Octopus Go and Battery Charging

I have a 4.2kwh array and 9.2 kwh battery and I'm on the Octopus Go tariff. At the moment I charge my EV and battery during the cheap night rate. My question is, does anyone NOT force charge their battery and/or EV on the cheap rate and let the system manage itself to get through the night. I'm pretty sure it doesn't make sense to do this but curious to see if people think there is a benefit to doing this, especially as we get closer to those (hopefully long, hot summer days.

I'm on Intelligent Octopus, and my batteries are set to charge 100% for the whole 6 hours, even if there is going to be sun the next day. I just want a full battery all the time paid for by cheap electric.

Hi The Mighty King Tubby I'm on Go as well. The answer to your question very much depends on individual circumstances. I personally micromanage my house battery. My goal is to export as little as possible.

If there looks to be sufficient solar the next day I don't charge my battery fully, sometimes not at all. This way there's space in the house battery to dump excess solar. If the car's on the drive I'll plug it in and charge so as not to max out the house battery for the same reason.

The calculation I choose to do is to look at the value of the electricity. If I charge my battery at night, then subsequently sell power during the day, that costs me the difference between what I sold it at and what I bought it at. 4.1p - 9.5p = -5.4p. If I don't charge at night, then that same power I would have sold gets saved in the battery during the day, that's the equivalent to saving the cheap rate tariff every kWh.

But then I'm a cheapskate. YMMV.

The Mighty King Tubby We do it slightly differently. We look at how much we need in the battery at the end of the off-peak to get us through to the next off-peak, assuming no PV. We set the Charge to % to that value and leave it alone. In the winter, we need the batteries charged to 100% to get us through to the next window. In spring and autumn, it's 70-80% and this time of year it's 60%.

In practice, if we end the timed charge with 60%, we get loads of solar and (with the longer sunny days) the battery is fully charged early doors and no demand from battery until after supper time. As a result, we enter the timed charge period with SoC higher than Charge to %, so the battery supplies the house until the timed charge period ends with battery at, say 70%. We charge the EV during the day from diverted solar export, but still export at times. We aren't looking to make money from import cheap/export expensive, just to minimise our grid import over the year, charging EV as much as possible from the roof as well. We find this "seasonal" strategy is pretty much "set and forget".

Just don't forget the round trip losses if you're charging from mains and the discharging to sell (if you're bothered about accurate calculations that is).

I tend to charge somewhere between 60% to 100% depending on the forecast.

Although sometimes if I expect a sunny day I just use the washing machine or dishwasher rather than leave room in the battery for solar gain.

It's the first May with battery and solar for me and the approach currently is to keep battery at Solar only. Having said this, a few overnight test charges to better understand the battery schedule and also Eddi heating have been tried in May. Usually, day consumption has been less than 10kWh at this time of year - but having solar, diverter, battery and an EV makes a mockery of previous statistics: already consumption this month has exceeded the average monthly usage.
The approach of @BobB resonates with me: it's all about minimal export - to which minimal import is also important. If solar utilisation in the summer months gets to anything over 80%, that's an absolute winner for me.
October or November will likely be the months to switch overnight charging on permanently, which probably means 60/70% for the twin battery system here.
Awaiting an export MPAN from Octopus (who are a breath of fresh air to deal with) so that these weeks around the solstice get something for the inevitable export. If the sun ever comes out to play, of course...

Tim
At present my battery is set to the default charge of 100% and I force charge between 0030-0430. The panels kick in at about 0800 by which time we are on 80% ish and we manage on PV/Battery (bar the occasional spike for kettles and ovens) until the cycle starts again.

If I have understood you correctly I should try reducing the % I charge too overnight to about 60% to reduce our grid import? Is that correct?

Cheers

The Mighty King Tubby there’s no right or wrong, it’s just what works for you. Reducing your charge to % will reduce your grid consumption, making you rely on PV, which is pretty reliable this time of year. Maybe work out how much you would have to have in the battery if it turned out to be a dark grey rainy day with minimal PV. What would you have to have “in the tank” to ensure you didn’t need grid import in the evening. It’s a balance of risk. Over charging off peak reduces the risk of having to import in the evening at peak rate. Our risk threshold in the winter is 100%, 80% in early spring and 60% now. We haven’t actually imported from grid (other than load change balance) since mid-March.

I am also on Go, with PV, 9.5kW battery and an EV. Over the winter I always charged the battery overnight to 100%, but since March I have been micromanaging it based on the estimated generation from Solcast plugin on the GivEnergy Cloud portal.

I set up my east/west panels in Solcast and I am surprised at how accurate the estimated generation is. If the estimate is less than my typical usage then I’ll charge 50-80% overnight. If more then I’ll often set it to 20% and that covers me until the sun comes out at 7am.

I always charge the EV overnight direct from the grid if I know I will need the range i.e. I am travelling on a long journey, but usually I just let it charge off solar during the day. I leave it plugged in all the time to just feed excess PV to the EV. Only time I use the battery to charge the EV is to use excess on a cloudy day to meet the 1.4kW minimum to charge the EV.

I am sure I could figure out some home automation to handle this logic if I had the time; it’s a shame there’s no common API standard for GivEnergy, MyEnergi, EV manufacturers to allow everything to talk. Chat-GivEV … where are you!

AlanG Chat-GivEV … where are you!

Only during office hours when someone is available.

AlanG I use the battery to charge the EV is to use excess on a cloudy day to meet the 1.4kW minimum to charge the EV.

If you have a Zappi (or your charger has similar settings), try adjusting the Minimum Green Level on ECO+. At 100%, it won't start to charge until there's at least 1.4kW available to divert. At lower values, it will blend export and grid import, except your inverter will reduce grid import and feed the EV from battery. There's likely a setting that would enable you to blend export/battery to achieve the 1.4kW?

The Mighty King Tubby I fully charge during cheap rate during winter months. October - March. But right now I am on Flux, even with an EV my grid use is under 9kwh. Just over 60 miles per day. 100% electric home. But I do have excessive amount of PV....

I do similar to above. My objective is simply to minimise peak import. I’m on GO and in the winter I charge battery and EV to 100% overnight. In the summer I charge battery overnight to less than 100% depending on the sun forecast ie I’ll leave some capacity in the battery for the solar to fill as soon as the sun comes up and before the house starts using it. I also only plug my EV in overnight if I need a full battery next day, otherwise I plug it in the morning and let the solar charge it throughout the day. However on a slight digression from the core topic, I’ve just started trying to change my house battery setting for this summer and despite changing it in the app and online it always resets to 100%. This worked for me last summer but not now. Has there been a software change I’ve missed ?

Glenbertram two typical causes

Web portal homepage - a tariff card has been added, tariff automations were switched on. It charges to 100% although it's supposed to use different values in the summer I thought?

GivTCP in use with some kind of custom automation. Smart target wasn't disabled in the GivTCP config/variables.

Or another possibility, the change from 100% failed to save due to interrupted Comms. Try saving it again, then check the logs to see if it actually saved (logs are off the MyInverter page, cog/remote control button, jump to logs button).

TX200 Thanks. I think it might be the tariff automation which I'd forgotten about. Have turned that off and will see what happens tonight.

Glenbertram

TX200 thanks again. Turning off the tariff automation worked .