1. A 12.48 Inch (1304x984) Three-Color E-Paper Display by Waveshare

    Tue 22 December 2020


    I'm running a solar-powered blog and I wanted to add a low-power display to show the daily solar 'harvest'1 and maybe some additional information.

    So I decided to use an e-paper display. I wanted a display that would be readable from a distance, so bigger would be better. I therefore chose the Waveshare 12.48 inch e-paper display2.

    "e-paper display"

    an example based on data from the summer, generated with Graphite

    This particular display costs $179 excluding taxes and shipping at the time this article was written.


    Waveshare sells a two-color (black and white) and a three-color version (black, white, red). I bought the three-color version. The three-color version is the (B) model.


    Screen size     :      12.48 inches
    Resolution      :      1304 x 984
    Colors          :      black, white, red
    Greyscale       :      2 levels
    Refresh rate    :      16 seconds
    Partial refresh :      Not supported
    Interfaces      :      Raspberry Pi, ESP32, STM32, Arduino

    The two-color variant of this display has a refresh rate of 8 seconds.

    This display is clearly quite slow. Furthermore, the lack of partial refresh support could make this display unsuitable for some applications. I was OK with this slow refresh rate.

    The image below demonstrates different fonts and sizes. I think DejaVuSansMono-Bold looks really well on the display, better than the font supplied by Waveshare.

    "e-paper display"

    The Interfaces

    The display includes a microcontroller that in turn can be driven through one of four interfaces:

    1. A Raspberry Pi (Worked)
    2. An ESP32 (Not tested)
    3. An Arduino (Didn't work)
    4. An STM32 (Not tested)

    I've tried the Arduino header with an Arduino Uno, but the supplied demo code didn't work. I did not investigate further why this was the case. It could be a problem with voltage regulation.

    "e-paper display"

    In the image above, the black plastic backplate is removed.

    Image quality

    These e-paper displays are mostly sold as product information displays for supermarkets and other businesses. However, the quality is good enough to display images. Especially the support for red can make an image stand out.

    Below is an example of an image that incorporates the third (red) color.

    "e-paper display"

    The display seems suitable to display art.

    "e-paper display"

    It looks quite good in real life (sorry for the glare).

    How the display shows three colors

    The display acts like it is actually two displays in one. A black and white display, and a red and white display.

    First, the black and white image is drawn. Next, the red and white image is put on top.

    Because the display has to draw two images in succession, it takes 16 seconds to refresh the screen. This explains why the black-and-white version of this screen does a refresh in eight seconds: it doesn't have to refresh the red color.

    Please note that the entire process of displaying content on the screen takes much longer.

    A demonstration:

    Displaying an image is cumbersome (On Raspberry Pi 3B+)

    At the time this article was written, I could not find any information or tools for this display3.

    Many Waveshare e-paper displays are popular and have a decent community support. However, it seems that this display is rather unknown.

    Therefore, it seems that there are no tools available to display an arbitrary image on this display. You can use the example Python code to display an image but you have to follow these steps:

    1. Create a black-and-white version of the image
    2. Create a red-and-white version of the image, that contains only data for the red parts of the image
    3. If the source image doesn't match the required resolution, you have to resize, crop and fill the image where appropriate.

    Both 'black' and 'red' images need to exactly match the resolution of the display (1304x984) or the library will abort with an error.

    As I found this proces tedious, I automated it.

    A new tool to make displaying an image easy

    I've used the python library as supplied by Waveshare and created a command-line tool (Github) on top of it to perform all the required steps as described in the previous section. I'm using Imagemagick for all the image processing.

    The script works like this:

    ./display -i <image file> [--rotate 90] [--fuzz 35] [--color yellow]

    The --fuzz and --color parameters may require some clarification.

    The color red is extracted from an image but it's not always perfect. By applying the --fuzz parameter (the argument is a percentage), it is possible to capture more of the red (or selected color) of an image.

    The --color option specifies which color should be 'converted' to red. By default this color is 'red' (obviously). The 'solar chart' (at the start of this article) is an example where a yellow line was converted to red.

    Very slow: it takes about 55 seconds to display an image using the Raspberry Pi 3B+. Half of that minute is spend converting the images to the appropriate format using Imagemagick.

    Informational: The Python program includes a modified version of the Waveshare Python library. This library has been altered to prevent double conversion of images, which significantly degrades image quality.

