Well, not exactly.
First, some background, and apologies in advance for the long post. Our five powerwalls were installed last week (after being ordered last March) in combination with our existing 38kw solar array, which was installed this past September. We use quite a bit of power here on our farm, where our home and business, totaling three occupied/heated/cooled buildings, are located. The solar array should 90 to 100% of our electrical needs over the course of the year. I decided to go the solar/battery back-up route after originally considering back-up generator(s) for grid down scenarios. The economics of backing-up our electrical needs via generator and propane turned out to be as expensive, or more expensive than installing the 5 powerwalls—especially when assuming outages of several days or longer, given the cost to run propane in a generator system that large. And, Maryland has an Energy Storage Tax Credit that 30% (up to $5000 for residential, $75,000 for commercial), which is on top of the Federal credit. So, after doing some research on the powerwalls, it was a no-brainer. I view the solar as an investment, and the powerwalls as insurance.
The solar install was a big project, and has not been exactly smooth sailing, although I am happy overall. We’ve had high grid voltage issues, which along with our large solar array during sunny days, often pushes the voltage above 260, and occasionally above 263. At 263, at least one of our three (3 x 11.4kw) SolarEdge inverters will trip, which then lowers the line voltage below the threshold, which allow the tripped inverter(s) to come back online after about 5 minutes. I’ve been hounding our utility company about the line voltage, which they admit is too high, and they’ve finally indicated that it should be fixed by this Friday. Fingers crossed, but not holding my breath. In the meantime, when I’m paying attention during sunny days, I’ve found that increasing the household electrical loads (e.g., time our laundry to run during peak solar production) reduces the line voltage, usually enough to avoid tripping the solar inverters. Despite these frustrations, I’m very happy with our solar production.
Back to the issue at hand. Everything had been running well with the powerwalls as far as I could tell. We ran through a number of grid-down simulations (first with the installation crew, and later by myself), and the system worked well, with our backed-up circuits all running as planned, including the largest of our hvac systems, a 5-ton heat pump (in which they insisted installing a soft start, even though it likely didn’t need it). The Tesla app also seems to be working right for the most part. Then, yesterday: as solar production was ramping up at ~10:30am, the grid power went out, and the powerwalls failed to kick-on. At the time, grid voltage was high, above 260, and the powerwalls were at 100% SOC. Power was out at our neighbors as well, so it wasn’t only our property. Power was out for only about 5 minutes, and my Tesla app shows that back-up power was on for 3 seconds, although it was difficult to gauge that in real-time. I don’t know if, had the grid power been down for longer, whether the powerwalls would have turned back on by themselves, but everything came back online when the grid power came back. No problems since then, and I've run another simulated grid-down, although I've not tried a simulated outage during peak solar production while batteries are at 100% (will do that today).
So, my questions are:
If you’ve read through this, I’m impressed and thankful. Any insight would be much appreciated—I’ve already learned quite a bit from this forum.
Matt
First, some background, and apologies in advance for the long post. Our five powerwalls were installed last week (after being ordered last March) in combination with our existing 38kw solar array, which was installed this past September. We use quite a bit of power here on our farm, where our home and business, totaling three occupied/heated/cooled buildings, are located. The solar array should 90 to 100% of our electrical needs over the course of the year. I decided to go the solar/battery back-up route after originally considering back-up generator(s) for grid down scenarios. The economics of backing-up our electrical needs via generator and propane turned out to be as expensive, or more expensive than installing the 5 powerwalls—especially when assuming outages of several days or longer, given the cost to run propane in a generator system that large. And, Maryland has an Energy Storage Tax Credit that 30% (up to $5000 for residential, $75,000 for commercial), which is on top of the Federal credit. So, after doing some research on the powerwalls, it was a no-brainer. I view the solar as an investment, and the powerwalls as insurance.
The solar install was a big project, and has not been exactly smooth sailing, although I am happy overall. We’ve had high grid voltage issues, which along with our large solar array during sunny days, often pushes the voltage above 260, and occasionally above 263. At 263, at least one of our three (3 x 11.4kw) SolarEdge inverters will trip, which then lowers the line voltage below the threshold, which allow the tripped inverter(s) to come back online after about 5 minutes. I’ve been hounding our utility company about the line voltage, which they admit is too high, and they’ve finally indicated that it should be fixed by this Friday. Fingers crossed, but not holding my breath. In the meantime, when I’m paying attention during sunny days, I’ve found that increasing the household electrical loads (e.g., time our laundry to run during peak solar production) reduces the line voltage, usually enough to avoid tripping the solar inverters. Despite these frustrations, I’m very happy with our solar production.
Back to the issue at hand. Everything had been running well with the powerwalls as far as I could tell. We ran through a number of grid-down simulations (first with the installation crew, and later by myself), and the system worked well, with our backed-up circuits all running as planned, including the largest of our hvac systems, a 5-ton heat pump (in which they insisted installing a soft start, even though it likely didn’t need it). The Tesla app also seems to be working right for the most part. Then, yesterday: as solar production was ramping up at ~10:30am, the grid power went out, and the powerwalls failed to kick-on. At the time, grid voltage was high, above 260, and the powerwalls were at 100% SOC. Power was out at our neighbors as well, so it wasn’t only our property. Power was out for only about 5 minutes, and my Tesla app shows that back-up power was on for 3 seconds, although it was difficult to gauge that in real-time. I don’t know if, had the grid power been down for longer, whether the powerwalls would have turned back on by themselves, but everything came back online when the grid power came back. No problems since then, and I've run another simulated grid-down, although I've not tried a simulated outage during peak solar production while batteries are at 100% (will do that today).
So, my questions are:
- Anyone have any idea what could have caused a failure in the back-up power? Is there a safety mechanism built into the powerwalls that turns them off in a high voltage spike scenario, like what happens with the solar inverters? I wonder if the same thing would have occurred had the powerwalls been at less than 97% charge (thereby able to absorb the solar that was being produced when the power went out, which was a little over 20kw).
- In a grid down scenario, would the powerwalls turn off the solar panels if the solar panels produce more than what is consumed—i.e., solar is producing 30kw and the 5 powerwalls (which to my understanding can’t charge at a rate of more than 5kw per powerwall= 25kw for 5 powerwalls) plus consumption is less than that?
- Has anyone figured out how to reliably keep the powerwalls from charging above a certain reserve level, say 70%? I tried a couple different Time-Based settings, where peak prices were set during solar production hours, and the powerwalls still charge beyond the reserve level with excess solar.
If you’ve read through this, I’m impressed and thankful. Any insight would be much appreciated—I’ve already learned quite a bit from this forum.
Matt