Battery, part 3

Slightly misleading as battery is charging!

I have just been going over the final handover and testing with Green Park for the Tesla Battery.

Part of it was making a power cut. This was interesting.

So a few facts that are useful to know.

• A real power cut means a couple of seconds of no power. It is not seamless.
• A deliberate "off grid" (done on the app) does not, so if it is a planned power cut then you can seamlessly go off grid if needed. Good.
• Going back on grid is seamless, a few seconds while it sorts phase match and back on. Good.
• It will take solar during a power cut, and charge the battery if needed. Good.
• If the solar exceeds its 5kW charging capacity it will shut down the solar (done using frequency change, apparently).

The last point is a pain as the solar can do 10kW. More importantly the solar can control what it makes by de-optimising the panels, so it if knew it was a problem it could reduce power. There seems no way to link these intelligently, sadly. But once I have a second battery we will be fine at it will match the battery, at least until the battery is full. What I don't know is if there is any way it tries to turn the solar back on in such cases, maybe trying it for a few seconds every now and then? Must find out.

And as for the first point, a power cut causing a blip - I need a very small UPS for my comms rack to last a few seconds, that is the easy part.

Second battery

One battery can handle 5kW in/out, and charge to 14kWh. This is fine for most cases for balancing the solar and usage and reducing export. It is also perfect for getting on the Octopus tariff for this where they manage the battery and I pay for net usage.

However, one battery does limit my options. It does not have capability to run the house for 24 hours, meaning that I cannot make use of "cheap charge at night and run of battery for the day". If I could, I would save even more, but without that I could be using more expensive electricity later in the day, especially in winter when less sun.

One battery is also likely to have the same issue if I went on an agile tariff, in that trying to match charge at low price and usage when high would be hard if I do not have a whole day's capacity.

So for these various reasons, a second battery is on order. For now, I am trying to sort the Octopus tariff, which is fun.

Off backup

The other work still planned is an additional small consumer unit that has a few circuits which will not be on backup. The Tesla can only do 5kW, so if I have the tumble drier on, or the car charger, it won't work. There are about 4 circuits to move to that. All good fun.

Battery, part 2

Tesla Gateway 2

This is just about the install. I have yet to get in to the details of APIs, and apps and so on. So just the install for now.

It is all pretty simple to be honest. Battery on the wall outside, and "gateway" box inside.

The gateway is put in line from the incoming power, so the tails in to the consumer unit had to be fished out and fed in to the gateway and then new tails to the consumer unit. The battery is then connected to the gateway. There is comms to the battery, and a current clamp for the solar incoming. The unit has ethernet, but also has wifi and cellular.

I say it is simple, but fishing the tails meant eventually making holes the other side of the internal wall. The holes through the wall to the battery outside involved big drills, and eventually an endoscope I happen to have! Both tasks probably involved about an hour of "no progress". But the job was done in the day, and nicely done by Green Park Power.

It is worth explaining, this "gateway" allows me to work off-grid as well, running just from the battery. Ideally, to do this, I need to put some circuits on a separate "no-backup" circuit. I'll get a small additional consumer unit installed for that. It will have the tumble drier, hot tub, heated kitchen floor, EV charger, on it. For now, we have the whole house on battery, which will not cope if we go over 5kW during a power cut.

Right now my solar and demand have, as normal, gone up and down, but the battery has balanced it all so zero grid usage, either charging or discharging the battery. That alone is quite amazing.

Tesla app

There are a lot of settings, and I have not even started to look at them. I need to read up on this, and work out the best way to keep my power usage sensible. I also need to mess with a couple more current clamps as I no longer see the final import/export on my own monitoring, or the solar edge.

Longer term I need to work out if there is a good tariff to be on, and separately if I can use an agile tariff in a clever way. What we do have is wiring for a second battery - but that may take 6 months to get.

First gripe: Cannot work out if any way to turn of WiFi AP SSID from it!

Battery, part 1

This post is literally just a teaser.

The solar install was to include a battery, but it has taken months to arrive. Finally it is fixed to the wall - that is it for part 1, bolted to the wall.

It is Tesla Powerwall with 13½kWh usable storage, with 5kW charge/discharge rate.

Later this week Some time next week, it will be wired up, including a "gateway" to allow me to run off grid during power cuts.

Should be fun, watch this space.

But yes, planning to explain what it is, how much, what it does, how the wiring works, how it works with the solar panels, the app, the API, the tariff I end up, etc...