Powerwall

Friday, 18 Mar 2022

Cleanest corner has been in about 20 years

Cleanest corner has been in about 20 years

Cleanest corner has been in about 20 years

This corner of the garage is now the cleanest it has been since the electric panel was upgraded in 2000. The reason is that we’ve been notified that the Tesla Powerwall battery we ordered about 20 months ago is going to be installed next week. Finally.

Monday, 21 Mar 2022

One way to add an extra bath

One way to add an extra bath

One way to add an extra bath

It’s really going to happen. This port-a-potty was left outside our front gate this Monday morning. Inatallation was initially scheduled for Tuesday and Wednesday, but I got notice that they are slightly behind schedule. That have to finish by Thursday as I head to So Cal for a family wedding Friday morning.

Tuesday, 22 Mar 2022

Battery comes tomorrow

Battery comes tomorrow

Battery comes tomorrow
Bracket for battery

Bracket for battery

Bracket for battery

The install team arrived this afternoon to inspect the site and plan for installation. The battery will be here tomorrow.

Sometime tomorrow or Thursday power will be cut to the house to move the circuits that will be backed up by the Powerwall. We will know more tomorrow.

Wednesday, 23 Mar 2022

Battery mounted

Battery mounted

Battery mounted
Control box

Control box

Control box
Control box and sub panel

Control box and sub panel

Control box and sub panel

The battery was mounted to the wall, conduit run, and the control pannels mounted inside the garage.

Wires (1)

Wires (1)

Wires (1)
Wires (2)

Wires (2)

Wires (2)
Wiring

Wiring

Wiring

Wires were run from the battery and between the various wiring panels. Wire access ports were covered after I took the picture.

Panels covered

Panels covered

Panels covered
Emergency disconnect will go here

Emergency disconnect will go here

Emergency disconnect will go here
Front view

Front view

Front view
Side view

Side view

Side view

The install crew will be back tomorrow to finish the job. The only thing I don’t like is the county requirement for a push button battery disconnect switch near the main electrical panel at the front of the house.

There is still some of the protective plastic stuck to the battery. I’ll need to do a little touch up painting when they are done, too. Wonder if I still have any paint left from the last time I bought a pint.

Connection Schematic

Connection Schematic


This is how (I think) the Powerwall is connected in our house.

Thursday, 24 Mar 2022

Today all of the circuits that can be powered by the battery were moved to the sub-panel. The installers estimate was for 3 to 4 hours. Accurate. Power was restored after about 3 1/2 hours.

Sub-panel for battery powered circuits

Sub-panel for battery powered circuits

Sub-panel for battery powered circuits
Main panel

Main panel

Main panel
Protective plastic removed

Protective plastic removed

Protective plastic removed
Ready for inspection and turn-on

Ready for inspection and turn-on

Ready for inspection and turn-on

Next step is inspection and battery turn on. That hasn’t been scheduled, yet. At that time they’ll cut power one more time by pulling the meter to replace the 200 amp main breaker with a 175 amp breaker. The loss of 25 amps won’t hurt us at all. I think the most we use at any given time is well under 150 amps.

Friday, 29 Apr 2022

Today is the day the Powerwall was supposed to be turned on.

The installer came and made everything ready for the inspector. He found that the communications line between Powerwall and its Gateway wasn’t connected. Fixed. The county inspector came and checked plans, the electrical work, various safety lables, etc. He also verified our house has the needed working smoke and CO detectors because they do that. All good.

The installer turned on the battery. It updated its software. It reported some kind of low voltage error.

In addition to the communications cable there are three power wires between the Powerwall and the sub-panel, a neutral and the two hot wires of a 240V connection protected with a 30 amp circuit breaker. Voltage is OK at the breaker. Voltage is not OK at the Powerwall end of the wires. There is 120V between the black hot lead and neutral. There is only about 10V between the red hot lead and neutral. Measurements were made with the leads disconnected from the Powerwall, of course. It looks like the red wire is bad. Grumble.

