I'm afraid of using my 2x18650 flashlight. Should I be afraid?

LED Flashlights – General Info 18650 Flashlights
1

Hi everyone.

I recently received the TrustFire X8 flashlight, which can be used either with 1 or 2 18650 batteries. I’m using 2 SenyBor 2800mAh Protected batteries.
I read some posts on how people should be careful when using multiple lithium batteries, like 2x18650 flashlights and how they can blow up even.
I charged my protected senybor batteries and checked the voltage and it was exactly the same. It seemed to work fine. The next day I tried out the flashlight again with the same batteries and the light flickered a bit. I turned it on and off twice and then it seemed to work fine.

I have no idea how common it is for the batteries to malfunction in flashlights, so I’m kind of nervous and took out the batteries before going to bed. I know this might sound silly to some, but I have no idea what the odds are of things going wrong.

So, should I be this cautious and nervous about using my 2x18650 flashlight? Or is the whole danger of multiple lithium batteries overblown?
Also, when something does go wrong with the batteries in a multiple lithium battery flashlight, what is usually the cause of this happening?

Thanks everyone.

2

Im also as described above. Could any expert please comment. Eager to buy a multi 18650 flashlight.

3

No, don’t be afriad. Also don’t be complacent. Give it the level of respect it deserves and you’ll be OK, but you don’t need to be afraid.

4

They are dangerous if used dangerously. They are safe if used safely. That being said its like getting your car broken into… the one time you let your guard down and leave the door unlocked, or your wallet on the seat thats the one time when something bad happens. You can NEVER let your guard down when it comes to safe charging and safe use.

The most common failures I have seen (and these two account for the overwhelming majority) are:

-Inter-mixing charged with depleted cells in the same light and deep-discharging the cells into polarity reversal.
-Charger / electronics failure combined with the unsafe practice of leaving the cells charging unattended.

Just use your X8, follow safety guidelines and don’t worry about it too much.

5

How big span can charged batteries have?
My batteries stops at 4.22.

  1. Can I safely use a battery that are 3.7v with above newly charged battery?
  2. Should I always let the batteries rest for about 30 min after charge?

Thanks in advance.

6

This is simple, but try just cleaning the threads of your light, my sipik sk68 was flickering, but then I took it apart, cleaned everything(mainly threads) just with some isoproyl alchohol and some cotton swabs and toothpicks. Put it a fresh battery, and it’s never flickered at all now. I think I had put too much silicon lubricant on the threads, and that was the problem.

I am unfamiliar with those cells you have, but usually it’s the flashlight that fails, such as the switch. But first, check the voltages of the cells, unless you used them, they should still be around 4.2 volts. Then, inspect the batteries to make sure they weren’t damaged, check for rips in the plastic casing of the cells, because if that’s ripped, the metal wall of the cell can contact the battery tube, and that’s not good. If that’s ok, put them in the light, then unscrew the tailcap. The tailcap is the switch, and you can substitute that with some aluminum foil connecting the threads to the negative end of the battery. The light should turn on as you remove and reapply the aluminum foil, cycling through the modes like you are clicking the tailcap switch as if it was on and working.

The whole danger of lithium batteries is overblown in my opinion. As long as you don’t damage your cells, and you get a trusted brand of cells, they have the same capacity and voltages, you’ll be fine.

If you don’t trust your cells, another thing to do is check the voltages as the light is running periodically. Say, charge the batteries up to full, then check voltage, then put in light and run for 10 minutes, take them out, check the voltage, and do this 2 or 3 times to be sure the batteries have equal capacity. Because if one battery has a significant difference in capacity, the lower capacity cell’s voltage will drop faster. And then you have a big problem.

Please report back after you have done these if it still isn’t working. Maybe someone else has had this problem with the light. After all it could be something such as a loose wire or something like that.

7

1. You cannot use a signacantly lower voltage cell with a freshly charged cell. It’s best to use very similarly voltaged cells.
2. You don’t have to let the batteries rest also. Scaru said I don’t have to, and I’ve done this probably 10 times, and my cells are still perefectly fine.

