Depending on the pack layout, you don’t need most of the nickel to handle 100A. For example, if I’m connecting 30Qs in series and I calculate 15A continuous then my series connection between then needs to only handle 15A continuous or 3 layers of nickel.
The issue as at termination, where all your parallel cells come together at a single (-) or (+) terminal and THAT does need to handle the full pack current. I ended up crimping a 10AWG bus bar to accomplish that.
It depends on the nickel width. You can find very different statements on the current for nickel strips, some says 15A, some says 5A, some says 8A. Can you underline your statement with a temperature measurement? I would be interested.
We are agreed that one stripe isn´t enough. And i saw pictures here with just one stripe. So it is very dangerous, because the nickel will heat up and could be a trigger for battery fire.
Best regards, Solar
It is not just the thickness, a nickel strip of 5mm wide vs 10mm is twice the current Just calculate the surface (like we do in EU with copper wires) 5x0,15 = 0,75mm2 and take the resistance /m for the strip, this way you could calculate the resistance over the length used, following to calculate the power lost over the wire and last calc the heat-up of that. Theoretically the wire is cooled by the cells mass. So,… it’s hard to tell the exact melting point of the nickel strip. I would care much more about the quality/quantity of the welds. A bad weld gives much more heat-up than overloading a piece of nickel strip
When I first saw all the single strip versions on these forum. I couldn’t believe the charts with these incredible low rating were correct.
So I took current injection tool and started inject 10-70A into different size of nickel. After these test I can confirm the table below from Endless Sphere is correct.
Many people have quite some luck. I think it’s a combination of lower loads during the ride and the max required power is only during short amount of time. Still it’s very risky to operate the nickel strips in this high current window.
12S3P - 2x 6355 motors, I used 4x 12x0.15mm (good for around 40-45A continous) 12S5P - 2x 6384 motors, I used 1x 12x1.0mm copper (overkill)
Difference in resistance between copper and nickel is incredible. That’s why spotwelding works very well for nickel 
Man, great overview! to add, it will get even worse with bad welds.
now I’ll consider to take my pack apart soon (used .15mm strips and set the vesc to 40A), I do monitor the cell temperature but not the strips. 
Thanks for doing this. I built my pack a year ago based on this table using optimal values, ie 5A per 0.15x7mm strips. IMO, its foolish to build your pack at the bleeding edge of capability. You always want to leave a large safety margin. As I said earlier, some guy here built his 90A pack using single layer 0.15 and claimed it was fine because his pack hadn’t blown up. 
A possibility you left out, while remote is still possible; a counterfeit cell(s) that didn’t hold up to the energies your system placed on it. It can also take time for the counterfeit to fail. All it takes is one bad cell and the entire system is at risk.
Even quality resellers suffer from the occasional counterfeit battery/cell. Counterfeit parts happen to the military, aerospace, hospitals, etc all the time even with their quality checks. They can be very difficult to detect and cull from a supply.
Should you double up the strips in between the p groups, I’m building a 12s8p using 10mm wide .2 pure nickel.
If it’s mounted to the deck, you may not be able to get to it when you need it. The general advice is to not store an extinguisher right next to the possible direct source(s) of fire (like in a kitchen, you don’t store the extinguisher right next to the stove).
Am I the only who uses 2 8mm or 2 7mm for parallel because its simply easier to weld? Anyone else out there doing this am I doing something wrong lol.
I did 2 10mmx .15mm strips for the parallel connections. Next time I will probably just do one layer after talking with some people more.
Yeah there shouldn’t be much current running between cells. But more nickel isn’t really a bad thing Imo lower internal resistance can’t be a bad thynj
series connections take the full current and the parallel connections see very little
Temperatures, Insufficient Cooling, Thermal Cycling: contributors to catastrophic failure
Something I’ve not seen much attention to on personal builds here, is heat-sinks and system ventilation. From what I see, most people seem to be more concerned about water-resistance than ensuring adequate cooling of electronics and the battery packs. I would think exposure to water should be the exception, and avoided wherever and whenever possible. Cooling should be a very high priority, especially on these high-power boards. Properly implemented heat-sinks can also significantly reduce system heat while maintaining water-resistance.
Also, do you have or have you considered any instrumentation that measures and reports the temperatures in your cell packs? Any warning alerts when temps get too high? One can also put thermal sensors at key locations of power bus elements. Real-time temperature sensing could give one minutes of warning before imminent catastrophic failures, even allowing one to avoid a failure. It can also provide data for improving future builds’ ability to dissipate heat.
Edit to add: Another important factor to consider is thermal expansion and contraction. Depending how the board is used/stored, some of the components might see VERY sudden temp changes of from say 32F to 200F (or higher with insufficient cooling). That could cause major structural dimensional changes in elements like the bus strips. In some cases it may thus be undesirable to have a completely rigid pack design that doesn’t allow for the physical changes in the nickel or copper strips, or the physical stress on solder joints. Expansion and contraction could potentially even cause welds to pop or partially pop, thus causing hot spots. Temperatures cycle repeatedly as the board is used thus the damage could be cumulative and failure appear only after days, weeks, or months of use.
Has anyone performed any before-high-current (cold) and during-high-current (hot) dimensional measurements on bus strips in battery packs? Or measured separating gaps under the same conditions?
I suspect thermal expansion/contraction plays more of a part than some may have considered in some electrical failures. I’ve noticed what appear to be millimeter or less “insulating” gaps in some projects. There are not only possible changes in length and width, but also the potential for warping in the thinner strips of metal as they heat up.
I’ve seen this phenomenon in high power battery packs that amateur radio operators have built and then sold at amateur radio conventions or to provide backup power for repeater stations. But, I don’t have practical exposure to any of these very high power skateboard battery packs.
So what is the general concensus on what thickness/width of nickel to use on the parallel connections on say a 10s5p pack? For the series connections I know to use a 12awg wire but am I right in thinking a single strip of 7mm x0.15mm nickel for the parallel connection would be fine also?
well depends what amps you draw. there is chart up there
Well according to the chart, to optimally carry 60 amps I need something like at least 6 strips of nickel? That’s where my confusion arises because I haven’t seen anyone using that many layers between series.
thats why people use copper, siliconwire or some kind of copper braid soldered onto the nickelstrip. there are alot of examples. search a bit in this forum and you will find plenty.
Lots of good points. One place I’d have to differ though is in the focus on waterproofing since sometimes it rains and you don’t expect it or you just still want to be able to ride. Agree on more thermal monitoring would be good but the vesc does some of that and can get that data through metr or believe using the ackmaniac firmware. Problem is when you’re riding you need to pay attention to the road and don’t typically have time to monitor gauges while going. Having thresholds with alarms/alerts in the apps would be nice if they don’t already exist. Problem with cell levelling thermal sensing is designing something flexible enough to work with all the various batteries configurations and in a way that makes it easy for battery builders or diyers to incorporate it. Points about thermal expansion and all are good though and not things I’ve seen brought up often.