Fox ESS EQ series batteries: models and specifications

The Fox ESS EQ range is a set of stackable high-voltage home battery modules rather than a single fixed unit. The models sold under the EQ name are the EQ2900 at 2.88kWh, the EQ4300 at 4.32kWh, the EQ4800 at 4.66kWh and the EQ5000 at 4.92kWh¹. Each stack is built from one master module (EQM) and additional slave modules (EQS), so capacity is decided by how many modules are stacked, not by choosing a bigger box¹.

That modular approach is the point of the range. A household can start with a small stack and add modules later, and the modules are floor-mounted and stacked on top of one another rather than wall-hung⁴. The trade-off is that the battery is only half a system: it needs a compatible Fox ESS hybrid inverter to charge and discharge it, and it communicates with that inverter over CAN¹.

The EQ range at a glance: EQ2900, EQ4300, EQ4800, EQ5000 and beyond

Fox ESS lists the EQ/CQ series as the EQ2900, EQ4300, EQ4800, EQ5000 and CQ7¹. The headline capacities are 2.88kWh for the EQ2900, 4.32kWh for the EQ4300, 4.66kWh for the EQ4800 and 4.92kWh for the EQ5000¹. The EQ3300 also appears in the maker's product listings as an expandable system, and the EQ5500 and EQ6000 Plus sit further up the same family⁶.

The naming is not a strict ladder. The EQ4800 and EQ5000 are close in capacity, and the CQ7 is a different sub-family with its own stacking limit of up to fourteen modules in series¹. What they share is the design intent: compact, floor-mounted modules that stack to build the capacity an installation needs⁴.

Specifications: capacities, high-voltage design and cooling

The EQ range is a high-voltage battery family, and Fox ESS describes the EQ5000 as high voltage with a 4.92kWh capacity⁹. The EQ4800 datasheet gives the same headline figure of 4.66kWh capacity and confirms the chemistry as LFP (LiFePO₄)². Fox ESS states that every model in its battery range uses lithium iron phosphate cells, supports modular expansion and is engineered for straightforward installation⁵.

Cooling is passive. The EQ battery range uses natural convection cooling, which means no fans and no moving parts in the battery itself¹. That is consistent across the wider Fox ESS battery line, and it matters for siting: a passively cooled battery has no fan noise, but it also has no active thermal management to fall back on in a hot plant room or a sun-facing cupboard.

The EQ4800 and EQ5000 both carry a maximum operating altitude of 3,000m, and the EQ6000 Plus lists the same figure². The EQ4800's indicator LEDs differ by module type: the slave carries one LED and the master carries six². The EQ5000 follows the same pattern, with the slave at one LED³.

Stacking and scalability: master (EQM) and slave (EQS) modules

Every EQ stack is built the same way: one master module (EQM) and additional slave modules (EQS)¹. The master is the module that talks to the inverter and manages the stack; the slaves add capacity. A stack therefore always has exactly one master and at least one slave, and the smallest configuration is two modules.

The maximum number of modules depends on the model. The EQ4800 takes up to nine modules in series, which is one master and eight slaves². The EQ5000 takes up to six modules in series³. The CQ7 goes further, at up to fourteen modules in series¹. The EQ6000 Plus datasheet sets out its configurations by module count, from one slave module up to six¹⁰.

Fox ESS describes the EQ/CQ series as a modular, stackable solution, and the modules are compact and floor-mounted so they can be stacked to build the capacity for an installation¹. The practical consequence is that a household is not locked into a single capacity at the point of purchase. Adding a module later is a matter of adding to the stack, subject to the model's series limit and to the inverter's own supported capacity.

Compatibility with Fox ESS inverters and other battery ranges

The EQ range pairs with compatible Fox ESS hybrid inverters, including the H1-G2 and K Series, the H3 Smart and the H3 Pro¹. The KH/KA series is a single-phase hybrid inverter available in 7, 8, 9 and 10kW options, and Fox ESS states that it pairs with Fox ESS high-voltage batteries including the EP, EQ and CQ ranges⁴. The KH/KA offers EPS output when a battery is fitted and is described as smart tariff compatible⁴.

The wider Fox ESS inverter line follows the same pattern. The PowerQ, the S28, the P100 and the S22 are each described as compatible with Fox ESS's own range of high-voltage batteries¹³. The H1-G2 and AC1-G2 hybrid inverters also offer EPS output with a battery, and the H1-G2/AC1-G2-WL models communicate with the inverter and support BMS upgrades over CAN¹⁷.

