This post is moved from tumich's thread.
I used these nice battery holders, apparently made of heat proof material. Some of the cells were a bit hard to fit so I used a deburring tool to chamfer the edges of each hole. When putting the second holder on I tapped it lightly with a hammer to set it in place.
The pure nickel I have here is made to fit the above holders. It has slits cut at each battery to make a better weld by forcing more current to travel through the battery rather than just through the nickel.
Here is some more info on the above items: https://endless-sphere.com/forums/viewt ... 5#p1096996
I made a spot welder from a microwave oven transformer. I based it on these two articles: http://www.avdweb.nl/tech-tips/spot-welder.html
, http://www.avdweb.nl/arduino/hardware-i ... oller.html
I have the parts to make arms, so I'll do that sometime. It's duty cycle (and probably max amperage) is limited by the nickel plated steel electrode holders which get too hot to hold after welding several cells. I'm going to replace them with copper. It uses an Arduino to control the SSR with a double pulse to set the nickel in place before doing the actual weld. A foot pedal means I can weld the cells pretty fast. I'll likely build a better controller which has more accurate timing by detecting the mains waveform but this works fine for now.
First of all I mounted all the cells in the holders
Then I used a dremel cutting disc mounted on an old 540 RC motor to grind off the remains of previous welds. I'd used some of the cells on the close end on a temporary pack for my first ebike so they have lots of welds. The other cells are cleaner.
This is what it looked like after welding all the nickel strips
And here is the current state of the battery. I used a Greentime BMS. I replaced all the leads on the JST-XH connector with silicone, but I don't have the right crimp tool and it probably wasn't a very good idea. The only wire I could find for the main leads was very stiff and you can see it bends the nickel here. I've taped the wires up so it's not a big issue at the moment. I ran out of solder so had to use some plumbing solder to finish it off and the connections are terrible.
I have ordered some big clear heatshrink tubing along with 12ga silicone wire and solder so I'll redo all the wires including the balance leads and make it look a bit better. I will also redo the single cell width nickel strips to have a tab at each end and I'll solder the discharge/charging wire at those points. I bought a standard behind-seat-tube battery case which this just fits in (possibly not once I've added heatshrink) which I'll show later.
I found a very cheap 60V ±10% Meanwell clone on Ebay which works well to charge the battery. Would have been nice if it included a terminal cover. It's only rated at 6.6A and the BMS is rated 5A but even though the charger is putting out more than 8A nothing has failed yet.
At my current fairly high power levels (25A peak) I can get about 80km range ( calculated based on my measured 9.8Wh/km) with the motor on the whole time and a little pedaling. I am seeing a bit of sag at those power levels, down to around 47V on my longest 60km trip, and once even 40V on my first trip if my GT power watt meter is to be believed (which is definitely not the case for it's Wh measurements). This may be partly due to my bad solder connections, positive and negative wire connections (limited by single nickel tab) and the BMS Mosfets and PCB traces. There is also the chance I hadn't charged it before that ride. The measured peak amps is always 25A so I don't know why the sag would be different unless the battery was charged less.
On my first 60km trip into the city the end stats were 52.39V (my GT Power meter always seems to measure a couple volts higher than my multimeters), 10.655Ah, 46.92 min V, 24.31 peak A.
For info on where I bought the parts for the battery refer to this post: https://endless-sphere.com/forums/viewt ... 6#p1096996