1.) Do I leave the battery in the charger? How long should I charge the battery after it's initial 24 hours? - What's the life expectancy of a rechargeable battery?

No harm is done by leaving the Battery in the charger. The BA151 battery lasts up to 2 years with 500 recharging cycles.

2.) How long are the batteries good for on the SET 100 and 250?

Two years

3.) How do I test the batteries?

Take receiver, go in another room and turn the volume to maximum and listen for a loud rushing noise.

4.) Where can I find that 5.6v battery (PX23) I need for my ....?

We have "PXBATT" - actually the silver oxide S23PX replacement for PX23. You may also directly phantom power your K3U.

5.) Why is my Evolution Wireless System "eating" batteries, I can only get 45 minutes out of them?

Use only batteries plainly marked "Alkaline" on them. Do not use those marked "Classic", "Carbon-Zinc" or "Heavy Duty". If you notice the LED on your transmitter glowing steadily, it is O.K. The LED will start to flash when the battery has approximately 1/2 hour of life left.