House load using grid not battery after a timed export

As timed discharge seems to no longer be working I tried a timed export in order to discharge the batteries ready to recharge overnight.

Timed export to 6% 18:10 to 22:50. I presumed the 6% would be enough to power the house load between 22:50 and 23:30 when the charge starts.

However instead of using that battery 6% the house load imported from the grid.

My understanding is that after the export, the settings should revert to eco and the house would use the battery rather than the grid.

The stats do not show Eco on/off at all during that time, neither True or false (the previous vale for Eco much earlier is true)

As you can see plenty in the battery between 10:50 and start of night charge

Does anyone know why this is happening? Thanks

What is your battery reserve set to, the default 4%?

The difference between 4 and 6% isn’t very much, and at the bottom end of discharging the discharge rate reduces automatically, so it could well be that with your battery almost exhausted the inverter couldn’t supply enough power for the home demand. I’ve seen one of my batteries bottom out at 4, 5 and 6% on different days, so maybe don’t discharge so close to the bottom - e.g. 10%?

OK will try 10% tonight. But I had assumed that 6% (of 19kWh) should be enough for most of the 40 minutes at about 0.2kWh. I just checked December graphs when I wasn't doing any timed discharge (heavy house load due to heat pump) and the battery would drop down to 2% before it stops supplying house

Pete Thomas As timed discharge seems to no longer be working I tried a timed export in order to discharge the batteries ready to recharge overnight.

Arguably it is finally working, in that it (should) now match the documented behaviour: covering house demand during the configured hours, and idle otherwise. ;-)

Pete Thomas However instead of using that battery 6% the house load imported from the grid.

GE systems don't seem terribly good at tracking the state of charge. So they often seem to suddenly find the battery flat when they think there's still some charge left. My battery typically goes idle when it gets to 6%, even though I have the reserve set to 4%. All a bit odd...

It may also depend on how well the cells are balanced - it has to stop discharging when any one cell gets to the minimum voltage, even if all the others still have charge.

What I'd do is repeat the experiment, but ending at 10%. That should be a big enough margin to confirm whether the system is able to continue discharging the battery after 22:50

A potential downside of using a discharge limit feature is that if it does reach the limit before the end of the time window, it goes idle, again requiring that the system imports from the grid to cover demand.

The left-hand part of your chart looks interesting - it seems to imply that export is higher than solar PV ?

geoffreycoan What is your battery reserve set to, the default 4%?

Sorry I missed that, I've just seen it s 6% perhaps that explains it all. I'll drop that to 4% and the timed export reserve to 10%

Pete Thomas But I had assumed that 6% (of 19kWh) should be enough for most of the 40 minutes at about 0.2kWh. I just checked December graphs when I wasn't doing any timed discharge (heavy house load due to heat pump) and the battery would drop down to 2% before it stops supplying house

19kWh => two batteries ? GE doesn't seem terribly good at managing multiple batteries either. Not sure, but does it stop discharging when one of them reaches the bottom? (So it's not just cell balancing you need to worry about, but also balancing the the two batteries.) But I have no personal experience of twin batteries...

Have you updated firmware since then? The BMS firmware updates do seem to be fiddling with the behaviour at the margins.

DD I was going to say the same, @Pete Thomas if you have two batteries then whenever one of them reaches the minimum or the maximum, both batteries stop discharging or charging. And SoC's can drift apart, sometimes by quite a lot.
The 6% reserve won't help either!

DD Have you updated firmware since then? The BMS firmware updates do seem to be fiddling with the behaviour at the margins.

Do you mean the firmware can change the reserve setting? I'll keep an eye on it but for now maybe have it at the n fault 4%, discharge to 10% and see what what happens tonight.

I wonder if there is any advantage to having a battery reserve, e.g. if it's bad for it to go down to 0%?

Pete Thomas Do you mean the firmware can change the reserve setting? I'll keep an eye on it but for now maybe have it at the n fault 4%, discharge to 10% and see what what happens tonight.

I wonder if there is any advantage to having a battery reserve, e.g. if it's bad for it to go down to 0%?

No, but the firmware can fiddle with voltage limits and things, and how much it will charge/discharge the batteries.

It's primarily cell voltage that the BMS worries about. Some more recent firmwares allowed the voltages to go lower or higher - I can't remember which - which caused people to report overvoltage and undervoltage alerts.

Yes, it's bad (possibly even terminal) for battery cells to go out of the specified voltage range.

Ok having set the battery reserve to 4% it has now gone up to 10% , ie what has happened is the battery reserve itselfit has taken on the timed export 10% reserve. That is annoying this isn't going to work then

I want to discharge to 10% but then be able to have the house load use the battery

I have another plan which is to set the reserve to 4% and set the export times from 18:00 to 22:20, that is 4:hrs 20 mins which theoretically it will reduce by 90%, ie by 22:20 it will stop and be at 10% but with the reserve at 4% so the battery should charge the house load until 23:30

Pete Thomas I think that's a bug/feature of the UI. The app/portal only offers access to the overall battery reserve. To get the per-discharge slot one, you'll probably want to use the remote-control section.

