I'm fairly new to this. I have a 13.5kWh AIO and Gateway. I've been trying to export energy between 1600 and 1900 and import it 0200 to 0500. The importing works fine but there's one big problem with the export. I set a limit of 50% on battery discharge to try to ensure there is enough left to power domestic use. But the moment the AIO has reached that limit, itstead of providing domestic use, it freezes the battery and starts importing (at peak rates). Is it me 😳?
RR50 I set a limit of 50% on battery discharge to try to ensure there is enough left to power domestic use.
Note that (in my region) peak export rate is very slightly higher than daytime import rate. So it's not really a big deal to export too much, and then have to pay for some import later on. Eg if you end up importing 2kW in the evening, then you exported 2kW too much during the peak. But you would have earned (in my region) an extra 226.6p and spent an extra 224.98p. (There are losses, but since the inverter had to convert battery to AC in both cases, I think those work out to be identical ?)
i.e. if you export too little, you miss out on some profit ; if you export too much, you're no worse off. So there seems little point saving any for evening use.
Conversely, daytime export is slightly less than nighttime import, so you lose out very slightly by charging overnight by more than you need, so that you end up exporting excess at the day rate.
(Can someone check my sums...)
[unknown] Thanks for your reply and, sorry, I'm new to the system and obviously the forum so please excuse me for not having the benefit of all the history. Your response was quite informative but can you please help me by telling me whether you are an informed user, a designer or designer's representative.
CW Thanks for your reply and, sorry, I'm new to the system and obviously the forum so please excuse me for not having the benefit of all the history. Your response was quite informative but can you please help me by telling me whether you are an informed user, a designer or designer's representative.
geoffreycoan Yes, it's a good point,. I'm asking this question assuming winter conditions really not the current spell of sunshine.
DD You're no worse off unless you start importing at peak rate - which is what I've found. Looking at the AIO directly, it seems to make sense. But the control overlay (App) doesn't make much sense to me atm. I'm a control engineer and I would like to see the requirement spec for the App.
RR50 I'm a control engineer and I would like to see the requirement spec for the App.
there are no specifications available that I have ever seen. There is an app user guide available if you search for it and there’s youtube videos, but GivEnergy isn’t great on documentation.
If you have specific questions about how things work, then do ask and I’m sure we can help.
On the point I made earlier about not charging the battery overnight and instead charging from solar, in my (Eastern) region, Flux night time import is 15.34p/kWh and day-time export is 13.64p. So on the face of it, charging the battery overnight so you start exporting all solar straight away will cost you more than charging the battery from solar.
It gets a bit more complex when losses are included as grid charging will incur one set of AC to DC conversion whereas solar charging (with an AC-coupled AIO) will incur two sets of conversion losses with DC to AC in the solar inverter and then AC to the DC in the AIO battery.
Charging overnight is of course simpler and you don’t have to deal with whether the solar forecast will be good enough the next day
RR50 Hi - I have a similar set up to you AIO with Gateway and a GE Hybrid Inverter so you could call me an informed user!
The behaviour you are describing is common to all the batteries as far as I know - the battery will discharge until the end time or go idle id when the SOC limit is reached before the end time (and stay that way until the end time is reached).
The same is true when charging - so for instance I have a 7 hour charge window and have my AIO to charge over the 7 hours. Typically the battery is full before the 7 hours are up and the system then sits idley until the charging period has completed - this means that over that period the house is then supplied directly from the grid (which is a better solution than filling up the battery with cheap electric and then powering the house in the cheap period due to conversion losses)
RR50 You're no worse off unless you start importing at peak rate - which is what I've found.
Yes, that's because you've set the 50% reserve, which stops battery activity prematurely. If you run the discharge until 7pm, with no lower limit, that shouldn't happen. (What might happen, of course, is the battery running out. Best way to avoid that is to choose a discharge power which means it will get to your target SoC at 7pm.)
Here are my thoughts on how to use flux intelligently:
CW Many thanks for the explanation. This is my first battery inverter system so I'm learning about it. Looking at the AIO on the portal makes much more sense. What is set up as 'exporting' in the App is seen as 'discharging' by the inverter and what is set up as 'discharging' in the App is seen as 'battery pause'. The App is quite confusing! My requirement to export to grid and then resume supplying my domestic load after reaching a particular SOC seems to make sense to me but doesn't appear to be available in that App directly - the way the system thinks, exporting and supplying the load are mutually exclusive yet it's what happens when your battery reaches 100%. To me, it's just the equivalent of saying change that value to another one of my choice. The way things stand, it would need to a supervisory script to achieve what I want. I wonder if that's what Intelligent Octopus Flux does.
RR50 My requirement to export to grid and then resume supplying my domestic load after reaching a particular SOC
I think to acheive that you will need some external control software that can interrogate the inverter for SOC and adjust the discharge end time to "now" if the SOC target is reached (or disable the "Enable DC Discharge" setting.
I don't use Home Assistant but I think this is something it would be able to do easily. Also Rubikcube's software (see link in their post above) would be able to do this if you purchase the control version (I use the opposite of this to discharge to the grid if the SOC is above a certain level) - both of these solutions work using local control - so no cloud access required
[unknown] I think to acheive that you will need some external control software that can interrogate the inverter for SOC and adjust the discharge end time to "now" if the SOC target is reached (or disable the "Enable DC Discharge" setting.
Or before the discharge, calculate a suitable discharge power such that the desired SoC will be reached by a particular time. I used to do it that way, using an API script - since it runs before hand, don't need close monitoring to catch the end being hit.
These days, though, I do use local monitoring. Currently have 4 time periods with desired SoC, and script will disable solar charge and/or enable discharge as required to try to maintain them (with 5% leeway either side). This forms part of strategy to ensure there's space in battery around noon to avoid clipping.
RR50 What is set up as 'exporting' in the App is seen as 'discharging' by the inverter and what is set up as 'discharging' in the App is seen as 'battery pause'.
The terminology is a bit confusing, and this is after GivEnergy have changed some of the app nomenclature to try to make it clearer.
The inverter can be in one of three states, charging, discharging or idle (doing nothing).
Within that you can be charging from the grid or solar, and when discharging you can be discharging just enough to meet house load (Eco mode does this), or discharging at a higher rate so the excess power over house load gets exported.
Within the app 'discharging' has been labelled that it allows the inverter to discharge to meet house load. Some people on a tariff with a peak period (e.g. Flux) want to preserve the battery for the peak period and not let it discharge outside of that period. Hence the discharge time period in the app. This is actually implemented as a battery pause for the inverse of the time you set.
For most people Eco mode on all the time and a timed charge from grid is all they need. Eco will charge the battery on solar and let it discharge to meet house demand. A timed charge will fill the battery overnight on a cheap rate.
If you want to do a forced export then this is setting the battery to discharge mode for the time period and at the rate/lower SoC limit you specify. As noted before if the battery reaches the SoC limit before the end of the time period, it won't drop below that limit, so any house load comes from the grid. Equally if your house load exceeds the battery discharge rate, it comes from the grid.
You mentioned Octopus Intelligent Flux, I do suggest you read the other threads on here about OIF. It is quite different, you hand over control of your inverter and battery to Octopus, they control it, not you. In return you get a better export rate which is the same as your import rate.
Its really only beneficial if you are generating lots of solar, as a rule of thumb 1.4x your house load