Earth Notes: Battery Sounds: How Does a Battery Sound in Time-lapse?

Updated 2019-10-19 14:48 GMT.
Audification: listening to my Enphase AC Battery state of charge and flows #podcast #tech #audification #battery
Enphase SoC Audacity screenshot

WARNING: some parts of this are quite loud!

"battery sounds" Uploaded . Duration 159 seconds. Download MP3 clip 3896kB (may not be available in data-saver/lite mode), download low-bandwidth MP3 clip 1379kB, hi-fi FLAC clip 7823kB.
Transcript:

Hi, I'm Damon Hart-Davis, and this is a quick bonus Earth Notes podcast episode for 13th October 2019.

Following on from the "rad sounds" I decided to "audify" some battery data. Enjoy!

I used the same techniques, including sampling faster than needed, and using Audacity to get down to 44.1kHz (Normalize then Resample) and thus one year per second.

The same strong 'daily' 365Hz tone is in there, a little 'buzzy' as usual because the data is messy real-life, and not a perfect sine wave.

Each of the datasets turned into audio here runs from early August 2018 (when the Enphase was installed) through to the end of September 2019. So each 'track' is just over 1 second in length.

First I tried listening to how full the Enphase AC Battery was, also known as its state of charge (SoC). Because this changes relatively smoothly this one is not very buzzy. It is quieter in winter when the battery often doesn't get a full charge for example.

[Twice Enphase-ACB-5m-SoC]

Then I tried listening to how the battery charges, which is being driven from my large PV array, so fairly abruptly goes from nothing to full on and back again most days. It does follow the sun in regularity, but charging is sometimes interrupted when we turn on a big load such as the kettle or oven. Like all of them, this has a seasonal element to it.

[Twice Enphase-ACB-15m-charge-13M-mono]

Next up is discharging, which is more random and buzzy, depending on when we run appliances. The fridge/freezer's regular demands for 80W half the time are in there somewhere.

[Twice Enphase-ACB-15m-discharge-13M-mono]

Then, in Audacity, I shoved charging into the left channel and discharging into the right. The stereo hints at something interesting.

[Twice Enphase-ACB-15m-flows-13M]

Finally, and very seasonally, is the PV generation as measured by the Enphase. Even this is more noisy than you might expect, as sunshine is significantly intermittent in the UK!

[Twice Enphase-ACB-15m-PV-generation-13M-mono]

There's more on my "Earth Notes" Web site at Earth.Org.UK.

The Sounds

First off, the Enphase AC Battery state-of-charge (SoC) with 5-minute sampling, then Normalize/Resample (.wav):

"Enphase ACB 5m SoC" Uploaded . Duration 1 seconds. Download MP3 clip 17kB (may not be available in data-saver/lite mode), download low-bandwidth MP3 clip 9kB, hi-fi FLAC clip 66kB.

Battery charging with 15-minute sampling, then N/R (.wav):

"Enphase ACB 15m charge 13M mono" Uploaded . Duration 1 seconds. Download MP3 clip 18kB (may not be available in data-saver/lite mode), download low-bandwidth MP3 clip 10kB, hi-fi FLAC clip 78kB.

Battery discharging with 15-minute sampling, then N/R (.wav):

"Enphase ACB 15m discharge 13M mono" Uploaded . Duration 1 seconds. Download MP3 clip 18kB (may not be available in data-saver/lite mode), download low-bandwidth MP3 clip 10kB, hi-fi FLAC clip 79kB.

Battery charging (left channel) and discharging (right channel) with 15-minute sampling, then N/R (.flac made in Audacity):

"Enphase ACB 15m flows 13M" Uploaded . Duration 1 seconds. Download MP3 clip 42kB (may not be available in data-saver/lite mode), download low-bandwidth MP3 clip 25kB, hi-fi FLAC clip 157kB.

PV generation as recorded by the Enphase with 15-minute sampling, then N/R (.wav):

"Enphase ACB 15m PV generation 13M mono" Uploaded . Duration 1 seconds. Download MP3 clip 20kB (may not be available in data-saver/lite mode), download low-bandwidth MP3 clip 9kB, hi-fi FLAC clip 67kB.

Bonus bonus, thinking ahead, maybe straying into "sonification"...

PV generation from same source, then: Normalize, Low-Pass Filter at 500Hz with 24dB/octave roll-off (to suppress anything above 'daily' and make seasonal stand out), Normalize, Resample:

"Enphase ACB 15m PV generation 13M LP mono" Uploaded . Duration 1 seconds. Download MP3 clip 11kB (i) (may not be available in data-saver/lite mode), download low-bandwidth MP3 clip 5kB, hi-fi FLAC clip 31kB.

Code

I locally record some Enphase AC Battery stats every 5 minutes, including state-of-charge (SoC), ie how full the battery is. I currently have data from 2018-08 to 2019-09 inclusive. (The unit was not installed until a few days into 2018-08.)

cat data/16WWHiRes/Enphase/201*.log.gz | gzip -d | sh script/mkaudio/EnphaseSoCtoWAV.sh > ~/tmp/out.wav

Flows in and out of the battery (charging and discharging) are also recorded and available remotely from Enphase at 15-minute resolution. I tweaked the script to select which parameter to audify, eg charge or discharge. Data from the same 2018-08/2019-09 range is used as above.

cat data/16WWHiRes/Enphase/adhoc/net_energy_201*.csv.gz | gzip -d | sh script/mkaudio/Enphase15mFlowsToWAV.sh > img/audio/mkaudio/Enphase-ACB-15m-charge-13M-mono.wav