    Slow performance

    If you use the provided Python library (Python3 compatible) it takes about 30+ seconds to draw an image on the screen. (This excludes the image processing performed with the 'display' tool.)

    Further testing showed that the Python library converts and dithers the image before it is sent to the display. And it does so for both black and red. Dithering is performed by looping in Python over every of the 1.3 milion pixels.

    Each of these loops (for black and red) take about 10 seconds on the Raspberry Pi 3B+, which explains why it takes so long to update the display. Therefore, I think the combination of Python + the Raspberry Pi 3B+ is not ideal in this case.


    I wanted to share my experience with this display to make other people aware of its existence. The tool I created should make it simple to get up and running and display an image.

    It clearly has some drawbacks but due to the size, resolution and third color, it seems to be unique and may therefore be interesting.

    Although I never tried the display with an ESP32, I think its an ideal for the purpose of a low-power picture frame.

    This article was discussed on Hacker News (briefly). This resulted in about 9000 unique visitors for this article.

    Appendix A - Remark on other displays

    Please note: Waveshare also sells a smaller 10.3 inch black-and-white e-paper display for a similar price with some significant benefits:

    Screen size     :      10.3 inches
    Resolution      :      1872 x 1404
    Colors          :      black and white
    Greyscale       :      16 levels
    Refresh rate    :      450 miliseconds
    Partial refresh :      Supported

    This particular display is smaller but has a higher resolution, supports 16 grayscale levels and updates in half a second. This display may better suit your particular needs. For example, I believe that this display may have been used in this project, a solar-powered digital photo frame.

    Appendix B - How to make the display work on a Raspberry Pi

    This information is straight from the Waveshare site but I include it for completeness and ease of use.

    PART I: Enable the SPI interface with raspi-config

    1. sudo raspi-config
    2. select Interfacing Options
    3. Select SPI
    4. Select Yes
    5. Reboot the Raspberry Pi

    PART II: Install the required libraries

    Install BCM283


    wget http://www.airspayce.com/mikem/bcm2835/bcm2835-1.60.tar.gz
    tar zxvf bcm2835-1.60.tar.gz 
    cd bcm2835-1.60/
    sudo ./configure
    sudo make
    sudo make check
    sudo make install

    Install wiringPi


    sudo apt-get install wiringpi
    cd /tmp
    wget https://project-downloads.drogon.net/wiringpi-latest.deb
    sudo dpkg -i wiringpi-latest.deb
    gpio -v

    Caution: The library seems to be deprecated. The Raspberry Pi 4 is supported but future versions of the Raspberry Pi may not.

    The wiringPi library is used as part of a compiled library called "DEV_Config.so" as found in the ./lib directory.

    @raspberrypi:~/epaper_display $ ldd lib/DEV_Config.so 
        linux-vdso.so.1 (0x7ee0d000)
        /usr/lib/arm-linux-gnueabihf/libarmmem-${PLATFORM}.so => /usr/lib/arm-linux-gnueabihf/libarmmem-v7l.so (0x76f1e000)
        libwiringPi.so => /usr/lib/libwiringPi.so (0x76f00000)
        libm.so.6 => /lib/arm-linux-gnueabihf/libm.so.6 (0x76e7e000)
        libc.so.6 => /lib/arm-linux-gnueabihf/libc.so.6 (0x76d30000)
        libpthread.so.0 => /lib/arm-linux-gnueabihf/libpthread.so.0 (0x76d06000)
        librt.so.1 => /lib/arm-linux-gnueabihf/librt.so.1 (0x76cef000)
        libcrypt.so.1 => /lib/arm-linux-gnueabihf/libcrypt.so.1 (0x76caf000)
        /lib/ld-linux-armhf.so.3 (0x76f46000)

    Install Python3 and required libraries

    sudo apt-get update
    sudo apt-get install python3-pip
    sudo apt-get install python3-pil
    sudo pip3 install RPi.GPIO
    sudo pip3 install spidev

    Apendix C - E-paper hacking

    I see myself as a consumer and I don't have any desire to hack the display for lower refresh-rates or partial refresh support, with the risk of damaging the display in the process.

    However one resource about this topic I find very informative is a video from the Youtube Channel "Applied Science" (By Ben Krasnow), called "E-paper hacking: fastest possible refresh rate".

