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How To Rechargeable Flashlights

Discussion in 'Gadgets & Gear' started by mdauben, May 9, 2019.

  1. mdauben


    Oct 24, 2005
    I did a search of this forum, and did not find much on rechargeable flash lights, and nothing very recent.

    I had my bedside flashlight crap out on my recently, so I'm looking to replace it. I see a lot of rechargeable flashlights when I look and I'm wondering about them. One of the problems I had with flashlights over the years was the tendency for alkaline batteries to corrode the inside of my flashlights (that's what happened to my current flash).

    The new unit I'm looking at uses a 18650 Rechargeable Li-ion battery. Are Li-ion batteries subject to the same corrosion problem as alkalines? My bedside flash may sit unused for months at a time, should I leave it on charge, or charge it up on some sort of regular schedule, or will it hold a change long term? Any other tips for the care and feeding of a rechargeable flash?

  2. eveled

    eveled Gold Member Gold Member

    Mar 11, 2016
    I use a Milwaukee rechargeable light. It gets charged with a USB cord. It’s a nice light. It does not hold a charge for months at a time. Model 2110-21.

    I have another larger Milwaukee light that uses the 12 volt battery from a drill. THIS IS THE ONE THAT IS ON MY NIGHTSTAND. It holds a charge for a very long time. Model 2355-20.

    I also have the 18 volt search light. It’s awesome too I use this one as a work light leaving it on flood mode for hours. It will light up an entire cellar. Model 2354-20

    I have a couple of the rechargeable head lamps 2111-21. I couldn’t get by without them. I have one around my neck all day everyday.

    Here are all the Milwaukee lights. I’ve used a bunch of them at work. They are all awesome.

    Last edited: May 9, 2019
    mdauben likes this.
  3. DocJD


    Jan 29, 2016
    Rest assured , invest in the better quality hi capacity 18650 batteries and you will be rewarded . Very low "self discharge " rate and they should last for years .

    You don't have to keep them on a charger . A good smart charger made for Li-ion will help your batteries have a longer service life . Slow charging is best . Overheating in fast discharging (use) and fast charging is what shortens battery life most .
    mdauben likes this.
  4. Bruceter

    Bruceter Gold Member Gold Member

    May 19, 2000
    I have a couple of Olight flashlights that use rechargeable 18650 batteries. They both recharge with a USB cable that connects magnetically to the tail cap, no need to remove the battery for charging. They seem to hold a charge well and I have had no leakage problems. I top mine up every couple of months or so.

    HwangJino and mdauben like this.
  5. bdmicarta

    bdmicarta Gold Member Gold Member

    Feb 16, 2012
    Lithium single use batteries and Lithium-Ion rechargeable are not prone to leaking like Alkaline batteries are. (Among Alkaline batteries my experience is that Duracells are much more likely to leak than other brands so just using a better brand might be the solution to your problem.) Lithium single use batteries are said to have 10 year shelf life so they would work well for bedside. If you don't use the light that much then no need to go with the expense of rechargeable. Plus if you are using the light and the battery is low then you can just put in another batter rather than plugging it in and waiting hours for it to charge. Nevertheless rechargeable Lithium-Ion batteries also last a long time without needing recharging so they would work well at bedside too.

    I carry a Fenix PD25 every day and it has proven to be very reliable. It uses a single Lithium battery and the battery lasts a long time. I have a Fenix PD32 that I carry in my briefcase but I would like to replace it with a PD35 with rechargeable 18650 battery, so I don't have a prejudice against either kind of battery.
    mdauben and metaxasm like this.
  6. Scott321


    Jul 20, 2016
    I think the corrosion issue is related to the alkaline. However, did you try the lithium disposable batteries?

    I have a few flashlights that are rechargable by USB cord. I also have flashlights that take Li rechargable batteries which I remove and place on the charger periodically.

    Flashlights with a built in charger add bulk. My rechargeable flashlights come from Fenix and Nitecore. However, I use odd sized Li rechargable batteries in my EDC light (Eagletac Clicky) and in my SF Tactician.

    IMO, for safety, if you are using rechargable Li batteries in your flashlights, get ones that only take a single battery.
  7. SpyderPhreak

    SpyderPhreak Rocketman for hire Platinum Member

    Apr 13, 2004
    DocJD likes this.
  8. mdauben


    Oct 24, 2005
    Good to know. Unfortunately, my current night stand flashlight is already ruined by the corroding alkaline battery in it so I have to buy a new flash in any case.

    Thanks to everyone who offered some advice!
  9. K.O.D.

    K.O.D. Banned Platinum Member

    Aug 21, 2013
    Late to the game, but I have a Nightcore MH10, which uses a single 18650 lithium ion battery or two CR123. I keep it in my EDC bag. Great light and it has a micro USB port on it for charging.

