When I want to check run times of batteries other than li-on I turn on the light and let it run until the light goes into a moon mode level. I do that with eneloop batteries also.
However, I have the impression that it is either dangerous or will ruin the battery to do that type of test with a li-on battery. So if that is correct how do I determine when the battery is depleted, but not ruined and safe? It is not practical to measure the remaining voltage every 30 minutes for example, and if the light was being used in the field it would not be reasonably possible.
How do I handle a li-on, such as an 18650, so that it can be used to the maximum and not ruined or be dangerous? I have a couple of Ultrafire 501b lights, and realize that they probably do not have the protection of more expensive lights.
Thank you both. I have used the 501b, and it soon is too hot on high, but not so bad on med or low. I do not have top notch batteries, but just Trustfire flames.
I would like to know the practical run times on my lights. In truth I have no use for most of them, and no longer hunt, fish, or camp, but enjoy fooling with them anyway.
jerm03, what do you mean by “moon mode”?
I have the exact same question as you, I am still a begginer with Li-ion, already read all safety stuff but I am not sure how to know when its time to recharge, I am a ocasionaly user, using the flashlights once or twice a week a few minutes… I am waiting for a couple of Panasonic NCR 18650 protected from DX
I am thinking about modding my Keygos M10a and M12 drivers to get some more output from the emitters and also adding that cool low battery warning feature!
Sorry about my english!
A low battery warning driver or a protected cell works good as long as your current draw is some what high say, 1 amp or more. The circuit is reading battery voltage to determine when to trip. The battery voltage sag under the load plays a big part in when the circuit trips. So in high current draw the circuit will trip much sooner keeping the battery in a safe discharge voltage range. In low current draw the battery will not have much sag and could drain the battery well below the recommended cut off voltage.
Its best to measure the cell at rest with a DMM as you use the light to tell just what kind of run time you should have without going below recommended voltage. Usually you will notice a dimming effect towards the end of the discharge (this does depend on the driver circuit). This is a good indication that the cell needs to be charged. The more you use the light you should start to learn its estimated usage before needing charged.
While alot of poeple do use the battery pcb to tell them when the cell needs to be charged. In my opinion it’s not good practice. The pcb was built as a protection for the cell not as stopping point every time its discharged. What happens if the pcb fails.
The flame trustfires I have will trip the pcb at around 2.7v. Under a high load thats fine, the battery will bounce back in voltage when measured at rest. Under a low current draw the battery would be well below the 3.4v recommended cut off voltage.
So using a flashlight with a driver that draws 1 or more amps, I can actually use the PCB as indicator to recharge (but i shouldn’t because it can fail), ok! So avoid using low modes! I think all drivers on xm-l’s draw more than 1 amp on high, right?
Thanks
Most xml led based flashlights on high will draw between 2 and 3 amps.
Its not just because they can fail (very rare occurrence) Its because the battery will be drained well below its recommended low voltage cut off point if the load is not high enough.
Using low mode is fine. I would just not use it until the pcb trips on the battery.
And also as scaru said, be sure and charge the battery up as soon as possible once discharged. Leaving it in a discharged state can cause irreversible cell damage.
Moderator007, wouldn't a buck driver actually cut off prior to the protection tripping? Being optimistic, a 7135 based driver needs .1 above vf in order to run. So if you get a nice extremely low vf (best case scenario) of 2.7, then the battery would need to be at 2.8 volts or more for it to be on. This means that if the protection trips at 2.5 volts (like for NCR18650A batteries) then the protection would never trip.
Hi SolarStorm,
By “moon mode” I mean a light level of something around 1 lm or less. I am sure I am not using the correct terminology, but some lights have a moon mode at which time they keep running, but at a very reduced level of light. That is usable in darkness when our eyes become accustomed to the dark.
I am appreciating the inputs, and learning how to better use lion lights. Here at home I will check the voltage every hour or so or when I can detect a dimming. I have my Hugsby running on low, using a Trustfire flame battery.
Thanks, all.
Thanks for clarifying that! Flashlights should have a digital voltmeter!
I guess I will be using my DMM often. Is it dificult to detect some dimmer when voltage goes under 3,7v?
Your are very welcome. It would be helpful if lights had a DMM. But, I could not figure how to use it. With all this technology someday we might go to the moon.
Actually I was in Korea when we made the first trip. It was exciting, and I watched the TV presentation. Now it is “old hat.”
Here in NM Virgin Galactic is supposed to take passengers on a space flight. I think 400 people or so have signed up for $200,000 (£121,000) to experience approximately six minutes of weightlessness during what will be a two-hour end-to-end flight.
I am not booking for anyone if you were thinking of calling me.
A buck driver takes the extra voltage and converts it to current. The higher the voltage over the output the less the current draw from the batteries. So if the buck driver was in low mode at a 100ma output with two li-ions the cells would only be drawing close to half the output, around 50ma. If the cells were at 3v each the buck driver could still operate correctly with a 6v input. A xml at 100ma would have some where around a 2.65vf according to the datasheet.
You are correct with the panasonics lower cut off voltage. Using the newer panasonic’s would pretty well insure their never over discharged with some type of protection circuit around 2.75v. But they do need to be charged up as soon as possible.
With the newer panasonics you are correct. When you added up the total voltage losses including the overhead for the amc7135 driver The led would probably cut off before the pcb tripped. I guess it would depend also on which panasonic reseller you purchased from. The pcb cut off voltage is different with some resellers. They dont all use the same pcb.
I guess I should have been more specific too. :zipper_mouth_face: I was refering more towards your normal budget type li-ion such as trustfire. The newer pansonics have a lower recommended max discharge voltage of 2.5v. The general rule for li-ions that I am aware of is cell is dead at 3.4v measured at rest. This again depends on the cell used.
Yeah, that's true. For anyone wondering HKJ did some great test on this subject, so if he tested your battery you can find approximate capacity left if you know the unloaded voltage.
Credit to HKJ
It always surprises me that NCR18650B only have 442 mah left at 3.4 volts and 102 mah at 3.3.
Heres is what i suggest, determine the battery capacity and the current draw of the light, then aim to use the light about 75% to empty then recharge. If your not sure how long you’ve run the light , say a few mins here and there over a few weeks then pull out the battery and check the voltage, 3.6V is empty, 3.8 is about 40%
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I was talking about a linear driver where the extra voltage is burned off as heat. E.g. 7135 based drivers. 