Technical Support

I could not find this anywhere else so I thought I would share in case it is helpful to anyone else.

I have a Sunsynk 3.6KW Inverter, 5.5KW of panels, a home built battery, a Zappi car charger, an electric car and I am an Octopus Intelligent customer. Octopus Intelligent provides cheaper electricity from 23:30 to 05:30

I have my house wired like this from https://support.myenergi.com/hc/en-gb/articles/10066139366161 (you can replace Growatt with Sunsynk in this diagram)

I have my Sunsync set as most of you have

- Zero export

- Solar Export

- Priority Load

On the System Mode System 2 page

I also have use timer enabled with

- SOC set to 10% between 05:30 and 23:30

- SOC set to 90% between 23:30 and 05:30 with grid charge ticked.

Crucially I also have

- Grid Peek-shaving turned on

in advanced and I find this is the setting most people forget.

What this means on a normal day is the battery charges overnight using cheep electricity to 90%. Then from 05:30 I use the battery for all my energy until the sun comes up. For a while I supply all my energy as a mix of solar and battery until the solar is more than I need, at which point the battery starts to charge,

If the sun goes in (or goes down later in the day) I start consuming from the battery and mixing that with solar until eventually it gets dark and I am only consuming from the battery. I have enough battery for one full day, (I have a second on the way). I like to make sure my battery is charged at night so I always have enough energy to power my home if there is no solar as the cost of not having a full battery (and paying full price for electricity on a day with no sun) outweighs for me the potential lost solar energy. You may make other choices. When my second battery arrives I will charge every night to 50% to achieve the same.

I plug the car in most of the day (more on that later), however on a normal day Octopus decide when to charge my car and normally that is between 23:30 and 05:30 (although some days they will pick windows outside of this but will only charge me the low price is they do). Until recently I just left the Zappi car charger on Fast charge all the time and the car set without a schedule,. This allowed Octopus to be in control. The only downside is when ever you plug in the car, it will start charging straight away from the grid and it takes Octopus a while to spot it is plugged in and turn off charging, which puts expensive electricity into the car. We have been switching to the Tesla App when we plug the car in and hitting stop charging to reduce that. I have just tried setting my Zappy to Eco Plus and setting a fast charge schedule from 23:30 to 05:30. Hopefully this will work well with Octopus but it is too early to report.

On a really sunny day I can recharge the battery to full during the day and then the configuration I detailed above means the inverter will start exporting to the grid. I do not get paid for that but at least it is some gas somewhere that does not get burned to supply someone else. However, we can do better than that. We leave the car plugged in all day. We switch the Zappy to Eco Plus and switch Octopus Agile to "Bump Charge" before it gets too sunny, (I have just changed to try using the Zappi scheduler to switch between fast charge at night and Eco+ during the day but it is too early to say if that will work). In this configuration, when the export to the grid rises above about 1.4KW the Zappi will start charging the car using the excess solar. This works well, mostly.

There are two challenges, especially if you are in the UK and the sun is pretty variable. Sometimes I generate less that 1.4 KW excess which is just wasted if the battery is full as the Zappi will not turn on under 1.4 KW export. Sometimes I generate more than 3.6KW which is the maximum my inverter can export to what it thinks is the grid (but is actually the car) so the rest has nowhere to be captured if the battery is full. Often I switch between these two states regularly during the day as the clouds go over and the car switches from charging to not charging very regularly. The charger implements a 30 second delay before starting charging again which means you lose power to the grid when a cloud goes over. Sometime flip flopping between charge an discharge too often will upset charger, car or both and you need to physically disconnect the car to get charging again.

I have found that a better solution is to recognize when the battery is on the way to filling up and intervening. If I have the car plugged in, with Eco+ mode set on the charger and Octopus set to Bump charge (as is my normal day) you can choose to tell the Sunsynk to divert all the energy it can to export before the battery gets full. This is useful if you actually want to export (perhaps you are an Octopus Flux or Intelligent customer), but in this case I am going to use it to charge the car, By doing this you charge the car at a relatively constant rate, the full export capability of your inverter minus whatever the house is using or your maximum export setting (which I have set as 3.68 KW). There is much less chance the charging will stop and start or that you will export anything to the grid. It is still possible for a heavy house use to cause this when your house needs exceed your inverter capacity (electric oven and a kettle for example) so it is not fool proof.

To achieve maximum export or charge, turn off grid peek-shaving and zero export. In the Sunsynk App this will show as having selling first selected. In this mode the maximum 3.6 Kw is exported from my inverter to the grid/car I do this on a sunny day so if I am generating more than 3.6KW of solar the rest goes into the battery (which is why it is crucial to do this before the battery is full). If the sun goes in, that 3.6KW is maintained by draining the battery. If I intervene early enough I can stop the battery getting to 100%

Obviously it goes without saying that if you left this configuration on when you are not generating electricity from the sun you will start to drain your house battery, so once you have got your battery down to a level you are comfortable with then you should go back to the settings at the top of this post.

If this seems like a lot of mucking about, I understand. I do plan to automate it in Home Assistant when I get the time. You could probably avoid this all by having at least twice your daily consumption in batteries and only charging to 50% each night but after a few days of sun you can still use this method to charge the car. There is also a rumor that Octopus will integrate with the Myenergi Zappi this year which could make things easier (or not).

Annoyingly Octopus will just randomly turn off bump charging for what seems like no reason. If you do not spot this then you can dump the contents of your battery to the grid without charging the car. Octopus Intelligent is a beta service but I hope they fix that soon. Switching to one of the less intelligent tariffs would be safer but give less time on cheep electricity and would increase your battery requirements. Again I feel some automation may help me here.

Hope this helps someone