Thursday, June 2, 2011
Yesterday I posted The Background, The Numbers, and The Setup for a battery test I ran overnight last night where I paired some regular Alkaline AA batteries against some rechargeable NiMH (nickel-metal hydride) AA batteries. And here are the results:
Click the graph for full size.
Note: The graph shows the length of time (in hours) along the bottom axis and the number of bars the battery indicator shows on each transmitter on the left axis ("-1" indicating that it fully lost power). I made the two Alkaline battery lines a green color to help group them together. Note that they are the two that stay at three bars the longest but they are also the first two to drop off.
There are three main things I took away from this:
1) The NiMH batteries won! No surprise here as Mike Sessler's battery test which this test is emulating (read about it here: Part 1 and Part 2) shows almost exactly the same graph. Just like in his tests the NiMH batteries lasted about 15% longer than the Alkaline batteries.
2) Also just like in Mike Sessler's tests, the NiMH batteries dropped bars quicker than the Alkaline batteries but in the end outlasted them. This is good to know so that when we are running the batteries we know not to freak out when we see two bars, but we should freak out when we see one bar!
3) My one surprise, and the one difference from Mike Sessler's tests, was that my test ran longer than his... by more than four hours (almost a third longer)! His test ran just under 14 hours, my test ran over 18! This could be for several reasons, including (but not limited to):
a) we may not have played music as loud as he did,
b) the transmitters were five feet away from the receivers,
c) we are using different transmitters than he is.
Anywho, I am super excited about the results from this test! Even worst case scenario we know that our new rechargeable batteries will last 16 hours, well more than we will ever need them!
If my opinion changes on this I will certainly let you know, but for now: I am excited that we went rechargeable, and I think other churches should too!
Matthew Kelling
Director of Media Ministry
Argyle United Methodist Church
Wednesday, June 1, 2011
The Background
About 6 years ago I tried to take our little 250 person church "green" by using rechargeable batteries for our wireless body packs. I went out and bought the cheapest rechargeable batteries and the cheapest charger I could find. I would put the batteries in to charge Sunday after church and a week later would use them Sunday morning.
I don't know why I was so surprised when my little plan failed! The batteries would last 30 minutes and DIE! What a waste of money and time! (In retrospect, I shouldn't have bought the cheapest stuff, and I shouldn't have charged them and then let them sit six days, but that is beside the point.)
Because of this we have always used regular old AA Alkaline batteries. They are reliable but can be expensive and a waste because you are throwing them away with charge still on them. (We would put ours in a small tub with a "Free Used Batteries" sign and let people take them for use in toys, remotes, clocks, etc.)
I never again thought about going to rechargeable batteries, that is until 14 months ago when Mike Sessler (the Technical Arts Director at Coast Hills Community Church in Aliso Viejo, CA) ran a "Battery Shootout" on some Alkaline and rechargeable batteries.
The results were surprising: ALL 5 rechargeable batteries he tested outlasted his Alkaline battery; they lasted from one hour to four hours longer!
Well, I thought, this is great proof that rechargeable batteries are a great way to go. But still I didn't act.
A year after his first test Mike Sessler did another test to see how the rechargeable batteries were keeping up after a year of use. Again the results were staggering. The Alkaline batteries once again lasted about nine hours, and again the NiMH (nickel-metal hydride) rechargeable batteries were the clear winners by a minimum of four hours!
THIS is the proof I need to finally take our church to rechargeable!
The Numbers
Due to Mike Sessler's tests I decided to go with Ansmann 2850 mAh NiMH batteries (24 in total). They aren't cheap ($3/AA), but they are top-of-the-line. I also got three 9V batteries ($10 each, yikes!) and an Ansmann charger than can charge 12 AA and 4 9Vs at once.
As I was making my purchases I ran some numbers to make sure we were going in the right direction. On January 12th, 2010 the church bought two cases (144 each case) of "Energizer Industrial AA Alkaline Battery (EN91)" from Medic Batteries. The total cost (with shipping) was $110.44, making each AA cost $0.38. However these two cases lasted us only 16 months, so on a per-month basis it cost us $6.90. Not a huge cost for a church our size (we have grown to about 500 in attendance each week). But that also means we are going through, on average, 18 AA batteries a month. What a load of rubbish (quite literally!).
Compare that to the new rechargeables we got in. I bought the AA batteries from Horizon Battery (a sponsor of Mike Sessler's tests) and the 9V batteries and charger from Amazon (I would have gotten everything from Horizon, but Amazon was cheaper). The final cost for all of the product was $208.98 (all shipping was free). If you compare that to the $6.90 a month for Alkaline batteries, we will break even after 30 months (two and a half years). If you assume that the batteries will last you five years before you have to buy the same batch again (I think that this is a very conservative number based on the packages advertising "1000s of charges"), the batteries cost us only $1.41 a month, a savings of about $65 a year. (Of course this doesn't account for electricity used by the recharger. If someone has a watt-hour meter I could borrow I would gladly run that math.)
Again, $65 a year isn't a huge savings for our church, but I believe that cutting back where possible and keeping hundreds of batteries out of the landfill every year is a great direction for our (or any) church to go.
The Setup
But it wasn't just enough for me to run the cost analysis, I had to repeat Mike Sessler's test myself. We have had the batteries for a few weeks now but haven't used them "live" yet as we want to make sure they will last plenty long for our needs.
Note: Click the images for larger size.
For the test I am using two types of batteries (Energizer Industrial Alkaline and Ansmann 2850 mAh NiMH) but I am using a total of six transmitters. (We have eight transmitters but only six receivers. I don't know if our Sennheiser microphones talk back and forth between transmitter and receiver or if communication is strictly one way, so I didn't chance it and only used six transmitters and I left the receivers turned on.) The green handheld transmitter has the Alkaline batteries and the blue handheld transmitter has the NiMH batteries. Of the body packs," Jim" has the Alkaline batteries and the other three ("Joe", "Kory", and "Liz") have the NiMH batteries. I have three body packs with the NiMH batteries because I want to see if there is a difference between different microphone types (lapel on left, over-the-ear on right). Will one use more or less battery power? Who knows, we will find out!
I set up all six transmitters in front of our sound booth iMac and used our camera to point down at them. I opened iMovie on the computer to watch the camera feed and used ScreenNinja to take a screen shot every 30 seconds (uploaded via Dropbox so I can check it from home). I also played songs from our modern worship band over the iMac's speakers to give SOME sound to the microphones (although the body packs' microphones are directly under the speakers and the handhelds are a bit aways, but this is just a rough test so it is OK).
(Between the body packs and the handhelds I am charging up two fully dead HiMH batteries because I am curious as to how long it will take. Also, because there is a light switch outside of the booth that controls the booth's lights, I set up a florescent work light to make sure that the area is alway lit.)
Seen here is a current screen shot. As you can see the NiMH transmitters are all at two bars while both Alkaline transmitters are still at three bars, but this isn't too surprising as the same thing happened in Mike Sessler's test; the NiMH dropped the first bar faster than the Alkaline but far outlasted it in the long run.
Tomorrow I will post the results from the test. Thanks for reading, hope this has been informative and helpful!
EDIT: Here are the results!
Matthew Kelling
Director of Media Ministry
Argyle United Methodist Church