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Thread: Why do I have to disassemble my flashlight to change the batteries?

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    *Flashaholic* fyrstormer's Avatar
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    Default Why do I have to disassemble my flashlight to change the batteries?

    I was just fiddling with my TC-R2, taking it apart, admiring the nice brass threading, checking the battery to see if the switch spring is chewing into the battery casing, etc. And then I dropped the head, getting oil on my shirt. That got me thinking, why are so many flashlights based on the design of a tripartite or bipartite cylinder that has to be disassembled to change the batteries? That would be like having to remove the gas tank from a car in order to fill it, or having to remove the oil pan to change the oil.

    One might say that devices which need to be refilled with liquids have an easier time of it, because the liquid can be poured through a small hole, whereas a solid battery has to be removed as a single piece, and that is a fair point; the comparison to filling the gas tank or changing the oil is just the first comparison that came to mind, and is almost certainly not the most accurate. However, flashlights are the only devices I can think of that require the device to be disassembled to replace what is intended to be a modular power source. (nuclear reactors also come to mind, but sadly, I can't snag those at Best Buy yet.)

    Yes, some electronic devices have permanently-integrated batteries, but they are different because replacing the battery requires soldering, not just dropping in a new battery once the device is laying in pieces on the workbench. That is not the same paradigm as a device that uses self-contained batteries that maintain electrical connectivity through "casual contact" alone.

    Devices that are designed to use replaceable batteries, such as remote controls and Walkmans, generally allow access to the battery via a removable cover that provides no structural support at all, and the device can be operated without the cover if necessary. Whereas, if I need to change the battery in my flashlight in the middle of the woods, I could easily end up dropping and losing a critical piece of the light, rendering it useless.

    Assembling the flashlight around the battery, instead of inserting the battery into a fully-assembled flashlight, seems like an outmoded design paradigm left over from when flashlights were simple tin or brass tubes fashioned from household parts, with a bulb and a reflector attached at one end. Given all the innovation that has occurred in the past few years, it seems odd that this one feature has gone un-addressed by almost everyone. Even the Cool Fall SPY, which is the most unconventional flashlight I can think of in every other respect, still integrates an electrical contact into the tailcap, rendering the light useless if the tailcap is lost or the spring somehow falls out.

    So I'm curious, why does CPF think this design paradigm has persisted? Is there an overwhelmingly good reason, does nobody care, are there no other feasible ideas, or perhaps all of the above?
    Last edited by fyrstormer; 07-16-2012 at 02:31 PM.

  2. #2

    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    There are several lights that can charge through a port or through inductive fields. It all comes down to cost. Batteries need to be cheap for flashlights to work (like cheap gas for a car). No one wants to buy a $10 battery everytime their light goes dead. Screwing down a cap also adds to water resistance as well. Laptops with removable batteries don't tend to get dunked in water too often... But you knew all that already. Made you should commission a project?
    My Lights: Arc Flashlight Arc6 http://www.candlepowerforums.com/vb/showthread.php?336795-Arc6-Upgrades-Mods-Thread!-Post-your-thoughts-and-mods-here!]You do it like this[/url], Ultrafire C3, Nextorch K1

  3. #3

    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    I've been chatting with a lot of CNC shops lately and their advice has always been the same.

    "See this shoulder? $5 more per unit"
    "This second set of threads? $7 more per unit"

    Maybe someday there will be a light in the Cool Spy price range that changes how the batteries are loaded. When that happens, I imagine I'll get to spend 5 minutes explaining how to change the batteries, very much like how everyone I hand my HDS Clicky to tries to twist the head like a MagLite.

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    *Flashaholic* fyrstormer's Avatar
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    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    Valid points, but I'm not thinking about high-priced custom-made metal flashlights. Even the cheesy rectangular plastic flashlight I had as a kid required an entire side of the light to be removed to replace the batteries, an operation that required a screwdriver. There's no way that light was ever going to be water-tight, but unlike any other plastic-bodied electronic device I can think of, it didn't use a snap-in plastic panel to expose a battery compartment with built-in electrical contacts.

