4 ms·

sarcher's example of JLC. It does look like a faulty optimizer, which is a DC electronic for each panel. As for Walmart, it's a lot to unpack. > dozens showin

sarcher's example of JLC. It does look like a faulty optimizer, which is a DC electronic for each panel. As for Walmart, it's a lot to unpack. > dozens showing hazardous problems such as loose wiring and “hot spots” on panels, according to court papers filed in New York State Supreme Court. Loose wiring? A lot of setups are mostly plug and go. If they had to splice one wire, it's only a minute process to do and if they used their eyes for a few seconds (I'm describing the literal process of splicing a panel wire. I'm not demeaning the work. It's minutes. 3 max, if you brought the parts on the roof.) As for the other connections a solar installation may need, the time it takes it one minute for all connections on the roof. For the 244 panel setup of Walmart, 30 minutes tops (20.3 minutes to be closer to realistic because there might be 21 j-boxes, each connecting 12 panels to the main array). Hot Spots? I have no idea about that one. It's too vague. At a different location, this is what Walmart said: >One of the fires happened months after the system was de-energized, Walmart said. I don't understand this one at all. Tesla/SolarCity must be using very cheap electronics because this shouldn't happen. Each panel's optimizer should be equipped for the situation when they aren't producing usable power. Source: I worked in residential solar for about 6 months and as an electrician for two years. I'm not a bona fide source but I'm better than most because I've paid attention to everything that was taught to me. Plus I'm looking into starting my own Solar company.

londons_explore 7y ago
The optimizer consists of MOSFETs, an inductor, and a microcontroller. The circuit is pretty similar to a BLDC motor controller. The circuit relies 100% on the microcontroller outputting the right signals, otherwise a mosfet gets stuck on (causing overcurrent, and burning out). Little boxes like that are hard to waterproof and make resistant to repeated temperature fluctuations. My guess is some water went in and shorted some control signals, or repeated temperature changes caused a solder joint to crack. That caused the MOSFETs not to get the right control input, so they got really hot and caught fire. It's just as likely to happen on a de-energised panel too - the optimizer is still connected, and the sun is still shining.
- heimatau 7y ago
  > The circuit relies 100% on the microcontroller outputting the right signals I'm not an E.E. but does that apply for DC optimizers? Older optimizers had no AC conversions in them. > Little boxes like that are hard to waterproof and make resistant to repeated temperature fluctuations. Hmm. I never checked to see if the warranty for the optimizers are 20 years. The panels are but I'd be surprised to see the optimizers be less than 20. Most, non-cheap, optimizers do have insulation to prevent moisture from getting in. > It's just as likely to happen on a de-energised panel too - the optimizer is still connected, and the sun is still shining. Based on your description, that makes it a possibility. Why aren't the optimizers equipped with some type of regulator to prevent output in situations like this?
  - rasz 7y ago
    DC optimizers seem to be DC to DC converters, you rarely do those with MCU in professional setting, there are dedicated chips for it. Googling pictures of PCBs there are a ton of products with Aluminum electrolytic capacitors, those are rated at up to 10K hours at 105C, thats probably less than 5 years of sun divided by days whole thing gets cooked on the roof. Still that would merely lead to product failing to output power, MLCC and tantalum capacitors are the real problem, those love to short HARD under mechanical stresses, and temp cycling is a perfect environment to induce it. mlcc fire https://www.youtube.com/watch?v=Q2rvAoO-MIA https://www.youtube.com/watch?v=Q2rvAoO-MIA , causes https://www.youtube.com/watch?v=QgKY5QWehME https://www.youtube.com/watch?v=QgKY5QWehME
heimatau 7y ago
> Tesla/SolarCity must be using very cheap electronics because this shouldn't happen. Each panel's optimizer should be equipped for the situation when they aren't producing usable power. It feels nice to see the truth come out. Cheap parts [1]. [1] https://www.businessinsider.com/tesla-project-titan-replace-bad-solar-panel-parts-2019-8 https://www.businessinsider.com/tesla-project-titan-replace-...

londons_explore 7y ago

The optimizer consists of MOSFETs, an inductor, and a microcontroller. The circuit is pretty similar to a BLDC motor controller. The circuit relies 100% on the microcontroller outputting the right signals, otherwise a mosfet gets stuck on (causing overcurrent, and burning out). Little boxes like that are hard to waterproof and make resistant to repeated temperature fluctuations. My guess is some water went in and shorted some control signals, or repeated temperature changes caused a solder joint to crack. That caused the MOSFETs not to get the right control input, so they got really hot and caught fire. It's just as likely to happen on a de-energised panel too - the optimizer is still connected, and the sun is still shining.

heimatau 7y ago
> The circuit relies 100% on the microcontroller outputting the right signals I'm not an E.E. but does that apply for DC optimizers? Older optimizers had no AC conversions in them. > Little boxes like that are hard to waterproof and make resistant to repeated temperature fluctuations. Hmm. I never checked to see if the warranty for the optimizers are 20 years. The panels are but I'd be surprised to see the optimizers be less than 20. Most, non-cheap, optimizers do have insulation to prevent moisture from getting in. > It's just as likely to happen on a de-energised panel too - the optimizer is still connected, and the sun is still shining. Based on your description, that makes it a possibility. Why aren't the optimizers equipped with some type of regulator to prevent output in situations like this?
- rasz 7y ago
  DC optimizers seem to be DC to DC converters, you rarely do those with MCU in professional setting, there are dedicated chips for it. Googling pictures of PCBs there are a ton of products with Aluminum electrolytic capacitors, those are rated at up to 10K hours at 105C, thats probably less than 5 years of sun divided by days whole thing gets cooked on the roof. Still that would merely lead to product failing to output power, MLCC and tantalum capacitors are the real problem, those love to short HARD under mechanical stresses, and temp cycling is a perfect environment to induce it. mlcc fire https://www.youtube.com/watch?v=Q2rvAoO-MIA https://www.youtube.com/watch?v=Q2rvAoO-MIA , causes https://www.youtube.com/watch?v=QgKY5QWehME https://www.youtube.com/watch?v=QgKY5QWehME

heimatau 7y ago

> Tesla/SolarCity must be using very cheap electronics because this shouldn't happen. Each panel's optimizer should be equipped for the situation when they aren't producing usable power. It feels nice to see the truth come out. Cheap parts [1]. [1] https://www.businessinsider.com/tesla-project-titan-replace-bad-solar-panel-parts-2019-8 https://www.businessinsider.com/tesla-project-titan-replace-...