Dorset Sound & Communications
Sound system design for the 21st Century
Wireless microphone manufacturers specify alkaline batteries. A fresh alkaline battery (or set of batteries) will run a wireless transmitter (depending on the system manufacturer) from eight to sixteen hours. Most wireless microphones that use 9 volt transistor batteries will stop working when the battery is below 6.5 volts. An alkaline nine volt cell will often start out at about 9.4 volts and has a great deal of storage capacity. New systems use more ecomonical 1.5 volt AA size batteries. Most of the time it does not matter if you use Duracell, Eveready Energizer, Ray-O-Vac Alkaline, Radio Shack Alkaline, Giant, CVS or any other store alkaline battery. Always have several on hand. You can get them at many discount warehouse stores such as Costco or Sams Club/Walmart in quantity. I have found as much as 25% failure rate in the top brands (dead or low voltage). If one does not work, try another before calling for service. Do not use the 79 cent carbon zinc (C/Zn) battery. It will only last about twenty minutes. The "heavy duty" (beefed up C/Zn battery) may last thirty minutes.
Many people ask about rechargeable batteries. You have to be careful. They are allowed, but until recently not generally recommended. The current selection is better than ever.
Nickel Cadmium (NiCad) used to be the only rechargeables available. They are still around, but are not the best choice. Use only NiCad batteries that are marked 8.2 volts or higher. NiCads will only run a microphone for about two hours. As they age NiCads build up "memory" if they are not completely discharged every time before recharging. As a result what may last for two hours today may only last one hour in six months and forty minutes in a year.
A better (and now more available) choice are Nickel Metal Hydride (NiMH) rechargeables. They charge faster and will run a wireless device longer without charge memory. Some will last up to 4 hours. On the horizon are Lithium Polymer (LiPo or lithium ion) batteries. Tests by Lectrosonics have been promising with battery life close to that of alkaline batteries and no charge memory.
I recommend having two batteries per transmitter. There is no telling when a rechargeable will decide not to charge and you need the time to charge. With NiCad batteries we recommend leaving the transmitter on after the last use and switching batteries from the charger only when you are about to use the microphone again. If using NiMH or LiPo batteries put them in the charger immediatly after use. Recharging may take as long as twelve hours for NiCads. Lithiums and NiMH battery quick chargers can take as little as one hour. Buy a "Smart Charger" to protect your investment.
For now normal alkaline batteries are preferred in all equipment. Never, never, never try to recharge alkaline batteries.