In the Field: The Sennheiser ew100ENG G3 Wireless System and Rechargeable Batteries
The Sennheiser Evolution 100 series of wireless microphones has always been very popular with event video producers. Through successive generations I've always appreciated the sturdy metal housings, the ability to choose among thousands of tunable UHF frequencies, and cross-compatibility with a line that includes handheld, lavaliere, and plug-on XLR transmitters paired with portable or rackmount receivers. Sennheiser is constantly improving its Evolution 100 G series offering. The original G1 portable line featured a rather large transmitter and receiver pair that required expensive 9V batteries. For original G1 owners, the decision to upgrade to the G2 was obvious. Sennheiser reduced the size of both the bodypack transmitter and receiver and switched to a pair of less-expensive AA batteries. Now, Sennheiser's latest offering is the G3, and aside from a pair of external charging contacts to charge the optional BA 2015 accupack rechargeable battery, it looks almost identical to the G2 that it's replacing. So the question I set out to answer for myself is this: Did Sennheiser make enough improvements to the G3 to entice me to upgrade my current G2s?
The Improvements and Their Benefits
The G3s now offer 1,680 tunable frequency options. The old ones had plenty at 1,400. But the big improvement is the increase from 8 presets to 20 channel banks, each having up to 12 frequency presets.
This is one way to make the job of selecting the same frequency for both the transmitter and receiver much easier. The other is to apply the new sync function in the menu that matches the receiver frequency to the transmitter using an infrared interface when they're both at close range (10cm max).
While these features are improvements, they offer limited performance benefits. By far the biggest improvement-and the best reason to upgrade-is not something that's found in the menu or is even visible on the outside. It's the way Sennheiser is using the shielding on the receiver's AF Out jack as a second antenna to enable adaptive-diversity reception. Diversity reception improves reception and reduces dropouts by switching receiving antennas automatically to the one that has the best reception. This is a standard feature on more-expensive systems. The active antenna is denoted by the Roman numerals I and II, which are visible on the orange backlit display panel (the old one was green).
In terms of reliability, my only complaint with the older models that apply to the new G3 is that I found the set screw for the 3.5mm mic/line and AF Out jack occasionally would back itself out and require replacement. At $3, the cost of the part is negligible, but I've had to replace four of them over the years. My other concern is with the quality of the lavaliere cable. I've repaired or replaced three cables (replacement cost $139.95), all of which have started pulling away from the jack due to the constant stress from tugging when a microphone has been mounted without enough slack.
I've started upgrading my lavaliere microphones to the more-expensive and higher-quality MKE-2 Gold lavaliere microphones, which I find easier to mount on my talent as the clip can rotate 360 degrees in 90 degree increments; this is helpful when you need to make quick microphone changes between men and women. If you haven't already noticed, men's and women's shirts button on different sides, so a clip mounted on a man's shirt pointing up would have the microphone pointing down on a woman's shirt.
The supplied ME-2 microphone can be adjusted at 0 degrees and 180 degrees, but it requires you to remove and replace both the windscreen cap and the clip in order to flip the clip. It also doesn't allow the mounting of multiple microphones like the MKE-2 gold clip does, nor does it allow vertical mounting of the microphone relative to the clip, which is very useful for accommodating a variety of shirts with different necklines.
Overall, I would recommend the Sennheiser Evolution 100 G3; I plan on upgrading my entire line to the new line, specifically to benefit from diversity reception. As far as features go, I would like to see Sennheiser upgrade its transmitter and receiver bodypacks to allow the user to set the battery type so that the battery-remaining display is accurate to the battery type.
As my test will demonstrate, the problem right now is that Sennheiser is calibrating to the discharge curve of an alkaline battery, which is very different from that of a rechargeable battery.
I recently saw the discard box of gently used AA batteries from rental equipment at one of my local suppliers, and I realized there has to be a way for us, as event videographers, to stop producing so much waste.
Although alkaline batteries are termed "disposable," they contain mercury and other caustic agents such as potassium hydroxide. Many jurisdictions, such as California, have banned the disposal of alkaline batteries with domestic waste.
I rarely see rechargeable batteries being used in wireless microphones-almost all video producers and A/V companies prefer single-use alkaline batteries. Why is that? We trust rechargeable batteries for our video cameras; long ago, photographers switched to rechargeables for both their DSLR cameras and flashes, so why not use rechargeables for wireless microphones? As early as 2004, I had firsthand experience of the benefits of rechargeable batteries. While on a vacation following a video shoot in Belgium, I took a lot of photos with a Fuji digital camera. I noticed that I would get very little battery life with alkaline AA batteries, but I never ran dead using rechargeable batteries.
