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Building your own electric bicycle battery isn’t rocket science, but it isn’t the simplest job either. When putting together an ebike battery pack, you want to make sure you’re using pure nickel strips and not nickel coated steel trips.
Conductive metal strips are spot welded between all the cells of an electric bicycle battery pack. Nickel is the material of choice due to its low relative resistance and ease of spot welding. Steel is cheaper than nickel, which is why many vendors sell nickel coated steel strips. It brings the cost down, but at the expense of pack health. Because steel has higher resistance, the same size strips will heat up more, wasting energy from your pack. This not only cuts down on your range but also damages your battery by cooking it slowly over time with extra heat.
Most vendors are honest and clearly indicate whether they are selling pure nickel (usually 99.95% pure or higher) or nickel coated steel strips. However, I’ve seen people get scammed by paying for pure nickel strips and receiving the steel ones instead.
The problem is that it can be nearly impossible to distinguish between pure nickel strips and nickel coated steel strips using only the naked eye. They look identical from the outside. They are both attracted by a magnet. The density of steel and nickel is so close that weighing them is also difficult. A sample long enough to have enough mass to make a measurable difference will also likely have enough small variations in size to destroy any chance of a fair comparison.
But don’t fret! I’ve devised two different methods for testing nickel strips to determine if they are pure nickel or nickel coated steel.
Method 1
The first option for testing the strips is with a Dremel or other rotary tool and a sanding or grinding attachment. Simply grind or sand at the nickel strip using a high speed setting. If you see sparks after a second or so, you know you’ve got a steel strip. Steel will spark when struck at sufficient speed with a sanding or grinding attachment. The wheel quickly goes through the thin nickel coating and reveals the steel below the surface.
If you sand or grind away for more than a second or two and still see no sparks, you know you’ve got pure nickel.
Method 2
The next option is better if you don’t have a Dremel or other rotary tool. Simply scuff up the steel strip with sandpaper or any other rough object (a wire brush, a screwdriver, even a house key) and place it in a cup of saltwater. Make sure you’ve scratched up the surface to expose any steel below, if there is any. You’ll know there’s steel present in a day or so if you see rust forming. Steel rusts easily, but nickel is highly corrosion resistant. If there’s no rust after a day or so, you’ve got a pure nickel strip!
Fun fact: I actually discovered Method 1 while preparing to test out my idea for Method 2. I used a rotary tool with a sanding wheel to scuff up some sample strips so I could put them in saltwater. That’s when I realized that some of the strips were throwing sparks. By completing the saltwater test, I confirmed my suspicion that it was the steel core strips that were shooting sparks while the pure nickel strips didn’t spark at all.
So now you know how to confirm that you’ve got pure nickel strips. Stay tuned for my upcoming article on how to use those nickel strips to build an ebike battery.
cagt15 says
Hi
What supplier do you recommend for Pure Nickel Plate? I would like to get really wide strips, about 3″ wide. Could be a sheet by square foot that I could cut.
Thanks!
Micah says
I’ve never tried using strips that wide myself, but I’ve found some suppliers here.
geekrebel says
Hi Micah & cagt15,
What do you mean by “Pure Nickel Plate”? Does Nickel Plate not imply Plated Nickel?
I’m looking at this item on eBay: http://www.ebay.com.au/itm/1m-Pure-Ni-Plate-Nickel-Strip-Tape-for-18650-Battery-Spot-Welding-Ni-Strip-/221871472190?hash=item33a891fe3e:g:u2wAAOSwT6pV5tqv
It’s a nice size as the ‘squares’ fit nicely over 4 batteries, thus reducing some welding work, but I’m not sure I understand the “Nickel Plate” term in the description correctly.
Micah says
It’s hard to say. It’s either a case of A) the seller’s english not be very good and they are poorly describing their pure nickel strips, or B) the seller trying to sell nickel plated steel and claiming that the nickel plating is pure, but including the word “plate” so they can try to not have to refund if someone claims they thought they were getting pure nickel. For a few bucks, if may be worth the risk, but that’s your call.
jaynil says
can i use copper or aluminium for wilding?
Micah says
I would imagine so but I haven’t tried spot welding either of them. Copper will certainly be more expensive. I’m not sure how well aluminum spot welds. I know you need a really high temperature to weld it traditionally, so it might not very easy to spot weld.
EgoKit says
Hello, I’m very interested in building my own battery but I was wondering if I purchase your videos and books will they provide me with the sites that you recommend buying the batteries from, the BMS, the Nickel, and all other parts needed. Also what about matching a custom battery to the right charger, can you provide that information as well.
Micah says
The books and video course is focused more on building the entire ebike and less on specific battery building. For that I actually have a free guide here: http://www.ebikeschool.com/how-to-build-a-diy-electric-bicycle-lithium-battery-from-18650-cells/
and also a free video here: https://www.youtube.com/watch?v=TY7FwffZ5vc