Intelligent Backup Power Screen Numbers Don't Add Up

[Jim Lewis]

Today, I retested backup power transfer by my Home Integration System, and for the 6th time in a row since 1/9/24, it worked. Power came on with 1'20" of cutting grid power.

TLDR; the estimate of how long the truck can power your house must include some considerations not shown on the Intelligent Backup Power screen. Perhaps one very important factor is that one can only read the Intelligent Backup Power screen in the truck when the truck is turned ON. Maybe the numbers don't make sense because the truck is considering its own energy consumption, as well as the power transferred to the house, but not blatantly telling you that it's doing so.

At the start of the test, my truck had been in a garage overnight at 53 deg F but had sat outside at 60 deg F for about 5 hours. The ER battery was charged to 55%. As a result recently of mostly very placid city driving, the DTE was 178 miles. Backup power was set to cut out when my DTE was 47 miles. The charge and miles figures mean that I had 131 kWh in my full-capacity ER battery x 0.55 capacity = 72 kWh left in the truck. But of this 72 kWh, 47 mi range reserve /178 mi total range x 72 kWh left = 19 kWh reserved. 72 kWh - 19 kWh reserved = 53 kWh available for power transfer to house.

Within a few minutes of the power transfer initiating, I turned on the truck and looked at Intelligent Backup Power Sync screen. There was a loud whirring noise for about the first 10 minutes of the truck being turned on (plugged in, Power button pushed while stepping on the brake pedal). I wondered if the coolant heater was turned on. If the truck is in a 60 deg F environment, this usually doesn't happen, but it had been in a 53 deg F garage overnight (see prev. paragraph) and had only sat out a few hours. Backup transfer consumed 0.5 of 9.6 kW available to transfer to my house, but the estimated runtime of power transfer was only FOUR HOURS. A BIG math problem here is 0.5 kW times 4 hours transfer time available = 2 kWh consumed before the truck supposedly runs out, whereas the math of the previous paragraph says I should have 53 kWh, over 26 times as much kWh to consume. The 4-hour runtime estimate was very steady during the first ten minutes of the test while the truck's whirring noise was present.

After a few minutes, the power transfer to the house dropped from 0.5 to between 0.2 to 0.3 kW. I figured the frig had been running and just shut down. After ~10 minutes, the whirring noise stopped, the power consumption by the house continued at 0.2 to 0.3 kW for the next 10' of the test, and the estimated power transfer runtime slowly climbed to 2 days and 20 hours. That's 68 hours of total runtime.

These numbers still don't make sense. 0.3 kW x 68 hours is 20.4 kWh. The available capacity of the battery is 53 kWh. That's 2.6 times more than needed; the estimated runtime purely on power transfer to the house at 0.3 kW hours should be 2.6 times longer.

Well, maybe I didn't take into account about 5 minutes where the frig might have been running, and consumption was, let's say, 0.6 kW. That's 25% of the 20-minute observation period. So, 1/4 of the observation period times 0.6 kW is a 0.15 kW contribution to the average, and 3/4 of the observation period at 0.3 kW is a 0.225 kW contribution, making the average energy consumption rate 0.15 + 0.225 = 0.375 kW. 0.375 kW x 68 hours is ~26 kWh consumption. In contrast, the unrestricted capacity available for power transfer is 53 kWh, ~2x what the Intelligent Backup Power screen says I'm consuming in power transfer to my house.

The truck has to be on to use the Intelligent Backup Power screen. The truck is consuming a lot of power relative to the little energy being transferred to my house in this particular experiment. I think behind the scenes, the truck runtime calculation must be taking the truck's own energy consumption into account. The problem may be that Ford doesn't think it should worry the owner's silly little brain with such considerations, but then, if you take the power transfer numbers at face value, the numbers don't add up, like some numbers you see displayed in FordPass. Ford should provide helpful background hints about what's factored in, as it does for range estimates, or allow more owner drilldown into what's going on in behind-the-scenes calculations. Don't leave owners ignorant of how calculations are done and have them befuddled by figures that, at face value, don't make sense.

 

[Sea Ranch]

Thank you for the overview of what you are experiencing. How long have you had the system operating (have you successfully done many repeated simulated outages) and is what you are currently seeing repeatable?

 

[Jim Lewis]

On the funny numbers on the Intelligent Backup Power Syn screen display, this is the first time I've really paid attention to what the numbers meant. The initial 0.5 kW transfer to the house with the screen telling me the truck could only transfer power for 4 hours at that rate jarred me and made me want to think about the numbers more carefully. Most of the time, when I test backup transfer, I never bother looking at the truck screen. The lights in the garage come on when the truck is transferring power, and I can always use the M Professional app to read power transfer via the Acrel meter in the HIS system. And now that I think about it, why would I want to run the truck just to read power transfer and the predicted backup runtime? My HVB % SOC and the power transfer rate read via the M Professional app should allow me to do a back-of-the-envelope calculation at any point during my outage to calculate how much longer I can go at my present transfer rate. It is just like using mi/kWh x remaining kWh battery capacity to figure out how many miles you can drive rather than trusting the GOM. That's what I'm suggesting here: unfortunately, the Intelligent Backup Power screen runtime estimate doesn't seem much better than the GOM reading on DTE.

On how long the HIS system has been working reliably, it's a long story. The system was installed on 6/12/23 and worked 2x successfully then. Then, it wasn't made to work until 12/4/23. A large part of this was firmware updates were needed for the FCSP, the Delta bi-directional inverter, and the truck Bluetooth module to improve the connectivity to the FCSP. These became available by early October, but my own system still wouldn't work until December. The tech who worked on it said he had to reinstall the Delta inverter firmware to get it working, but it's also possible my truck had lost its BT pairing to the FCSP, and I didn't realize it. In December, after the refresh of the inverter firmware, it worked 4x in a row, then failed 2x in a row in mid-December. But since 1/9/24, it's worked 6x without fail.

I suspect the predicted runtime for available backup power will be more accurate at higher power transfer rates. But just as for GOM readings, it's better not to waste time and electricity firing up the truck to read predicted runtime off the Sync screen when HVB % SOC and the Acrel meter reading should allow a faster and more accurate prediction.

Ford should put the Intelligent Backup Power screen in the FordPass app. Perhaps it's not there now because in an extreme power outage (Category 5 hurricane, blockbuster tornado, M7+ earthquake) not only will your Wi-Fi be out but cell towers might be down, too). But in most power outages in Texas, cell towers are still working. My ignorance is showing here, but maybe FordPass should be able to read certain data directly from the truck or the FCSP and do its own Intelligent Backup Power Estimates or read the values the truck is calculating internally without having to turn on the truck. and waste precious backup power doing so.

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