Pete Thomas I have another plan which is to set the reserve to 4% and set the export times from 18:00 to 22:20, that is 4:hrs 20 mins which theoretically it will reduce by 90%, ie by 22:20 it will stop and be at 10%

That's more or less the way I do it, but I use a script to calculate what discharge power will drop from current to 8% by 22:30 - I tend to discharge at a reduced rate rather than full power. Though since you have two 9kWh batteries, even at full power they're not being taxed.

DD The app/portal only offers access to the overall battery reserve.

On both the app and the portal I have a slider for battery reserve on both Timed export and battery options.

But is not there on Timed Discharge which I don't use as it doesn't seem to work.

Pete Thomas On both the app and the portal I have a slider for battery reserve on both Timed export and battery options.

the inverter has several control registers which do similar things. There's an overall battery reserve, below which the battery won't go in any mode (eco or forced export). It may dip into it when it's in backup mode for a power cut. So if you set that one, not only will it stop a timed export when it gets there, but it will also prevent eco mode from discharging any further.

In addition, when there are multiple discharge timers, there can be a discharge limit per discharge slot. That one applies only during that particular discharge slot.

But is not there on Timed Discharge which I don't use as it doesn't seem to work.

It should work, but it should now implements the documented behaviour: "This mode will discharge your batteries to your home during a period you define". Ie it covers only house demand within the time window, and pauses discharge entirely outside of that.

While you might infer from the fact that there's a limit on the timed-export, but not the timed-discharge, that the reserve is specific to timed-export, but in fact that doesn't seem to be what they've done. (Just double-checked on my system - they all modify the overall battery reserve setting.)

Pete Thomas I am glad i am not the only one who thought that it should work as you describe. But as @DD said the battery % reserve register in the inverter remote control page can be changed in the app when you set the battery reserve under battery options or when you set a discharge to value in either timed export or timed discharge. This isn't the only register than can be set from different controls in the app. I tied some tweaks over here

https://community.givenergy.cloud/d/4549-timed-export-settings/47

But, even the vide that GE posted to explain the difference between timed discharge and timed export (also linked in an earlier post in the linked thread above) fails to mention the issues we can see here.
In my case i only have a single battery and when i first tried it i set a battery discharge limit of 40% (timed discharge). Now i can't remember whether i used the app to disable the timed discharge period or whether it timed out. But i was left with a case like you where my system imported from the grid. My workaround for this feature is to leave timed discharge enabled and just change the time slot and i leave the battery discharge at 4%. And i manually check and adjust each day as required. Not ideal. I have also found that to make sure the app and remote portal page are synced that I have to ensure the app has refreshed otherwise i get the app and portal settings out of sync.

re: my situation, I thought I had it solved by relying in the time settings to stop the export, not on the battery reserve (whicg is useless because the global battery reserve changes when you set it in the Timed Export)

So this time I set the timed Export to stop at 22:20 at which time the battery was at 6% so had 2% over the global serve of 4%. I would have expected it to use that 2% for the small house load before switching over to grid import, however it didn't, it went immediately to grid import at 22:20

Maxwell But, even the vide that GE posted to explain the difference between timed discharge and tim

I cannot find that video, are you able to give a link

Pete Thomas whicg is useless because the global battery reserve changes when you set it in the Timed Export

Or "which is less than useful than it could have been since you have to go to the remote-control page to change the limit"

BTW I think wonderwatt.com has support to automate this sort of export. Or I have python scripts to do the same

I am on IOG so the cheap rate starts at 23:30, I set my discharge to end at 00:00, this way I have an half hour window of discharging in the cheap rate in case the battery empties and switches over to grid power.

MickWheater window of discharging in the cheap rate in case the battery empties and switches over to grid power.

Y try hat wouldn’t work for me as I use 23:30 to 05:30 as timed charge. I presume you can’t have charge and discharge at the same time

Pete Thomas I cannot find that video, are you able to give a link

Perhaps this Q&A one, about 4:30 in - https://www.youtube.com/watch?v=rqFfm_eHCns

I presume you can’t have charge and discharge at the same time

Correct. But looks like it took less than 5 hours to discharge from 100% down to under 10%, so 5 hours ought to be enough to recharge overnight ? (Though maybe it slows down a bit charging up at the very top end, on the latest firmware ?)

(Since I only have 9.5kWh battery, I actually idle the battery for an hour until 00:30, which I think can help it to rebalance, before charging until 05:30)

DD so 5 hours ought to be enough to recharge overnight ?

Yes it slows down so does need 6 hours at night

Pete Thomas GE's own pages. Although it fails to highlight the issues we are having here over how we all think this should work. And as far as i can tell you and i are in tht minority camp on this one. But for my non software engineeer head this is the way i'd like that to work, ie the overall system battery reserve that was in force during eco mode to be revereted to once the timed discharge period ends or the batery reserve limit set during the timed discharge limit is reached, whichever comes first.
https://givenergy.co.uk/givenergy-eco-mode-other-battery-charging-settings-explained/