Importing from grid when battery almost full

Hi, I have a solar PV system with 9.5kw battery and 5Kw inverter which were installed just before the shortest day in December. Now that the days are getting longer I am regularly exporting 2 to 3 kwh to the grid during the afternoons and have 50 per cent or more left in the battery in the morning. I currently don't have a feed in tariff set up so am looking to maximise my use of the electricity generated. This has led me to order a smart timer for my electric immersion heater so that I can heat some water before the gas boiler kicks in for the morning or evening. While waiting for my new timer to arrive I have manually switched on the 3kw immersion heater a few times and then monitored what is happening via the GivEnergy app. I was surprised to find (for example) this afternoon that when I switched on the immersion heater I was drawing between 1 to 2 kwh from the grid, despite my battery being 96% full and the solar array generating around 1.5kwh (It's a bit dull today). Meanwhile I was simultaneously exporting power to the grid. I checked again 15 minutes or so later and the same thing was happening. I am now concerned that if I set my immersion heater to come on for an hour or so at 5am that I may end up paying for electricity from the grid despite having a reasonable amount in the battery and if I set it to come on at 3pm it may not make reasonable use of whatever power is being generated by my solar array. I should mention that this issue only seems to apply to the immersion heater. Recently I have been regularly importing less than 1.5kwh per day from the grid despite fairly indiscriminate use of ovens, dishwasher, washing machine and tumble dryer. I'd very much like to hear if anyone has experienced similar issues or any insights as to what might be happening. Thanks in advance for your help.

moore789 Post an image of you energy flows graph so we can see a bit more detail and how much may just be transient. One thing to note is that if the immersion has a simple mechanical thermostat then once the tank gets hot it may well call for load intermittantly and this will cause transient grid input as the grid responds immediately but your inverter takes a few seconds. Ultimately, what matters is the total grid input which, if things are working correctly will actually be much less than the apparant input reported on the GE portal/app.

cluelesscris Many thanks for your reply - very much appreciated. It sounds like I should take your advice and monitor the overall impact over a few days rather than worry too much about the 'real time' snapshots. When I've done that, I'll post an image if there still seems to be an issue. At present I have only switched the immersion heater on for very short periods of time so it might be difficult to interpret. My smart switch has now arrived so I'll get it installed and let it do it's thing. Really grateful for your input.

Data from my GivEnergy inverter gets uploaded to Givenergy avery 5 minutes (or longer if no internet connection) so the Givenergy portal and app shows what has happened in 5 minute chunks so it isn't real time. In that 5 minutes it is possible to have both imported and exported to the grid. If you have an In Home Display from your smart meter, that reacts more quickly to the load and is more like real time.

However, some us us have experienced the situation where the battery is full (or has enough charge) but the inverter still imports from the grid for a long time (20+ minutes) rather than use the battery.

alan_johnston Thanks Alan. That makes a lot of sense. When I tried the immersion heater again this afternoon I seemed to get exactly what I wanted, i.e. solar array providing all the power - so maybe I should just accept that there will be occasions when power will be drawn from the grid for a while, when the battery is charged. Overall, I'm very happy with the system and now that we are on longer days I'm often importing less than 1kWh per day. I'm also conscious that the maximum discharge from the battery is 2.5 kWh, so if I use a 3kWh immersion heater overnight I'm going to end up with some power being drawn from the grid anyway. Grateful for your help.

The inverter is always going to lag behind the actual demand slightly because it is monitoring the current load and has to adjust things to meet it. I have a few watts going in and out all the time on the In Home Display as the inverter tries match what is being used.
As well as the battery having a maximum kW it can supply, there is also the maximum kW that the inverter can supply (3.6kW in my case) so any house load over that will require grid top up regardless.

I will be demanding this GivEnergy system be removed and a full refund given. The system is uncontrollable and is costing more than it saves as it imports from the grid at peak times even though the battery is over 80% charged. This just doesn’t happen for a few minutes or seconds until the battery ramps up, the battery just never responds. Massive waste of money.

hazelst3 Hmmm, pity. Mine is working fabulously and has been since installation last September. I was speaking with my installer the other week as I want to install a load more panels as we are about to become an EV house. They have over 500 installations and have had less than a dozen callbacks. Two of their customers are indeed waiting on the SOC firmware fix. I notice this is your first ever post on this forum. We have no way of knowing the root of your disatisfaction or, indeed, what installation you have. Why not post your issues in detail with evidence. There are a ton of people on this forum that just may be able to help you.

hazelst3 Wen i fist had ours installed i naively went into my settings and switched off eco mode and made some other chnages to control what i thought was controlling when the battery discharged. All i ended up doing was completely discharging the battery to the grid....the controls don't do what you think they should and some folks here helped out on that. Of course you could also reach out to your installer and or givenergy for help.

Maxwell I’ve tried resetting the inverter to default settings and all is well for a couple of days and then the battery refuses to discharge to meet home demand, therefore using power from the grid. I know the inverter will only allow around 3.6kw discharge with anything above this coming from the grid, but the battery is reluctant to part with more than a few hundred watts at most even though the battery is showing 80% or more SOC.
The whole idea of having a battery is to cover home usage when there is little or no sunshine, but this GivEnergy system isn’t fit for purpose.

hazelst3 Post your graph so we can see what is happening and maybe spot a pattern seen before. Someone may even be able to give you a workaround whilst you get your money back - which is unlikely to be immediate. Maybe we can lessen your pain for a while.

