Good day,

I have a 8kw sunsynk invertor with 2 x 5.12kw batteries, with 8 solar panels.

I had my timer setup to use the batteries between 05:00 and 07:30 to 20%. However, of recent, it stops using the batteries at around 6:00 to about 42% and switches to grid.

I have changed the timing thinking maybe that time slot is acting up but no luck.

Please help.

Check the basic time settings of the inverter (the clock time, not the timer), and you might find it's set to GMT+2 (Cairo), as opposed to GMT+2 (Johannesburg/Harare).

The issue if I recall is that Deye does not make the Johannesburg time a selectable option.

In South Africa we do not observe daylight savings time, whereas in Egypt the clock changes from GMT+2 to GMT+3 between April and October.

If this is the case, you could set your time slot one hour earlier, or play around with settings; I think there was an option to set the time manually and lock out changes. Might be wrong. It was some time back that I looked at this issue on my Deye, and I don't really know how the Sunsynk version handles it.

Edited July 6, 20251 yr by GreenFields

Thank you for the prompt response. The clock is manually set with the sync option selected.

3 minutes ago, Ash124 said:

Thank you for the prompt response. The clock is manually set with the sync option selected.

Try taking away the "sync" option/tick so that you run on an internal clock, not synchronised with an external time server.

Good day,

I removed sync and sadly, the power still switched to grid although SoC was set to 20%.

Please advise on any other thoughts.

Thanks you

On 7/6/2025 at 1:29 PM, Ash124 said:

Please help.

the last value should be 23:59 not 00:00 @GreenFields @Ash124

32 minutes ago, Ash124 said:

Good day,

I removed sync and sadly, the power still switched to grid although SoC was set to 20%.

Please advise on any other thoughts.

Thanks you

Just place a pic of your timer settings. As said if timer is at 20% and battery at 40% it should not use grid.

@Scorp007 Please find timer settings attached.

@esmail-kassir When I change the last time to 23:55 (it doesn’t allow 23:59). It changes the next time frame to start at 23:55 and not 00:00. Seem like there should not be a gap in time.

Thank you

On 7/7/2025 at 5:39 PM, Ash124 said:

When I change the last time to 23:55 (it doesn’t allow 23:59). It changes the next time frame to start at 23:55 and not 00:00. Seem like there should not be a gap in time.

The Deye/Sunsynk timer does not work reliably if you start the first timeslot at 00:00 it has to begin on a different day, OR well into the day by letting the last timeslot cross midnight.

01:00 -> on first slot, and 23:00 - 01:00 on last slot works and there is a reason why it defaults to such a setup.

On 2025/07/07 at 4:39 PM, Ash124 said:

@Scorp007 Please find timer settings attached.

@esmail-kassir When I change the last time to 23:55 (it doesn’t allow 23:59). It changes the next time frame to start at 23:55 and not 00:00. Seem like there should not be a gap in time.

Thank you

I would try the 5h00 to 07h30 at 30% and also ensure that you tick the use grid at this slot.

I see none of you settings allow grid but yet you say it uses grid from 42%

Thank you @Scorp007 I will try this. I unselected sync for the time and it worked for a few mornings but since 3 mornings ago, it would only power down the batteries to 21%, 22% and 25% (this morning) instead of 20%.

30 minutes ago, Ash124 said:

Thank you @Scorp007 I will try this. I unselected sync for the time and it worked for a few mornings but since 3 mornings ago, it would only power down the batteries to 21%, 22% and 25% (this morning) instead of 20%

Deleted by myself.

Edited July 14, 20251 yr by Scorp007

On 2025/07/10 at 5:53 PM, Scorp007 said:

I see none of you settings allow grid but yet you say it uses grid from 42%

Could this not be a reserve set on the battery? In that case the system would revert to grid at 42ish % unless the grid is down

2 hours ago, Bobster. said:

Could this not be a reserve set on the battery? In that case the system would revert to grid at 42ish % unless the grid is down

I have not seen any battery with such a high minimum SOC. I still feel the 42% could be a total wrong SOC and the BMS will only correct itself after a 100% SOC but then looking at the graph the battery was at 100% so this rules out the above possibility.

59 minutes ago, Scorp007 said:

I have not seen any battery with such a high minimum SOC.

What I'm guessing is that the system is set to reserve some of the battery for grid outages.

My system is set to not discharge past 40% when there's grid. That way I will always have useful life in the battery when the grid goes down.

If the grid goes down and there is no PV then the inverter will run the battery as low as the BMS goes down.

The grid on situation looks like what @Ash124 is reporting. Battery discharges until the reserve SOC is reached. At this point and with the grid up, the system will not draw from the battery unless the grid goes down.

Good morning, feedback after ticking grid. Switches to grid at 28%, instead of when SOC reaches 20%.

1 hour ago, Ash124 said:

Good morning, feedback after ticking grid. Switches to grid at 28%, instead of when SOC reaches 20%.

Drawing your battery down from the deep 70% at a load of over 2750W can perhaps explain the 8% wrong level. Not sure and I do see at times that a BMS can easily be 10-25% out until it is reset after a 100% charge. Not easy to say without taking some measurements.

Your load from 05h05 to 06h40 was over 4125Wh. SOC dropped about 50% to 28%. Your battery at 2x5kWh you used about 40% of the storage capacity. So the total "error" is about 10%.

Edited July 15, 20251 yr by Scorp007

10 hours ago, Ash124 said:

Good morning, feedback after ticking grid. Switches to grid at 28%, instead of when SOC reaches 20%.

Do you have access to individual cells voltages?

Based on the few examples you have posted you are seeing inconsistencies at the SOC level when the inverter switches back to grid. The only constant in the examples is a large load on the battery bank before the switch back to grid.

My guess is that the BMS forces the inverter back to grid because of a weak cell reaching the UV protection point due to large load. So basically a battery issue and nothing to do with inverter settings.

You can try and test this by reducing the load to something more manageable for the battery and see if the same happens (obviously you will have to discharge for a longer period).

You can also see if the same occurs by removing the communication between the battery and the inverter (and using voltage settings) thereby removing the BMS ability to force the inveter to grid. You might however end up with a battery that has gone into protection mode should it really be due to weak cells.

Those GRID tick boxes do not mean "USE GRID", they mean "CHARGE FROM GRID IF THE SoC is below the configured value". The rows marked 100% are not going to take the battery to 100% if there isn't enough solar.

Hello, thanks for the responses.

I did a few changes to the setup, I started supplementing the solar power from the battery during the day and it works perfectly. Drops the SOC to the right levels etc.

I changes the SOC from 20% to 15% in the mornings when the geyser turns on. This worked perfectly for a few days then the powering from the battery stopped at 16%, then 17% and today at 20%. Even though its set to discharge to 15%.

I don’t know if its the load in the morning that doesn’t allow it to discharge to a consistent set SOC of 15%.

Any suggestions/questions?