Zoom F4 Battery Life

Posted: 6th January 2020 by Cheap in Filmmaking, Technology
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In early 2017, I purchased a Zoom F4 digital recorder. Though I had been recording location sound for film for years, this is the first device I have owned that was designed for filmmaking. Prior to that, I had been using a Roland R-26, which was a step up from my Zoom H4n, which was designed for musicians.

Here is some important advice for anyone with new gear that runs on batteries that will be used on film sets or at events: understand the battery life. There is nothing worse than running out of battery in the middle of a production and not having sufficient replacements. How many spare batteries should you have? That depends on how long a good set of batteries lasts. You should find out from reliable sources, or you should perform your own tests.

(The manufacturer is not a reliable source. Case in point, Zoom suggests that the F4 will run for 3.5+ hours on NiMH batteries, but my own testing ran the device for over 10 hours.)

Eneloop Pro

Eneloop Pro NiMH batteries have a stated capacity of 2550 mAh.

For my battery tests, I set up the recorder to record on four inputs, supplying phantom power on each to my most power hungry microphones, and plugged in a set of headphones. I informed the recorder that it had NiMH batteries. (As far as I can tell, this only affects the battery display.) The XLR outputs were turned off (which, you will see below, is relevant). I set up a video camera to watch the recorder. With a freshly charged set of batteries, I turned on the recorder, started it recording, and then walked away.

After 2 hours 13 minutes, the battery status dropped down to 3 bars. Remaining time, 78%.

After 4 hours 28 minutes, the battery status dropped down to 2 bars. Remaining time, 56%.

After 7 hours 57 minutes, the battery status dropped down to 1 bar. Remaining time, 23%.

After 9 hours 50 minutes, the battery status dropped down to 0 bars, and a window began popping up every 30 seconds warning, “Low Battery!” Remaining time, 3%.

After 10 hours 9 minutes, the device shut down. The end of the file was properly saved.

Other Battery Types

I conducted tests using the same test scenario with non-rechargeable alkaline and lithium batteries. Unfortunately, I deleted the data once I found they weren’t useful. All I can really say for sure is that lithium outlasted alkaline, and NiMh outlasted both.

Configuration Matters

I was on a film set for which the Director requested IFB. I didn’t own a legitimate IFB radio set, but I hooked up a pair of Sennheiser EW 100 radios fed from one of the XLR outputs on the F4. As the day wore on, I was shocked at how quickly the batteries in the F4 ran down. I had a second set charged and ready, but I wasn’t even halfway through the day before I had to switch out to them.

The next time I used the recorder, the same thing happened. Then I realized that the XLR outputs were still turned on, and I disabled them. That seemed to resolve the battery life issue. My conclusion was that enabling the XLR outputs had a bigger impact on power consumption than anything else.

A few months ago, I learned a new trick. I have an AC power meter which measures power consumption in watts (and amps, but that isn’t as useful). If I have an AC adapter for a device, I can run it through the meter, and then I can experiment with different settings to see their effect on power consumption.

About the lowest I can run the recorder is at 1.7 watts. This is about 177 mA at 9.6 volts (the nominal output of 8 NiMH batteries). That is with one input enabled, and no phantom power.

Enabling more inputs matters. With all four inputs enabled, the power consumption goes up to 1.9 watts.

Phantom power matters. Enabling phantom power on the four ports brings the power consumption up to 2.3 watts.

Outputs matter. Turning on either the XLR or the 3.5mm output brings it up to 2.7 watts. Turning on both brings it up to 2.8 watts.

Microphones matter. Plugging in four (AKG P170) condenser microphones brought it up to 3.5 watts.

There may be other things that affect power consumption that I’m not aware of. The manufacturer specifies the power consumption at 12 watts, which must be a maximum, but I don’t know how they achieve it.

Things that did not make a measurable change in power consumption: recording, connecting headphones, the number of SD cards.

I could measure power consumption more precisely on the DC side using my Fluke meter, but I would have to rig up a way to tap into it. I would need to make a short 4-pin Hirose extension cable that routes one part of the power circuit through the meter. I may do that, because I have a Sound Devices MixPre-10 II on the way, and I will want to investigate these same questions for that device.

Recommendations

Use NiMH batteries. (Or use an external battery pack through the 4-pin Hirose connector.)

Disable the outputs (XLR “main” and 3.5mm “sub”) when you aren’t using them.

Disable phantom power where it is not needed (on radio receivers, for example).

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