Overcharged Protected Li-Ion?

[johnyradio]

Ok, i know you guys are going to laugh at me for even attmpting to do this, but here goes:

i purchased this battery. from a us-based vendor.

http://r.ebay.com/TNTDiK

i checked the battery voltages on delivery. All were about 3.7 volts. Good sign.

i peeled away the base of one of the batteries, and indeed there was a little circuit board, with a conductor running up the side of the battery to the top.

i connected FOUR of these batteries in series. They gave 15.7 volts.

then i connected a 19 volt wall wart to the ends. after 15 minutes the batteries were warm, not hot. i disconnected, and the pack gave over 17 volts! That's too high-- a 4-pack should max at 16.8 V.

i checked each battery-- 3 batteries were under 4.2 V, but one battery measured 4.9 volts!

How could a protected battery charge to 4.9 V?

thx

[pebe]

I hope you did not tamper with the little PCB at the end of the battery. That is there to prevent the cell from being overcharged!

When you say you disconnected, I assume you mean disconnected the wall wart from the mains supply. Then it is probably because the cell is charged and the PCB has cut off the supply to it, and you are reading the volts across the capacitor in the wall wart - less the voltage of the other 3 cells.

Whatever happened to the charger that was the subject of your other thread?

[johnyradio]

because the cell is charged and the PCB has cut off the supply to it, and you are reading the volts across the capacitor in the wall wart - less the voltage of the other 3 cells.

no, i am measuring battery voltage each cell independently, separate from the other cells or the charger.

Whatever happened to the charger that was the subject of your other thread?

i received these batteries and had to test em. If they work, this is my preferred method (instead of a pcb in that other thread).

would be awesome if someone could recommend a reputable source of not-overpriced li-ions.

[pebe]

I cannot account for your over-voltage cell. It doesn't seem to make sense.

The price you paid for 8cells is quite good - I just paid £5 for two of the same make. UltraFire is a good make and they have overcharging protection circuitry built in. There is a lot of cheap rubbish out there, so 'not-overpriced' ones may not be good value for money.

[johnyradio]

ha, the vendor just gave me a full refund, when i asked why it charged past 4.2 v. He said "occasional bad battery!". what the....?

i found this "false plates without any protection function". They are identical to the plates on the bottoms of these batteries.
http://bit.ly/1dfEL0K

Question, can that 4.9V cell explode on the shelf?

[pebe]

You may find this link interesting.
http://www.lygte-info.dk/info/battery%2 ... %20UK.html

If I were you I would discharge the cell with a suitable resistor and then dispose of it.

[johnyradio]

You may find this link interesting.
http://www.lygte-info.dk/info/battery%2 ... %20UK.html

thx! i am familiar with that page, it's very informative. but i dont think it will help me with this problem.