Samsung Galaxy Fold Z2 Battery Dropping to Zero from 50%

Hey fourm, sorry for the long read but if anyone is technically savvy with batteries or voltages/electrical components please read! this might not be specific to a Fold but any device may suffer from what my device is suffering from.

I have recently had issues with my Galaxy Fold Z2 and it unexpectedly dropping to 0% charge, the first time this happened yesterday i was in an application and was switching from the larger display into the smaller one, upon closing the display the phone shut down and i wasn't able to get anylife out of the phone except a vibration when holding the power button, but nothing on the screen. I had about 35% battery at the time but all of a sudden it was at 0, after putting it on the charger it spring back into life. Today however i experienced an even worse problem… My battery was around 55% and i was connecting my phone to my cars bluetooth and importing contacts to the cars console, suddenly the battery went from 55% down to 9% instantly! i was shocked and took a screenshot of the battery graph showing its gradual decline from 100% to 55% but not to 9% to highlight the sudden drop, the battery status on the top of the notification bar was showing 9% all of a sudden but the graph wasnt just to actually see the drop! after that drop in battery it only took about a 30 seconds for that 9% of battery to jump down to 1% again in an instant fashion, following this only a few seconds later it shut down.I was thinking it could just be a dodgy battery for whatever reason but after trying to charge my phone after this sudden crash from 55%-9%-Flat i was unable to charge it up. The phone would signify that it was charging but not giving me a percentage, it would show the charging animation (the animation you get when phone is off and charging) but would only last for around 3-5 seconds before shutting off again and showing the charging icon again, and then shutting off again and rinse and repeat on a loop without charging but attempting too and resetting every few seconds! So for about an hour i couldnt get it to boot/charger properly and i almost gave up, but i decided to try a different charger, i was using the 25w supplied charger but i switched to a 15w older one and the phone ran the charge animation again however this time it identified the battery was charged at 55% rather that it not showing any charge level and resetting and trying again as it did before, this time it went right to 55% and from here the phone booted up and is working normally again!

Im really not sure whats wrong, im starting a process to send the phone back but i really wish to know whats wrong with my device and make sure its also covered by consumer law! if anyone has any clue to this strange behaviour please let me know!


  • needs paragraphing

  • disclaimer: not an electrical engineer

    your battery is faulty and cannot reliably output a voltage that your phone expects to see. Let us assume that your phone constantly requires 3.8v, and the cut-off voltage is (also assumed) to be 3.0 volts.

    When you wake the phone up from sleep it pulls more power from the battery but because the battery is faulty, there is a voltage sag and it couldn't output the correct voltage for a brief moment. If the voltage sag is bad enough — the phone shuts down because the electronics inside your phone isn't designed to operate below 3.0v.

    (They also do this to protect the battery because if you discharge lithium cells to under 3 volts, you end up causing a bunch of unwanted chemical reactions in the battery that will permanently damage it.)

    Your phone's battery management system (or BMS) sees a sudden drop of voltage as either a symptom of an uncharged or near-dead battery and updates the battery percentage to what it thinks the current power level is.

    • Oh wow thats very insightful! Thank you, i do hope this is the cause as its an easy fix and hopefully covered! I didnt notice any battery swelling however but maybe due to the ridgid chassis, however i do hope its just the battery as you described!

  • Yeah sounds like a battery issue

  • Galaxy Fold Z2 Battery Dropping to Zero from 50%

    Screen size also instantly drops 50% when folding..

  • The BMS in new phones sometimes need to be calibrated by fully charging and discharging to near flat a few times. Keep using your phone and see if this problem disappears after two weeks. If it doesn't, send the phone in for warranty as the battery is faulty.

    Small chance that the charger is faulty but unlikely.

  • Fun Fact, the Z Fold 2 actually has 2 batteries instead of one

    From the sound of things, as you are folding and unfolding it, the connection to one of the batteries is getting cut somehow, which easily explains the sudden and instant loss of 50% of your battery.

    Definitely a warranty thing at this point. Good luck mate, love those phones, sorry you're having issues.