With the holders i am using (3 strip) i would have to remove the busbar and cells around it to get to one cell. having this holder on top does make things harder in that sense and would lead to even more work, hummmm

Time for plan B...or C, cant remember :D.

Thanks for the help
 

OffGridInTheCity

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One of the advantages of the standard cell holders a lot of folks buy is you can break the tabs, unsolder the fuse wire, and push the cell(s) out and new one in.
1650549680387.png


Nickel spot-weld (w/fuse) from BatteryHookup like this - https://batteryhookup.com/products/...uous-roll-by-the-foot-18650-cell-level-fusing - also allow one to push a cell out of a holder (I believe) - the hole is big enough.
1650550107172.png



In my case, I built my packs with empty slots so I could add a few cells to tweak them to be more balanced with the others - and I added cells after the fact in this manner. I've done this with about 10 out of 84 packs so far.
 
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Gamble63

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One of the advantages of the standard cell holders a lot of folks buy is you can break the tabs, unsolder the fuse wire, and push the cell(s) out and new one in.
View attachment 27357

Nickel spot-weld (w/fuse) from BatteryHookup like this - https://batteryhookup.com/products/...uous-roll-by-the-foot-18650-cell-level-fusing - also allow one to push a cell out of a holder (I believe) - the hole is big enough.
View attachment 27358


In my case, I built my packs with empty slots so I could add a few cells to tweak them to be more balanced with the others - and I added cells after the fact in this manner. I've done this with about 10 out of 84 packs so far.
Ah that makes a lot more sense with the break out tabs for replacement, i didn't know that was the case. I started redesigning my holder last night and then just treated myself to some fused nickel from the US to make things easier for me. Ill then just need busbars and mounting.

the Shipping was the same price as the nickel to the UK haha
 

Gamble63

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Received my fused nickel and am starting to build a test pack. Got the spot welder dialed in and have fixed one side of the cell. The plan is to soldering on this copper busbar on either side to join to the next cell.

Can you see any issue with using this copper busbar? 7mm X 1mm

Thanks

Jo
 

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Gamble63

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It shouldn't block anything to any massive degree. But, also think it would be very hard to get a cell out, would need to cut the nickel away and then the plastic on the holder, so may just end up being stuck in there if it blows.

I'm also debating if I use use two strips per side and then joining them to however I'm going to connect the cells together. What do you reckon?
 

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Mazlem

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It's probably fine with the small current draw, but to optimize it you could have one copper strip for the pos/neg but put them at opposite ends of the pack.
 

floydR

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Might be better to solder the busbar on to the BHU fuse sheets before spot welding to the cells. Two or more copper busbar strips per side would be how i would do it. or use thinner copper and use the nickel sandwich methold t
Later floyd
 
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