Test Results: Rechargeable Batteries for Wireless Mics

I ordered a set of Panasonic Enloop Pro AA batteries my theater. They have a HUGE 2500 mAh capacity, can be recharged 500 times, and claim to maintain 75% of the charge after a year in storage. Yesterday I started a battery drain test. After a full fresh charge, I put them in both a Sennheiser EW 100 G3 Handheld and matching beltpack. I turned them on at 11:30am and left them in the booth. When my last crew guy went home at 10pm, they were still reading 2/3 bars on the battery meter. This morning when I came in I turned them back on. After 2 1/2 additional hours (about 13 hours total) I took them out for a walk around the stage. Although the beltpack had dropped to 1/3 bars, they still sounded crystal clear. An hour later, after nearly 14 hours of use, they both stopped working.

I paid a little over $80 on Amazon for 12 batteries, a 12 battery Tenergy Charger (with maintenance trickle charge and a drain/refresh function) and a little plastic box to store them in. If I can truly reuse them 500 times, that's a little over 1 1/2 cents per battery per charge.

The only negative I see is that they take over 6 hours to recharge so you may have to stock some extras for a really long show day.

Those are good results, I question the science behind them though. 2500mAh puts them towards the higher end of an alkaline battery range, but mAh aren't everything. Batteries with higher mAh have been found to actually die faster than those that are lower rated in some devices. So you can't always assume that higher is better. What I really question though is the testing method. I would have to think that just sitting and having nothing to transmit to the receiver wouldn't be nearly as hard on the batteries as having someone talk into them for that long.

All that being said, even if they only last 4 hours under real conditions they'll be just fine since that will get them through most shows with plenty of extra capacity to spare.

Yeah I wondered if they use more battery if there is a louder source of sound or not. I suppose I should put them in front of a radio and see if the results differ.

The biggest user of power in a beltpack or handlheld is the radio transmitter itself (one of the reasons to only use as much transmit power as you actually need, prolong battery life).
Since radio mics generally use FM transmission, the amplitude of the RF wave will stay constant irrespective of the program content.

The reason why you didn't notice any difference in the audio is that Sennheiser use a DC - DC converter, at least in the G3 series (and maybe in others, but I know it's in the G3s).
So that gives the internals a constant voltage to work with throughout the discharge curve of the batteries...

Thanks for the results on this. I've read a few discussions on rechargeable batteries, but no one has really posted anything like this. I've been using the cheap Energizer batteries a few times a year for the past 5 years and they have yet to disappoint. However, I (unfortunately) have made the transition to 9v's. Still trying to find an affordable alternative for them.

Chris15 said:

The reason why you didn't notice any difference in the audio is that Sennheiser use a DC - DC converter, at least in the G3 series (and maybe in others, but I know it's in the G3s). So that gives the internals a constant voltage to work with throughout the discharge curve of the batteries...

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That also explains the battery meter. The handheld was showing 2/3 bars when I checked it at 13 hours but dead at 14 hours. The belt pack dropped to 1 bar at 13 hours and was dead at 14. The batteries must have suddenly dropped below the amount of charge required to maintain that converter.

When I get a chance I'll put one in front of a Radio for a day to see if it makes a difference and post the results.

Regardless of all that, I'm pretty sure these results show they will fully match, if not exceed, alkalines for normal use.

gafftaper said:

That also explains the battery meter. The handheld was showing 2/3 bars when I checked it at 13 hours but dead at 14 hours. The belt pack dropped to 1 bar at 13 hours and was dead at 14. The batteries must have suddenly dropped below the amount of charge required to maintain that converter.

When I get a chance I'll put one in front of a Radio for a day to see if it makes a difference and post the results.

Regardless of all that, I'm pretty sure these results show they will fully match, if not exceed, alkalines for normal use.

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I can corroborate that quick decline as well. Our church just switched over to rechargables (can't remember the brand, I think they're 2,300 mAh), but they almost immediately drop to 2/3 and then go down to 0 when they're within minutes of failing. I would estimate we get approximately 8-10 hours of good use. Also on Sennheiser ew100's with one Audio-Technica pack.

Here's a chart of the discharge of 2 Imedion rechargables in a Sennheiser EK2000-IEM beltpack. I've been using Imedions (and the PowerEx charger) for about 4 years with the same batteries, and the Imedions have only dropped from 2500mAh to around 2300mAh in that amount of time and hundreds of shows.
The right rechargables and charger, treated properly, can last a very long time and are more reliable than non-rechargables. They can last longer than alkalines in many products like wireless that have a high current draw and internal regulators.

FTR: Akalines are 1.5VDC nominal. NiCd and (I think) NiHM are 1.25V. Not sure about the Eneloops. You can have the amount of power between either the max loaded battery voltage of the cells (or the limiter in the device) and the minimum cutoff voltage of the device -- assuming it's battery controller has a minimum voltage, which anything designed for rechargeables will.

