Nickle Strip Cell Level Fusing

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Bobbych

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Feb 18, 2020
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I would like to use the Nickle fused cells strip but It cant be found in the UK. See attached image. I can order from Batteryhookup in the US and have it shipped. a bigger order would be cheaper. they have it in 2P to 6P. Anyone in the UK interested in a group purchase? I would be willing to make the initial purchase then sell it to any individual who has asked for some.
 

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Oleksii said:
There are other ways ...
View attachment 27991View attachment 27992
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Hi Oleksii. my first pack was done this way although the fuse wire was soldered to the cells not welded as you have done. see below.
20211102_084315.jpg
I found the creation of the copper busbars time consuming and costly. I have now tested spot welding nickel strips and found it to be much faster so I wanted to go that way but still want cell level fusing for safety.
 
Yes, I know it's time consuming. But characteristics will be different.
I'm not sure what wire you used here for fuse, but having some experience and looking in the picture I guess it's 0.4mm in diameter, ~10 mm long.
If that is tinned cooper, each connection is ~1 mΩ resistance, current to burn it would be 50-60 Amps.
Your cooper bus but is really solid, maybe oversized. How many mm2 section those twisted bus bur cables?
I'd evaluate the bus-bur as contributing ~0.5mΩ or less resistance per one side. It's hard to express that but this number is good compare with cell and fuses resistance.

Note - per data from @Wolf fuse on the nickel strip has ~22 mΩ resistance. If I understood it correctly - sheet of 50P (5*10 cells): 20сm length has 5.5mΩ.
So Wolf used cooper bus bur on top of the nickel sheet, see here https://secondlifestorage.com/index.php?threads/wolfs-powirwall.7804/#post-61125

All these details contribute to resistance, so you should consider that.

p.s. I use very thin tinned copper wire on positive side, 0.16 mm in diameter, ~10mm long, has ~10 mΩ resistance, burns at ~12-13A current which I tested practically. On negative side I used thick wire - 0.5 in diameter, ~6-7 mm long, has 0.75 mΩ resistance.
Bus burs to collect current 3*2.5=7.5 mm2.
 
btw, if your cells are from laptops etc (not from power tools) and have IR AC 40-60, it's quite possible they will not be able to burn down your fuse wires on positive side. You would need to test that.
 
@Oleksii

hanks for all the good info and defiantly need to mull over more data.

My fuse wire is 30 SWG 0.315 mm Diameter

Copper bus bars are 6 mm2

None of the cells are from laptops. all from power tools

@Wolf setup is interesting and I had not thought of connecting adequate pos and neg connectors. maybe I will stick with twisted copper bars.

I like your selection of fuse wire so I may go that way also. All good stuff.
 
Bobbych said:
My fuse wire is 30 SWG 0.315 mm Diameter
Copper bus bars are 6 mm2
None of the cells are from laptops. all from power tools
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0.315 mm Diameter for power tool cells is ok, I'd predict current to burn them 30-40A. They should do their job in case of disaster.
6 mm2 for bus bur (current collectors actually) is acceptable, IMO.

What did you use on negative side? The same 30 SWG 0.315 mm Diameter? I'd suggest to use there as much thick cable as you can. They should not be like a fuse there, not needed at all and only increase resistance.
 
Is it really important if the fuse wire is killed at 10 or at 20 Amp? As long as there are enough batteries to get the power, it is fine.
The picture looks like there are enough cells.
I will have 30 Cells in a pack and there I am really thinking if 30 cells x 1A will kill the wire if one cell gets shortened internally. Maybe all cells can deliver 2A, then it will work, but what is if the battery is quite low?
The question that is relevant is: Will the remaining power be enough to heat the cell up to 180 degrees? Because that is the temperature where the fun starts.
 
You must plan for worst case situation. So for example, 30 cells in parallel. Let's assume the voltage is 3.2V. If a cell goes dead short, then at 3.2V per cell, you won't get 1A per cell. You might get closer to 500mA, if that, depending on which cells are used.

Just because you have a large number of cells doesn't mean the fuse will pop. It is also depends on the voltage level of those cells. Current flow goes up as voltage drops only to a point, then current flow will drop quickly.

The other thing is that you want the fuse to fully pop, blow completely clear. Not just heat up and become a read hot mess. The only way this happens is with high current.

So if you calculate 30 cells in parallel, and at 3.2V they can output 500mA, then that's only a total of 15A. If you use a 15A fuse, it will just glow hot and slowly burn out over time. If you use a 10A fuse, it'll pop faster. And if you use a 5A fuse, it'll pop quickly.

Shadowblues said:
Is it really important if the fuse wire is killed at 10 or at 20 Amp?
Click to expand...
So to answer this question, yes it actually is important to have the lower Amp rating.
 
After re-reading your post Shadowblues, I see we are on the same page :p
 
But how to get a 5A fuse?
I was told that 0.2mm copper wire would do the trick and burn at around 5A.
But in my tests it only got hot and did not burn :-(
So I hope it will burn at my 30 cell packs ...
In normal operation I will have 2 packs in parallel, so 60 cells.
 
Shadowblues said:
But how to get a 5A fuse?
I was told that 0.2mm copper wire would do the trick and burn at around 5A.
But in my tests it only got hot and did not burn :-(
So I hope it will burn at my 30 cell packs ...
In normal operation I will have 2 packs in parallel, so 60 cells.
Click to expand...
Some use Xamp 'axial fuses' to get a more precise burn-thru than just wire.
 
Shadowblues said:
To get back to topic: How good are that nickel fuses mentioned here at melting?
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BatteryHookup sells nickel Fuse (spot weld) rolls - https://batteryhookup.com/products/...uous-roll-by-the-foot-18650-cell-level-fusing

Down in the description it says...
".... The fuse will blow fast at 8 amps. The fuse can carry 3 amps continuous while staying cool and without voltage drop. The connecting strips between the cells will handle 10 amps. ...."
They go on to discuss doubling up for higher amps and other tips on how to control what you want out of a pack.

I mention this particular one because if you're US they are a reliable vendor and their descriptions are usually spot-on.

Doesn't mean there aren't other sources with different specs, it's just the only one I know of :)
 
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