Yesterday, I went through a daypack-sized kit I assembled to put in whatever vehicle I am using (i.e. in my truck usually, on vacations it gets tossed in the van to travel with us). Anyway, went to check the 2 AA mini-mag-lite that I keep in it, and it would not come on. Went to open the battery compartment and the screw cap would not budge. I knew something was wrong so after using pliers to remove the stubborn cap I discovered that one of the batteries had leaked/corroded. I'm not exactly sure what caused this but I have some suspects.

My first suspect is the type of batteries DW buys. No, they weren't lithium but they were the standard duracell alkaline. I know, I know, ditch the alkaline and switch to the lithium. I am going to use this as an example to get her to spring for the lithium batteries next time per another recent flashlight thread which mentioned lithium batteries won't leak.

A second possible suspect is the weather. Since this kit almost exclusively rides in vehicles, the constant exposure to heat and cold may have caused the batteries to leak/bust.

Another suspect is the flashlight itself. Could the aluminum construction of the mag-lite be acting as a sort of super-conductor for the heat and cold extremes, making the batteries even more likely to fail? The reason I ask is I had this happen once before with a full-sized 3-D-Cell mag-lite that was kept in the car. I could not save that one and had to throw the whole flashlight away. It looks like I'll have to ditch this 2 AA mag as well.

My final suspect is ... me. Perhaps I am not doing a thorough enough equipment check, or I am not checking often enough.

Any thoughts or comments would be most appreciated. I do know I need to make the leap to upgrading to lithium batteries, and I need to check all the gear in all our kits on a regular basis ... thoroughly. Anything else? How often should I check the gear? I commented to DW that I need to check at least every season change (roughly every 3 months) but I am wondering if that will even be often enough. How often do you check your gear and what is your que to do so? I may have mentioned before I am absent minded and it would be really helpful to me to have some que to check my gear - say every holiday, or the first of every month, or ... well you get the idea. Anyway, I look forward to anyone's insight on this, or if anyone has had similar problems, or what flashlight/battery combo you use in your car kits that has been relatively trouble and maintenance free. Thanks in advance.

I check my gear about three times per year, sometimes four. Checking gear means going through every item in every FAK to replace anything that's expired (replacing expended items happens almost immediately), checking every device and every battery, checking every tool and servicing any that need it. The rechargeable battery in the weaponlight on my shotgun gets charged as well.

Every month I recharge the jumpstarters kept in each car and charge my wife and daughter's low-end HTs. My high-end HT has a very low self-discharge rate and doesn't need charging as often; I do that with the gear check. My super-cheap-I-won't-cry-if-it-gets-stolen-from-my-car HT also, weirdly enough, has a very low self-discharge rate. Other rechargeable devices are recharged as they are used.

Water kept in the vehicles gets replaced as it is used -- when I hit half a case of bottled water I put in a full case.

Temperature extremes can definitely have an impact on an alkaline battery leaking. It seems unlikely to me that the flashlight had a significant impact on that -- back when I kept alkalines in the car this would happen to them in the cardboard package.

+1 on the lithium cells. I use lithium Energizers in nearly all of my lights and pack electronics so the shelf life has been pretty good. I do check my kits every 6 months (there are MagLite LEDs in almost all of them). The easiest way to schedule this is to do it at the daylight savings time changes. Google Calendar is scheduled to mail me when it's time to check the smoke detectors, carbon monoxide detector, extinguishers, weather radios, go bags, etc. It sounds like a lot but you'll probably be done in 30 minutes. Write the date on the battery with a Sharpie before you put it in.

A lot of this may have to do with the temperature and humidity of the particular environment you're storing them in. This week in Virginia, it's been 100+F with high humidity pretty much every day. In a car, that probably spikes to 125-130 easy. That does nasty things to the battery chemistry.

I don't think there's anything inherently about the Maglite that is causing the batteries to fail. A polymer light will also get hot or cold, just maybe more slowly. But it will freeze or boil just the same as a metal light.

It's really the battery and the "wrapping" inside it that is breaking down and allowing the chemicals to leak. How long were those AA's in your light? I never let the alkalines in my car lights to go for more than a year before changing them out and I've never had any cells leak. And by "change" I mean using replacements that haven't also been stored in the car that whole time.

For a AA Mini-mag that you think you may need to put into service on a moment's notice and you really want to avoid any more leaking batteries, then it's probably best to just bite the bullet and put a couple of lithium cells in there. For replacements, it's fine to have a stash of alkalines that you burn up during some actual situation. Just keep them in a container or plastic bag that will catch any spills if one of the cells leaks in storage. If you're not that concerned about being able to put into service right away, there's nothing wrong with storing the batteries separate from the light, too.