This whacked me on the bazoo when I got a LaCrosse smart charger for my Oly E-1, and discovered that those "2450mAh NiMH's" were only giving me 1600 from full charge to cutoff.

One other note: any NiMH over about 2200mAh is *unreasonably* susceptible to dropping. You bounce them off anything, and you'll short the (ridiculously thin) plates and they'll stop holding a decent charge.

gafftaper said:

That also explains the battery meter. The handheld was showing 2/3 bars when I checked it at 13 hours but dead at 14 hours. The belt pack dropped to 1 bar at 13 hours and was dead at 14. The batteries must have suddenly dropped below the amount of charge required to maintain that converter.

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Actually no...
The reason the battery meter becomes inaccurate is that it's calibrated based on the discharge curve of an alkaline cell.
NiMH tend to stay flat for a lot longer and then drop off suddenly, whereas alkaline has a more gradual decline that can be sensed as a voltage...

I think it could have been Shure in the UHF-R, but I know at one stage someone had a menu option for the type of battery to better calibrate the telemetry.

It would be interesting to see how accurate the battery metering is accurate when the BA2015 Sennheiser rechargeable pack is in a beltpack...

I noticed this post and decided to report back on how those rechargeable batteries are doing. It's been almost 4 years since my original post.

In the 4 years I have never had a problem with the batteries not making it through an event. We have often run them as follows: turn the packs on at 12:45pm, run a 2pm show put them back on the chargers from 5:00 - 6:00 and then make it through a 7pm to 9pm show. I believe they could probably do the whole day without recharging, but I don't want to take the risk.

Over the last two years they have slowly started to fail. When they fail they work fine, then simply don't take a charge. I've never had a failure to work which is great. I lose about 1 battery a month and most of the originals are gone now.

My unscientific observation is that they last about 3 years on average. In that three years, those batteries have been used about 250-maybe 300 times.

Branding has changed and these batteries are now called Enloop Pro (available on Amazon). They cost about $3 each.

Tip: Check out the silverware drawer organizer options at Target. I found a perfect tray that holds AA batteries sideways and I keep all 36 batteries in there when charged.

gafftaper said:

I noticed this post and decided to report back on how those rechargeable batteries are doing. It's been almost 4 years since my original post.

In the 4 years I have never had a problem with the batteries not making it through an event. We have often run them as fillows: turn the packs on at 12:45pm, run a 2pm show put them back on the chargers from 5:00 - 6:00 and then make it through a 7pm to 9pm show. I believe they could probably do the whole day without recharging, but I don't want to take the risk.

Over the last two years they have slowly started to fail. When they fail they work fine, then simply don't take a charge. I've never had a failure to work which is great. I lose about 1 battery a month and most of the originals are gone now.

My unscientific observation is that they last about 3 years on average. In that three years, those batteries have been used about 250-maybe 300 times.

Branding has changed and these batteries are now called Enloop Pro (available on Amazon). They cost about $3 each.

Tip: Check out the silverware drawer organizer options at Target. I found a perfect tray that holds AA batteries sideways and I keep all 36 batteries in there when charged.

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@gafftaper Please pardon my naivety but what is / are "fillows" (Quoting you.)??
Toodleoo!
Ron Hebbard

RonHebbard said:

@gafftaper Please pardon my naivety but what is / are "fillows" (Quoting you.)??
Toodleoo!
Ron Hebbard

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Ahh. . "As follows" took me a while to figure out what I meant.

after doing some reading on the Shure site, they recommended the iPower brand, AA $8.75 ea, 9v $19.95 ea(they started out at $13 when I started down this road)
I have been using ipowers(2600mWh 1.5v) in my shure qld's, have only had them a year, and they last easily 6+ hrs...

I also have a 10 ulx's that use 9v's, and have had great luck with the ipower 9v 700mAh 7.4v, I get a good 8hrs of usable life

two years ago I recycled over 2k worth of 9 volts, this year will be about 10.....

Sean....

Scarrgo said:

after doing some reading on the Shure site, they recommended the iPower brand, AA $8.75 ea, 9v $19.95 ea(they started out at $13 when I started down this road)
I have been using ipowers(2600mWh 1.5v) in my shure qld's, have only had them a year, and they last easily 6+ hrs...

I also have a 10 ulx's that use 9v's, and have had great luck with the ipower 9v 700mAh 7.4v, I get a good 8hrs of usable life

two years ago I recycled over 2k worth of 9 volts, this year will be about 10.....

Sean....

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The other benefit people don't realize is the huge convenience of not having to deal with battery inventory. The hassle of ordering batteries in advance, last minute runs to buy more, and proper disposal of batteries is a huge time suck.