/diy/ - Do It Yourself

I bought a police auction shimano steps ebike a year ago (for $600 which is not great but it looked cool), but it turned out the bike was missing components adding up to about $500 (charger, display, speed button, mount, speed sensor magnet, and wires), and the battery life meter doesn't display when you press the button.
So my plan is to replace the BMS and controller with chinese parts, and pray it will just work.
When I opened the battery, it turned out that 9 of the series groups had 3.5v, but one group had 1.5v.
I bought a TP5000 (which arrived today) to recharge that singular group, and I am waiting for it to charge right now.
If it doesn't charge... I will probably buy the cheapest batteries I can find and use a knife to cut the bad group out, and solder the batteries using an iron.
One downside is that I will not be able to get pedal assist, and it's probably not legal because the controller is designed for hub motors, and the speed limit uses the motor spin (plus a ratio) for limits, but because I have a shifting that value isn't accurate. I knew this before I started and I don't care because it's 250watt (the motor's rating) so it's not capable of going fast (maybe).
right now it's at 3.4v (maybe 1 hour), I know that if a cell goes below 2.7 and you leave it at that charge for a long time the battery life degrades, but it would be great if it just worked a little bit so I can test the bike.
Overall I spent about $200 on replacing the cassette and tools (the bike came with a 10 speed shifter, with a 7 speed cassette. the auction did not mention that).
$100 on tools to open the motor (mainly crank removal, wrench, screw bits, and a torque wrench).
$100 for the controller, throttle, display.
$30 on the BMS
$150 I bought a crimper, stripper, and a bunch of crimp bits and enclosures (not necessary could have saved a bit of money here, but I felt like knowing that I have to brute force the brushless phases, it would be nice to be able to quickly swap the wires)