Waterproof Your Batteries in Seconds!





Introduction: Waterproof Your Batteries in Seconds!

About: Dan Goldwater is a co-founder of Instructables. Currently he operates MonkeyLectric where he develops revolutionary bike lighting products.

If you do a lot of outdoor work or play in foul weather, you've probably noticed that keeping your batteries dry can be a bit of a hassle - they are metal so they attract condensation. And you've probably also noticed the considerable importance of keeping them dry. Not only will a wet battery rust rapidly, the water can create a conductive path around the top of the battery which rapidly discharges it - leading to a nasty surprise if you are counting on your gps or flashlight! I've also discovered that even if i keep my spares in a ziploc bag, some of my "waterproof" electronics (like my gps) are actually waterproof on the inside, but not the battery compartment - so while the gps electronics are happy and dry, the batteries powering it are sitting out in the damp cold still!

so, for a while now i've been waterproofing my batteries. its incredibly easy! so easy in fact that i really wonder why some of the manufacturers don't do it already.

This project is brought to you by MonkeyLectric and the Monkey Light bike light (which now includes a 100% waterproof battery holder so this tip isn't needed)

Step 1: What You Need

All you need is a waterproof coating material. There are a wide variety of products which work well: at your home improvement store there are lots of options such as urethane waterproof coatings, rubberized paints, etc. from an electronics supply story you can find silicone and urethane conformal coatings which also work very well. these coatings soak in well, stick to metal, and dry to a rubbery finish. if you are in pinch, you can do quite well just using standard oil-based paint, or nailpolish. these soak in and stick well, but are a bit hard when they dry so i suspect they may chip off over time (although i have not tried them enough to say for sure).

Step 2: Do It!

all you need to do is put a dab of your waterproofer around the dimple-end of the battery!

ideally you want a waterproofer that starts as a thin liquid so that it soaks in well - there is a fiber washer around the metal dimple, which should soak up your waterproofer, and it will also soak into all the corners under the washer.

that's it! .... unless your battery is already well used? the 2nd photo below is a battery that had already suffered quite a bit of wear and tear - the plastic wrap was partly ripped, and the fiber washer was damaged so i removed it. in this case its still very easy - just put a few drops into the dimple area, and use something thin like a paper clip to spread it all around into the gaps.

if you accidentally get some on the dimple, you can wipe it off before it dries, or scrape off afterwards.

Step 3: How It Works

of course you are wondering - how does it help to put the waterproofer only around the dimple? what about the rest of the battery?

The entire can of the battery is made from stainless steel - totally rust-proof. so why does it rust? its because right around the dimple area is where the positive and negative of the battery meet at their closest point - and when water gets into this area, it allows electrolytic corrosion to occur - the electricity from the battery flows through the water, and this causes corrosion of our otherwise impervious stainless steel (as well as rapidly discharging the battery!)

So - all we need to do to make the battery impervious is to apply our waterproof coating around the dimple area, covering the area where the positive and negative are near each other.

Check out the photos below, where i've peeled away the plastic wrapper at the top of a battery to show this in detail. the bottom (negative) end of the battery actually extends under the label and up the sides of the battery all the way to the top - where it is separated from the positive (dimple) end only by a thin rubber seal. its very easy for water to get in the groove next to the seal and create a conductive path from positive to negative. the battery also is made with a fiber washer around the dimple - this protects this area from getting damaged (without it it would be too easy to short out the battery by dropping a screw next to the dimple) - but the standard fiber washer that is used soaks up water quite well, providing lots of nice water to corrode the battery.

in the 2nd photo i show the safety-pressure valve. if you accidentally over-charge your battery this valve will open to prevent the battery from exploding. if you are using a fairly thin or flexible waterproofing material the valve should not have a problem still working, but you probably don't want to use epoxy or any really thick or strong material as it will block the pressure valve from working in the rare case that it needs to.

Step 4: What About Other Types of Batteries?

You can waterproof other shapes of batteries too, the main thing is to take care to keep the contacts clean while you seal all the gaps. you might need to put some tape over the contacts (cut to shape with a knife), then apply the waterproofer, then peel off the tape after it is dry.



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    Perhaps you could use Tyvek as a coating. It prevents liquid water but allows air flow (and thus calms some of the "OMG VENTS" worrying). It does allow water vapor through so I suppose high humidity could still be damaging. Also I'm not sure how well it melts down for coating.

    You kids are way to paranoid about the "vents". No one has pointed out that if you have corrosion on the top of the battery, the venting won't work anyway because they'll get stuck.. It takes a lot more to make them vent then the average charger is likely to do.. I've seen it done, and a) you'll know and b) you're unlikely to use them afterward anyway.

    3 replies

    i completely agree. several of the commenters seem to think that the cells are continuously exchanging gasses with the outside during use, this is totally untrue. as i've written in the instructable and in the comments, venting only occurs during extreme overcharge or overdischarge to avoid the cell exploding. as you correctly point out - the cell is destroyed when it vents, and the even the venting action is very violent (like a weak explosion) anyone who thinks it is venting all the time has never seen a cell vent.

