Odd power situation (not charging)

I just had an odd power problem, resolved now, so FYI.

I used my Reform battery powered (charger unplugged) then forgot to plug it in; when I noticed battery was at 7%. I plugged the supplied charger 2.1mm into Reform; the battery continued to drain, 6%, then 5%. The blue LED on the charger was pulsing bright ~once/sec.

I unplugged the charger again, did shutdown -h now (see below…), OLED was on, so I did circle-0 to power off.

I waited a few minutes, the blue LED is on steady, plugged charger 2.1mm in, circle-B, now it’s charging. The blue LED is on steady. It’s now at 25% and rising.

To hazard a guess, Reform loaded the charger too much, which folded back. Shutdown reduced current draw, battery came up and all’s well.

  • Upon reboot, fsck fixed a lot of errors in one of the drives; I missed which drive and which error… I have an external SSD plugged in for rotating backups. Drive is OK now.

Before I issued shutdown I ritually ran sync a couple times (what can I say; I’m old) so the fsck surprised me.,

FYI I guess.

If you have motherboard 2.5, then it can happen that the reform tries to draw more power than the supplied stock AC adapter is able to provide. This is more likely to happen the more empty your battery cell are because the cells are charged faster the more empty they are (and slower the fuller they are). There is a patch for the LPC firmware which works around this issue.

@minute did you add your patch to the original firmware? I am unable to find it in the git log.

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This is good to know. I’ve had this happen to me a bunch with the LS1028A firmware, where the notebook would not start charging if I plugged it in while it was running. But when it’s shut off it works reliably.

I haven’t had the time to investigate this as of yet, but this explanation sure seems to make sense.

That patch you mention sure would be appreciated.

These are 18650 cells, variously 1200 to 2000 mAh… the recommended maximum charge rate is C/10, so max would be 120 mA to 200 mA. Faster than that shortens cell life… if all eight are in series then over 2.5A draw implies that those batteries are getting cooked. Have I got this wrong?

Can the firmware set a configurable max charging current?

Speaking of the patch (I guess you mean the “delayed charging” patch):

It did help me, but if the batteries are nearly empty, the delayed start of the charging did not resolve the issue reliably on my device…

I currently switch off the screen as a workaround, but I’m already considering getting a different charger…

OK I loaded Reform2 in kicad and had a look at the schematics. The LTC4020 has 0.01 ohm sense resistors, which should be 0.2 amps max current. NEVER MIND my foolishness.

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I have looked into this a bit more. Not with any specific goal in mind, just for fun.

I have a batter bank that shows input and output. It’s probably not terribly accurate, but still fun to watch.

The battery bank has DC input / output, allowing me to use the MeanWell power adapter shipped with the MNT Reform to charge the battery. According to that, the power adapter, although labelled to max power out of 60W, is able to deliver up to 68W.

When attaching the laptop, I don’t use the DC output since I don’t have an matching cable. I use a Type-C to barrel adapter instead.

I have discharged the laptop battery down to 25% and then started running stress-ng to create load and further increase power consumption of the device. I am doing this on the LS1028A, since that one is more power hungry than the stock CPU module.

In this state, when I plug in the MeanWell power adapter, the laptop does not charge. Even if I stop stress-ng it still won’t.

When plugging in my battery bank, the power draw spikes up to 93W for a short moment. It then settles down at just below 80W. So still a good bit more than the MeanWell can deliver, but should be easily handled by a 100W USB-C power brick.

This mirrors my observations. I wrote about this in IRC: 2024-01-19.log

This video shows a power draw of 75 W: https://mister-muffin.de/reform/delayed-charging-usb-pd.webm

I did not take a photo of it but the IRC log also shows me having observed a power draw of 88 W which is close to what you saw.

So the delayed charging patch is nice but it does not fix the situation where the overall power draw is far above what the meanwell adapter is specified to deliver. I have successfully used this 100 W USB-C adapter without any problems since January: https://www.reichelt.de/de/en/-p344620.html

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