    Envision a Maglite with a panel that pops off the side; one battery pulls out through the hole, and the other battery drops into view and can be shaken out. The light can be run without the panel in-place, with the user's hand preventing the battery from popping out, because the battery contacts are built into the light and are non-removable. This paradigm is how almost every device powered by removable batteries works, and yet I can't think of a case when it's been applied to a flashlight. Even the few flashlights with pop-open battery compartments always seem to have one of the electrical contacts built into the removable panel, so you'd better not lose that panel.

    I'm not going to argue that there's no benefit to the current design; it does make water-tightness easier to achieve, yes, but that's only one consideration, and only important to some people. Most people could care less about having a water-tight flashlight, because they're already used to electronics that can't stand a splash of water, but if they lose the electrically-conductive tailcap on their light, or they cross-thread the head putting the light back together, they'll never use it again. If the batteries were contained by a snap-in plastic panel, they could replace it for 50 cents, or just cover it with tape if they're super-cheap.
    Last edited by fyrstormer; 07-16-2012 at 03:04 PM.

  5. #5

    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    Form follows function. The battery is basically the form giving piece here. But it would be possible to build a sealed flashlight useing some sort of half pipe type deal.

    A real mil spec light *should* have a sort of chain to prevent the tailcap from dropping to the ground, similar to mil dtl 38999 connector covers.

    Mods incoming!

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    Flashaholic* Morelite's Avatar
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    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    The biggest reasons have been mentioned, cost and water resistance.
    Seeing that most flashlights are round it would be a rather hard to find a method of changing cells that doesn't require unthreading a tail cap or battery tube and even harder to find a way to have the light operable with its "battery door" still open. I'm open for ideas but I don't want my lights looking like remotes or made of plastic.

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    *Flashaholic* fyrstormer's Avatar
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    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    See above.

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    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    Quote Originally Posted by fyrstormer View Post
    See above.
    You must have been busy typing that when I posted as it was not here before started.

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    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    Water resistance is one benefit another is strength. A threaded cylinder is probably stronger than a cylinder or flat design with a removeable or hinged door cut into the side. I believe that would make a weaker body.
    Lee

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  10. #10

    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    Regarding post# 5, the 2xAA Streamlight Sidewinder does have a short internal length of cable 'tether' that keeps you from losing the tailcap, and external plastic body 'nubs' that let you know which way to insert the batteries in the dark. Interesting design, but a funky beam pattern.

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    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    Apart from the issues of cost and complexity that others have mentioned, I'd venture that it's something to do with the fact that the largest component in a flashlight is typically the battery tube, with the batteries being the largest single components. In the remote control you described, you have a much bigger device to start with so that there's more unused space, making it easier to incorporate a door/lid/something else. In a flashlight, any such door will be adding to the size of the tube the light is in, although I suppose an exception could be made for something that stacks batteries side by side.

    From a maintenance point of view, finding an o-ring is also much easier than finding a gasket that fits.

    The most elegant solution I can see (and it's not elegant at all) would be a battery holder integrated into the tailcap that is captive so it can slide out to replace the battery, but not come out completely, so you can't lose it. That way to replace the battery you just unscrew the tailcap, slide out the holder, replace battery then push it back and screw it in. Cons are the number of contact points, added size and cost.
    Finning does help dissipate heat. This is why the fins are removed before cooking fish. Otherwise it will throw off the heat and not reach the proper cooking temperature. --Duglite

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    *Flashaholic* fyrstormer's Avatar
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    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    Some electronics I own have battery doors with injection-molded gaskets integrated into the edge of the battery door. You never need to find a proper-fitting gasket, and if you ever need to replace the gasket, you replace the battery door along with it; it's so cheap, there's no reason to care about replacing two parts at once. Or, again, you could tape it shut if you're super-cheap.

    A few people have mentioned the battery tube and the constraints surrounding it, but flashlights don't need to be machined from metal tubes. Plastic is easy to mold into its final shape, and if heat dissipation is a concern there are any number of brass and zinc alloys that can be die-cast inexpensively. A guy cutting bar-stock on a lathe by hand has a romantic quality to it, but it's hardly the way things need to be made, especially when targeting a wide market.

    Why not a remote-control-shaped flashlight then? Plastic body, side-by-side AA batteries hidden under a snap-in battery door, an LED/reflector assembly in the front, and a single button on top that serves the same purpose as it does on any other light. Think "Zebralight" but with a wider, flatter, plastic body. We could argue endlessly about whether it would be nice, but it's certainly a viable design, and much more similar to the little rounded plastic electronic bricks people are used to dealing with on a daily basis.