Another option not mentioned yet is to use NiMH rechargeable AA's. Best would be a good quality, low self-discharge kind. I don't think I've heard a single report of them leaking, and the new ones can hold a good charge for a long time in contrast to the older NiMH cells that would be dead in a couple weeks. Of course, there's a higher upfront cost to buying the cells and charger compared to buying some lithiums, but it does give you the option of being able to recharge them during some situation, for example, using your car's accessory jack or maybe a small solar panel. Might come in handy in case you aren't able to find a way to buy more batteries later on.

my bicycle headlamp is a miniMag LED with Sanyo Eneloops...it gets exposed to the Sun and bounced around a couple of hours daily, and gets wet at least once a month...since switching to the Eneloops, have not had a problem with swelling... but have been using the Eneloops for only about 6 months...

I saw the minimag packaging says to not use rechargeables, I wondered if the higher current capacity would cause issues.
I've found the cost per cell of an eneloop and a lithium to be about equal and eneloop seems to have about 90-95% of the run time at least in my GPS (which has a calibration setting for each) so once you get a decent charger the cost is then pretty even.
I have two chargers, Maha c401fs and maha c9000 and bought one in 2006 and one in 2008 and they have probably already paid for themselves.

Sanyo Eneloops are 1.2V, Alkalines 1.5V, Energizer lithium @1.6V. Eneloops are the way to go for everyday usage. Perfectly fine to use in Maglites. I keep lithiums in the glove box flashlights and as backup. Alkalines don't go in any flashlight anymore and I even store them separately from other batteries. Yes, I've had new, unused alkalines leak.


FYI, if you can get the batteries out, distilled vinegar helps neutralize the alkaline battery goo.

As LED says, Eneloops are fine -- they're excellent and won't hurt anything that's expecting a AA cell. Don't use 14500 lithium rechargeables. Their nominal voltage is 3.6-3.7V, way more than a AA cell's 1.5V.

Thanks for all the input everyone.

Chaos, that sounds like a great gear check system you have in place. Hopefully I can get that organized. One question though (and I'm sure I'm gonna kick myself when I find out), what is "HT?" Also I would agree that the recent extreme heat wave has had a possible effect on the batteries ... except ... the bag has been in the house since we returned from vacation over father's day weekend. That said, before that time it was riding in my truck or in DW's van, driven in to work, left to sit in the sun all day, and return home where it sat further in the sun and through the cool-down of night temps.

Izzy, with what you said about the contraction/expansion thing, and what arney mentioned in his post, I think I will likely store the batteries OUTSIDE the flashlight and in a zip-loc bag or other container from now on. And yeah, I'm pretty sure I'm not checking gear often enough, but I plan to change that.

Powerring, I like the idea of writing the date on the side of the battery. I'm sure temp and humidity has had an impact as I am here in about the same neck of the woods as you are, though like I said above the light/bag has been in the house since father's day weekend so the recent extreme heat has been a non-factor.

Arney, putting the light into immediate action is not an issue, so I'll start storing the batteries outside the light as you suggested. I'm not sure how long those batteries were in the light. It's not that they have been in there all that long, I'm just very forgetful, which is why I am going to step up on my gear checking and work harder at making that a better habit.

Oh, and I did get the old batteries out, but the leakage damaged the screw on butt cap and the light, thus far, is inoperable (looks like I'll be needing a new light, seems like for me lessons have to be learned the hard way).

So, I'll be getting some lithium batteries, dating them, storing them outside the light in a separate bag or maybe one of those battery caddy's, checking my gear more frequently, and rotating out old stock for newer stock (my inner cheapskate is crying out and my inner prepper just smacked him upside the head). Thanks again for all the input. And any further insight or suggestions are welcomed.

If you're willing to go through the trouble and it's worth it to you, the battery manufacturer may replace your flashlight. I know I've read people do that for various products ruined by leaking batteries, but it might be too much hassle for a Mini-Mag.

Or you might try salvaging it. It may not turn on because of corrosion. The liquid inside the battery is alkaline, so you could try using an acidic solution to neutralize and clean it out. Some vinegar or lemon juice would be convenient acids, and an old toothbrush or skinny bottle brush will help. (To be safe, use gloves, eye protection, and good ventilation any time you're combining acids and bases together.) Then let it air dry thoroughly.

However, if the liquid got into the electronics part of the head, I'm not sure there's much hope. I've saved one or two flashlights from leaking batteries this way, but the corrosion was limited to the tailcap end of the tube.