    Apendix D - Available libraries

    Example code for all supported platforms can be found in this github location.

    I also found this github repository that may support this display. This code (also) didn't work for me on my Arduino uno. This could be due to a voltage mismatch, but I'm not willing to solder and potentially destroy the display.

    Apendix E - Links to other e-paper projects

    Very large and expensive display (Medium paywall)

    E-paper calendar

    Solar-powered digital photo frame

    1. During fall and winter, there is almost no power generation due to the very sub-optimal location of my balcony. 

    2. You can go larger but at a cost

    3. My google skills may be at fault but that point is now moot. 

    Tagged as : Hardware
  2. Most Technical Debt Is Just Bullshit

    Fri 25 September 2020


    I made an offhand remark about technical debt to a friend and he interrupted me, saying: "technical debt is just bullshit". In his experience, people talking about technical debt were mostly trying to:

    • cover up bad code
    • cover up unfinished work



    Calling these issues 'technical debt' seems to be a tactic of distancing oneself from these problems. A nice way of avoiding responsibility. To sweep things under the rug.

    Intrigued, I decided to take a better look at the metaphor of techical debt, to better understand what is actually meant.

    Tip: this article on Medium by David Vandegrift also tackles this topic.

    A definition of technical debt

    Right off the bat, I realised that my own understanding of technical debt was wrong. Most people seem to understand technical debt as:

    "cut a corner now, to capture short-term business value (taking on debt), and clean up later (repaying the debt)".

    I think that's wrong.

    Ward Cunningham, who coined the metaphor of technical debt, wrote:

    You know, if you want to be able to go into debt that way by developing software that you don't completely understand, you are wise to make that software reflect your understanding as best as you can, so that when it does come time to refactor, it's clear what you were thinking when you wrote it, making it easier to refactor it into what your current thinking is now.

    In some sense, this reads to me as a form of prototyping. To try out and test design/architecture to see if it fits the problem space at hand. But it also incorporates the willingness to spend extra time in the future to change the code to better reflect the current understanding of the problem at hand.

    ... if we failed to make our program align with what we then understood to be the proper way to think about our financial objects, then we were gonna continually stumble over that disagreement and that would slow us down which was like paying interest on a loan.

    The misalignment of the design/architecture and the problem domain creates a bottleneck, slowing down future development.

    So I think it's clearly not about taking shortcuts for a short-term business gain.

    It is more a constant reinvestment in the future. It may temporary halt feature work, but it should result in more functionality and features in the long run. It doesn't seem short-term focussed at all to me. And you need to write 'clean' code and do your best because it is likely that you will have to rewrite parts of it.

    These two articles by Ron Jeffries already discuss this in great detail.

    A logical error

    Reading up on the topic, I noticed something very peculiar. Somehow along the way, everything that hinders software development has become 'technical debt'.

    Anything that creates a bottleneck, is suddenly put into the basket of technical debt. I started to get a strong sense that a lot of people are somehow making a logical fallacy.

    If you have technical debt, you'll experience friction when trying to ignore it and just plow ahead. The technical debt creates a bottleneck.

    But then people reason the wrong way around: I notice a bottleneck in my software development process, so we have 'technical debt'.

    However, because technical debt creates a bottleneck, it doesn't follow that every bottleneck is thus technical debt.

    I think it's this flawed reasoning that turns every perceived obstacle into technical debt2.

    Maybe I'm creating a straw man argument, but I think I have some examples that show that people are thinking the wrong way around.

    If we look at the wikipedia page about technical debt, there is a long list of possible causes of technical debt.

    To site some examples:

    • Insufficient up-front definition
    • Lack of clear requirements before the start of development
    • Lack of documentation
    • Lack of a test suite
    • Lack of collaboration / knowledge sharing
    • Lack of knowledge/skills resulting in bad or suboptimal code
    • Poor technical leadership
    • Last minute specification changes

    Notice that these issues are called 'technical debt' because they can have a similar outcome as technical debt. They can create a bottleneck.

    But why the hell would we call these issues technical debt?

    These issues are self-explanatory. Calling them technical debt not only seems inappropriate, it just obfuscates the cause of these problems and it doesn't provide any new insight. Even in conversations with laypeople.

    A mess is not a Technical Debt

    A blogpost by Uncle Bob with the same title3 also hits on this issue that a lot of issues are incorrectly labeled as 'technical debt'.

