Nokia Lumia 520 problem - some demystification!!!

[Muse]

I now think there's probably nothing wrong with the battery charger described and linked in the OP. I also am thinking that the onset of the problem with the introduction of the charger was just an odd and very unfortunate coincidence. I'd decided to try to work up some charts or graphs to help me to determine the correspondence of charge on the batteries with voltages across the terminals and time needed in the charger to get to target charge levels. To do that I used a digital multimeter to get voltages across the batteries' clips. In so doing I undoubtedly widened those clips to the extent where they made at best so-so contact with the phone's battery studs, ergo the problem.

The last post (mine, #25) with its link to Battery University's li-ion technical page has in depth info. The skinny from my point of view in a nutshell is that most chargers charge to 4.20 volts and call that a full charge. If you charge to only 4.10 volts you will get a 90% charge but get twice as many charges before battery failure. The Battery University page says this:

Most Li-ions are charged to 4.20V/cell and every reduction of 0.10V/cell is said to double cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles (which they say is ~90%); 4.00V/cell should deliver 1,200–2,000 and 3.90V/cell 2,400–4,000 cycles. Table 4 summarizes these results. The values are estimate and depend on the type of li-ion-ion battery.

That tradeoff of 10% of capacity for double the longevity is one I'd like to make. However, commercially available chargers don't give you that option according to the Battery University page. I wish there were an app that would let me do that! It might not be technically possible given the nature of the hardware, I don't know. My workaround generally has been to take something off a complete charge ASAP, thus my hesitation to put my phone on a charger before I go to bed. However, I may start doing that. Prices of li-ion batteries seems to have dropped a great deal in recent years!

 

[Muse]

Oh boy, now I'm not so sure. To make sure of my theory that it was just the battery contacts not making good connections I removed the original battery from the phone and put it in the external charger. The phone had reported the charge level at 82% prior to removal. Before putting in the charger I measured the charge between the 3 terminals, one always gives zero, the other two were 3.53v and 3.92v. After a couple of hours I looked at the charger and it had the blue light signifying full charge. I removed the battery and measured the voltages: 3.51v and 3.90v. Why would they be less? I put the battery in the phone and turned it on and got the battery display indicating low charge of 5%, WTF! I probed the battery clips with a pin to make sure they were making good contact with the phone battery studs and reinserted and turned on. Showed a low battery symbol. I put it on charge, the phone started and the Battery app showed 17% from the getgo. Then the phone turned off by itself and then back on. What's going on? The charger is again suspect. I am having a hard time making heads or tails out of this. ATM, the phone display says "NOKIA" in white letters, nothing else, it's on the charging cable...

I removed that battery (the original), put the OEM replacement in (which had not even turned on the phone after charging in the external charger the first time I used that charger), but this battery + phone were working just fine for a couple of days. So, I figure if they work together fine now I can conclude that the phone is fine, it's just the original battery that's FU now. Indeed phone + OEM battery are acting just like they were when they last parted yesterday. Conclusion: The charger fucks up batteries. I'm going to contact the seller again. I suppose I can get a replacement from them and keep my fingers crossed. The charger and packaging and the seller all appear legit.