Why does my Growatt APX system feed power back while the battery is not full?

A Growatt APX battery does not start charging immediately with every small PV surplus. When the available charging power is too low for an extended period, the battery can enter SLEEP mode. A small surplus is then temporarily fed back to the grid. Growatt does this to reduce energy loss, prevent unnecessary switching, and support the system's lifespan.

Why is power being fed back?

It can happen that your Growatt APX battery is not yet full, while the solar panels still feed power back to the grid. This does not automatically mean something is wrong.

The battery automatically enters SLEEP mode after two hours when these three conditions are met:

1. The battery is in a charge-only state, without discharging. This is internally indicated with alarm code 701.
2. The total charging power is less than 50 watts per active battery. (so per 5 kWh)

For one active battery, this means a charging power of less than 50 watts. For two active batteries, the limit is below 100 watts.

Why does the battery not charge with that small surplus?

Charging a battery also consumes energy. The inverter, battery electronics, and the Battery Management System must be active for this.

For example, when only 30 watts of PV surplus is available, the system's energy consumption can be relatively large compared to the amount of energy stored. Additionally, the battery may switch on and off repeatedly with changing cloud cover.

Growatt therefore uses SLEEP mode to:

• make the system work more efficiently;
• prevent unnecessary self-consumption;
• limit frequent switching on and off;
• support the hardware's lifespan.

How much energy is fed back?

Suppose that for two hours, 30 watts more is generated than consumed.

The calculation is:

30 watts × 2 hours = 60 watt-hours

That is:

0.06 kWh

For one active battery, the SLEEP threshold is below 50 watts. When the charging power remains just below that limit for two hours, it concerns less than:

50 watts × 2 hours = 0.1 kWh

The amount of energy temporarily fed back is therefore limited. Moreover, it can be more efficient to feed this small surplus back than to keep the entire battery system active.

When does the battery wake up again?

The battery is automatically woken as soon as sufficient energy is available again or when a set charging command becomes active.

This happens, among other times:

• when PV production rises sufficiently again;
• when AC charging and night priority charging are set;
• when in Load-first mode, more than 200 watts is fed back for longer than five minutes;
• when in Grid-first mode, after full feed-in, there is still PV surplus available;
• immediately during AC charging in Battery-first mode.

Not a fault, but smart control

That a Growatt APX system feeds back a small amount of power while the battery is not yet full can therefore be part of normal operation.

SLEEP mode prevents the system from remaining continuously active for very small amounts of energy. This way, Growatt limits unnecessary losses and switching moments and reduces hardware stress.

Want to know more about Growatt storage systems? Check out our [Growatt products]. 

Still have questions? Please feel free to contact us:

(024) 204 20 90

sales@4blue.nl