Don’t know when this will be fixed. Assuming the problem was diagnosed properly the installation company will have to pull a new wire to get things up and running. I hope this happens soon. We’ve been waiting since July 2020.

Saturday, 30 Apr 2022

The problem annoyed me. Thinking about it I realised that the wire from breaker to Powerwall goes through an emergency cutoff push-button switch. I don’t think the switch was ever tested. I can do that.

The switch should, I think, connect or disconnect both hot leads. Button “in” is emergency off – both leads disconnected. Button “out” is normal operation, both leads connected. That is not how the installed switch works.

Button “out” only connects one of the leads. Button “in” swaps the connected leads. At no time are both leads connected (or both disconnected). The proper switch needs to be installed. I emailed what I found to the company installing the system.

Wednesday, 11 May 2022

PGE and the Powerwall install company were here this morning. PGE disconnected power to the house so the installers could swap out my 200A main breaker for a 175A breaker. When they were done PGE hooked the house back up and left. That took about 10-15 minutes.

The installers next took on my emergency cut-off button issue. Simple fix: the guys who installed the Powerwall did not correctly hook up the emergency cut-off. The switch isn’t intended to switch power directly. It switches leads in a communications cable connected to the Gateway. The Gateway is responsible for disconnecting the power. Advantage is that the switch doesn’t have to control full battery power. Also, one switch can cut off multiple batteries in larger systems.

With everything up and running the main breaker was switched off to test. The house maintained power using the battery. Non backed-up circuits like the pool pump turned off. Pushing the battery disconnect button dropped power to the house. Pulling the button restored the battery connection and house power. The main breaker was turned back on and the electrical panels buttoned up. I think the entire vist was about an hour.

Solar panels power the house and charges the battery. Any excess is sent to the grid. If more power is needed than is generated the power is pulled from the grid. Grid power is not used to charge the battery (although I think that is an option in some jurisdictions). The battery was 100% charged from our solar panels by 2 PM.

At 3 PM our electric rates rise (and the pool pump turns off). Our solar panels power the house with excess power sent to the grid. Rates hit their maximum at 4 PM. As I type this (5 PM) our panels are providing about 0.7 kW to the house and 3.0 kW to the grid.

I’m using the default Powerwall settings which will use battery power in place of grid power when the solar panels stop generating power. Battery power is used until the battery gets to 26% capacity at which point the system switches to grid power. That keeps a battery reserve in case of a power outage. I’m curious to see how much power we use over night. I can play with the reserve percentage if I like.

Friday, 13 May 2022

Some observations after about a day and a half of sunny springtime battery usage.

About 45% of available battery power is used powering the house between roughly sundown and sunup. Solar generation doesn’t get above a kW until almost 2 hours after sunrise. If falls below 1 kW about an hour and a half before sunset. No power to speak of is generated within 20-30 minutes of sunrise/sunset. With current sunrise/sunset times that means the battery if fully powering the house for about 11 hours and partially providing power an additional 2 1/2 hours.

The battery reached full charge a little after noon yesterday and today; both days of clear blue skies. During the time the battery is being charged very little power is being delivered to the grid.

Home Usage

Home Usage

Crop of a screen shot from the Tesla App showing home usage. Green is power supplied from the battery. Yellow is power supplied from the solar panels. There is some gray (power from the grid) in there, too.

I don’t know the cause of that spike in power drawn from the battery around 8 AM.

Impact

Impact

The app says that we were 99% self powered on the 12th. I like. Not sure why we used power from the grid, but in any case it was a very small amount. Grid usage will be higher on days we use our oven. The oven is not backed up by the battery and its use would most likely occur when there is little to no available solar power.

The Solar Offset of 228% is a bit misleading to my way of thinking. 100% would mean we generated exactly the power we needed. 228% say we generated 128% more power than we need. That excess power is sent to the grid. On the 12th that was 20.8 kWh.