Since then, I've had the feeling that rechargeable AA batteries were equal to or better than alkaline for certain applications. I now know that much of the reason for the difference is that rechargeables perform better than the alkaline batteries in high-drain devices, due to a lower internal resistance. But what about in low-drain devices such as wireless transmitters?
Armed with this hypothesis, I set out to determine specifically if rechargeable AA batteries were equal to their disposable alkaline counterparts when used in wireless microphones.
A Battery of Tests
In my research for this article, I came across a forum on DVcreators.net discussing the use of rechargeable batteries that I feel sums up what is commonly and incorrectly believed. One forum member wrote, "AA batteries are generally 1.5V so the rechargeables you mention at 1.2V may work, but the life expectancy would of course be much shorter."
In theory, it makes sense that the stated voltage difference would be the deciding factor. But in testing, the opposite held true: Nickel-metal hydride (NiMH) batteries had a higher voltage than alkaline batteries at about the 5-6 hour mark, which is when it matters the most.
My test batteries fell into three categories: alkaline, NiMH rechargeable, and low self-discharge NiMH rechargeable. For the record, I conducted full tests only on the transmitters, as they have higher power requirements, but you can expect up to a 50% longer run time with the same batteries in the receiver.
Sennheiser ships its Evolution 100 kits with standard 1.5V Duracell brand alkaline CopperTop batteries, so I used those supplied as my baseline. I recorded the voltage under load every half hour and counted how many bars were remaining on the battery meter. Three bars corresponded to a voltage exceeding 1.3V; two bars >1.16V; one bar >1V; and no bars corresponded to a voltage under 1V.
The Duracell CopperTop batteries started at a voltage under load just below 1.6V and lasted 3 hours at three bars; an additional 5 hours at two bars; and another 3.5 hours before flashing the low-battery indicator, which lasted less than 30 minutes. Sennheiser states that G3s with supplied alkaline batteries give 8 hours of operating time. My test revealed that this brings us just to the point where the battery-remaining bar enters the one-bar range. With alkaline batteries, the bars corresponded nicely to the manual's suggestion that three bars = 100%; two bars = 70%; and one bar = 30%, although it should probably read three bars =70%-100%; two bars = 30%-70%; and one bar = <30%.
I then tested a pair of Duracell Ultra Digital batteries. I read an account from a user on the same DVcreators forum that a Duracell rep told him that Duracell PROCELLs were the same as the regular CopperTop Batteries, but the rep "recommended using the Duracell Ultra battery, which has a 50% longer life, which would be ideal for high-drain devices." Surprisingly, the Ultras have the same discharge profile for the first 8 hours but had a shorter life onward. I attribute much of that to the fact that the Ultras were set to expire in March 2015 while the CopperTops were an entire year newer with a March 2016 expiration date; also the transmitters are not what you would consider a high-drain device, such as a camera flash or a remote-controlled vehicle.
NiMH batteries come in two varieties, and, although they share the NiMH designation, they perform differently. Regular NiMH rechargeable batteries are rated in mAh (million-ampere hours), and they're the modern replacement for NiCad batteries, which suffered from a memory effect that reduced subsequent capacity if not properly discharged and recharged. The higher the mAh rating, the longer a battery is supposed to last.
My testing revealed that the starting voltage of NiMH batteries is initially lower than that of alkaline batteries-all my test NiMH batteries started at about 1.4V-but unlike alkaline batteries that spend 40% of the time in the two-bar range, NiMH batteries spend 70% of the time in the two-bar range.
So calculating battery life using the remaining bars would not be a fair comparison for the alkaline batteries, or the user, and I decided to calculate useful life as the point in which only 30% of the battery charge remains. This meant running the battery until it reached the voltage cutoff point-and doing a bit of math to find the equivalent point.
The problem with NiMH batteries is that they discharge relatively quickly in storage. While alkaline batteries retain 85% of their initial capacity after 5 years, NiMH batteries will lose 25% of their charge in a month and 80% of their charge in only 6 months. So a new type of NiMH battery was developed. These are commonly known as low self-discharge (LSD) models or precharged rechargeable batteries. SANYO Eneloops are the most common brand. I have been using these batteries for 2 years. They retain their charge much longer between uses, so they are great for last-minute situations when you don't have the time to
top off traditional NiMH batteries.
I continued my testing with a fresh set of Eneloops that were rated at 2,100 mAh. Right away I could see that the discharge rate was much different from that of the alkalines. The Eneloop batteries spent very little time at three bars, due to the lower nominal voltage of rechargeable batteries-only 1 hour. But when the batteries were fully discharged and I calculated the 30% remaining mark, the Eneloops equaled the Duracell pair.
