Rechargeable Batteries (Part 2)

By , February 2, 2015

In the last post, I talked about using rechargeable batteries instead of standard, one-use alkalines (see Rechargeable Batteries (Part 1)).

Many battery powered tools and accessories stipulate that one should not use rechargeable batteries in them. Some imply that using rechargeables may actually damage the device. We always try rechargeables in these devices anyway. To date, I can’t think of a single one that couldn’t run well on rechargeables. True, some might drain a rechargeable very quickly, but with our collection of rechargeables and the devices to recharge them, that’s little more than a minor annoyance. Most run as well, if not better on rechargeables than they do on alkalines.

Two different NiMH AA batteries (Photo: Mark A. Zeiger).

Two different NiMH AA batteries (Photo: Mark A. Zeiger).

We even use rechargeables in smoke and carbon monoxide alarms, which everyone “knows” is not safe. I’m here to tell you: the alarms will emit a low battery “chirp” to warn us long before the batteries run out, so we’re never in danger of running out of power without warning.

I’ve reached the conclusion that the standard “don’t use rechargeables” admonition in device instructions come from the company lawyers, who don’t want a faulty battery to lead to their product’s poor performance. That’s typical, but I have to ask if the device is in any more danger from a quality rechargeable than from a poor quality alkaline? My theory’s backed up by the more recent addition of extra stipulation that only “high quality” [or insert brand name of partnering alkaline battery manufacturer here] be used.

In practical applications, I’ve found rechargeables better than non-rechargeables. As I said in the previous post, I won’t go into the science of batteries, but alkaline batteries start out with an initial voltage of 1.5 per cell, then gradually decline as charge gets used. Rechargeables operate at a steady 1.2 volts per cell. The difference here can be most easily illustrated with a headlamp.

If I use alkaline batteries in my headlamp, I’ll have a few hours of bright light from the lamp. Often this translates into a week or two of normal use with excellent, bright light. However, the light grows steadily, almost imperceptibly weaker with the battery. It’s hard to notice, because after a bit of rest, the batteries will offer that original brightness for a little bit, then begin to dim sooner and sooner as I use the light.

Eventually, the light will be dim enough to notice. We’re frugal people, of course, so we continue to use the batteries until the light’s just too dim to be helpful. Generally, we take out the alkalines and reassign them to other, less vital uses, such as powering remote controls or clocks. They limp along for weeks or months longer before finally expiring. Once that happens, of course, they have to be disposed of in an environmentally responsible manner.

Rechargeable batteries in the same lamp provide full, bright light until the the battery becomes almost fully discharged, then it dims suddenly, and noticeably. This can be disconcerting halfway home on a dark night, but we live this life—we either have a second light with us, or a container of charged batteries in our pocket or pack as a matter of course. We change out the batteries, charge the old ones, and continue on our well-lit way. No limping along, trying to eake out that last bit of power. What’s the point of that?

Next time, I’ll describe the advantages and disadvantages of the two types of rechargeables we use.

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