    It's a small bag, but it stays on my nightstand. Also on my nightstand is a copper Olight I3E EOS. It takes a single AAA. Mine came with a rubbery, plastic lanyard, and I wear it around my neck at night, as I have night vision issues. I use it every night. Burns through the cheap batteries fast, but the Energizer lithium batteries work well. It's plenty bright.
  10. indischI

    indischI Gold Member Gold Member

    Oct 19, 2014
    The Fenix lights I have used daily for years are highly reliable and well built. I agree the 18650 battery is the way to go. I got sick of alkaline batteries ruining good stuff and fighting with companies like Duracell to make good on their guarantee. Another alternative that lends itself to low use flashlights (like emergency use in a car) are Enloop Ni-MH rechargeables. They loose very little of their charge when not in use so you can rely on them to work when you need them. And no leaking problems.
  11. bikerector

    bikerector Gold Member Gold Member

    Nov 16, 2016
    I don't think I've had issues with any rechargeable lights in the last 10 years or so that I've been using them. Li-ion are much nicer and usually last a lot more charge cycle than NiMh. I've gone through quite a plethora of lighting options on bicycles and rechargeable is quite convenient if the light will see a lot of use and the run time is sufficient for the task or swapping batteries is simple.
  12. KNelson


    Jan 9, 2019
    I love my Olight S1r Baton II, magnetic recharge so no unthreading anything. bright settings and run times are good!
  13. 22-rimfire

    22-rimfire Gold Member Gold Member

    Nov 20, 2005
    I have a lot of flashlights and leaking alkaline batteries are a huge problem because I don't pay attention to them. Best to check them and use them periodically. Just bought a Nitecore 920 lumens with rechargable battery via a micro usb connection. Hoping this one lasts. It was purposefully purchased to go with my day hike kit.

    If you want to stick with alkaline batteries, I would suggest you consider a C sized one for the night stand. They don't seem to leak like the AA and AAA alkalines do.
    Last edited: Jun 11, 2019 at 5:41 PM
  14. bdmicarta

    bdmicarta Gold Member Gold Member

    Feb 16, 2012
    I've seen 18650 batteries that you flip the end up and plug in a USB cord to recharge. I wonder if these are as good as the 18650 batteries that you place into a separate charger.
  15. MatthewSB

    MatthewSB Gold Member Gold Member

    Feb 1, 2013
    Alkalines cause corrosion because they can release corrosive gas due to the materials used in the battery. I wouldn't recommend using them in anything you care about.

    Rechargeable lithium ion 18650 cells make up most of the battery packs (the 18650 tubes are arranged in a series inside of the pack) that you use for power tools, laptop computers, etc. 18650 batteries can be safe, or not, depending on who made them and how they are used.

    There are "protected" and "unprotected" cells. Unprotected cells can be shorted out easier causing an explosion or fire. Protected cells have a gadget inside the wrap that manages how quickly power can go into or out of the battery, but the protection gizmo makes the battery very slightly longer and they don't fit in all lights. Protected cells sometimes won't work in the most powerful lights because they have limited output (how they stop from over-discharging during a short) although they should work in anything that isn't ridiculously demanding.

    Many of the 18650 batteries you see on ebay are old junk removed from 'recycled' battery packs and can be dangerous and unpredictable. Many of the name-branded 18650 are cheap cells of questionable quality. I highly recommend buying high powered batteries from a reputable company. I use and recommend Orbtronic 18650 batteries, the ones I bought are Japanese cores with Japanese protection circuits.

    In order to avoid a short situation with high powered batteries never carry or store them loose. The best carriers have threaded caps that fully enclose the battery and protect it from submersion without taking up much additional space. I use carriers from CountyComm and Oveready.

    18650 batteries don't do well in heat, do not leave them out in a hot car. They also slowly degrade over time regardless of how you care for them, so plan on replacing them every 5 years or so but they can last longer. They degrade faster if left fully charged so I store mine at 3.4V except for the battery in my EDC light and a spare that I keep in a fully enclosed carrier.

    There are all kinds of chargers, from cheap to expensive, simple to elaborate. I recommend spending enough ($30 or so) to get one that measures capacity (to monitor degradation) as well as voltage. Then get an inexpensive single cell charger (like the XTAR MC1Plus) for travel.

    I hope this helps.

    Edited to Add: Like someone else said, if you're fine with AA and AAA power levels you can use nimh AA and AAA rechargeables, they're way easier to use and a lot less to worry about. Eneloop brand used Japanese cells the last I checked. I believe they do better in heat and don't degrade as much over time, but you'd have to do the research to confirm. You can get a 4 pack of Eneloop AA or AAA with a smart charger for $15-20
    Last edited: Jun 12, 2019 at 2:07 PM
    DocJD likes this.
  16. K.O.D.

    K.O.D. Banned Platinum Member

    Aug 21, 2013
    I just switched from disposable alkaline AAA to Energizer lithium for my Olight I3E EOS copper. Major difference in both longevity and brightness. I always used them in my camera, they are great.

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