Solar output capped when battery is full
Two very different reasons, only one is a problem
If you have a solar battery, you may have noticed that once the battery reaches 100%, your solar generation stops climbing the way it did earlier in the day. The generation curve in your app can flatten or even drop, and it is easy to read this as a fault.
There are actually two very different things that can happen when the battery is full. One is completely normal and needs no action at all. The other is a setting issue that we can usually fix for you remotely. This page helps you tell the two apart.
Which one applies to you?
When your battery is full, which one happens?
...and you are exporting power to the grid. This is normal.
Your generation flattens at roughly 5 kW total instead of climbing further, and your system is still sending power out to the grid. All is working as it should. Read more about the 5 kW cap.
...and you are not exporting power to the grid. This is likely a mistake in the settings.
Your generation drops to roughly the same level as the house is using, which can often be as low as 200W - 500W, and nothing is being exported. This points to a mistake in the settings, which is easily corrected. Read more about this fix.
Neither pattern sounds like what you are seeing? If the drop happens at random times rather than when the battery is full, a different cause is more likely. Please contact us and we will investigate.
Normal: capped at 5 kW
Through the morning, the panels produce power. Some of this power runs the house, and the rest charges the battery. The moment the battery hits 100%, it stops taking a charge, so all remaining solar is used by the house or sent to the grid.
Every solar system has to balance a simple equation: the power the panels generate must equal what the house is using, plus what is going into the battery, plus what is being exported to the grid. Once the battery is full, the amount going into it drops to zero, so the equation becomes:
Solar generation = house load + grid export
Your inverter is connected to the grid through a single-phase supply, and that connection is approved to export up to a set limit, typically 5 kW (25 A). This is the microgeneration export cap agreed for your connection. If the panels try to push total output above that cap, the inverter clips the surplus and holds generation at the cap instead.
This is how any inverter behaves on a single-phase connection with a set export cap. It is not brand-specific and it is not a fault. The panels, inverter and battery are all working correctly, and the system is still exporting whatever the house does not use. There is simply a limit on how much can flow to the grid at once, and the inverter is respecting it.
How the export cap works
Export is whatever is left over after the house takes its share, so if your home is using 1 kW at the time, the most you can export is around 4 kW, not the full 5 kW. That is expected and is not a sign that anything is underperforming.
Needs fixing: export limit left on
The second pattern is different. Instead of flattening at the 5 kW cap while still exporting, the system stops exporting altogether. With nowhere for the surplus to go and no battery left to charge it, the inverter throttles the panels back so they produce only what the house is using at that moment. The generation curve drops to trace the house load curve.
This is usually caused by an export limit setting that is still enabled in the inverter. On Solis systems it is called the Feed in Power Limit Switch and it shows as ON in the monitoring platform. Other brands use different names, such as zero export, export power limit or feed-in limit, but the effect is the same: export is blocked even though your connection allows it.
The setting is sometimes overwritten by a firmware upgrade, and this can happen without notice. We are not notified when these updates take place, so it's worth to keep an eye on the system just in case you notice it.
Export limit settings are only accessible to installer accounts. Customers cannot switch this off themselves, but the fix can usually be applied remotely, so no site visit is required.
When we look into it for you, we check the Feed in Power Limit Switch and, if it is on, we turn it off. Once that is done, the generation curve rises back up to the normal 5 kW cap described above instead of tracking your house load.
What happens next
There is nothing you need to do to the system itself, and we do not recommend changing any inverter settings yourself. Here is what happens once we are involved:
- You get in touch, letting us know that your solar is capped or dropping when the battery is full.
- We check your monitoring data, confirming whether your generation is flattening at the normal cap or tracing your house load with no export.
- We update the setting remotely, switching the export limit off where it has been left on, so your panels return to full generation up to the 5 kW cap.
- Your system returns to normal, exporting the surplus your home does not use instead of throttling the panels.
Need a hand?
If your solar generation is capped or dropping when the battery is full and you are not sure which situation applies, get in touch with your installation team at PureVolt.ie. Let us know:
- What you are seeing in your app, whether generation is flattening at a set level or dropping to match your house load.
We will take it from there. No jargon. No pressure. Just the straight answer on getting your system generating as it should.
You might also find these guides useful:
- Battery charging and discharging explained, understanding normal battery behaviour.
- Battery percentage jumping up and down, what it means when the percentage moves in sudden steps.
- Solis remote access setup, how to give us remote access to your inverter so we can help faster.