Additional Battery

I'm a newbie at this having just had my 5.2KWh solar panels with Givenergy Hybrid 3.6KW inverter and 8.2KWh battery installed in August and loving the system so far during all the sunny days. However looking ahead to winter I can see the benefit of filling the battery overnight on Octopus GO for use during the short dull days. The problem is I doubt 8.2KWh will be sufficient to meet our needs and therefore I'm considering adding another battery.

The questions I have on this are:-

1. Can I add any size battery, especially the 9.5 ?
2. Would both batteries be charged separately or as a single unit ? ie on the Octopus Go tariff I can charge during their 4 hour overnight window upto 10KWh - could I therefore fill both batteries in the 4 hours window or still only upto 10KWh across both ?
3. In 2, if I’m restricted to 10KWh across both batteries, would I need to install another inverter with the second battery in order to fill both batteries in the 4 hour overnight window ? If so, would this just need to be another 3.6KW ?
4. In 3, if I need to add a second 3.6KW inverter, would this be connected directly to the grid ? ie would I need to submit a G99 application to the DNO ?
5. How is the second battery shown in the app - as a separate battery or just aggregated with the existing ?

All help/advice gratefully received. Thanks

Glenbertram

1- Can I add any size battery, especially the 9.5 ?
Yes, There is a limit of how many batteries you can add to a single inverter (I think it's 5, from memory).

2- Would both batteries be charged separately or as a single unit ? ie on the Octopus Go tariff I can charge during their 4 hour overnight window upto 10KWh - could I therefore fill both batteries in the 4 hours window or still only upto 10KWh across both ?
Both batteries appear as a single battery. I have 2 x 8.2s connected and they appear in the portal to be a single battery.
You are limited to the throughput of the inverter. My gen 1 inverter has a maximum charging rate of 2.4kW, so that's the maximum rate that I can charge regardless of how many batteries are connected. Likewise, the discharge rate will be limited by the inverter throughput.

3- In 2, if I’m restricted to 10KWh across both batteries, would I need to install another inverter with the second battery in order to fill both batteries in the 4 hour overnight window ? If so, would this just need to be another 3.6KW ?
The only way to increase the throughput would be to add an additional inverter. You could add a second AC coupled inverter and connect the battery to that.

4- In 3, if I need to add a second 3.6KW inverter, would this be connected directly to the grid ? ie would I need to submit a G99 application to the DNO ?
It depends. As i understand it an AC coupled inverter would be connected to the grid and a second battery. if you were adding more PV then you might want a second hybrid inverter connected to the new panels.
I have gone through this very scenario and decided to just add a second battery and see how it performs. If I find out that I need more throughput then I can always add an AC coupled inverter and move the battery to that. More costly for sure and it comes with another set of problems

5- How is the second battery shown in the app - as a separate battery or just aggregated with the existing ?
Aggregated with the existing.

It might be worth considering Intelligent Octopus. That offers 6 hours of off-peak at 7.5 pence/kWh, which is cheaper than the 5 hour variants of Go Faster.

It can also get additional off-peak periods. For example, I got from 8:00 to 10:30 this morning as off-peak in addition to the 6 hours last night.

Zakalwe
Thanks, but unfortunately I don't have the right EV to qualify.

Glenbertram Other suppliers might be worth a look? EDF has GoElectric35 offers 5 hours off-peak.

Tim

I think that they withdrew that some time ago, certainly new customers.

Just to close out this thread, here are the answers I got from Givenergy tech support...

1. Yes you can add any battery to your current inverter including the 9.5
2. Both batteries would be charged as a single unit but due to the restriction on your inverter each battery would charge at 1.3kW for a total of 2.6kW on the inverter meaning you would not be able to fill both batteries during the 4 hour window you're limited to 10kWh over those 4 hours regardless how many batteries you add
3. Although we do not recommend installing dual inverter setups if you do wish to do this you'll need to look at installing our EMS when this is available as this is a controller for dual inverters with current setup without this you may experience some graphical display errors and some operational errors
4. Yes were you to add a second 3.6 Inverter you would need to go through the application process again for that second inverter