Is it safe to let the protection kick in on a normal basis for low voltage on 18650? Or could this create a fire hazard?
I want to give a co worker an s2+ and a Samsung pink protected battery. He is not very tech savvy. I was thinking about giving a litkala l 100 charger to
In theory yes. Although if there is a finite number of times the protection circuit can be triggered, then I’m not certain, but suspect maybe.
The only real issue is, the protection circuit is almost a last resort, I personally very rarely discharge batteries that low.
In all honesty, if they aren’t prepared to learn a little about li-ion and how to use them safely, then they should stick to NiMh and primaries.
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I do not think that protection is going to wear out… it is a series of active parts, not mechanical parts. But, you are trusting that it is not taking the batteries down to low.
I recharge before I see my lights dim significantly. Except for my armytek wizard I end up re charging around 3.30 volts because it stays 100% bright on turbo until about that range o f 3.30 volts
Is it safe to see a noticeable dimming in output before charging? Or is that damaging the cells? I have never had a cell protection kick in, but I use mostly unprotected cells.
Generally, with a linear driver and a single 4.2v lion yes, it is safe. When you will notice dimming definitely depends on the driver, the drive current, the led, and to a lesser extent the battery. Some Cree LED’s have forward voltages as high as ~3.7 volts at high drive currents and there is also some voltage drop through the driver. When the cell gets below the voltage required to keep the output “in regulation” you’ll probably start noticing a reduction in output. Panasonic cells (like the NCR18650B) can safely be drained to a minimum level of 2.5 volts, other manufacturers recommend termination at 2.8v or so with their cells. There are LED’s like the Nichia 219C that have a very low forward voltage, like ~3.3 volts at 3 amps. You’d still notice a reduction in output on HIGH when the battery was sub 3v though I’m sure, although if the driver only ever drove the LED at 350mA… or you generally only operated it in a low mode, well then you might not notice dimming until the battery was very low.
That said, I have a FourSevens mini MLR2 (XP-G2) that I EDC with an RCR CR2 (15266) in it, which isn’t recommended by 47’s but works fine and is super bright compared to primaries. It will however drain the battery to sub 2v, which I’ve done a few times without noticing all too much until the light refuses to change from medium to high mode. It probably has a “buck-boost” driver in it. I “revived” the battery with a 100mA charge which is as low as my RC charger goes. Still using the cell. :-x
Years ago the RC and flashlight community used to be very cautious and recommend discharge levels only down to 3.4v and such, but now adays no one is too concerned with draining down to 2.8v or even 2.5v depending on the cell. I tend to keep my EDC cells pretty topped off though just for maximum output and capacity.
So they are a bit more robust than we treat them. I have some panasonics just because I’ve read that they can be discharged lower than others without damage
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I’d say the risk of anything catastrophic happening for a single cell overdischarging (besides permanently damaging the battery) is reasonably low.
However, I wouldn’t say the same for the charging process. That’s where safe practices are needed to ensure someone’s house doesn’t burn down. If the new user isn’t willing to learn how to recharge his battery safely, I’d suggest sticking to NiMH or primaries as Chicken Drumstick said.