Consider a battery backup for your mobile DJ rig

Let’s set the stage. I am getting ready to announce the wedding party in and an unexpected thunderstorm comes in. I announce them in (to the way too appropriate Back to the Future theme and Power of Love) and start the first dance. 30 seconds into the first dance, the building takes a lightning strike. The power takes a hit and everything comes down for a full second, long enough that everything resets.

Back To The Future II Meme

And with that, it takes about 45 seconds for everything to come back up. So, spur of the moment, I get the crowd to continue to clap to the cadence till things come back up. Kept everyone in high spirits. The system comes back. Crisis averted. The couple could not have been more awesome about the situation, especially given their musical selection, and chalk it up to an awesome memorable moment.

However, as a DJ, I’m overly concerned that equipment may be damaged. I actually had some weirdness going on with a speaker that seemed to sort itself out in the end but this was a too-close-for-comfort moment, both from having a significant interruption at a critical part of the wedding, and a potential for fried equipment. As a DJ I try to minimize or eliminate risks that are presented to me, and I had always considered a brief outage as something that would be a low-risk situation. But it happened, and now that risk was right in my face. I needed to at least re-investigate what options were out there to reduce or eliminate this from happening again.

As a 20+ year IT person, I knew quite a bit about UPSs, but I also knew that the devices were large and heavy that would meet the basic requirements for sensitive audio equipment. But in the past couple years a couple consumer-level models came on the scene that shrunk the size and made these attainable for the mobile DJ. It’s time to examine those models.

Not all UPSs are the same

First things first, there are a lot of battery backup devices out there, and a lot of price points to consider. But most importantly, there are a lot of battery backups that would do more harm than good to your sensitive equipment. To meet the criteria needed for a mobile DJ rig these essential elements are needed before you dive into a battery backup solution.

Ride. The. Wave.

There are numerous types of battery backups that produce a few different types of outputs, the most common are square wave, modified sine wave (also called approximated sine wave or simulated sine wave), and pure sine wave. As shown in the picture below you can see the smooth curves of a pure sine wave, where a square wave has more of a binary up/down look. A modified sine wave tries to follow more closely the pattern of the pure sine wave, but as you can see it still has a very rigid step in its output.

Waveforms

If you are sensitive electronics you do not like those edges!

Here is the problem. Finding a pure sine wave UPS tended to be in only the super heavy, super large, and super expensive server-grade equipment. However there are some gems that can be found that are not technically pure sine wave, but their output is the same. But we’ll get into that in a minute.

Automatic Voltage Regulation (AVR)

An automated voltage regulation device, well, automates voltage. In most UPS, this is done through coils of wire and a special transformer switches between the coils. Keeping the voltage consistent is a very desirable thing to have. Most UPSs now have AVRs in some way.

Switch this!

There are different designs on how a UPS switches its power from the source to a battery. The three most common are stand-by, line-interactive, and on-line. A stand-by design has a switch that detects when power is cut off and switches to the battery which can take 5-15ms depending on models. A line-interactive combines both the switch and the inverter into a single unit, in some cases cutting down transfer times. Lastly, there are on-line designs that passes all the power through the battery, converting from AC > DC > AC and is the quickest at 0ms and not coincidently the most expensive option of the three with the cheapest on-line UPS I could find on Amazon clocking in at $530 and it’s a massive server-room type device.

Stand-By-Design

Stand-By Design is the oldest but the most inefficient

Line-Interactive-Design

Line-Interactive improves on the Stand-by design, but it’s not the quickest

On-Line-Design

The On-Line Design is the quickest, but most expensive

So the general thought of mind here is that the line-interactive is the best compromise to have. With the interruption published at 4ms and real-world testing having it at 4-10ms, most sensitive systems can handle that.

Watts, VA, CAPACITY!!!

So when researching for battery backups you may see an odd combination of ratings on a unit; VAs and Watts. What’s with that?

In this corner, we have the Volt-Ampere (aka VA) and this is typically described as apparent power. Then we have the Watt which represents the real power that is drawn. OK, this probably makes even less sense now. Even worse we have this expression called the “Power Ratio” which is the ratio of VA to Watts to indicate essentially efficiency.

So what does it all mean? In many of the middle sized units you will see, you will see somewhere around 1500VA and 900W. This is a power factor of 60% and is pretty typical. Higher power factors typically have a much higher price tag involved.

As for sizing your battery right, it really does come down to investing in the largest unit you can get. The larger you get, the more battery time you get. After testing out the configuration I would be using, I was consuming in a typical 160-260W with peaks at 300W. If an outage occurred I would likely cut back a little bit to maximize my runtime, between 25-30 minutes.

What’s that noise?

While most noisy UPSs can be attributed to the type of wave output it has (a modified sine wave or square wave tends to introduce some noise in the line) you still need to be aware that many UPS models may have inferior equipment that may bring unwanted noise to the party like Electromagnetic interference (EMI) and Radio Frequency Interference (RFI). That buzzing that you would head on a speaker? That could be a combination of the power output plus EMI and/or RFI. Make sure to look for a unit that has EMI and RFI filters.

There is a battery backup that does all this?

