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[Dan Kreider]

Hi guys,

We use 9V batteries for our lavs, and we buy 'em in bulk.  We have a multimeter to test them.

When should I stop using the batteries for live sound - when they drop below what level?  If it's not live enough for live sound, I can still use it at home for something less crucial until it totally dies, right?

How are these numbers different for AA and AAA?

I've been searching the web, but I can't seem to find answers to these questions.

Thanks!
Dan

[Mike Wright]

I typically don't use them below 8V. My experience has been that
anything below that and they usually go dead during the service. I actually started using Varta rechargeable batteries and they hold up very well. They don't have a memory so they charge up to about 10.5V and I change them out after every service at my church. I don't have any professional number to give you though. Sorry.

[Jon-Paul Bullard]

I don't like taking chances with the speaker's lavalier, I'm big on a new battery for each service - or worst case two services/messages/sermons, then I test the voltage and will use for the Hand-helds for worship if it's above 8.4 (shure sm58 or 8.6 if it's a beta 58), rehearsal if it's above 8.0 and discard at anything 7.9 or below.

No reason not to use them in your garage opener or other household, low-draw devices either at any of those stages

AA's you would want to do some testing but I still stand by the maximum of two messages/sermons rule.

[Don Sullivan]

If you use alkaline batteries (and you should) you will notice that the batteries maintain a high voltage until nearly their end of life, then they die rather rapidly. Using our AT wireless units, if the battery level drops one bar (out of four) we have about ten minutes until the battery is dead.
As such, the voltage is not a good indicator of remaining life, so here's what I do.

Begin all Sunday mornings with NEW batteries.
Use old batteries for rehearsals only.

[Brian Kent Tennyson]

Don Sullivan wrote on Sat, 10 October 2009 13:33

If you use alkaline batteries (and you should) you will notice that the batteries maintain a high voltage until nearly their end of life, then they die rather rapidly. Using our AT wireless units, if the battery level drops one bar (out of four) we have about ten minutes until the battery is dead. As such, the voltage is not a good indicator of remaining life, so here's what I do. Begin all Sunday mornings with NEW batteries. Use old batteries for rehearsals only.

Ditto. Used batteries are for rehearsals and non essential services like youth group, Sunday school dinner and so on. New batteries are for Sunday mornings, funerals and weddings.

[John Fiorello]

Brian Kent Tennyson wrote on Mon, 19 October 2009 15:41

and non essential services like youth group,

I resent that comment  


But using them for rehearsals is great, or putting them in a box and offering them for free works well too




We use Senny stuff with 3 bar battery indicators.  We just put the battery in, and if it reads anything less than 3 bars, we don't use it.  The G3 stuff is great because you get to see a battery indicator where your receiver is located (ours is FOH), so if it goes low, we can replace it between services.



JF

[Brian Kent Tennyson]

John Fiorello wrote on Tue, 20 October 2009 21:57

Brian Kent Tennyson wrote on Mon, 19 October 2009 15:41  and non essential services like youth group, I resent that comment   JF

I knew that would flush out the youth pastors.  

[Irvin Pribadi]

We're moving to use use MAHA powerex 9V reachargeables and a MAHA charger with auto trickle charge.

For non rechr batts, I found that just measuring over the battery terinals can give false readings. That's because once the battery is under load, the voltage across can drop dramatically.

I usually plug the battery in a mic and measure while the mic is on. Anything above 7.5v is good for me, anything below is for rehearsal only.
This also depends on what wireless mic you have, but most consume the same amount of power.

[Justin Bartlett]

For Sunday mornings, all mics get new batteries - we run two or three services per location, and we don't want to take any risks.

For events where the batteries only need to last an hour or so, using Sennheiser G2 units (and AA batteries), I'll use the old batteries if the meter shows a full charge.  Anything less and I'll toss them and put in new ones.

We can afford new batteries every Sunday, though the expense is an annoyance.  We can NOT afford a shoddy service marked by dead wireless mics.

[Keith Shannon]

John Fiorello wrote on Tue, 20 October 2009 22:57

Brian Kent Tennyson wrote on Mon, 19 October 2009 15:41  and non essential services like youth group, I resent that comment   But using them for rehearsals is great, or putting them in a box and offering them for free works well too We use Senny stuff with 3 bar battery indicators.  We just put the battery in, and if it reads anything less than 3 bars, we don't use it.  The G3 stuff is great because you get to see a battery indicator where your receiver is located (ours is FOH), so if it goes low, we can replace it between services. JF

+1 here. We also use rechargeables in our G3s, just ordinary Energizer 2300mAh. They last a Sunday, you drop them in the smart charger and they're good in another 3-4 hours if you need em, or you can leave them there all week.

About alkalines; I'm guessing Don was saying you should be using alkalines instead of "heavy-duty" or other disposable chemistry. Lithium would also work well, but I digress.

NiMH rechargeables, though, should be used in any device that will tolerate them. Our Sennheiser Evolution Wireless setups, for example, are spec'ed for 2.4V nominal voltage. Your garden-variety 2300-2500mAh NiMH cell will easily last a Sunday morning in this kind of system, and then you just pop it back in the charger overnight. We use ordinary Energizer NiMH cells (2300mAh, slightly less than previous incarnations but handles more charge cycles) and we've had no problem. If you guys are retiring alkalines after the same time, our NiMH cells will pay for themselves after just 4 charges, and they're good for 300.

Also, I disagree with Don on alkaline voltage behavior; voltage under load on an alkaline drops fairly quickly from full charge. In fact, the drop is more linear and pronounced compared to NiMH. It's the rechargeables that are generally touted as being "flat". Have a look at these discharge curves: http://www.powerstream.com/AA-tests.htm. Even at low draws, the NiMH stays at or above 1.2V at least as long as the alkaline, and its voltage is more constant through its life (which is comparable to an alkaline, and better at high draws).

The only issue is, when a rechargeable cell dies, it has a heart attack. Like many have said, when a NiMH shows anything less than full charge in an indicator calibrated for alkaline, you've got maybe 15 minutes left on it.