FOX ESS KA10 - single-phase AC-coupled inverter 10 kW.

FOX ESS KA10 is a single-phase AC-coupled inverter rated at 10 kW for use with high-voltage LiFePO₄ batteries. It is a solution for sites where a solar installation is already running and storage needs to be added without reworking the existing system. Battery voltage range 85–480 V, charge and discharge current 50 A, IP65 protection, mass 27.5 kg.

What 'AC-coupled' means and why it matters

A classic hybrid inverter connects to the panels directly and manages the whole chain: panels, battery, grid, loads. Fitting one to an existing installation means dismantling the current grid-tied inverter and reworking the entire DC side.

An AC-coupled inverter works differently. It connects on the AC side — that is, to the same board your installation already feeds. The panels, their wiring and the existing inverter remain untouched and carry on working as before.

The practical conclusion: if you already have a working solar installation without storage, this is the cheapest and fastest way to add a battery. There is no need to dismantle equipment, revise the design, or void the warranty on the installed inverter.

Ten kilowatts and peak loads

Nominal current at 230 volts is 43.5 amperes, with a maximum output of 45.7 amperes. That is a level sufficient for full backup of a large house together with heavy equipment.

Battery charge and discharge current reaches 50 A in both directions. A high discharge limit means the system can deliver a great deal at once — exactly what is required when a borehole pump, an air conditioner compressor or a welding set starts up.

Efficiency of 97.8%

Peak efficiency is 97.8% and the European weighted figure 97.4%. For an inverter performing double conversion — charging the battery and supplying the loads — that is a high result.

It is worth understanding a characteristic of the AC-coupled arrangement: energy from the panels passes through two conversions before reaching the battery — first in your existing inverter, then in this one. Each stage has its own efficiency, so total losses are slightly higher than in a direct hybrid arrangement. That is the price of not touching a working installation, and in most cases it is repaid by the saving on rework.

Equipment built for outdoor installation

• IP65 protection — wall mounting outdoors with no dedicated room;

• operating range from −25 to +60 °C, climatic category 4K4H;

• aluminium alloy housing, natural-convection cooling;

• noise level under 30 dB — inaudible even beneath a window;

• operation at altitudes to 2000 m, humidity 0–95%;

• 5-year manufacturer warranty.

Control and integration

Communication is over Wi-Fi or wired LAN, with control through the FoxCloud mobile app. Integration with third-party automation over Modbus TCP/RTU is provided, including Home Assistant support.

The unit can work with a generator and features an integrated DC switch, Type II surge protection on both sides, earth fault monitoring and night-time monitoring. Certification: CE, IEC 62109-1/2, IEC 62116, IEC 61727, EN 50549.

What to allow for before ordering

A mass of 27.5 kg requires a solid wall and two-person installation. Dimensions of 450 × 527 × 208 mm are substantial too, so the position should be chosen in advance.

The second point is the battery. The inverter works with high-voltage LiFePO₄ modules in the 85–480 V range. Low-voltage stacks at 48 or 51.2 V will not do, and this must be taken into account when selecting storage.

If you already have a solar installation running and are considering storage, tell us which inverter is fitted and how many panels are installed. We will work out which is better value in your case: an AC-coupled solution or replacement with a full hybrid.