Fox ESS Grid Backup 5-15kWh Energy Storage System with 3.7kW AC Charger Inverter

By Fox ESS

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Elevate Your Energy Security with the Fox ESS Grid Backup 5-15kWh Energy Storage System

A Grid Backup Energy Storage System empowers you to store energy from economical sources, such as mains power at the off-peak Octopus tariff. This stored energy can be strategically utilized, providing an alternative to exporting power at low feed-in tariffs or depending on costly peak-rate power.

The Fox ESS Grid Backup 5-15kWh Energy Storage System, equipped with a 3.7kW AC Charger Inverter (5.12kWh/3.7kW ESS), comprises:

  • 2x - 6x Fox ESS HV2600 2.56kWh High Voltage Battery V2
  • 1x Fox ESS 3.7kW AC1 Charger Inverter
  • 1x Fox ESS HV BMS-V2 High Voltage Battery Management System
  • 3x - 7x Fox HV Battery Brackets (pair)

The 5-15kWh/3.7kW Grid Backup ESS adeptly manages energy usage, ensuring a consistent electricity supply and facilitating cost reduction (e.g., charging a battery with low-priced Octopus electricity). Using an ESS with a private power source, such as on-grid solar panels, enables you to supply electricity for 24/7 home power.

The 3.7kW AC1 Charger Inverter seamlessly integrates with an external backup generator, ensuring a continuous power supply during prolonged grid outages when the battery stoage is emptied.

  • Fox ESS HV2600 2.56kWh HV Battery V2 is a high-performance, scalable battery storage module. The modular design allows for maximum flexibility with storage. Additional batteries can be installed in series, allowing a maximum storage capacity of 20.48kWh (1 master and up to 7 slaves). Installation is easy, with a plug-and-play solution that can save valuable time for installers. The batteries have a 98% charge/discharge efficiency and 90% depth of discharge. The batteries have a cycle life of over 4000 cycles.
  • Fox ESS 3.7kW AC1 Charger Inverter is a high-quality inverter which converts solar energy to AC energy which is stored in a battery. The inverter can be used to optimise energy consumption, store energy in the battery for future use or feed energy into the energy grid. System advantages:
    • Advanced DSP control technology
    • Utilises the latest high-efficiency power components
    • Advanced anti-islanding
    • Max. efficiency up to 97.8%, THD<3%
    • Export limitation (CT/Meter/DRM0/ENSTOP)
    • Export limitation (CT/Meter/DRM0/ENSTOP)
  • Fox ESS 3.7kW AC1 Charger Inverter has four work modes:
    • Self-use: The battery will discharge for local loads first, and the grid will supply power when the battery capacity is not enough.
    • Feed in priority: In the case of an external generator, the power generated will be used to supply the local loads first, then export to the grid. The redundant power will charge the battery.
    • Force time use: This mode is used in the area which has peak and off-peak prices. The user can use off-peak electricity to charge the battery. The charging and discharging time can be set flexibly, and this also allows one to choose whether to charge from the grid or not.
    • Back up (EPS) mode: When the grid experiences an outage, the system will supply emergency power from PV or a battery to supply the home loads.
  • The Fox ESS 5-15kWh Grid Backup Energy Storage System has been designed to work seamlessly with smart Octopus tariffs. The first energy supplier to offer such a tariff is Octopus Energy, but the Fox energy storage system also works perfectly with any other energy provider. The Fox energy storage system can be controlled automatically to take advantage of Plunge Prices and super cheap prices. With solar panels and the battery storage system, your electric unit price can be drastically reduced!
  • Fox ESS HV BMS-V2 High Voltage BMS is a communication module which is required for each stack of HV2600 batteries. The use of the FoxESS BMS battery control system extends battery life, which is a very profitable investment. It reduces the risk of failures related to energy storage in batteries. It also allows you to constantly monitor the charge level. It is distinguished by compact dimensions, a wide operating range in terms of voltage and temperature, as well as the presence of RS485 and CAN communication interfaces. Weight 8.75kg.
  • Fox HV Battery Brackets allow vertical stacking of the HV2600 batteries.  1 pair of battery brackets per battery is required.
  • TWO WORKING DAY DELIVERY within the UK (longer to the Highlands, islands and Northern Ireland).
Battery Type: Lithium Iron Phosphate (LiFePO4)
Nominal Capacity: 2.56kWh
Maximum Charge Voltage: 2pcs 116.8V 3pcs 175.2V 4pcs 233.6V 5pcs 292.0V 6pcs 350.4V
Discharge Cut Voltage: 40V
Rated Charge/Discharge Current: 50A
Peak Discharge Current: 60A
Peak Charge Current (30sec): 60A
Operating Temperature: -10 ~ +50°C
Storage Temperature: -20 ~ +50°C
Charge/Discharge Efficiency: >98%
Protection Level: IP21
Weight: 27kg
Size:  443 * 410 * 116mm
Cycle Life: >6000
Depth of Discharge: 90%
Battery Type: Lithium Iron Phosphate (LiFePO4)
Battery Voltage: 85-450V
Max. Charge/Discharge Current: 40A
Communication Interface: CAN(Communicate With Inverter), RS485 (Upgrade BMS)
Max. AC Input Power: 7680VA
Max. Input Current (per phase): 34.9A
Rated Output Power: 3680W
Max. Output Apparent Power: 4048VA
Rated Output Current (per phase): 16.0A
Max. Output Current: 17.6A
Rated Grid Voltage: 220-240VAC
Rated Grid Frequency: 50/60Hz
Power Factor: 1 ( Adjustable from 0.8 leading to 0.8 lagging )
THDi: <3% @rated power
Max. Output Apparent Power: 5000VA
Peak Output Apparent Power (60sec): 6000VA
Max. Current (per phase): 21.7A
Rated Output Voltage: 220-240VAC
Rated Output Frequency: 50/60Hz
Power Factor: 1 ( Adjustable from 0.8 leading to 0.8 lagging )
THDi (linear load): <2% @rated power
Switch Time: 20ms
Max. Efficiency: 97.80%
Max. Battery Discharge Efficiency (BAT to AC)(@full load): 97.00%
Operating Temperature: -25 ~ +60°C
Protection Degree: IP65
Size:  430 x 410 x 178mm

Net Weight: 23kg


  • 2x - 6x Fox ESS HV2600 2.56kWh High Voltage Battery V2,
  • 2x - 6x Fox ESS HV Battery Brackets (pair),
  • 1x Fox ESS AC1 3.7kW AC Charger Inverter,
  • 1x Fox ESS HV BMS-V2 High Voltage Battery Management System, and
  • 3x - 7x Fox HV Battery Brackets (pair).

 Don't know an answer to your question? Call us on 020 8064 0335 or email

Watch 3.7kW AC1 Charger Inverter + 2x HV2600 System Installation Video