Are Protected Li-ions necessary??

[^Gurthang]

Being new here I've been lurking a great deal, reading reading reading and taking in all the great info. Now I have a question... Is a protected Li-ion cell necessary in a light w/ a regulated driver? From what I've read, some drivers have a LDO [low drop out] voltage point and will abruptly shut off, saving a cell from overdischarging. I understand that a direct-drive light could easily overdischarge a cell. Am I [somewhat] on the right track or have I derailed???

 

[xenonk]

Battery protection is meant as a last line of defense. The first line of defense is your own judgement of when to stop using the battery. This could be from dimming on direct drive or drivers that drop out of regulation at low voltage, or estimation of run time for lights that don't cut off or drop out of regulation soon enough. Even if a driver has a cutoff, it's nice to have an additional failsafe.

Protected batteries aren't necessary. They're just a very, very good idea.

 

[^Gurthang]

Protected batteries aren't necessary. They're just a very, very good idea.

Got it! I'll just pop for the protected cells when I order... Now I just have to decide to buy a RTR light or build something. Thanks

 

[vali]

Using protected li-ion cells is like using your safety belt in your car. For most of the time you shouldnt need it, but if you need it and you dont have it... well, you get the idea.

 

[VidPro]

Using protected li-ion cells is like using your safety belt in your car. For most of the time you shouldnt need it, but if you need it and you dont have it... well, you get the idea.

and if you have to ask WHY there are seat belts in a car :thinking: then you really need them.

(i think the OP actually showed an ability to understand the purpose of protection, so ....)

with direct drive, and white leds , single li-ion type, the led will stop drawing current as the voltage drops, although they still can take the voltage To low. EX: led gate stops triggering at about 2.4V
It is with "BOOST" type of drivers, that are Fully capable of depeletating a cell well beyond the safe low point, and quite harshly too when they are at thier low points. Ex: single cell boost drivers can depleate a cell to below 0.7v

multicell drivers, have various low-cutoff points, and just simply points where they will not further work, because the curcuit in them stops at lower voltages, depending on the voltage, or the Purpose of the cutoff (for primary cells) , the cutoff might not be usefull to protecting li-ion. And, li-ion used in SERIES would want to have protection anyways, cutoff or not, your usual cut-off points will not solution an "out of balance" situation, so the driver (with a cutoff) cannot protect all the cells under all conditions.

 

[^Gurthang]

Thanks to all, I have a much better understanding about protected cells. In my instance I use my light every day for at least 1/2 hr [walking dog] so I'll be recharging cells fairly frequently so its unlikely I'll discharge a cell to its low volt limit.

 

[xenonk]

Note that cell protection applies to charging as well. In fact protection is most crucial during charging, because while over-discharge will ruin a cell and render it useless, overcharging may cause it to explode and catch fire.

A good charger should have built-in cutoff protection, but again it's very nice to have that second safety.

 

[Bullzeyebill]

Treat every LiIon cell like it unprotected, so do not depend on the so called protected circuits built into some LiIons. The best protection is a built in protection circuit in your flashlight that has been tested to be reliable, and/or a very well constructed protection circuit in a battery pack. I use unprotected LiIon cells mostly and monitor, monitor, monitor them.

Bill