Monday, October 27

Batteries Are Not Simple Anymore

Poorly Designed Cateye Light Breaks if You Try to Use Rechargeable Batteries!

Many LED bicycle lights, such as the Cateye HL-EL520 pictured above, use "AA" size batteries. It is also the size that my Fujifilm camera takes. Over time, I've come to discover that AA batteries come in different sizes and power outputs. SOME will make your camera or bike light perform less well than others, and what's good for one may not be best for the other. As I discovered, SOME will physically break your bike light. Here's the rundown.

Alkaline Batteries - These are the garden variety battery that most devices are designed around. They work fine, but are not rechargeable and don't last long in my camera. It'd also be nice to not have to stock up on batteries for a bright headlight. That started me on a search for better. Highly relevant to this story is that Duracell AA Alkaline batteries, when fresh, are rated at 1.5 V and have about 2500 mAh capacity. As you can see from the Duracell service life graph, when voltage gets down much below 1.2 V, the batteries are on their last legs.

Alkaline Battery Next to NiMH Rechargeable

Duracell Voltage Drop Over Time - FROM Duracell Site
NiMH Batteries - The current standard for rechargeable AA lights are NiMH. These are pretty much a direct substitute for alkalines in many applications. HOWEVER, a AA NiMH does not have the same nominal voltage as an alkaline battery. They start at 1.2 V and drop from there. What this means is that if you have a camera that takes AA batteries, it won't take very many pictures or flashes before it poops out. There's ANOTHER problem with NiMH batteries. While it is difficult to see in the photo above, NiMH batteries are a little bigger than their alkaline cousins. In the case of my Cateye light, I put a set of NiMH batteries in and it broke. Yup, that light lasted all of two minutes. Using a micrometer, the NiMH batteries scope out at 0.565 inches compared to 0.550 inches for the alkalines. Luckily, my bike shop was still open and they exchanged it. The clerk broke it worse so he simply shook his head. Now I ONLY use alkaline batteries in that light. Their bigger light, the 530, CAN accept NiMH batteries and the LED stays pretty bright for many hours. Then I recharge.
NiZn Rechargeable is Superior for Camera Usage and Not Bad for Bike Lights
NiZn Batteries - NiZn are a fairly new type of rechargeable. While they don't fit into my Cateye much better than the NiMH, (they are about 0.558 inches diameter) they drop right into my camera. What's more, while the NiMH start out at 1.2 V, the NiZn start out at 1.7 V. What this means is that they last in my camera much better than either NiMH or disposable alkalines. They also work well in bike lights that can accept them. They're a bit "hotter" than an alkaline, but not by much.
Other Rechargeables - There are two other main types of rechargeable batteries that you might want to use in your bike light, and one that you DO NOT. The first of these are NiCd batteries. They were what people used before NiMH came along. They don't last as long, have toxic cadmium, and have memory effect problems. NiCds are on the way out. The second are rechargeable alkaline batteries. I don't have any experience with them, but looking at Wikipedia, they don't look like they'd work well as camera or as bike light batteries. One that you do NOT want to use is the lithium rechargeable battery. The problem with them is they put out 3.6 V. That'd fry your camera, and might also fry a bike light.
Last Words - In summary, I'm quite happy with my NiZn batteries in my Fujifilm camera. I use the NiMH batteries in my Cateye HL-EL530, where they make a snug, but acceptable fit and last quite well. I AVOID using anything but old-fashioned alkalines in the HL-EL520 since NiMH will break it and the NiZn are tight enough that I'm reluctant to try. One wonders why Cateye did not provide even a smidge of clearance on that light. As a back-up light, it works OK. Alkalines will last for years when you rarely use them. One more thing. Disposable lithium batteries are now available. According to Wikipedia, it looks like they will probably last about 50% longer than disposable alkalines, but are a LOT more expensive.


Khal said...

One wonders why the manufacturers did not make all AA batteries the same size! Jeziz!

Steve A said...

Khal, I must say I was surprised when my bike light broke when the NiMH batteries were only 0.015 inches bigger diameter. In truth, however, even the alkalines are a tight fit.

Khal said...

By the way, when using rechargable Li-ion batteries (Radio Shack) in my REI headlamp, which I used to put on my helmet, the light abruptly dies within minutes when the batteries run down. I don't know if that is a function of the battery discharge cycle, the headlamp electronics, or a combo. At any rate, after one too many times when it suddenly died in me, I relegated it to less critical use and put an old Light and Motion Li-ion cub back on my helmet. Works nicely and throws a nice beam.

Justine Valinotti said...

So the bicycle industry isn't the only one guilty of a lack of standardization!

RANTWICK said...

Nice post, Steve. I like how the engineer in you shows, using the graph and stuff. This post made me like my new hub dyno and light set even more, if that's possible.

Steve A said...

Rantwick, You'll note that Cateye doesn't make hub dynos, which is probably why yours is reliable.

KD5NRH said...

If you take a look at your NiMh AAs were well within spec. Cateye should have actually looked up the specs rather than designing for whatever batteries they pulled out of their kids' toys.

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