Fox ESS EP6 5.76kWh Battery with Heating Element

The Fox ESS EP6 is a 5.76kWh high voltage LFP battery with a heating element, and the useful thing about it is the footprint: 380mm wide against the EP12's 710mm, so a bank of them can go where one large cabinet will not. Fox's documentation calls the heated version EP6 Plus (w).

Buy it as a single unit or as a pack of two, three or four. Capacity is added by paralleling identical units, so a pack is simply the quantity decision made up front – 11.52kWh, 17.28kWh, or the 23.04kWh ceiling Fox publishes for four units.

EP6 at a glance

Fox's performance warranty is the source of that last figure: at least 70% of nominal energy retained for ten years from commissioning, conditional on registering the battery and on the ambient temperature during operation staying within Fox's stated limits.

Choosing between one unit and a pack

A single EP6 suits a house with a modest array and an evening-and-overnight load. Two units is the common pairing for a family home on a time-of-use tariff, charging cheaply overnight and running through the following day. Three and four units exist for a larger roof with genuine surplus, or for a household that wants the bank finished in one visit rather than revisited.

One detail is worth knowing before you mix orders. The warm-up function only works if every battery in the system is a heated version – Fox is explicit that the wiring must be right and all batteries must be the warm versions, or warming will not operate. A pack of these is heated throughout by definition. Fox separately prohibits mixing different battery models in one system.

What is in the box, per unit

The heating, and the limits it removes

Fox's published operating limits are the reason the heated version exists. The battery will only discharge above −10°C and only charge above 0°C. With warming active the charge and discharge window both widen to −25°C to 55°C; with it off, charging is held to 0°C and above.

The behaviour is specific: between −25°C and 0°C the system brings the cells up to 10°C, stops, and restarts if they fall below 1°C. It reads internal cell temperature rather than the air in the room. Energy for warming comes from PV first; if PV is short, the order depends on state of charge. Warming is switched on from the inverter's own screen, under Setting, Battery, Battery warm up – so the inverter has to be one that offers that menu.

A thermal aerosol fire extinguishing device is built into the pack and deploys on detection. Fox publishes the presence of the feature but not the agent quantity or the standard it was tested to.

Where it can go

Floor or wall, indoors or outdoors, always upright – Fox rules out tilting it in any direction and will not have it laid flat or inverted. Cooling is natural convection, so it needs at least 300mm clear above, to the left, and between adjacent units, and the casing must not be boxed in or covered.

Fox's siting guidance is more specific than most: keep it away from the seaside, because of salt spray and humidity; choose somewhere cool and out of direct sun and high temperatures; and keep flammable or explosive materials away from it. Rated IP65 for 5 to 95% humidity without condensation, and up to 3,000m altitude. Storage, as opposed to operation, is specified at −10°C to 40°C.

Inverters Fox lists as compatible

Compatibility is published by series, not by individual model: all series of H1, KH, H3, H3-Pro and US. The battery communicates over CAN to the inverter's BMS port and is monitored through the inverter's app rather than directly. Switch the inverter on before the battery at start-up. Certified to IEC62619, shipped under UN38.3, protective class I.

Order alongside

• Fox Junction Box for Paralleling up to 4 EP Series Batteries

  Needed for any pack of two or more and sold separately. Fox's box is specified for the EP5/6 and EP11/12 ranges and supports four-way parallel connection.

• Fox H1 3.7kW Hybrid Inverter with EPS 1PH Gen 2

  A sensible single-phase match for one or two EP6 units. Fox sells this inverter and this battery together as a factory bundle.

• Fox 7kW K Series Single Phase Hybrid Inverter

  More headroom for a larger array or a three and four unit bank, from the KH series on the same compatibility list.

• Fox WLAN-WW Monitoring Stick

  Wireless monitoring at the inverter where the router reaches it, with the LAN stick as the wired alternative.

The rest of the heated EP range

• Fox ESS EP5 5.18kWh Battery with Heating Element

  A slightly smaller step, and the notice below confirms the EP5 and EP6 expand together.

• Fox ESS EP12 11.52kWh 384V Battery with Heating Element

  Double the energy per unit in a 710mm cabinet, taking a four-unit bank to 46.08kWh instead of 23.04kWh.

Browse the full solar battery range, or the hybrid inverters that run them.

Fox's published feature list

• Battery heating and fire suppression
• Scalable to 23.04 kWh
• 90% Depth of Discharge
• Floor or Wall Mounting
• Compact & Easy Installation
• IP65 Protection Level
• High Voltage and High Efficiency
• 10-year warranty upon registration

Fitting is work for a qualified electrician. Fox's manual is written for authorised and qualified technicians, and warranty cover depends on registration being completed after commissioning.