    Everyone should be aware that alkaline batteries produce hydrogen gas under 2 conditions: 1. normal oxidation that occurs all the time whether the battery is being used or not. 2. over discharge. Duracell and Energizer both have guidelines that ask the batteries be in vented compartments, or have materials in the compartments that absorb the hydrogen gas, i.e., "polypropylene, polyethylene, or some other gas permeable material should be considered." You should not take the handling of these devices lightly. Bad things have been known to happen when misused.

    This does a pretty good show of what happens... note the "crater" and "smell" comments... the smell is really bad..... but when they're charged wrong, you typically know because they get REALLY hot... like melting their way out of a plastic case hot.

    Alternatively, you could use automotive dielectric grease. It's used to keep automotive and marine bulbs and contacts from corroding in moist environments. I used it on the batteries in my solar pathway lights as they were always corroding and oxidizing from the rain. Worked quite well ans is reasonably cheap. Just remember, a little goes a long way.

    1 reply

    Vasoline will work in a pinch.

    I would suggest using a plastic paper clip, wooden or plastic toothpick or other non conductive tool as a metal paper clip could short the battery momentarily if the plastic insulator is damage or you poke the clip under it.... Overall a very good Instructable

    This is dangerous! Alkaline batteries vent hydrogen when in use or being charged, sealing the batteries can cause them to bubble and burst! Not advised.

    7 replies

    if you'd taken 3 seconds to look at your nearest Duracell, you would notice that it DOES NOT HAVE ANY VENT. also, alkaline batteries can't be charged anyway.

    The tops of the battery are the vents, and if you go to Duracell's website, under AA usage(pdf file download), it states that alkaline AA batteries need general ventilation for normal use. Notice how the batteries always seep out the top vents, or come out the bottom as they age also? Normal alkalines are not "supposed" to be recharged, but the rechargeable alkalines are basicly the same thing and I have used AA batteris after 25 recharges with no problems except they dont last long and after about the 25th time(if that, some work once or twice) they dont hold a charge anymore. not trying to insult this instructable at all, but it needs a stupid people warning, ie. "warning this can cause batteries to burst", or "do not store once sealed" etc. Good job anyway.

    Actually there are some chargers (one made in Australia, in particular) that seem to do a good job recharging alkalines. It will recharge most brands except for Duracell - they tend to leak in that particular charger. You won't get as many cycles as a secondary battery but its good for about 10 - 15 charges. So far it seems to work on the AAAs and AAs I've put in it.

    Ummm . . . you're thinking of "rechargeable alkalines". Ordinary alkalines are still one-shot -- rechargeable alkalines give you a dozen or so cycles (much more if fastidiously managed).

    There were a couple mfr's who made chargers for standard alkaline's... But they never really caught on in Canada or the US... too many people growing up being told not to charge them lest they explode to overcome. That said, NiMh batteries are close enough to alkalines these days in both capacity and cost... *shrug*

    Just finished recharging some AAA Energizers and a Panasonic Digital (from a set that was included with my TV remote). None of these are marked rechargeable alkalines. Best I can tell, they are "standard" alkalines. Also charged a bunch of Red Cell AAAs (bought at CompUSA - made in Germany). Also charged an Energizer Titanium. Best I can tell, these are all standard primary cells. I'm using a ReZap charger (made in Australia) and it seems to be doing the job well enough. I personally like to use the ultra low discharge NiMH cells such as Eneloop or Hybrio as they keep the charge for quite a while. My wife continues to buy alkalines and I hate to throw them out after one go round. After getting rid of the "duds," I've got about 40 cells which are now being recycled rather than heading for the landfill. I figure I'd rather "use them up" rather than use once and throw away. I saved alkalines for six months before buying this charger. I had about 60 batteries - mostly AA and AAA. I still have a bunch of Duracells in a bin which will supposedly leak in my charger. Haven't wanted to try them yet.

    First heard about the charger on this site which reviews batteries and chargers:


    Here's another couple of links - one is the manufacturer's page:



    >>are actually waterproof on the inside, but not the battery compartment - That's not waterproof, that's splash or water 'resistant'. I had cause to take some D cells apart and found in my case that the "closest point" was actually on the negative end of the cell. When the outer plastic jacket was removed, I found the dimple was in a disc that touched the outer case of the cell. I confirmed this on Ever.. and Dura.. brands. I had D,C and AA to check.

    1 reply

    yes that's correct, it looks like for rechargeable batteries the seal is usually on the button-end, for non-rechargeable it is usually on the flat end. i'll be updating the project to add some photos of non-rechargeables.

    Great idea! Petroleum jelly works well on outdoor battery terminals as well, but use a super light coat (unless you want a big, gooey mess in your battery compartment). I know it's kind of off the subject but I use it in all my flashlights. It reduces thread galling and keeps the seals from getting nicked as you're replacing the the caps. I put a light coat on the spring inside to reduce oxidation and I can honestly say that I have never had to replace a spring in any of my Mag lights -the oldest one I have is pushing 20 years or better.