The battery builders club

yeah but you get the distinction? with the vesc seeing individual cell voltages it can “detect the issue” much sooner ie at it’s low voltage cutoff start(/cell) value. so it can slow down gradually as we’re used to.

Only using the binary signal from the BMS means detecting the moment undervoltage (or other fault) occurs. at which point to signal back to the rider you have to do something more dramatic. can still be smoother than just cutting off though.

thus i think both paths are interesting.

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I mean it’s not great, but it’s slightly better than soldering a 12awg wire to each

It’s like, you wouldn’t be as mad stepping on a bunny poo, than stepping in a cow pie. yknow?

That aside, the rest looks cool

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should have known I’d get roasted coming in this thread :sob:
still proud of it for my grand budget of $0

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Hey - I said the rest looks cool






Friend’s exway flex ER battery only charges to 48.1v, there’s no warranty anymore so he says he’ll open it up. Could somebody already guess what’s wrong with it? :smiley:

Parallel group is out of balance because a cell went bad, run it down till it dies before opening it and check all the group voltages, then charge it (don’t need the board back together just make sure nothing shorts out and note CF is conductive) and verify everything is balanced again, if it is then either the cell is toast or it’s connection is

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It could also be broken welds leading to an imbalanced group. The group or groups in question would charge/discharge more quickly than the other groups causing the bms to shut down the charge when the group(s) reach to overvoltage cuttoff.

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I was going to try something like that, wasn’t 100% sure so thank you a lot for your advice :grin: I doubt there’ll be CF around. Thank you!

two places should be enough.

Step 1. Plug the spot welder into a standard 120v outlet.

Step 2. Wait for voltage display to reach 5.3v. When you initially power up the spot welder it will take about 15 minutes to fully charge the capacitors. After the initial charge the power supply will normally keep up with your spot welding speed.

Step 3. Adjust the power setting from 005-080.

Step 4. Spot weld batteries

This sounds really interesting


This is quite interesting. Wall powered with a small power supply, welder isn’t too huge. Seems compelling if its consistent

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LoL: “Don’t eat the spot welder.”

Even says it can do copper. Hmm. Kind of hard to believe. I suppose super thin copper might be possible.

Bodged together with custom and China modules but for the price that is expected. What counts are the results and I’m not sure how the pulse is handled…varying just power it seems?

If consistent and powerful enough then perhaps worth trying out (not by me, love my kWeld).

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Maybe someone here can help our friend

Sooo… I bought a lot of cells from I bought 50 for my pack (haven’t measured those yet) and 10 reclaimed of another model for test welding etc.

Their product page says:

These batteries come from battery packs in which welding errors have been found. The batteries have never been charged or discharged.

The cells we offer have:

  • Minimal damage to cell
  • Never charged during production (from the box) (each cell is tested)
  • Resistance is according to datasheet, never worse (every cell is tested)

5 out of 10 cells are lower completely dead or lower than 1 V. What a load of bullshit.


You should try and get your money back. Perhaps make a short video showing the voltages, and send it to customer service. It’s nonsense.

Shoot them an email, I got a partial refund for my clearly-previously-welded cells that they sold me as new. It’s the second fuck up that we know of in a short period of time, but they make it right

Yeah, it’s not at all about the money because I literally bought those 10 cells cheap just to have as tests or to do some random side project with but still, claiming they are tested and never discharged… Can I trust anything they say now?

The 50 new cells that I’m actually gonna use were all good though :+1: