Building first battery, need some advice.

[caseylain]

So I'm building my first battery and was curious if my way of paralleling the batteries was sufficient.

https://i.imgur.com/6gtSsdI.jpg

I originally wanted to make cutouts of my copper sheet that would cover the whole area but I found that it took a lot of pressure to get the copper down into the pits made by the battery holders and that made me uncomfortable. Also once the plate was there it was hard for me to visualize where I would need to place the sandwich strip and make my welds. I opted for copper strips to make the series connection with overlapping nickel strips to make the parallel connections.

The uneven strip was the last one I made. I noticed during the first 3 parallel strips that welding on top of the sandwich welds caused those welds to weaken. At least I'm pretty sure as I heard a metallic popping sound as if a weld was letting go. Hence why I made many extra welds at other locations on the first 3 strips.

I figure as long as every battery has a electrical path to every other battery in the parallel group then the strips don't need to connect directly from one battery terminal to the other. But I'm not a electrical engineer so I don't know that for sure. Any advice or info on this would be appreciated. Thanks!

 

[caseylain]

Nevermind LOL out or curiosity I tested to see how strongly the copper was welding to the batteries and was able to pull the copper off with little effort. It did form some bond but I was able to break it with the strength of my fingers. Oh well, I'm just using a modified sunkko 737g anyway. Guess I don't have enough power to do strong sandwich welds after all.

 

[spinningmagnets]

The layout is good. Copper for series, nickel for parallel...

 

[caseylain]

So I tried out using brass and it didn't work either but it has a different issue. The brass strip welds to nickel and ni-plate easy but the strip easily tears away from the welds, leaving 2 little brass buttons where the welds are lol. I assume the brass is simply being melted straight through by the pulse welder. However if I turn the power down enough to not weaken the brass, the weld does not adhere to the nickel/ni-plate. I've tried every possible setting with no luck. I think this is a problem with trying to weld 2 metals with very dissimilar melting points. Brass melts at 900c but nickel and steel melt at 1455c and 1370c respectively. So any weld hot enough to melt nickel/steel will just destroy the brass.

Also yeah I'm being really anal retentive about weld strength. My steel bike does not have suspension and the roads in my city are very rough. That's never bothered me, because I know how to roll with the punches. However my frame mounted battery will not be able to do the same. It will need to be able to eat every bump, vibration and pothole and grin. My test criteria is pretty simple, if I can pull the test strip off with my fingers, its too weak. If I need pliers to get it off, the weld is good.

Anyway its fun learning this stuff. It's a shame I seem to be stuck using nickel to make my series connections. I know its less then a ideal material and that really bothers my gearheaded tuner mind.

 

[caseylain]

Build Pictures!

https://i.imgur.com/ffQ5VvV.jpg
https://i.imgur.com/5PyMvy3.jpg

and on the bike: https://i.imgur.com/XX6n8i0.jpg

I forgot to take a picture of the cladding I put on it. But it was 2 layers of cardboard and 1 sheet of aluminum all cut to shape on every side. That bulked it up a bit but I was able to juuust squeeze it in. Had to cut open the triangle bag, then sew it back together to get it in the bag though.

Took it for a spin immediately after I was done. I really went out of my way to reduce voltage sag but it still sags about 4 volts when max load is applied. I thought taking 45 amps from a 48ah battery would mean 0 volt sag.

The cells are Liitokala lii-50e and were reviewed by a russian youtuber. Here's a link to his results: https://youtu.be/mXOg3mCTYcc?t=1129