My wireless mic uses 9v batteries. I don't want to risk losing power during a crucial shoot, so I generally use fresh batteries each time. It's such a waste (Even though I do save them for smoke detectors, toys...)
Is there an accurate little meter that would give me confidence in what might be left in a battery.

Thanks, Myron

I started using rechargeable NiMH 9v batteries Sept 2003. I set the countdown timer on my watch for 3 hours to make sure I replace them in time (250 mAh).

Just switched to Lithium Polymer 9v batteries and they seem to run for 5.5 hours now (400 mAh).

It's running an ATW-101 transmitter. The receivers run off a 12-volt pack consisting of 10 AA batteries with a total of 2.5 AH capacity.

Considering 9v alkalines are about $1.75 each from Costco, the rechargeables have more than paid for themselves, and I'm assured a predictable run time.

I used to use rechargeables but found that when they started to lose power they dropped like a rock. Without warning the mics just stopped working. The shoot before these batteries worked fine, this time they only held charge for twenty minutes!!

I use this little battery checker. With a little experience you learn to adapt the reading to your purposes. For instance, I've found tha a 9V battey that tests "good" is good enough to be trusted to power my BeachTek DXA-8 for a two act play with phantom power on only if the needle reaches the middle of the second "O" in "GOOD." If it only reaches the "G" it's starting to tank, but it will still power my Rode VideoMic for several hours.
http://www.radioshack.com/product/index.jsp?productId=2103165&cp=&origkw=battery+tester&kw=battery+tester&parentPage=search

Just the answer I was looking for. Thanks Fred.

Myron.

Battery drain is an interesting topic. As with a lot of things, there's a lot more to it than meets the eye. There are three basic types of circuitry designed to use battery power; constant resistance, constant current and constant power. Constant resistance is the worst and constant power the best in terms of efficient use of the energy stored in a battery. Info courtesy of Duracell's website. I checked it out a while back when I was studying the power consumption behavior of my DXA-8 (http://www.dvinfo.net/conf/showthread.php?t=57763&highlight=DXA-8).

I use the following and like it a lot as it places a load on the batteries and I never had any problems or false readings plus you can test more that just 9v batteries.

ZTS Mini-MBT Multi Battery Tester

http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=321271&is=REG&addedTroughType=search

Hmmm. looks good Hart. Thanks for the reply.

Myron