A word of caution when using NiMH batteries: Because the battery-remaining meter is calibrated to an alkaline discharge slope, once the bar goes to one, the time remaining is much shorter with an NiMH than with an alkaline. And batteries should be changed as soon as possible.
Other Battery Options
I also came across a costly Sennheiser rechargeable battery option, the BA 2015. The company claims the unit's battery life is "comparable to non-rechargeable batteries," and I decided to see just what "comparable" meant in this case. I was quickly disappointed.
After only 30 minutes, the display showed two bars and reached the 30% remaining mark in only 6 hours, indicating that it provides only 75% of the capacity of alkaline batteries. Overall, at $300 for a pair of batteries and a charger, this battery was both the most expensive and shortest lasting.
Unlike all the other batteries, which are single AA cylinders, the BA 2015 is a pair joined with a plastic shell and requires its own charger. Granted, the charger can charge the battery packs on their own or while inserted in the new G3s, using the outside charging contacts. But the fact remains that this solution was too costly, proprietary, and of too limited durability to be practical.
I then moved on to a pair of batteries offered by German battery manufacturer Ansmann, the NiMH 2850 Energy and the LSD NiMH 2500 Max E. I had a feeling that these models would end up with the best performance-they had the highest mAh ratings-and my tests validated this. Both batteries bested all the others I tested with 10 and 9 hours, respectively, before they hit the 30% remaining mark.
So my conclusion is that NiMH batteries can outperform alkaline batteries. In my tests, the LSD models performed very well despite their lower mAh ratings, and they hold their charge much better between uses, so I am comfortable recommending them over the traditional NiMH models, which need to be topped off before each use.
When I switched to using rechargeable batteries exclusively, I quickly realized that I would also need to upgrade my battery chargers both in quantity and quality. Inexpensive wall chargers are generally limited to two or four batteries at a time. So if you have more than one device that uses AA batteries, your charger needs will increase. In order to properly maintain a rechargeable battery and ensure that it stays as close to capacity for as long as possible, it's important to use a smart charger.
Chargers use one method or a variety of methods to calculate when a battery is full. Basic models simply use a timer that assumes that all batteries are discharged, which is rarely the case, and charges for a set time. Unfortunately, this method can be very harmful to the battery, as overcharging creates too much heat and can damage the battery. Smart models use a combination of temperature and a delta-V calculation, which is a characteristic that NiMH batteries exhibit that the battery voltage will drop 20mV when fully charged, triggering the charger to switch off or change to a trickle-charge mode.
Many smart chargers do more than just charge a group of batteries. Even when in the same device, batteries don't always have identical voltages or discharge at the same rate, so you want to select a charger that charges each battery independently. And although NiMH batteries don't exhibit a memory effect, over time if they're not occasionally conditioned (discharged and recharged), NiMHs develop crystalline formations that reduce their battery life. Because it is possible to reverse the polarity of a battery that has been completely discharged, it is best to use a smart charger with a built-in condition mode to keep your batteries in top shape.
I tested a smart-charger model, the Ansmann Energy 8 Plus, and was impressed with its performance. The smart charger can charge six AA or AAA batteries at a time or up to four C- or D-cell batteries, plus two 9V batteries. Each battery is independently charged, and the status is displayed with its own LED light that flashes or is solid in red or green. Although it sounds complicated, the five mode-decipher keys are printed on the top of the charger. While the Ansmann model lacks sophisticated displays and the ability to change the charge voltage from the default of 1,000 mA (about 2.5 hours for a 2,600 mAh battery) or force a discharge or refresh, a microprocessor detects when a battery needs to be refreshed and initiates this cycle automatically.
Originally, I planned on reviewing two battery chargers for this article, and in fact I did. But just before this article went to print, one of the battery chargers (not the Ansmann) overheated, caused the charger to melt, and started smoking. So while I won't be discussing that debacle any further in this article, you can read about it on my blog: www.shawn lam.ca/blog/battery-charger-meltdown.
For more details on battery performance in the tests I did, see the Voltage Under Load chart (below).
In my business I'm proud to report that during the month of November 2009, I saved 110 AA batteries from going to the landfill by simply using rechargeable batteries instead of alkaline batteries in my wireless microphones and Litepanels Micro LED light. Imagine how much of a difference we could make if we all stopped using single-use batteries and switched to rechargeable NiMH batteries.
In a world where switching to environmentally friendly alternatives usually means reduced performance, rechargeable NiMH batteries are the rare exception that actually deliver improved performance.
Shawn Lam (firstname.lastname@example.org) runs Shawn Lam Video, a Vancouver video production studio. He specializes in stage event and corporate video production and has presented seminars at WEVA Expo 2005–9 and Video 07. He won a Silver Creative Excellence Award at WEVA Expo 2008 and an Emerald Artistic Achievement Award at Video 08.