    Unfortunately there is another situation that is sometimes called “technical debt” but that is neither reasoned nor wise. A mess.


    A mess is not a technical debt. A mess is just a mess. Technical debt decisions are made based on real project constraints. They are risky, but they can be beneficial. The decision to make a mess is never rational, is always based on laziness and unprofessionalism, and has no chance of paying of in the future. A mess is always a loss.

    Cunningham's definition of technical debt shows that it's a very conscious and deliberate process. Creating a mess isn't. It's totally inappropriate to call that technical debt. It's just a mess.

    I think that nicely relates back to that earlier list from wikipedia. Just call things out for what they actually are.

    Is quibbling over 'technical debt' as a metaphor missing the point?

    In this blogpost, Martin Fowler addresses the blogpost by Uncle Bob and argues that technical debt as a metaphor is (still) very valuable when communicating with non-technical people.

    He even introduces a quadrant:

    Deliberate"We don't have time for design""We must ship now and deal with consequences (later)"
    inadvertent"What's Layering?""Now we know how we should have done it"

    This quadrant makes me extremely suspicious. Because in this quadrant, everything is technical debt. He just invents different flavours of technical debt. It's never not technical debt. It's technical debt all the way down.

    It seems to me that Martin Fowler twists the metaphor of technical debt into something that can never be falsified, like psychoanalysis.

    It's not 'bad code', a 'design flaw' or 'a mess', it's 'inadvertent & reckless technical debt'. What is really more descriptive of the problem?

    Maybe it's just my lack of understanding, but I fail to see why it is in any way helpful to call every kind of bottleneck 'technical debt'. I again fail to see how this conveys any meaning.

    In the end, what Fowler does is just pointing out that bottlenecks in software development can be due to the four stages of competence.

    Concious"We don't have time for design""We must ship now and deal with consequences (later)"
    Unconscious"What's Layering?""Now we know how we should have done it"

    I don't think we need new metaphors for things we (even laypeople) already understand.

    Does technical debt (even) exists?

    The HFT Guy goes as far as to argue that technical debt doesn't really exists, it isn't a 'real' concept.

    After decades of software engineering, I came to the professional conclusion that technical debt doesn’t exist.

    His argument boils down to the idea that what people call technical debt is actually mostly maintenance.

    So reincorporating a better understanding of the problem at hand into the code (design) is seen as an integral and natural part of software development, illustrated by the substitute metaphor of mining (alternating between digging and reinforcing). At least that's how I understand it.

    Substituting one metaphor with another, how useful is that really? But in this case it's at least less generic and more precise.

    Closing words

    Although Cunningham meant well, I think the metaphor of technical debt started to take on a life of its own. To a point where code that doesn't conform to some Platonic ideal is called technical debt4.

    Every mistake, every changing requirement, every tradeoff that becomes a bottleneck within the development process is labeled 'technical debt'. I don't think that this is constructive.

    I think my friend was right: the concept of technical debt has become bullshit. It doesn't convey any better insight or meaning. On the contrary, it seems to obfuscate the true cause of a bottleneck.

    At this point, when people talk about technical debt, I would be very sceptical and would want more details. Technical debt doesn't actually explain why we are where we are. It has become a hollow, hand-wavy 'explanation'.

    With all due respect to Cunningham, because the concept is so widely misunderstood and abused, it may be better to retire it.

    1. I discovered this image in this blogpost

    2. if you are not working on a new feature, you are working on technical debt. 

    3. I think that Uncle Bob's definition of technical debt in this article is not correct. He also defines it basically as cutting corners for short-term gain. 

    4. See again Martin Fowlers article about technical debt. 

    Tagged as : None
  3. This Blog Is Now Running on Solar Power

    Mon 06 July 2020


    This blog is now running on solar power.

    I've put a solar panel on my balcony, which is connected to a solar charge controller. This device charges an old worn-out car battery and provides power to a Raspberry Pi 3b+, which in turn powers this (static) website.

    For updates: scroll to the bottom of this article.


    Some statistics about the current status of the solar setup is shown in the sidebar to the right. The historical graph below is updated every few minutes (European time).


    Low-tech Magazine as inspiration

    If you think you've seen a concept like this before, you are right.

    The website Low-tech Magazine is the inspiration for my effort. I would really recommend visiting this site because it goes to incredible length to make the site energy-efficient. For example, images are dithered to save on bandwidth!

