The Fox ECS 4.14 kWh High Voltage Battery Master (FE-HV-ECM-4300 / ECM4300) is the control unit and BMS module at the heart of a Fox ECS high-voltage battery stack. Every Fox ECS stack requires exactly one Master module — it contains the Battery Management System, CAN communication interface, and six LED status indicators. Paired with one to six Slave modules (FE-HV-ECS-4300), it enables a scalable storage system from 8.29 kWh up to 29.03 kWh in a single stack. Built on LFP (LiFePO₄) chemistry with a 90% depth of discharge, over 6,000 cycle life, and IP65-rated outdoor/indoor enclosure, it is designed for both residential and light commercial solar storage applications.
>95%
Round-trip efficiency
29.03 kWh
Max stack capacity
⚠ Installer Note — Must be installed by a qualified electrician or MCS-accredited installer. This is a high-voltage DC battery system. Register the install with Fox ESS to activate the extended 12-year warranty — without registration, the standard 5-year warranty applies.
⚡ System Requirements — A minimum of 1 Master + 1 Slave is required for operation. The Master cannot operate alone. Maximum 1 Master + 6 Slaves per stack (29.03 kWh). If expanding an existing ECS stack, confirm module compatibility before ordering — consult your Fox technical contact with a photo of the existing stack. Compatible with Fox H1, KH1, and AIO inverter ranges.
Features & Benefits
✔ Modular & Scalable
Start with 8.29 kWh and expand post-installation by adding Slave modules up to 29.03 kWh — no need to replace existing hardware. One stack supports up to 7 modules (1 Master + 6 Slaves).
✔ Integrated BMS (Master only)
The Master module contains the Battery Management System that monitors and balances cell voltages, manages charging and discharging, and protects against over-voltage, under-voltage, over-current, and overtemperature conditions.
✔ LFP Chemistry — Safe & Durable
Lithium Iron Phosphate (LFP) cells offer superior thermal stability and fire safety compared to NMC alternatives. With a cycle life of ≥6,000 cycles at 90% DoD, the battery is designed to last the lifetime of a solar installation.
✔ High Voltage, High Efficiency
High-voltage DC architecture minimises current losses in cabling, enabling >95% round-trip efficiency — more stored energy becomes usable electricity compared to low-voltage alternatives.
✔ Plug-and-Play Installation
Buckle-fix mechanical connections and a simple CAN/RS485 daisy-chain wiring make stack assembly fast and repeatable. Modules can be added post-installation without restarting or reconfiguring the inverter.
✔ Wide Temperature Tolerance
Operating discharge range of –10°C to +55°C ensures reliable performance year-round in UK garages and outbuildings. Charge derating occurs between 0°C and +15°C. IP65-rated for outdoor and indoor installation.
✔ FoxESS Cloud Monitoring
Real-time state-of-charge, charge history, and system health are visible via the FoxESS Cloud platform and app — giving homeowners and installers full visibility over energy storage performance.
✔ Extended 12-Year Warranty
5-year standard warranty, upgradeable to 12 years by registering the installation on the Fox ESS portal. Standard registration is free and should be completed by the installer at commissioning.
Technical Specifications
| Manufacturer |
Fox ESS |
| Part Number (Master) |
FE-HV-ECM-4300 / ECM4300 |
| Module Type |
Master (includes BMS — 1 required per stack) |
| Battery Chemistry |
LFP (LiFePO₄) Prismatic Cell |
| Nominal Energy per Module |
4.14 kWh |
| Depth of Discharge |
90% |
| Round-Trip Efficiency |
>95% |
| Cycle Life |
≥6,000 cycles @ 90% DoD, 0.5C |
| Recommended Charge/Discharge Current |
35 A |
| Max Charge/Discharge Current |
50 A |
| Peak Discharge Current (30 s) |
65 A |
| Communication |
CAN / RS485 |
| Display |
6× LED (Master); 1× LED (Slave) |
| Max Modules per Stack |
7 (1× Master + 6× Slave) |
| Max Stack Capacity |
29.03 kWh |
| Operating Temperature — Discharge |
–10°C to +55°C |
| Operating Temperature — Charge |
0°C to +55°C (derating 0–15°C) |
| Installation Location |
Indoor or outdoor (stand-mounted) |
| Ingress Protection |
IP65 |
| Max Altitude |
2,000 m |
| Dimensions — 2-module stack (W × H × D) |
570 × 350 × 380 mm |
| Certifications |
IEC 62619, IEC 61000-6-1/2/3/4, UN38.3 |
| Warranty |
5 years standard; 12 years with online registration |
Frequently Asked Questions
What is the difference between the Master and Slave module?
The Master (ECM4300 / FE-HV-ECM-4300) contains the Battery Management System (BMS) and is the communications hub for the entire stack — every stack requires exactly one. The Slave (ECS4300 / FE-HV-ECS-4300) is an additional energy storage module with no BMS of its own; it connects to the Master and receives instructions from it. You cannot run a stack with Slaves alone — always start with one Master.
Can I add more Slave modules after installation?
Yes — the ECS system is designed to be expanded post-installation. Slave modules can be added at any time up to the maximum of 6 Slaves per Master (7 total). Before ordering additional modules, confirm compatibility with your existing stack by consulting the Fox ESS technical portal with a photo of your current battery setup, as different ECS generations may have mixed-compatibility limitations.
Which Fox inverters are compatible?
The ECS4300 battery stack is compatible with Fox ESS H1, KH1, and AIO hybrid inverter ranges. Always verify inverter firmware is up to date before commissioning. Refer to the Fox ESS Battery Limits Guide for the exact maximum battery capacity supported by each inverter model.
