How safe is a single 18650 flashlights

For storage , aim at 3.8 3.9volts . the 10440 is a little low @ 3.66v but nothing critical , but I would charge it back to 3.8v if storing it ..

Otherwise , looks fine

Thanks a lot for the Reply's, maybe I really shouldn't be concerned in using 18650 lights even during extensive usage. Learning a lot this few days and now using a multimeter to test my batteries.

Hmmm, another Qs, does it affect battery life if I charge the batteries before they are at 3.5v maybe 3.8v?

Abuse of batteries usually happen when going to camping/hiking trips where in at times I tend to charge my stored batteries before the trip to have max voltage and drain them during the trip to maximize batteries as I usually bring only a spare for my 18650 lights, got several spares for my headlamp and other flashlights powered by AAs.

In theory in anyway , should last longer [ cell integrity ]

you must not own a dell then,lol - I believe there were a few lap top fires from dell laptops. You are right though we do abuse batteries in laptops and don't worry about them.

My company uses Dell system exclusively! So far, I have never experienced a <poof> moment...

I didn't take any empirical tests on mine, but frequency doesn't look very good. Very noticeable trail even when moved slowly. The other problem with the light is that there's no regulation at all, and output quickly drops. Perhaps worth it for the good build quality if you can it for the low price some of us gotten them for on ebay, but IMO not the best light.

You can look for older threads where this was discussed in more detail, but single cells are pretty safe. Almost all the "explosions" publicly known (esp. in our hobby) are from multiple cells, probably when cells in drastically different states of charge are used together.

The battery manufacturers will insist on correcting you – lithium batteries never “explode”, they “vent with flame”…
(Yes, that’s their official terminology)

I feel completely safe using any one cell light of any type... When I go multi-cell I try to use LiFePo4s or LiMns... I'll occasionally trust LiCos in pairs or more even as long as they're protected and I check them all first (Also, when I buy cheap batteries I usually buy a dozen or so at a time, charge and test them all, then pair, triple, or quad them up depending on equality of ratings). I'm lucky enough to have never had a full blown incident, but I've always checked my lithium batteries before using multi-cell setups.


Not really a Dell issue. It was a bad batch of packs made for them by Sony. It was a case of one companies f*** up affecting another's reputation (remember firestone after fords f*** up with the explorer recommended tire pressure?).

Dell being a household name and one of the (if not THE) largest mfgrs of laptops, they happened to sell many packs with the faulty cells (or charging circuits, I can't remember). Everyone remembers dell laptop fires, not that it was sony' packs that went poof. I remember having to go through every battery pack in my company and cross reference its number against the recall list.

Apologies to dell. Damn Sony. I'm not sure what the problem was but there were fires. My toshiba laptop battery just died. 5 years old and almost always plugged in. Not too bad. The batteries are sanyo's and the lowest was 3.2 v highest 3.8v.

The Sony lithium-ion batteries were placed in laptops shipped between April 2004 and July 2006.

They were included in some models of Dell's Latitude, Inspiron, XPS and Precision mobile workstation notebooks.

"In rare cases, a short-circuit could cause the battery to overheat, causing a risk of smoke and or fire," said Dell spokesman Ira Williams.

"It happens in rare cases but we opted to take this broad action immediately."

Dell has already launched a website - - telling customers how to get a free replacement battery.

No injuries had been linked to Dell laptops with defective batteries, the company told Reuters news agency.

The CPSC has identified 339 incidents in which lithium batteries used in laptops and cell phones - not just Dell products - overheated between 2003 and 2005.

Some incidents involved minor skin burns or actual injuries as well as property damage, Mr Wolfson said.

Check the voltage after you charge and have a good look at it. I would watch it while it is charging too. Actually I would dispose of it I think. Its a pretty average battery to start with.

Might be. Seemed to charge very quickly. Leave it overnight (off the charger) and test it to see if it holds a charge.

I don't know your charger specifically, but I find mine will charge quickly until around the 4V mark and then slowly creep to the finish line at 4.18/4.19V. Battery experts please correct me if I am wrong, but I am pretty sure the slow down is from changing from CC protocol to CV protocol in the charging sequence.

I check the voltage on mine regularly while charging (and have the charger in a steel pot with the lid next to it) to make sure that the charging slows as it gets closer to completion. I also am checking the temperature of the battery regularly, I guess I don't fully trust DX electronics.