    Low-tech Magazine goes off-line when there isn't enough sunlight and the battery runs out, which can happen after a few days of bad weather.

    In January 2020, the site shared some numbers about the sustainability of the solar-powered website.

    The build

    My build is almost identical to that of Low-tech Magazine in concept, but not nearly as efficient. I've just performed a lift-and-shift of my blog from the cloud to a Raspberry Pi 3b+.

    I've build my setup based on some parts I already owned, such as the old car battery and the Pi. The solar panel and solar charge controller were purchased new. The LCD display and current/voltage sensor have been recycled from an earlier hobby project.


    I've used these parts:

    Solar PanelMonocrystalline 150 Watt 12V
    Battery12 Volt Lead Acid Battery (Exide 63Ah)
    Solar Charge ControllerVictron BlueSolar MPPT 75|10
    Voltage/Current sensorINA260
    LCD DisplayHD44780 20x4
    ComputerRaspberry Pi 3b+
    Communications cableVE.Direct to USB interface

    The Solar Panel

    The panel is extremely over-dimensioned because my balcony is directed towards the west, so it has only a few hours a day of direct sunlight. Furthermore, the angle of the solar panel is sub-optimal.

    My main concern will be the winter. It is not unlikely that during the winter, the panel will not be able to generate enough energy to power the Pi and charge the battery for the night.

    I have also noticed that under great sunlight conditions, the panel can easily produce 60+ Watt1 but the battery cannot ingest power that fast.

    I'm not sure about the actual brand of the panel, it was the cheapest panel I could find on Amazon for the rated wattage.

    The Solar Charger

    It's a standard solar charger made by Victron, for small solar setups (to power a shed or mobile home). I've bought the special data cable2 so I can get information such as voltage, current and power usage.


    The controller uses a documented protocol called ve.direct. I'm using a Python module to obtain the data.

    According to the manual, this solar charger will assure that the battery is sufficiently charged and protects against deep discharge or other conditions that could damage the battery.

    I feel that this is a very high-quality product. It seems sturdy and the communications port (which even supports a bluetooth dongle) giving you access to the data is really nice.

    The controller is ever so slightly under-dimensioned for the solar panel, but since I will never get the theoretical full power of the panel due to the sub-optimal configuration, this should not be an issue.

    The battery

    In the day and age of Lithium-ion batteries it may be strange to use a Lead Acid battery. The fact is that this battery3 was free and - although too worn down for a car - can still power light loads for a very long time (days). And I could just hook up a few extra batteries to expand capacity (and increase solar energy absorption rates).

    To protect against short-circuits, the battery is protected by a fuse. This is critical because car batteries can produce so much current that they can be used for welding. They are dangerous.

    If you ever work with lead acid batteries, know this: don't discharge them beyond 50% of capacity, and ideally not beyond 70% of capacity. The deeper the discharge, the lower the life expectancy. A 100% discharge of a lead acid battery will kill it very quickly.

    You may understand why Lead Acid batteries aren't that great for solar usage, because you need to buy enough of them to assure you never have to deep discharge them.

    Voltage, Current and Power Sensor

    I noticed that the load current sensor of the solar charge controller was not very precise, so I added an INA260 based sensor. This sensor uses I2C for communication, just like the LCD display. It measures voltage, current and power in a reasonable presice resolution.

    Using the sensor is quite simple (pip3 install adafruit-circuitpython-ina260):

    #!/usr/bin/env python3
    import board
    import adafruit_ina260
    i2c = board.I2C()
    ina260_L = adafruit_ina260.INA260(i2c,address=64)

    Please note that this sensor is purely optional, the precision it provides is not really required. I've used this sensor to observe that the voltage and current sensing sensors of the solar charge controller are fairly accurate, except for that of the load, which only measures the current in increments of 100 mAh.

    The LCD Display

    The display has four lines of twenty characters and uses a HD44780 controller. It's dirt-cheap and uses the I2C bus for communications. By default, the screen is very bright, but I've used a resistor on a header for the backlight to lower the brightness.


    I'm using the Python RPLCD library (pip3 install RPLCD) for interfacing with the LCD display.

    Using an LCD display in any kind of project is very simple.

