So, just a random thought on this issue. Is it possible that one or two of the balancing resistors could be somehow left enabled when the LPC is shut-down? It could explain how only a small number of cell are being discharged somehow.
It looks like I pushed by Reform a bit too far and one of the batteries now has “reverse voltage”. I am going to see if I can revive it, but am curious how my situation happened as it was while I was using it. I was using the Reform (possibly in a very low charged state due to it being disconnected from the charger) and I was able to boot successfully, but after about a minute, the computer turned off with a “click” (which sounded like something let out magic smoke). There was no smell or smoke, so either that was the audio amplifier getting cut quickly, the battery “going reversed”, or there is some component I should be worried about…
I see there is a Protected Battery Board now available. I understand this board provides “proper” (minimal logic involved) protection for each cell and from this thread, the current charging/balancing circuit on the latest mainboard may not readily allow cell level undervoltage lockout disconnection.
I read that the LPC is responsible for measuring and balancing the cell voltages
It appears the LPC should shut off the SOM if there is a critical undervolt on one or more cells.
There are battery voltages for over/under-volt mentioned here and an older suggestion for these features here.
Given this occurred while I was using the device, is this critical threshold too low and possibly damaging the batteries? (not based on the datasheet excerpt linked above)
Is the LPC not reacting fast enough when powered on?
Did I somehow get an LPC which does not what this critical undervolt shutdown? I have version displayed as 20220621
I cannot tell you if the LPC worked properly but you should not re-use a battery that has seen reverse voltage.
All Lithium-XXX Batteries start to get damaged irreversible below a certain threshold (2V ish) and no Battery likes to get reverse charged.
It will start to chemically change. The electrolyte will start to break down (form gases and may bulge the battery), Lithium will get plated onto the anode, the internal resistance increases and capacity decreases significantly. If you reuse the battery you just make the issue worse.
Best would be to replace it and match all batteries by capacity to avoid reverse polarity.
Reverse polarity normally happens if you use batteries with significant different capacity or damaged cells or no BMS or a system that doesn’t fully cut off the current
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I got the new cells in and everything worked as expected. Took a bit of time to balance them. Of course, then I left the laptop unplugged for a bit and it drained the batteries under 1.7V…
Upon plugging it in, the LPC kept rebooting, but it trickled the batteries back to charging voltages.
Video of the LPC rebooting and slowly bringing up the batteries to voltage.
Has anyone found a good place to buy LiFePO4 18650s in America? Most of my batteries died and I can’t find anywhere to buy them at a reasonable cost :'(.
Unfortunately 18650 battery store has been sold out for a while now. I’ve been able to order cells from Aliexpress, but shipping can take weeks. I got cells last week that I ordered on May 18 from this vendor, for example.