BATTERIES - Selecting the Proper Battery for your 365nm UV Flashlight, Convoy S2, Convoy C8, FyrFly


This GlowNotes post is compiled from a post in our Fluorescent Mineral Facebook Group. Several folks added some great information about a frequently recurring question to a PSA battery post I made. Archived here for future reference.

Be very careful - there's a lot of junk coming from China, much of it counterfeit, much of it fake. 18650 and CR123 batteries are a ripe area for this fakery. One company in our hobby is (was, I hope) selling yellow Etsair 9900mah batteries) along with a new light they area selling. This battery is not only fake, it's outright dangerous. Available on Ebay for $2/ea (much less in quantity) the specs are an outright lie; 9900mah is a ridiculous claim. These types of batteries can overdischarge, overheat, and burn. I would NEVER bring this battery on a plane. Lots of websites will help you spot a fake:

Buy only from trusted dealers and manufacturers. Midnight Minerals and Engenious Designs both sell batteries for their lights, and are very knowledgeable in the area. Be very wary of batteries on Ebay, batteries over 3500mah, and cheap prices. Panasonic, Orbtronic, Sanyo, EBL, are some of the trusted brands.

A quote from EEVblog Electronics Community Forum:

"In general, the Ah capacity of batteries sold from China are not worth the plastic they are printed on. The vendors/manufacturers lie so they can get you to click on buying theirs over some other fraudster's batteries. Best to buy genuine Sanyo Eneloop or genuine Panasonics. Problem is the Chinese are so good at pirating the genuine article you cannot tell the difference from the outside. This is particularly the case with mobile and cordless phone replacement batteries. There are many "Genuine" Samsung batteries (complete with barcode or hologram) that are just fakes, imported from China and sold locally via eBay. If you want to eliminate the risk, buy from a reputable dealer in your country, not from eBay. Most of the torches sold on eBay from China are also rubbish. They don't last very long. Best to pay more for a reputable brand from a reputable retailer. Years ago retail stores sold boom boxes (AM/FM cassette stereos you carted on your shoulder) that boasted "20,000 mW of Peak Power!". One I saw stated something like "1,000,000 uW power output" on a cheap no-name cassette stereo! They were marketing to the ignorant masses. The manufacturers did not lie, just exploited non-technical people by making the numbers look good. With the 9900 mAh batteries they not only marketing to the ignorant masses, they are straight out lying. In the end you get what you pay for."

Members of our group posted recommendations based on their experience. These can be a great starting point in selecting a good battery for your flashlight. Be very aware that name brand batteries are often counterfeits - the best protection is buying from a reputable vendor. Ebay is NOT a reputable vendor. There are of course many reputable sellers on Ebay - just make sure you know who they are.

Much of the discussion below is centered around 18650 batteries, but they all also apply to the shorter RCR123 batteries (rechargeable CR123's) which are used in the Convoy C8 FyrFly (my preferred size - I just like a short flashlight). Two sections archive the general information posts, with specific battery recommnedations below that

General Information (poster names removed, no particular order)

  • So what's the moral of this story? Frankly, you can take the capacity ratings on the cells with a grain of salt. As a matter of fact, some of the good cells label their part numbers and other data and don't put mAh capacity ratings on them. They know how to print the fakes ones the same way. Put a cell on a scale. "Generally", I find the weight of the cell is proportional to the measured specs I get on cells I look at. Your good name brands are going to be on the heavier side, the mid-grade "fakes" are going to be in the middle and the real junk cells are usually lighter. Just an observation. So I would say there are sort of three classes of these cells. Ones that are downright underpowered and dangerous, there are some mid-grade average cells with labels that are all lies, then higher performers with higher capacities and some with or without protection. I don't run a battery test lab by any means. But I do check everything I receive in to ensure reliability as I receive it. If the battery is feather light and it heats up on a charger like a bagel in a toaster, DON'T RUN IT IN A UV FLASHLIGHT!!!!! And don't charge it again! Properly discard it!

  • There's a guy that does battery testing that i always check before buying a new cell.

  • There is no such thing as a 9800mah 18650 battery. At best, your batteries are just lies. At worst they can explode if shorted out, or improperly charged/discharged How long they will last depends on what kind of Convoy you have (the first version draws under 700ma and will last the longest). But "last" doesn't mean the light is putting out full brightness. As t