The EP range is the other high-voltage option, available as the EP6 at 5.76kWh and the EP12 at 11.52kWh, with up to four units connectable in parallel⁴. So a household choosing between Fox ESS batteries is choosing between the EP's larger fixed modules and the EQ's smaller stackable ones, both of which run on the same high-voltage inverter platform.

What an EQ battery costs in the UK

Fox ESS publishes no UK list price for the EQ2900 or any other EQ module. Prices are installer-quoted, and the figures that circulate come from distributor listings rather than from the manufacturer.

For wider context on what a home battery costs in the UK, an independent guide published in May 2026 records EDF Energy selling batteries starting from £3,995 for a Sunsynk battery, or £7,795 for a Tesla battery¹⁹. Those are different products from different suppliers, and they are useful only as a sense of the market rather than as a guide to EQ pricing.

Because there is no published EQ price, the honest position is that a household cannot compare EQ modules on price from public information. What can be compared is the structure: a stackable module system lets capacity be added in steps, which spreads cost over time, but each step involves an installer visit and the associated labour. The VAT treatment of the figures above is not stated, so they should be read as quoted rather than as confirmed VAT-inclusive prices.

Safety, certification and communications (CAN)

The EQ4800 datasheet lists IEC 62619 for safety and EN IEC 61000-6-1/2/3/4 for electromagnetic compatibility². The EQ5000 lists IEC 61000-6-1/2/3/4³, and the EQ6000 Plus lists IEC 61000-6-1/2/3/4 plus UN38.3 for transport¹⁰. The older ECS series, which the EQ range follows, listed IEC 62619 for safety and EN IEC 61000-6-1/2/3/4 for EMC²⁰.

Communications across the range are CAN. The EQ battery range uses CAN communication¹, the EQ4800 datasheet states CAN communication², the EQ5000 lists CAN³ and the EQ6000 Plus lists CAN¹⁰. On the inverter side, the KH/KA offers CAN and RS485 interfaces¹², and the H1-G2/AC1-G2-WL models use CAN to communicate with the inverter and to upgrade the BMS¹⁸.

Fox ESS publishes certificates among its product resources¹⁷. The KH/KA inverter carries G99, EN50549 and NRS 097-2-1 certifications, and its safety certifications are IEC62109-1, IEC62109-2 and IEC 62477-1¹². Those are inverter certifications rather than battery ones, but they matter because the two are installed as one system.

Warm-up function and other model differences

Battery warm-up is the clearest difference between EQ models. Fox ESS states that warm-up availability varies by model and system configuration, that it is not available on the EQ4800, and that it is available on the EQ2900, EQ4300 and EQ5000 only when the system includes both EQ master and slave units¹. Warming is disabled when EQ slave batteries are paired with legacy ECS versions¹.

That conditionality is worth reading carefully. Warm-up on the EQ2900, EQ4300 and EQ5000 is not a property of the battery alone; it depends on the stack containing both a master and a slave, and on the slaves not being legacy ECS units. A single-module stack, or a stack mixing in older ECS slaves, does not get it.

Other differences between models are smaller. The EQ4800 and EQ5000 both cap operating altitude at 3,000m², and the EQ6000 Plus matches that¹⁰. Indicator LEDs differ by module role rather than by model: six on a master, one on a slave². The EQ5500 and EQ6000 Plus are listed as expandable systems, as are the EQ3300 and EQ4800⁶.

Where EQ sits in the Fox ESS ecosystem and the UK market

Fox ESS states that it has been independently verified by SunWiz as the UK's number one brand by volume for both inverters and energy storage systems, as of Q2 2026²¹. The company also reports that InfoLink Consulting's 1H26 global ESS shipment rankings placed it first among residential ESS suppliers¹¹, and that it achieved the number one market share in Europe's residential energy storage market²¹. These are the maker's own statements about its market position.

Fox ESS describes itself as a Sino-British partnership, supported by significant international shareholders alongside UK-based stakeholders²¹. That structure is relevant to a household weighing where a battery comes from and who stands behind it.

The EQ range sits within a wider Fox ESS ecosystem that includes hybrid inverters, the EPS-BOX-SP backup gateway and the PowerQ modular system. The EPS-BOX-SP sits between the Fox ESS inverter, the utility supply and the household circuits, and works with the H1-G2, KH, EVO and PowerQ inverters²². For a household, the EQ's contribution to energy independence is real but bounded: it stores solar or cheap-rate electricity for use later, and with a suitable inverter and backup gateway it can keep selected circuits running in a power cut. What it does not remove is the grid connection, the electricity supplier, or the dependence on a compatible Fox ESS inverter and the manufacturer's own system for control and monitoring.