The battery builders club

[Evwan]

@newbiee

this is a huge fucking difference. Something is wrong here. Be careful.
It charges to full too?

[newbiee]

Have not yet reach to full. Now all other cell group is 3.63v, but cell one is 3.61v.

[MysticalDork]

I would suspect that group 1 is missing a cell connection, effectively making it 6p rather than 7p.

Bad welds, or a failed weld, could do it.

[newbiee]

Checked all the welds, all are intact. I was assuming if there’s a missing connection, when I’m charging the battery, it would charge first compared to the rest. But in this case, cell group 1 is behind.

[MysticalDork]

In that case I’d say run it through a full charge/discharge cycle and see if that p-group tracks with the others. If it doesn’t then more investigation is warranted.

[Evwan]

Could be a loose balance lead.

[MysticalDork]

Or a BMS that’s draining that group when it shouldn’t.

[newbiee]

@MysticalDork

In that case I’d say run it through a full charge/discharge cycle and see if that p-group tracks with the others. If it doesn’t then more investigation is warranted.

Yep will do that once the pack is full. Will test it this weekend.

@Evwan

Could be a loose balance lead.

Noob question, would this probably be the reason why the cell group 1 to discharge rapidly on load rather than the rest?

[newbiee]

I started my ride with the pack full, is it possible to drain that much on a 2 hour period while I’m in the long ride?

[MysticalDork]

@newbiee

Noob question, would this probably be the reason why the cell group 1 to discharge rapidly on load rather than the rest?

No, but it’s possible for the BMS to get a bad voltage reading due to a loose wire. The voltage could be fine, but if the BMS thinks it’s too low, it’ll get upset.

@newbiee

I started my ride with the pack full, is it possible to drain that much on a 2 hour period while I’m in the long ride?

No, but unless you were looking that the cell voltages, you could have had a “full” battery that had one p-group that wasn’t full while all the others were full.

[newbiee]

@MysticalDork

@newbiee

Noob question, would this probably be the reason why the cell group 1 to discharge rapidly on load rather than the rest?

No, but it’s possible for the BMS to get a bad voltage reading due to a loose wire. The voltage could be fine, but if the BMS thinks it’s too low, it’ll get upset.

Balance wires was fine. Check the group with a voltmeter and it’s the same with the BMS reading.

@MysticalDork

@newbiee

I started my ride with the pack full, is it possible to drain that much on a 2 hour period while I’m in the long ride?

No, but unless you were looking that the cell voltages, you could have had a “full” battery that had one p=group that wasn’t full while all the others were full.

Hmmm I started with full, all groups were balanced when checked in the BMS app. Don’t have a screenshot though.

I guess I’ll just observe in my next discharge test to see if this is just a weird issue or something is wrong with one of the cell in the group. Damn it would be a pain to disassemble and reweld.

[Evwan]

Did you probe the group or the harness?

[newbiee]

@Evwan

Did you probe the group or the harness?

Direct to the group. Haven’t tried the harness since my voltmeter pin are too big.

[Fosterqc]

How to Make Rechargeable 9V Li-Ion Battery | DIY 9V rechargeable battery

You all need to see this stop motion battery circuit after 2 min in

[Linesflag]

That’s was pretty cool.

[xsynatic]

@Fosterqc

https://youtu.be/SLWJuKQD030

I was today years old when i learned how a 9v battery looks from the inside.

[TheBoardGarage]

For your enjoyment.

3 cell test failure

[Oddcomo]

Nice, i have 70 of those aiming at my balls!

[Linesflag]

Damn, what did you do to them?

[TheBoardGarage]

Placed a cartridge heater at the center. This was a proof of concept, leading to a much larger test.