The Great Battery Debate

One of the most frequent (and heated) debates with audio folk is the question of using rechargeable batteries in wireless microphones and other gear. With the footprint dead alkaline batteries can make in a landfill, it's a reasonable topic to bring up.

For me personally, I'm a strong advocate of rechargeable for wireless headsets, back-up mics, and for smaller mic numbers or shorter run shows. Long show duration and large numbers of mics, I'm more inclined to want to use a mix of rechargeable batteries and standard alkaline batteries. That said - rechargeable ARE a viable option, if you're willing to spend the extra time nursing them along.

In my experience, rechargeable batteries CAN be used IF they are first, high quality batteries that aren't prone to developing "memory." NiMH AA 's seem to have a better discharge rate than other rechargeable. Not to be mistaken with rats or Mrs. Prisby, NiMH stands for nickle-metal hydride. They are also supposed to have a more even discharge curve than a traditional alkaline batteries. (I've never personally tested that theory.) Not only do they need to be NiMH - they also need to have a high charge capacity - which is measured in an mAH rating. Batteries are manufactured in a wide range - and the higher the number, the longer the battery cell will last. They are available from 1100 mAH to 3100 mAH. For practical show purposes, they have to have a high mHA rating to last - at least 2600-2700 mAH's.

There are several other things to consider.The cost out of the gate can be daunting when you add batteries and chargers to the list. Although you'll certainly get use out of them - if only do one or two small musicals a year, the initial overhead may be hard to justify.

Next is the extra time you're going to put into minding batteries to deal with recharging. Most AA charging stations charge AA batteries in pairs or in groups of 4. The charging station sees those sets of batteries together, rather than reading the voltages separately - so instead of recognizing one battery is at 1 v and the other is at .5 it sees a total of 1.5, not distinguishing between batteries. (Think about your mag light - if your batteries die and you can only find one new one, the flashlight will still work, just at about half capacity.) One of the biggest problem I've discovered with this characteristic in charging stations, is that if the batteries going onto the station are at widely different remaining charges, the discharge function sometimes over drains one of the cells, and under-drains the other. (Most discharge levels don't completely drain the battery, which is what is recommended for performance.) In other words, if you have 2 1.2v batteries placed on the charger, one with 1 v remaining, the other with say .5, at the end of the discharge, the .5 will be dead, and the 1 will have .5 left. (These numbers are guesstimates. I've not metered them to see after a discharge.) When the batteries are then charged, the lower level battery doesn't get a full 1.2v and the higher battery overcharges. It doesn't happen every time - it seems to be if one of the batteries gets too drained - it seems to not take the charge right so the other battery takes more than it should. The solution to this is metering batteries BEFORE and AFTER charging to make sure batteries going to charge are at the same voltage, and have charged appropriately. If a specific battery consistently undercharges, the cell may be going bad.

Another thing to pay attention to is that unlike and alkaline, a rechargeable battery may not hold onto it's ultimate 1.2 v's for weeks or months. From the batteries I've used, it seems that if they sit to long they experience some drain. This means keeping them in quick rotation to insure that what you're using is fresh.

Perhaps the biggest challenge to using rechargeable is overcoming the stigma they've developed from their poor track record in history. Just about anyone whose tried rechargeable batteries has had a problem at one time or another - and no matter if the audio person used them as a scape goat or not - directors and designers knee jerk when they hear "rechargeable." If I'm using rechargeable batteries and the director knows this, often times as soon as we encounter a mic problem, no matter what the cause the batteries are going to be called into question. It's very hard to overcome that stigma - never mind if you do actually have a problem with a battery. The stigma is so strong, despite some success with rechargeable here at ASF, I've told to keep buying Alkaline disposables.

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Tags: batteries, green, microphones, mics, rechargable, wireless

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Comment by Brian Carter on May 26, 2015 at 12:23pm

So in 2015 are you all using the same rechargeable systems? Or have you found something better?

Comment by Richelle Thompson on November 21, 2011 at 9:37am

Richard -

Thanks for your comments!

I have used various rechargeable batteries in wireless com - some that were manufactured rechargeable sleds and others that were sleds that took AA batteries - in both cases it seemed to work well, as long as the op on the headset paid attention to a "low battery life" indicator! :)

And good questions about one hour chargers. I have used a home charger, and a semi-professional model that both worked the same way - though other chargers may certainly behave differently. I've looked at rack mount professional chargers in the past, but wasn't able to afford them. No idea if they work on the same principle. Something certainly to check out if/when purchasing chargers!

Cheers!

R

Comment by Richard B. Ingraham on November 21, 2011 at 7:01am

Great topic, thanks for bringing it up.

I've used rechargeable batteries in wireless COM for years now. Or at least I did back when I was working in a place where we could afford and they wanted to deal with wireless COM. Those were not even NiMH, just Ni-Cad type batteries. And they worked fine for many years. Of course it doesn't hurt with COM that there are 6 batteries in a sled on the models I'm thinking about. We had two sets for each pack, plus an couple of alkaline sleds for spare/back ups and long tech days. It worked well.

But I didn't really use rechargeables for wireless mics until just recently. It was a bit more work as you mentioned and we also had a supply of both alkalines and lithium batteries on hand as well. The lithiums are great for long tech days, so you can run the mics all day and not have to change batts. Then we went to the rechargeables and I don't think we use any of the alkalines. Or darn few anyway. They worked a lot better than I thought they would. We had a few single cell transmitters on this show so we would swap those at intermission to be safe and get the run times we needed. But we would have probably had to do the same with alkalines as well. Only the lithiums give long enough run times with those single cell transmitters to do the daily mic fitting, sound check and a full run of the show it seems. At least in the case of the systems I had rented in.

Thanks for bringing the potential issue with the chargers. I had never heard that before. I wonder if the larger, so called professional chargers work the same way. I also wonder if the one hour chargers have any downsides in comparison to the ones that need to charge overnight. I suspect it's only that the you won't get as many cycles on the batteries, which may or may not be a big deal.

Comment by Richelle Thompson on November 16, 2011 at 4:58pm

Good questions David. A former coworker uses 9v rechargeable batteries all the time in his wireless and has no problems, or so he says. I don't know what brand he uses or what style of rechargeable... I will see if I can find out. I only have AA needs so I've never used them.

Comment by David McCall on November 16, 2011 at 8:19am

I've mostly heard that ~1.5 volt rechargeables are useful, but that 9 volt units are not to be trusted at all. Does anybody have experience with these?

Comment by Richelle Thompson on November 15, 2011 at 1:39pm

Thanks Dillon. It's a switch I hope to make - and convince the powers that be to make with me in the near future.

Comment by Dillon on November 15, 2011 at 12:51pm

I made the switch 2 years ago to rechargeables for the Broadway tours I work on and haven't looked back. One of the bigger obstacles to overcome is establishing a system to rotate sets of batteries to ensure you're never powering up with a half-dead battery. The brand that I've been using has seems to need to be replaced every 6 months (that's about 100+ shows per set) -- they still easily outweigh alkalines in cost and eco factors though.

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