I’d like to just pair up freshly charged cells. But I’d think that having a .1 voltage difference would be the max difference I would feel safe with. Also, I wouldn’t say it’s dangerous to let your cells charge up past 4.20 volts, it’s just a little tiny bit determental to the longevity of the battery. There’s a thread that linked nasa’s testing of 18650’s, where they overcharged, overdischarged and use them in pairs and single cells by themselves. Some of the comments will give you some info. NASA blows up a lot of 18650 batteries I’d prefer if you’d take the cells off the charger and test them once in a while and just take them off at 4.20 volts, but it’s no big worry. A big worry is leaving cells on the charger when a charger just trickle charges after it reaches 4.20 volts. Because alot of cheap chargers don’t monitor the voltage when trickle charging, they just give it a little charge very slowly. But if you leave the cells on the charger for several hours after they are done charging, your cells could get up to 4.25 and higher voltage, which is sorta dangerous then, and bad for the batteries health. But really, don’t worry about the 4.22 volts, if it’s 4.3v i’d worry actually. My charger actually charges to 4.21 volts after letting them settle a little.

8

You are fine charging to 4.22V. The cells will settle down a little to ~4.18-.19 after some indeterminate amount of time. This is normal and healthy. Its not really a safety issue at hand. Its more the lifespan and longevity of the cell. Generally the lower you charge the cell, the longer lifespan it will have. I have a hobby charger that I set to terminate at 4.16V. But I have also used an ultrafire WF-139 for 5+ years. It charges to 4.22V and I haven’t noticed any ill-effects of this over a 5-year span. I dont really use the WF-139 that much. I just use it to top off my cells before use.

1. No, NEVER (EVER!) do that. A full charge is 4.15-4.2V. I have harvested cells from laptop packs that measured 3.7V, yet still soaked up ~8-900Ah (at least) when I went to charge them up. Always top off the cells at the same time before using them together. Thats the only way to really ensure they are at equal levels of charge capacity. A depleted cell voltage will “bounce back” and recover V. So you can’t use that as an accurate way to measure the charge-level of a cell when you meter-read a voltage of 3.7.

2. I don’t think thats necessary. I have never seen anything concrete, or data analysis to show there is any benefit in “resting” Lithium cells before use. I mean look at cell phones, i-pads and laptop PCs their Lithium-based cells are in a CONSTANT state of either charge or discharge.

9

Only if you have a morbid fascination with achieving a fiery and oh, so painful death…

Mixing lithium cells that have ANY difference in capacity and state-of-charge is the best way to blow up a light.

10

Thank for great answers and clarifications. Will ofcourse take precations when using multiple batteries, and keep in mind to always check batteries before use.

Recently threw away my xxxxxfire batteries and bought Panasonics instead.

11

Sure np… if they were Ultrafire reds, that was a wise choice. There just too much history of forgery and counterfeiting surrounding these cells for me to recommend them. Panasonic CGRs are my favorites, and countless others have had great results with NCR. They are a smart choice for a light like the X8 which is not going to draw more than ~1.5A from the pair.

12

I’ve always wondered what C is. For example, instead of having a max discharge in amps, they’ll say 1.5C. What is C?

13

unit-less ratio:

Current draw of the application in Amperes / Cell capacity in Ampere-hours

14

Only use cells that are matched. Start with two of the same brand and model charged fully. Measure them to be sure they are the same voltage. Use the light for a while to run it down a bit then take them out and measure again. If they are still the same voltage as each other then they are safe to use together with no worries. If one measures lower than the other then they are not matched and you should try another cell combo together and test the same again until you get a matched pair.

If they are matched then you should relax and not worry. Mark them as a pair you you know which cells they are in the future.

15

I have dozens of 2,3,4 and 6 cell lights that use lithium rechargables. One of the 6 cell lights is a M6 with a Lumens Factory 1000 lumen LA, running 6 AW (red) 16340 IMR’s. Never had any battery failures - yet. Then again, maybe I’m just lucky. I DO pay close attention to the condition of batteries though.