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Rechargeable AA batteries for UHF wireless mics?

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Brian Ehlers:
Building on what Shawn said:

1/  The voltage vs. energy curve of rechargeables makes them inherently very difficult to predict how much longer they will last before needing a recharge.  It doesn't matter if it's the battery indicator circuit inside your wireless transmitter or a human holding a volt meter.  With rechrageables you get less warning of "the end," and the accuracy of your prediction of when the end will occur is less than with alkalines.

2/  As they age, rechargeables hold less energy and their discharge curve becomes even less predictable.  Their constant use and handling also makes them more likely to develop a mechanical failure (short or open).  For these reasons, it is prudent to replace rechargeables BEFORE they become a problem, just as you do for alkalines.

There's nothing wrong with using rechargeables if they fit your needs.  Just don't kid yourself into thinking they are equal in performance and reliability to alkalines.

For me, the hassle of removing and recharging them all the time (and the risk that the last guy forgot to recharge them) rules them out.  My church uses 2 - 5 wireless mics per service, I throw away (dispose of properly) the alkalines well before they're drained, and still we use only about $50 worth a year.

Kent Thompson:
Most of the problems people have with rechargables come from unreasonable expectations.

Do they last as long maybe not. So do not expect them to go through as many services. Have a rotation stock on hand so that you always have fresh batteries available to use.

Make sure that they are properly charged with a proper charger that shuts off when they have a full charge.

As Brian stated make sure you replace them when they start aging.

Mike Jaspers:
I want to address the rechargeable battery debate here.  Our church started to use rechargeable AA and 9v batteries after the economy tanked to save money on batteries.  Also, it has been said that rechargeables are a lot easier on the environment.

We use the Maha Powerex 2700mAh AAs and the iPower US 500mAh 9 volt.  

I use(d) the 9v batteries in PSM 700r(now updated to Sennheiser) product as well as ULXP product.  I have not had a battery die on me yet.  I replace my batteries roughly after 2 uses (6-8 hours, depending), alkaline or rechargeable.  The cheapest I was able to find good alkalines was about $1; the iPower batteries are $18/ea.  So, they make up their value after about 20 charges.  Charge time is usually under an hour.

The Powerex are in use for Shure UHF-R transmitters and Sennheiser g3 receivers.  Freshly charged, they last at least as long as the Procell or Energizer product.  No failures as of yet, either.  I bought some extra batteries so that I could cycle through the product and have enough spare in case I did not have enough time between charges.  I always slow charge the batteries and it takes anywhere from 1.5-4 hours.  Not including the charger, they make up for their cost after 11 uses.  

I still use alkaline AA in our UR1 bodypacks, but only because the pack does not latch well when using the rechargeables.  Since I change the batteries every time for our Pastor, I am able to use old alkalines in other bodypack situations (baptistry, etc.).  

We saved about $1000 this year using rechargeable batteries.  Hope that helps.

Sincerely,
Michael D. Jaspers
Director of Technical Services
First Baptist Church of Springdale

Paul Wilson:
We use some rechargeable batteries and some regular batteries. Obviously the regular ones hold a charge for longer, but knowing when to change them is exactly the same. For me, when the mic gets below full/three bars/whatever battery indicator you have its time to change them.

The fact is once they get below three bars, for instance, they tend to die faster. For example...it might take three hours of use for the mic to go from three bars to two bars and only one hour more for the batteries to completely die. So keep that in mind.

The other thing to realize is that rechargeable batteries still need to be replaced from time to time. It is NOT once you have them you are set for life. Just like a laptop that can't hold a charge after so long a time such is the case with any rechargeable batteries....eventually they need to be changed.

JAOgann:
Thanks to all of you who commented. Some excellent info.  Jim O

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