Fox ESS AC1-3.7-E-G2 3.7kW AC-Coupled Charger Inverter Gen 2 for HV Battery Storage
The Fox ESS AC1-3.7-E-G2 (part number FE-AC1-3.7) is a 3.68 kW AC-coupled charger inverter designed to add high-voltage battery storage to existing solar PV systems or to operate standalone. This is a battery inverter with no DC/PV inputs; it charges and discharges batteries on the AC side, making it suitable for retrofitting storage to any existing PV installation. The AC1 Gen 2 works with Fox ESS high-voltage batteries including the HV2600, Energy Cube, and MIRA HV25 ranges, requiring a BMS and a minimum of two HV2600 batteries. It includes built-in EPS (emergency power supply) for backup operation, a CT clamp in the box, and a WiFi data logging stick for monitoring via the Fox Cloud platform. IP65 rated for indoor or outdoor wall-mounted installation, it measures 434 x 418 x 185 mm and weighs 22 kg. Available from DECO Group, a UK-based solar wholesaler for trade installers.
Key Technical Details
- Part number: FE-AC1-3.7
- Supplier part number: AC1-3.7 (with EPS)
- Model: AC1-3.7-E-G2
- Product type: AC-coupled charger inverter (no DC/PV inputs)
- Topology: Non-isolated
AC Output
- Rated AC output power: 3,680 W
- Maximum AC output apparent power: 4,048 VA (G98) / 3,680 VA
- Rated output current: 16.7 A (G98) / 16 A
- Maximum output current: 18.4 A
- Grid voltage: 220 / 230 / 240 V
- Grid frequency: 50 / 60 Hz
- Power factor: 1 (adjustable from 0.8 leading to 0.8 lagging)
- Total harmonic distortion: less than 2% at rated power
AC Input
- Maximum AC input power: 5,500 W
- Maximum AC input apparent power: 7,680 VA
Battery
- Battery type: Lithium battery (LFP)
- Battery voltage range: 80 V to 480 V
- Maximum charge/discharge current: 40 A
- Battery communication: CAN
EPS (Emergency Power Supply)
- EPS rated output power: 3,680 W
- EPS maximum apparent power: 4,400 VA
- EPS rated current: 16.7 A
- EPS rated voltage: 220 / 230 / 240 V
- EPS frequency: 50 / 60 Hz
- EPS switch time: less than 20 ms
Efficiency
- Maximum efficiency: 97.08%
- Euro efficiency: 95.70%
General
- Cooling: Natural convection (fanless)
- Noise emission: 35 dB
- Ingress protection: IP65
- Operating temperature range: -25°C to 60°C
- Humidity: 0% to 100% (no condensation)
- Standby consumption: less than 15 W
- Communication: RS485, DRM, Ripple Control, USB, CAN
- Monitoring module: WiFi (included); LAN and 4G optional
- Display: LCD, app, website
- Installation: Wall-mounted
- Dimensions: 434 x 418 x 185 mm (W x H x D)
- Weight: 22 kg
Key Features
- AC-coupled design adds battery storage to existing PV systems without changing the solar inverter
- 3.68 kW rated output with built-in EPS for backup power during grid outages (less than 20 ms switch time)
- 97.08% maximum efficiency with natural convection cooling
- High-voltage battery platform supporting Fox HV2600, Energy Cube, and MIRA HV25 batteries
- Up to 10 inverters can be installed in parallel for large-scale or commercial systems
- CT clamp and WiFi data logging stick included in the box
- IP65 rated for indoor or outdoor wall-mounted installation
- Fanless operation at 35 dB
System Compatibility
- Compatible with Fox ESS HV2600 high-voltage batteries (BMS required, minimum 2 batteries per stack)
- Compatible with Fox ESS Energy Cube batteries (up to 9 x EQ4800 per inverter for over 40 kWh capacity)
- Compatible with Fox ESS MIRA HV25 batteries
- Master and Slave battery modules must be the same size within a stack
- Up to 10 x AC1 inverters in parallel, each with a full battery stack
- A second CT clamp is required if a second generator is present (e.g. PV, wind, or other)
- A meter is required if the distance between inverter and incoming power connection exceeds 30 m
Installation Notes
- Wall-mounted on a solid, non-combustible surface with adequate clearance for airflow and cable routing
- At 22 kg, a two-person lift is recommended
- CT clamp must be fitted on the correct conductor with correct orientation (arrow direction matters) for accurate grid sensing
- BMS plus a minimum of 2 x HV2600 batteries required to form a working stack
- Ensure correct HV cable polarity and CAN communication to BMS
- When installing batteries side by side rather than stacked, the longer cable pack FE-HV2600-EXT-1M is recommended
- EPS backup circuit must be wired exactly as specified with correct isolation and protective devices
- Qualified installer only; all work must follow local wiring regulations and Fox ESS documentation
Included Components
- 1 x Fox ESS AC1-3.7-E-G2 charger inverter
- 1 x CT clamp for import/export sensing
- 1 x Fox WiFi data logging stick
Warranty
- Standard warranty: 5 years
- Extended warranty: 10 years when the installation is registered with Fox ESS online
Common Questions
Click a question below to reveal the answer.
What does "AC-coupled" mean?
The AC1 charges and discharges batteries on the AC side of the system. It has no DC/PV inputs. This makes it ideal for adding battery storage to an existing solar PV installation without changing the existing PV inverter.
What batteries are compatible with the Fox ESS AC1 Gen 2?
The AC1 Gen 2 works with Fox ESS high-voltage batteries including the HV2600, Energy Cube (EQ4800), and MIRA HV25 ranges. A BMS unit is required and a minimum of 2 x HV2600 batteries are needed to form a working stack. Master and Slave modules must be the same size.
Is a CT clamp included with the Fox ESS AC1 Gen 2?
Yes. One CT clamp is included in the box for grid import/export sensing. A second CT is required if there is another generator on site (e.g. existing PV, wind, or other). Correct orientation of the CT clamp is essential for accurate metering.
Does the Fox ESS AC1 Gen 2 support backup power?
Yes. The AC1 Gen 2 has built-in EPS (emergency power supply) with a rated output of 3,680 W and a grid-to-backup switch time of less than 20 ms. The EPS circuit must be wired as specified with correct isolation and protective devices.
How many Fox ESS AC1 inverters can be installed in parallel?
Up to 10 AC1 inverters can be installed in parallel, each with a full battery stack connected. This enables scalable storage for larger residential or commercial projects.
What are the dimensions and weight of the Fox ESS AC1 Gen 2?
The AC1 Gen 2 measures 434 x 418 x 185 mm (W x H x D) and weighs 22 kg. It is wall-mounted; a two-person lift is recommended.
DECO Group supplies Fox ESS AC-coupled charger inverters alongside HV2600 batteries, BMS controllers, Energy Cube modules, wall-mount brackets, extension cables, and monitoring accessories. Browse our Fox ESS storage catalogue for complete AC-coupled battery retrofit system components.
About DECO Group
We are a UK-based solar and energy storage wholesaler supplying AC-coupled charger inverters, high-voltage battery modules, and all associated system accessories to professional installers and electrical contractors. Our Fox ESS range covers the full AC1 and H1 Gen 2 product lines with batteries, BMS units, and cabling in stock for complete system builds. Visit decogroup.co.uk for the full catalogue.