    Don't get me wrong, I like my metal-tube flashlights, it just strikes me as odd that virtually nobody is doing anything different.

    It also occurs to me, looking at the state of most functioning devices in the world, that the devices which get used the longest are not the ones which have the best initial quality, but the ones that can be limped-along until the proverbial wheels fall off. We have LED emitters that are rated for tens of thousands of hours of continuous use, but will any of them actually get to run that long in a flashlight? If you have a metal-tube light and you drop the head and break an electrical connection, or lose the tailcap in the woods or in a parking lot somewhere, the light is done -- only a couple brands even bother to carry spare parts longer than a year or two. Maybe you're a one-percenter and you have a lathe at home to make a new tailcap, or you get lucky and find one on eBay, but for everyone else, the light is junk. But if you don't have to take apart the functional parts, then the risk of damage is much lower, and if you can fix it with duct tape, you can make it work forever.
    Last edited by fyrstormer; 07-16-2012 at 08:09 PM.

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    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    Quote Originally Posted by fyrstormer View Post
    Some electronics I own have battery doors with injection-molded gaskets integrated into the edge of the battery door. You never need to find a proper-fitting gasket, and if you ever need to replace the gasket, you replace the battery door along with it; it's so cheap, there's no reason to care about replacing two parts at once.
    But then you're in the same place from the maintenance point of view I described earlier, instead of replacing a cheap and easy to find/buy o-ring you need to buy a new battery door which I doubt will be a "standard" and readily available part like an o-ring is.
    Finning does help dissipate heat. This is why the fins are removed before cooking fish. Otherwise it will throw off the heat and not reach the proper cooking temperature. --Duglite

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    *Flashaholic* fyrstormer's Avatar
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    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    Quote Originally Posted by Th232 View Post
    But then you're in the same place from the maintenance point of view I described earlier, instead of replacing a cheap and easy to find/buy o-ring you need to buy a new battery door which I doubt will be a "standard" and readily available part like an o-ring is.
    Forget the water-tight seal for a minute, and focus on whether the device will work at all. It's not the same place from the maintenance point of view, because you don't need the little plastic battery door for the light to work. You do need the tailcap on a metal-tube flashlight.

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    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    Fair enough, I suppose we just have different views on what maintenance is. From my work maintenance has been about stuff you'll have to do to bring a device back to full working condition following from normal use (in this case replacement of O-ring when it wears out, lubrication when it dries out or rubs off) while repair is when doing so following something happening that normally shouldn't (losing the tailcap/door).

    Hence I would classify replacing the tailcap or door as repair since it isn't something you'd expect to do. Same way that I'd call changing the oil in my car as maintenance, but replacing the bumper as repair.
    Last edited by Th232; 07-16-2012 at 09:27 PM.
    Finning does help dissipate heat. This is why the fins are removed before cooking fish. Otherwise it will throw off the heat and not reach the proper cooking temperature. --Duglite

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    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    I think the main reason is that the current method works pretty well. Are there really a lot of tail caps being lost while changing batteries?

  17. #17

    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    i think its designed like this so you have to dissemble your flashlight. i think it would never do better with any other function...

  18. #18
    *Flashaholic* fyrstormer's Avatar
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    Default Re: Why do I have to disassemble my flashlight to change the batteries?

    Quote Originally Posted by gcbryan View Post
    I think the main reason is that the current method works pretty well. Are there really a lot of tail caps being lost while changing batteries?
    I don't know; amazingly, Gallup hasn't collected any data on this subject. CPF wouldn't be a very good source of data either, because CPFers are pretty much by definition going to be more careful than most people.

    But I do know that parts get lost from miscellaneous household items on a regular basis, because I have friends who are less fastidious than I about maintaining and organizing their stuff. The way flashlights are currently designed, they are incapable of operating if any parts get lost, and yet they have to be taken apart to perform a task too basic to even be called "maintenance".

    Having to disassemble the light to change the batteries, which ordinarily is such a mindless task it requires no attention at all, just makes the potential for loss, damage, or contamination that much more likely.

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