Two problems this past weekend

[Wynnd]

You're right about run time, but you're incorrect about performance.  The 1.2 volt batteries also have less internal resistance, so they flow more current at 1.2 volts than the 1.5 volt alkaline batteries.  Basic Ohms law involves resistance, voltage and amperage.  Can't just look at one without considering the other two.  Now I have found some devices that won't work at the lower voltage and in those cases, the NiMH just don't work.  I still hate throwing batteries away.

[WK154]

Another consideration of useless rechargeable batteries. AA batteries are 1.5 volts each, rechargeable AA batteries are only 1.2 volts, so a rechargeable can not compete for performance and run time.

Not my experience over many years and brands. As I stated the NiMH actually lasted slightly longer in the Sennheiser EW100 body pack ~180 mAh drain than the alkalines. Most quality Alkalines are 1900 mAh to 2000 mAh rated and NiMH are in the 2100 mAh to 2700 mAh rating. Life will depend significantly on drain and at high drain NiMH wins hands down. In long term usage such as flashlights Alkalines are king.

[sam.spoons]

Accepting the technical performance of NiMH batteries for wireless mics it's the human element that lets the side down. The superiority of NiMH batteries entirely depends on a rigid adherence to a charge/discharge procedure and religious monitoring of usage. Old NiMHs become unreliable and part charged batteries can be a problem too if mistakes are made in the management scheme. Also, for theatre use with multiple mics keeping up with charging 30+ AA batteries per show would be extremely difficult especially on a touring show.

[Wynnd]

Very valid points.  We shouldn't be discouraging those that don't have a problem with making sure they've been charged recently and discharged very completely before charging.  Outside of frequently having to find alkaline batteries and willingness to pay more per use, there isn't much of a downside to single use batteries.  (And every grocery store and 7-11 has them in stock.)

[sam.spoons]

Equally good point.  I agree for non critical use or if you only run one or two wireless mics NiMHs are the way to go (and I do use them myself in that context).

[WK154]

Sam  the very reason that I use Alkalines for performances with only 6 mics (12 batteries) was that it would take 3 charging cycles to refresh the NiMH's, usually 2 days. For $3 per show for Alkalines it made little sense. Had I a charger to handle 12 at a time I might have had a different approach, but handling both audio and video per show I had my hands full with camera batteries and other issues. Like you stated "the human element".

[Wynnd]

I've seen chargers that handle more batteries.  I like the third charger I bought.  It catches batteries that need to be retired, can charge a single pair in about 90 minutes.  The earlier chargers weren't so good.  (Though my first is the only one with a NiMH 9 volt connector on it.)