Let me get back to you later after I review this further, but I think from the discussion I’m beginning to understand what you’re seeing - but unfortunately, not what’s causing it (root cause). Here’s something to consider for now. If you’re seeing what you indicate, and I understand correctly, your charger is indeed likely overcharging (too high voltage), and I’d recommend you stop using it until you get it sussed out.
It sounds like your charger is indeed charging to an incorrect CV value which is much higher than the correct 3.6V, and is likely exactly what your voltmeter indicates. If it is higher than 3.6V, which it should NOT be by any significant amount, the VP2 will not show the correct value - it will only show 3.6V, although your voltmeter certainly will and apparently does.
The key is this: Go back to your LYGTE link to the test / review, and I think you’ll see why after completion of the charge cycle, what you see on the VP2 display, and what you see if you check the batt voltage w/ your voltmeter do not agree, and it’s apparently because the charger is exceeding the correct CV phase voltage. Here’s the key text:
“The voltmeter has a good precision, when charging it will show slightly above the battery voltage, as expected. Sadly it will not really work above max. charge voltage: it will show one value and then stop updating.”
So, if it’s overcharging (voltage), you will not see it on the VP2 display, but will only see it with your meter. Believe the meter, because it will be the correct value. Good thing you have one, just for situations exactly like this one.
So that only leaves the question of why your charger is charging to CV value approprate for a 3.6/3.7 V chemistry cell (which is 4.2V), instead of the CV value appropriate for your 3.2 V (LFP) chemistry (which is 3.6V). If so, it’s a serious malfunction of the VP2, which is why I recommend not using it at this point.
Given that text from the review (thank you LYGTE), this is starting to make sense to me. It probably means your charger has a fatal problem, which is not good news, but at least it’s making sense.
Is this making sense to you too, or is it just me:-)