    #!/usr/bin/env python3
    from RPLCD.i2c import CharLCD
    lcd = CharLCD('PCF8574', 0x27, cols=20, rows=4)
    lcd.cursor_pos = (0,0) # (line,column)

    12 volt to 5 Volt conversion

    I'm just using a simple car cigarette lighter USB adapter to power the Raspberry Pi 3b+. I'm looking at a more power-efficient converter, although I'm not sure how much efficiency I'll be able to gain, if any.

    Update: I've replaced the cigarette lighter usb adapter device with a buck converter, which resulted in a very slight reduction in power consumption.

    Script to collect data

    I've written a small Python script to collect all the data. The data is send to two places:

    • It is send to Graphite/Grafana for nice charts (serves no real purpose)
    • It is used to generate the infographic in the sidebar to the right

    Because I don't want to wear out the SD card of the Raspberry Pi, the stats as shown in the sidebar to the right is written to a folder that is mounted on tmpfs.

    The cloud as backup

    When you connect to this site, you connect to a VPS running HAProxy. HAproxy determines if my blog is up and if so, will proxy between you and the Raspberry Pi. If the battery would run out, HAProxy will redirect you an instance of my blog on the same VPS (where it was running for years).

    As you may understand, I still have to pay for the cloud VPS and that VPS also uses power. From an economical standpoint and from a ecological standpoint, this project may make little sense.

    Possible improvements

    VPS on-demand

    The obvious flaw in my whole setup is the need for a cloud VPS that is hosting HAProxy and a backup instance of my blog.

    A better solution would be to only spawn a cloud VPS on demand, when power is getting low. To move visitors to the VPS, the DNS records should be changed to point to the right IP-address, which could be done with a few API calls.

    I could also follow the example of Low-tech Magazine and just accept that my blog would be offline for some time, but I don't like that.

    Switching to Lithium-ion

    As long as the car battery is still fine, I have no reason to switch to Lithium-ion. I've also purchased a few smaller Lead Acid batteries just to test their real-life capacity, to support projects like these. Once the car battery dies, I can use those to power this project.

    The rest of the network is not solar-powered

    The switches, router and modem that supply internet access are not solar-powered. Together, these devices use significantly more power, which I cannot support with my solar setup.

    I would have to move to a different house to be able to install sufficient solar capacity.

    Other applications

    During good weather conditions, the solar panel provides way more power than is required to keep the battery charged and run the Raspberry Pi.

    I've used the excess energy to charge my mobile devices. Although I think that's fun, if I just forget turning off my lights or amplifier for a few hours, I would already waste most of my solar gains.

    I guess it's the tought that counts.


    In the end, it it was a fun hobby project for me to realise. I want to thank Low-tech Magazine for the idea, I had a lot of fun creating my (significantly worse) copy of it.

    If you have any ideas on how to improve this project, feel free to comment below or email me.

    This blog post featured on hacker news and the Pi 3b+ had no problems handling the load.


    Car battery died

    After about two weeks the old and worn-down car battery finally died. Even after a whole day of charging, the voltage of the battery dropped to 11.5 Volts in about a minute. It would no longer hold a charge.

    I have quite a lot of spare 12 volt 7Ah batteries that I can use as a replacement. I'm now using four of those batteries (older ones) in parallel.

    Added wall charger as backup power (October 2020)

    As we approached fall, the sun started to set earlier and earlier. The problem with my balcony is that I only have direct sunlight at 16:00 until sunset. My solar panel was therefore unable to keep the batteries charged.

    I even added a smaller 60 watt solar panel I used for earlier tests in parallel to gain a few extra watts, but that didn't help much.

    It is now at a point where I think it's reasonable to say that the project failed in my particular case. However, I do believe it would still be fine if I could capture the sun during the whole day (if my balcony wasn't in such a bad spot, the solar panel would be able to keep up).

    As the batteries were draining I decided to implement a backup power solution, to protect the batteries. It's bad for lead acid batteries to be in a discharged state for a long time.

    Therefore, I'm now using a battery charger that is connected to a relais that my software is controlling. If the voltage drops below 12.00 volt, it will start charging the batteries for 24 hours.

    1. the position of the panel is not optimal, so I will never get the panel's full potential. 

    2. You don't have to buy the cable supplied by Victron, it's possible to create your own. The cable is not proprietary. 

    3. It failed. Please read the update at the bottom of this article. 

    Tagged as : solar

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