On Jun 16, 8:38 am, " wrote:
On Jun 13, 11:36 wrote: Noticed their review states that they had better runtime on NiMH.
Make sense to some degree. Medium-drain devices tend to be very
inefficient at using alkaline capacity. Alkalines tend to last longer
than NiMH when the drain is really low, like with a low-power LED.

I was told that NiMH cells had a higher self-discharge rate and that
alkaline cells were better if you were not constantly charging them.

True to a degree. There's approximately a 1-2% loss of capacity daily
with typical NiMH batteries; it's actually a logarithmic loss.
However - I find advantages compared to alkaline. There's no
appreciable self-discharge loss if you're maybe taking a light on a
1-2 week camping or backpacking trip. I've left NiMH batteries in my
Petzl headlamp for four months, and the light output was just fine.
You can "top off" NiMH batteries at any time (gets you to a point
where you know that an LED lamp is good for a while), while with
alkalines you might not know exactly how much energy is left (short of
measuring each cell). I've also found alkalines left in too long have
leaked (one got fused in a Mini Mag-Lite I owned). With an LED lamp
with a rated life of 80+ hours on alkalines, I've never had one run
out on NiMH batteries.

I went on a cave tour last year. They had a bunch of Mag-Lites
available. It was someone interesting how they kept on digging for
ones where the batteries hadn't expired or were dim.

There are also the newer "hybrid" NiMH batteries. They trade off a
little bit of theoretical capacity for low self-discharge (about 15%
per year). This is fine for someone who will at least recharge it
every 3-4 months. Even alkalines have a small amount of self-
discharge.