As I noted above, the world of UPSs is pretty vast, and the past few years has seen new battery enhancements, better quality parts for lower costs, but as more UPSs are being sold to customers with home entertainment systems, desktops, and the like, they all are missing one or more key feature needed for sensitive audio equipment. But there are a pair of UPSs out there that tick off all the major checkmarks.

One of the biggest features that both of these UPS have is that the sine wave output is as close to a pure sine wave as you can get, well without it being technically a pure sine wave. Apparently, this is a digital manufactured sine wave output but with incredible resolution in its steps. This tidbit of info can be found over at Tom’s Hardware about the CyberPower UPS:

“No digitally created wave can be a true mathematically curved analog wave. But the number of digital steps used to create the wave can be great enough that the electronics used in even the highest efficiency computer power supplies are unable to distinguish them from an analog wave. The total harmonic distortion of the output on battery is under 2% which means the output of the UPS is closer to a mathematically ideal analog wave than the powercoming out most peoples walls.

From all the videos and articles I have seen on this series of UPSs, many with oscilloscope readings, they universally have said the same thing, they cannot distinguish this from a pure sine wave and with that, the price point on this is considerably lower than anything else on the market with this capability. And to prove the point here is the oscilloscope capture of both of these units in action and comparing it to a similar APC model I have that has a stepped sine wave output.

Combine that with a line-interactive design, AVR, 1500VA/900W capacity, EMI/FRI filters, a both have a connected equipment guarantee, and a 3-year warranty, this unit hits all the right marks for use in a mobile DJ’s rig.

The practical use

Since I had a need for two UPSs (one for ceremonies, one for receptions) I decided to buy one of each, that way if one was really superior for everyday use I could gauge that, but how will I use it in my setup? To maximize the battery output for my reception rig, I am going to put one of my speakers on the surge side, while my other speaker, and the rest of my core setup on the battery side. This should net me an additional 5-10 minutes of use. In addition, I will turn off unneeded equipment.

From initial tests on real-world loads, I typically net 20-25 minutes of a real-world time on my reception rig and an amazing 60+ minutes on my ceremony rig. This certainly replaces the portable batteries that I was using that were square-wave output and gave some really bad side effects of their use.

Battery backup? Absolutely!

There are a number of real-world practical reasons to consider investing in a battery backup solution for your ceremony or reception setup:

  • Provides steady power to your equipment, prolonging its life
  • Protects against brownouts, spikes, and noisy power
  • Provides 20-60 minutes of off-the-grid power
  • Can be a reasonable substitute for ceremony battery solutions that cost more or have undesirable attributes

For me this is a now brainer. I’ve invested in a pair, and I feel far more at ease that I have incorporated a solid source of power in case of the unthinkable.

Stand Alone Power? Really??

I have had a few inquiries about real-world testing in the way of ceremonies, specifically if they would work as a stand-alone battery. I’ve also seen a couple comments out there that says this would not be a recommended solution. Well the only way to figure the details out is to put it into a real-world simulation. Here are the parameters of the test.

For the test, I ran a mix of music, from classical, jazz, R&B, hip-hop; trying to mix in heavier bass notes in some tracks while others having a more rounded midrange sound. I muted for about 5 minutes and worked the microphone to simulate that kind of draw which seemed to have no increase or decrease in the battery’s output.

The end result was the following:

  • Initial load indicated 83 minutes of runtime with no sound playback after 2 minutes of power
  • 3 minutes in and the APC indicated 69 minutes of runtime with sound playing
  • 16 minutes in and the APC indicated 63 minutes
  • 60 minutes in and the APC indicated 38 minutes
  • 1:13 minutes in and the APC indicated 28 minutes
  • 1:30 minutes in and the APC indicated 14 minutes
  • 1:47 minutes in and the APC indicated 4 minutes

Again, I can’t stress enough that performance will vary depending how much draw you have from your equipment. But in at least my case, where a pre-ceremony and ceremony lasts 60 minutes or less, this works amazingly in my situation.

Transporting Your UPSs

One difficulty to consider if you buy these UPSs is transporting them between gigs. With the cost so low, it’s hard to justify getting a 3U case or a custom sized flight case for it. And you will likely need to replace this every year or two with the amount of use you could get out of it. In addition, this is not a standard rack size device so you have to cobble something together to make it secure in its transportation box.

I’ve tried a number of things, and the best thing I have found to date are these Geargrip “CPU Holders” that snugly secure around the UPS and have a properly angled handle to use. While this only offers minimal protection for it, this seems to be the best tradeoff of keeping it simple with getting these UPSs to and fro.

  • Original Article: 5/16/2018
  • Update: 9/4/2018: I finally found some decent straps to carry around these UPSs.
  • Update: 6/7/2018: I’ve added a real-world test of my typical ceremony solution, complete with video, that you can check out below.

Author - Lou Paris

Author Biography: Lou Paris of Paris Creative

Lou Paris has been DJing since 1988 and has a deep passion for music of all styles and genres and became and wedding DJ in 2012. Coincidentally Lou is also a successful 20+ year IT professional and has merged many technology concepts to ensure a successful night of entertainment. Click here to learn more about Lou's background.