I have read that it is important not to over-discharge lithium-ion batteries, and to use a Digital MultiMeter to check the voltage, so I bought a DMM in Maplin yesterday; this one:
Early last year, I bought an Ultrafire Protected 3000mAh Lithium-Ion 18650 from Ultrafire Shop:
I have cycled the 18650 about 12 or 15 times since then; takes about 6 hours to charge, and about 4.5 hours to discharge completely (to the point where the LEDs stop producing any light) on an Ultrafire 210 Lumens 501b and about 6 hours and 7 hours on two separate G&R 210 Lumen red green and white LED flashlights.
So, yesterday, I charged the 18650 for about 2 hours and 30 minutes, shoved it into a G&R, and it worked fine. Then, I tested the voltage and the amperage with the DMM. After several attempts (I have no previous experience of DMMs) I got one voltage reading of 3.56 / 3.54 which seemed likely correct. I can’t remember what the Amp readings were, but a couple of them indicated error readings, that I was doing something wrong.
After finishing with the DMM readings, I re-inserted the 18650 into one of the G&Rs. Nothing happened when I switched on the torch. I tried again with the other G&R….nothing. Then I tried the 501B. Nothing.
I tried to recharge for about 5 hours on the WF-188 charger, checking the 18650’s temperature every 15 minutes or so. No good.
Did I short-circuit without knowing it? What did I likely do wrong?
in a proper DMM it should blow the fuse… but if you don’t have a voltage reading anymore, probably the cell protection circuit is in the PCB heaven…
the amp meter measures the current running through the dmm, closing the circuit. if you use only the DMM in the cell without a load, you are making a short circuit. you need to use some load in parallel (normally the flashlight in our cases)
probably your DMM has also a fuse inside. If you made that short-circuit, it can be blown. It depend on the PCB burning time
if it burned very fast, probably the fuse is still alive inside the DMM, but if not, the fuse should give you the protection against a nice explosion in front of your nose. (edit 2… well, maybe this is a bit of a exaggeration, i suppose the explosion wont be very big, but i don’t want to try)
open the DMM and check the fuse, its maybe blown too
edit: your cell can still be used if you remove the PCB, using it as a non protected cell, but remember to be careful….
It’s probably still good. You just have to reset the protection circuit. Scaru posted some insctructions here on how to do it, but I’m too lazy to hunt them down at the moment.
No, normally they have two separate channels to measure current and the other readings (and also two fuses)
if you need to change the red probe possition to measure current, it means it uses separate circuits. in this case, the fuse of the current measurement circuit can be gone, and the other is perfect.
If you don’t need to change the position, or if you have only two holes to connect the probes, it can have those two circuits or not. i cant tell you how to check without opening (well, yes, you can measure continuity between the probes in the current measurement mode using another DMM, but i assume you have only one )
The protection circuit probably cut off at a lower current than the fuse would have blown at. Just reset the protection circuit and you’ll be good to go.
I really do hate seeing threads like this though… Lithium Cells are not toys. If you don’t know what you’re doing - its probably not a smart move to be connecting wires across them. Please everyone - being safe means being well-informed. If you don’t know what you’re doing (and thinking you can read current/amps by connecting a DMM directly across a LiIon battery means you don’t know what you’re doing) then stop and learn first.
I’m sorry to come across so strongly, but really, this is safety. Connecting random wires across a (especially unprotected) LiIon cell can lead to very bad things happening.
To reset the protection circuit - most controllers require a modestly high voltage (4.2-4.5V) be applied to the cell terminals. Since the cell is ‘shut-off’ by the protection circuit, most chargers won’t “see” the battery, and therefor won’t attempt to charge it.
For a good number of protection circuits, one of the easiest ways to reset them is to connect a fully charged good cell to the tripped cell (+ to +, - to -) for a quick second. This will reset the protection circuit in most cases.
I was thinking this after i wrote my last post. I was able to reset some new PCB I installed just putting them in the charger, but of course it depends of the controller and charger.
501 sea, if you try to reset it with other battery, be sure to connect + with + and - with -. we don’t wont to make it worst
Because I wanted to find out how powerful or poor the cell was in terms of delivering power…I guess I was sort of taking the cell’s specifications. I was basicially just testing the battery to see what it could do, and if it’s readings were normal.
