keltex, good ears. I raised the volume and heard the sound but, luckily it doesn’t sound like a baby to me.
OK, so I’m beginning with a simple discharge test. I’ve had my flashlight lit for hours and the battery measures 2.5V now.
I take it, if it has discharge protection it should kick in at any moment now right?
How low can it go before I can confidently conclude that there’s no discharge protection?
As for the charger, I’m leaning towards this LiitoKala Lii 260
What do you think?
Feel for the edge of the protection board at the side of the battery near the negative end. If it’s just solid all the way / no edge than no protection.
Many of the manufacturers utilize 2.5-3.0 for cut-off. IMO that’s for nothing more than supporting exaggerated capacity claims.
Most knowledgeable people don’t recommend going below 3.0v. The more you get under that, the more likely you do permanent damage. Take a look at some of HJK’s discharge graphs > there is essentially nothing left of functional use below 3.0.
So…if you haven’t hit cut-off by 2.5v either the PCB doesn’t work, isn’t there, or something is wrong. I would never go lower than that for any reason.
I don’t know man, here’s a pic (sorry about the quality, my phone’s camera sucks)
The highest cut-off voltage I have seen is 2.5 volt, the lowest is 2.0 volt.
Battery manufacturers often specify 2.5 volt, do you not count them as knowledgeable?
I would be surprised if the over discharge protection trigger above 2.5 volt.
The 2.5 volt is with the battery loaded, when the load is removed the voltage will jump above 3 volt.
I consider them to be knowledgeable. I also think they have an agenda, that agenda being sales, not necessarily more reliable performance from the user for the long term. Of course the spectrum goes from horrible to quite decent. I’m just suspicious. 
In this case……Trustfires. The suspicion is off the charts. 
He said he measured it at 2.5v. I would guess that means he took it out, not under load, so the loaded voltage should have been below 2.5v.
I think you don’t recommend going below 2.8v on general principals. I believe you even use that as a stopping point even if the manufacturer specifies 2.5v. :bigsmile: Am I right?
Thanks for your input HKJ
Looks like it’s going to be painfully slow to get much lower than 2.5V because the flashlight is barely lit at this point.
Is it dangerous to try to discharge like this it to check the protection? I thought this was the easiest, safest way to check if there’s at least some protection built-in.
I probably should stop messing with my batteries until I’ve done some proper reading on the subject
I took it out, correct. I’m now letting it recover.
It was at 2.49V right after that, some 5 minutes later, it’s at 2.52V
But keep in mind the load must have been minimal while lit. The LED was really dim
I’m not sure that follows, isn’t the driver working harder at lower efficiency and producing more heat when trying to push the LED with a low voltage input?
Except not every manufacturers specifies a 2.5v cutoff. And we have no idea who even manufactured this cell in question. When you don’t know the allowed cutoff it’s best to recommend 3.0v, no?
I don’t currently have a second DMM to test load voltage, but the load current is just 3mA in the tail cap
What if I just take this one apart and post pictures?
Any other suggestions on how to check if it’s a safe/properly protected battery please?
OK, the flashlight just shut off.
Now the battery reads 0V, is it dead or what? Does it mean that there’s proper protection built in?
I take it I shouldn’t even try recharging it with a potentially dangerous charger like mine right?
Taking it apart will show if it has a protection circuit or not, but wont show if it is functioning safely.
From your picture of your trustfire it does appear to have a protection board at the tail. The diameter of your battery narrows near the tail end, that is because the battery cell end there and the protection board is slight smaller diameter.
But all protection chips are not created equal. And there have been reports of junk protection chips failing.
Thanks for your input guys
The thing is that something seems to have tripped the battery. The flashlight finally gave up and shut off. The battery now reads zero volts in the DMM
Any relevant conclusion? Is that how discharge protection is supposed to mean or did the battery just die?
EDIT: Apparently it just rose from the dead! It now reads 3V
I’m utterly confused, LOL
0v means the protection “tripped”, cut off the connection to the battery. Putting the battery in a charger usually “resets” the protection. The protection chip reconnects the battery when it sees incoming power (like from most chargers). Note: some chargers will not charge if they can’t detect a battery / it’s been tripped and at 0v. In that case you can reset the protection by manually applying 2 - 3v (with a small amount of current) to it. You can use two alkaline AAA batteries in series to give 3v. Do not use another li-ion, they can supply more current then you should.
The non Fire cells are fine.
The LiitoKala are good also, the new 300 is great.
and if it did not trip by 2.4 well it probably wont.
If you look there is a way to reset the cell (somtimes) but you can also cut the protection circut out and have an un proteced cell (more risky with more risky cells).
**fire are more risky cells