If you have a gen 2 inverter you could be experiencing the bugs in the firmware where it starts acting weird when the battery has a high charge. They have apparently fixed these issues in the latest beta firmware and I have been told it will be released soon. Apparently these bugs are not present on the gen 1 inverters.

This could be the problem:

In New GivEnergy Inverter & BMS Firmware Beta Testing Chat
Woodstock2 days ago
Got to the bottom of why battery discharge was sometimes halting at 25% SOC.

It did turn out to be the "Battery Cutoff % Limit" setting that was causing it, but boy was it subtle!

I changed this setting to 25% quite a while ago when forcing the charge spike at 01:00 anomaly (the two are linked but still not exactly sure how). Many "reset to defaults" had been run since. The first of these showed a change from 25% to 4% and all subsequent ones showed no change (4% before and 4% after).

Battery discharge mysteriously stopped at 25% again today. I went into Remote and checked the "Battery Cutoff % Limit" setting (which was showing 4%). Took it one step further this time and performed a read on the setting. Hey presto it showed 25% and updated the displayed value!!!

I then manually changed the setting to 4% and battery discharge recommenced.

hazelst3 My system started doing a similar thing a few weeks post installation, ie the battery would only give several hundred watts to the house even though it had plenty to spare. I went through my installer showing them the graphs of what was happening and they took it up with GE and some tweaks were made (not quite sure what as there were no obvious changes to the settings i could see). And hey presto back to what it was originally, so using as much battery and/or solar when needed. Boil that kettle from the battery again...

Maxwell Cheers Maxwell, my system seems to be behaving at the moment after yet another reset. So many bugs with this system that it becomes extremely frustrating.

Calling moore789
I use an iBoost system to provide immersion heater hot water and since my installation in January, I've learned how to tune it to suit our needs. We use Economy 7, so I time charging and heating to happen between 1am and 6am.

If there's battery power available, the iBoost will draw power from the battery at up to 2.6kWh. The rest up to 3kWh comes from the grid. It uses about 30% battery power (my battery is 5.6kWh) for 40 mins iBoost heating. I then recharge the battery using the GridEnergy timer for 15 mins just after the iBoost has finished and that replaces the 30%.

When battery power was low overnight in Feb and March, I charged and used iBoost at the same time. Grid supplies everything. This avoided battery power reaching the 20% level cutoff I have set.

My system has started importing from the grid even though the battery is full. It seems to behave for a few days and then becomes uncontrollable. Thousands of pounds wasted on a system that won’t function correctly.

hazelst3 Does the import data you see in the portal/app etc match what you see in your smart meter ? Although i know that there are differencies between the GE data and what my smart meter says. On here there are some statements that these differencies are down to the accuracy of the current clamps that are installed with your installation. So, for Sunday 29th of April GE shows no grid import on mine. Yet the smart meter says i spent £0.44 but if i switch in the EDF app to kwh instead of cost it reports the same as GE ie 0.0kwh. Didn't notice that before in the EDF app. And then also in the edf app i can see some days when reports .1kwh used with £0.47 spend. Again on days when GE says zero import...

Maxwell maybe just use the kWh values as I think the £ values will include the standing charge?

Exactly the same again this evening, battery fully charged but nearly all electricity imported from grid. I’m on Octopus Flux so I’m importing electricity at premium rates. What is the point of having a GivEnergy battery? I’ve told my installer that I have been mis-sold this GivEnergy system and will be seeking compensation for a system that isn’t fit for purpose. Also informed my credit card company as part of the payment was made using this

hazelst3 Give Givenergy a call or web chat tomorrow. There are bugs in the system, but mostly the kit works really well; you just need to find out what's not right with your system to get back on track. We had our system installed early last year and we've had hardly any issues at all; it just works. It'll be a setting somewhere, or maybe you have fallen unlucky with something, but speak to the company and get it sorted.

Tim Just checked the EDF app and on a day where it shows 0kwh used you can see the standing charge in the cost view for that day. And like others have said in the forum you can see other days where GE say 0kwh used by the smart meter has recorded 0.1kwh. Must admit i find it frustrating that EDF take a day or two to show your usage accuratley yet they are taking readings every 30mins. Is that just an EDF thing or are other suppliers any better ? I still don't have my April total. Must be runing a few zx81s in the background...

Octopus seem to be a day behind as well. Whereas Bright are a lot more up to date and even provide almost live readings if you purchase their energy meter.

Maxwell I use the bright app API to download 30 minute data. However, what I have noticed is that the data changes after the event. If I download data after a 30 minute slot and then download it again the next day, it is usually different. I have no idea why this happens but it's probably the reason why energy suppliers' data is usually 24 hours behind. I've no reason to question the validity of the final data; it looks right.

Tim what Bright doesn’t know about is export. So you’ll often see minus figures in the live data. Tomorrow the minus figures will be zero.

They are looking to add export at some point.

Hook My Bright app doesn't know about export at all. It only receives data from the import register. I'm hoping for a SMETS2 installation in a couple of weeks to get better visibility of time of use registers, but the Glow dongle will have to be replaced with a SMETS2-compatible device to maintain the data.

Hook Tim Thats interesting, I dont see any negative readings either. I am sadly exporting for free, as octopus apear to be unable to connect to my meter despite the DCC having it and Bright displaying it :-(. Although I have an export MPAN I assume that unless octopus have paired with the meter, then the second export register will not be picked up by the DCC ?.

justpassing it’s rectified itself today.