I have a grid tied Sunsynk 8kVA Charger / Inverter system with 20 kVA batteries and 7 kW panels.

Amongst other things I have three computers each connected to the system via a UPS.

The UPS’s give a beep whenever the Eskom power is reconnected after load shedding. I assume this must be due to some or other voltage fluctuation.

My question is the following:

Can grid-tied Charger / Inverters be damaged by this voltage fluctuation when Eskom is reconnected?

Any comments would be appreciated.

10 minutes ago, moija said:

I have a grid tied Sunsynk 8kVA Charger / Inverter system with 20 kVA batteries and 7 kW panels.

Amongst other things I have three computers each connected to the system via a UPS.

The UPS’s give a beep whenever the Eskom power is reconnected after load shedding. I assume this must be due to some or other voltage fluctuation.

My question is the following:

Can grid-tied Charger / Inverters be damaged by this voltage fluctuation when Eskom is reconnected?

Any comments would be appreciated.

These models will disconnect from grid automatically (swapping back over to battery) if supply drops too low - the exact voltage can be specified in the Grid menu. The inverter then re-connects when voltage comes back into target range.

So the inverter is built to handle this. Since some equipment can be sensitive to low voltages (fridges for example), this also protects those devices.

We suffered from this issue in the past; what helped us was moving our geyser heating to the day and keeping them powered off at night when the grid is most sensitive. Our local supply used to drop more than 15V when both our geysers were on after evening-loadshedding. Since no longer doing this, we no longer have our Sunsynk automatically disconnect from grid in the evenings due to low voltage. A side-benefit is our lights (which are dimmed through voltage) stay at near-full brightness after grid restoration as well.

4 hours ago, JayMardern said:

We suffered from this issue in the past; what helped us was moving our geyser heating to the day and keeping them powered off at night when the grid is most sensitive. Our local supply used to drop more than 15V when both our geysers were on after evening-loadshedding. Since no longer doing this, we no longer have our Sunsynk automatically disconnect from grid in the evenings due to low voltage. A side-benefit is our lights (which are dimmed through voltage) stay at near-full brightness after grid restoration as well.

This is very interesting to me. I've often had problems with low voltage on reconnection, but I assumed that the cause of this must be spread across a wide area, a node of the grid. That the cumulative loads on that node would drag the voltage down. 

But what you report suggests this is a more local problem with a local solution. 

Or your property is all by itself electrically. 

14 hours ago, Bobster. said:

This is very interesting to me. I've often had problems with low voltage on reconnection, but I assumed that the cause of this must be spread across a wide area, a node of the grid. That the cumulative loads on that node would drag the voltage down. 

But what you report suggests this is a more local problem with a local solution. 

Or your property is all by itself electrically. 

Indeed - voltage drop under load isn't unheard of (and it gives me lead-acid-battery PSTD, where when measuring the SOC of an LA battery requires knowing it's current load, since voltage is inversely proportional to output!), but it was pretty noticeably in our case.

Also now that I think about it, it was a large load indeed - post-load-shedding was 7kW of geysers, plus 3kW battery of charging; the Mrs would often flick on the kettle after, etc. This is why Eskom has requested users delay charging their inverter batteries post-load-shedding as it's not great for the grid to have this level of inrush...

We eased this post-load-shedding load by keeping the geysers off at night (and during the day they're on just one at a time, and powered by solar); and we used the Sunsynk's time-of-day settings to step SOC down as the evening progresses such that when load shedding ends, the battery no longer even charges at all most of the time; instead waiting until the next morning to charge via PV.

The difference has been significant. And of course this reduced overall consumption as well; so it was win-win!

On 2023/11/28 at 10:35 AM, JayMardern said:

Indeed - voltage drop under load isn't unheard of (and it gives me lead-acid-battery PSTD, where when measuring the SOC of an LA battery requires knowing it's current load, since voltage is inversely proportional to output!), but it was pretty noticeably in our case.

Also now that I think about it, it was a large load indeed - post-load-shedding was 7kW of geysers, plus 3kW battery of charging; the Mrs would often flick on the kettle after, etc. This is why Eskom has requested users delay charging their inverter batteries post-load-shedding as it's not great for the grid to have this level of inrush...

We eased this post-load-shedding load by keeping the geysers off at night (and during the day they're on just one at a time, and powered by solar); and we used the Sunsynk's time-of-day settings to step SOC down as the evening progresses such that when load shedding ends, the battery no longer even charges at all most of the time; instead waiting until the next morning to charge via PV.

The difference has been significant. And of course this reduced overall consumption as well; so it was win-win!

I also use the Sunsynk's time-of-day settings to charge the batteries from PV during the day with no charging at night, instead waiting until the next morning to charge via PV again.

The average load at night is about 600W. There are no geysers connected.

When the load shedding period ends in the day {and also at night} I get a small voltage fluctuation that sets off the UPS buzzers as described above.