Headlamps on the Homestead: A Troubling Event

By , April 29, 2017

As I teased in the previous post (see Headlamps on the Homestead: Princeton Tec) the Byte seems to be my current favorite headlamp, despite one serious setback I experienced while getting started using it.

Princeton Tec Byte and burned battery

The replacement Byte and the burned battery from the first one (Photo: Mark A. Zeiger).

Princeton Tec, unlike the majority of manufacturers of battery-operated tools, specifies in its instructions that rechargeable batteries can be used in their products.

Apparently, though, not all rechargeables are created equal. I ran into trouble using one of our particular favorite rechargeable batteries in my first Byte.

I wrote a rather detailed series on rechargeable batteries a few years ago (see Rechargeable Batteries (Part 1)). Tenergy batteries are our current favorite. We use two of their styles, depending on the application: Centura and Premium (follow links to detailed descriptions of each at All-Battery.com). Premiums are best, providing maximum power, but we find Centuras useful because of their long storage life, which allows us to carry spares on the trail, or store a loaded headlamp until needed.

Between these strategic uses, we tend to use Centuras and Premiums indiscriminately.

I loaded a couple of Centuras into my Byte one day. I soon realized that one of the batteries in the light had heated up—a lot! I removed it and found it too hot to hold. The battery’s thin plastic wrapping had even melted and split!

I assumed I had a bad battery. It happens from time to time. I set it aside, put in new batteries, which were apparently Premiums, and went about my business.

The next time I needed new batteries, I again put a pair of Centuras into the Byte. I turned on the light to test it; it didn’t light up, so I tried to remove the batteries. One came right out, but the second one appeared to be stuck in the light. As I worked to release it, I noticed that the headlamp had heated up considerably. In fact, the battery compartment began to smoke!

Oddly, this occurred while the battery compartment was open, which means that the contacts in the lid of the compartment, which normally complete the battery circuit, were not engaged.

Luckily, I managed to eject the smoking battery. Again, I found it too hot to touch. In fact, the positive button of the battery appeared burned.

I’m no expert, but the positive button might have pressed into the headlamp terminal enough that the battery’s body contacted the terminal as well, creating a short.

The ramifications of this are extremely troubling. Suppose I’d installed those batteries and left the light unattended? The thing could have burned the cabin down!

I contacted Princeton Tec, and they asked me to send the light in. Soon, they sent me a brand new replacement. That well and good, but I received no feedback on what might have happened, or how to avoid it!

As often happens, the company replaced my light with a better model, one that provides slightly higher lumens. I suppose it might run safely on Centuras, but I won’t risk it. I’ll never put a Centura in this particular headlamp style again.

This is the only case, among many possibilities, where we have had any trouble with Centura batteries. They still seem to be a viable choice in our household—just not for a Princeton Tec Byte.

Other than this one incident, the Byte seems to offer everything I require from a headlamp.

4 Responses to “Headlamps on the Homestead: A Troubling Event”

  1. Ekij says:

    Are the physical dimensions of the Centura (particularly around the +ve terminal) different from the Premium?
    Typically the whole case of a AA or AAA is -ve except for the +ve terminal however most of the case (except the bottom) is insulated by a plastic sleeve.
    What may be happening in this case is that the sleeve of the Centura is particularly thin or weak and the +ve terminal of the headlamp is rubbing/cutting through the insulation to short out the battery.
    While this may be considered a design weakness of the battery it’s also a flaw of the headlamp to be designed such that the +ve terminal touches the case of the battery and only doesn’t short due to the plastic cover, the headlamp shouldn’t be designed to rely on this cover being intact.

  2. Mark Zeiger says:

    Hi Ekij, If there are physical differences between the two batteries, they’re too small to tell by looking. I haven’t taken a caliper to them to check. Both have a plastic sleeve that appears identical, so I doubt that one is better than the other.

    I have no way of confirming at this point, but you may have hit on the problem. As I’ve indicated, we use these batteries a lot. I know that on some of them, the plastic has flaked or been torn away. IThe company says not to use batteries with damaged sleeves, but didn’t explain why, and, being frugal, we continued to do so. It’s very likely that these two instances of batteries heating up could have been caused by a battery that had damaged insulation. Once we installed it, and it heated up, it damaged the insulation further, and it would be difficult to say what caused it after the fact. From now on, we’ll inspect batteries carefully before installing!

    Now that you’ve explained why that wrapping’s there, we will not to use damaged batteries anymore (as with so many instructions/warnings/etc., a moment of explanation would have been very helpful!). I will look into the company’s policies–it seems like they’re conscientious enough that they might take back batteries and re-insulate them. Even if we couldn’t get them back, or receive credit for them, it’d be better for the environment.

    As an alternative, it seems like the same material is available to the home user–I know people who make custom battery packs with the stuff, which is usually green. I imagine it’s the same material as the shrink-wrap for wiring. I bet we could re-insulate them ourselves without a lot of trouble or expense.

    Thanks for your help on this!

  3. Ekij says:

    There typically isn’t a lot of extra space around batteries but you could consider repairing the external plastic sleeve with a wrap of electrical tape. This will make the battery a little fatter so it may not fit all appliances but it would be easier than heat-shrink.

  4. Mark Zeiger says:

    Ekij, I thought about electrical tape. That would definitely exclude these batteries from any of my Princeton Tec lights, as the battery compartment is already extremely tight. I’m wondering if the heat-shrink for wiring might be too thick as well, which is why I’m thinking of the green stuff that battery packs are coated with. I’m also thinking of liquid electrical tape, although I know for sure I’d have to learn to apply that a lot more thinly than I have in the past.

    To begin with, I’ll probably try to lay peeling insulation back down with super glue. That seems smarter, as I’d probably need to peel off all remaining commercially-applied insulation before adding heat-shrink. If I fail, I lose the whole battery.

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