Engineering report · reviewed against NEC 2026 & BS 7671:2018+A2
Engineering Breakdown: Running a BMW i4 / iX (Flexible Fast Charger 24A) on the Fox ESS EP5 Modular Hybrid
When pairing the Fox ESS EP5 Modular Hybrid (5,180 Wh LiFePO4 capacity, 5,000 W continuous, 7,500 W surge) with a BMW i4 / iX (Flexible Fast Charger 24A) (5,760 W running, 5,760 W starting surge), the system operates at 110% of continuous inverter capacity on a 230 V UK/EU/AU circuit. Our UK/EU/AU verdict is Continuous Overload, so the runtime figures below are theoretical battery-energy values only. Wiring the connection over a 7.5 m run calls for a 25 A MCB and 2.5 mm² copper, terminated at a Type 2 EVSE · IEC 60309 32A Commando connection.
1. Compatibility Verdict & Inverter Load Utilization
In UK/EU/AU 230 V mode the BMW i4 / iX (Flexible Fast Charger 24A) loads the Fox ESS EP5 Modular Hybrid's inverter to 110% of its 5,000 W continuous rating and 74% of its 7,500 W surge rating. Because continuous demand exceeds the inverter by 520 W, the unit will shut down within seconds of starting the load. The EcoFlow Delta Pro Ultra (1 Inverter + 1 Battery) is the smallest compatible upgrade.
| Check | Load requires | Fox ESS EP5 Modular Hybrid provides | UK/EU/AU |
|---|---|---|---|
| Continuous output | 5,520 W | 5,000 W | Fail |
| Start-up surge | 5,520 W | 7,500 W | Pass |
| Voltage | 230 V | 230 V | Pass |
| Connection | Type 2 EVSE · IEC 60309 32A Commando | Hardwired consumer unit (RCBO protected) |
An EVSE is a constant-current device: the vehicle draws exactly the current advertised by the J1772/NACS pilot signal, so the 5,760 W figure is both the running load and the start-up load — there is no motor inrush. That makes the calculation unusually clean. If you want to stay under the 80% sustained-load guideline, set the charge current in the vehicle app to 16 A or less, which keeps the Fox ESS EP5 Modular Hybrid at roughly 3,840 W. A full battery delivers about 4.0 kWh into the pack after inverter and on-board charger losses, worth roughly 14 miles (22 km) of driving at 3.5 mi/kWh.
The Fox ESS EP5 Modular Hybrid combines a hybrid solar inverter with stackable battery modules, wired permanently into the home's distribution board. Its 6,500 W PV input lets one unit handle both rooftop solar and storage.
Compatible alternative: the EcoFlow Delta Pro Ultra (1 Inverter + 1 Battery) with the BMW i4 / iX (Flexible Fast Charger 24A) report shows the full sizing for a unit that passes all three checks.
2. Real-World Runtime by Duty Cycle
Nameplate capacity is not usable capacity. DC-to-AC conversion, battery management overhead and cell protection reduce the 5,180 Wh rating to about 4,403 Wh of deliverable AC energy (85% system efficiency). EV charging runs at a fixed current, so the 100% row is the realistic figure; lower rows apply only if you schedule charging in intervals.
| Duty cycle | Average draw | Runtime (no solar) | Energy per 24 h |
|---|---|---|---|
| 25% | 1,380 W | 3.2 hrs | 33.1 kWh |
| 50% | 2,760 W | 1.6 hrs | 66.2 kWh |
| 65% | 3,588 W | 1.2 hrs | 86.1 kWh |
| 100% | 5,520 W | 48 min | 132.5 kWh |
Even at a 50% duty cycle the battery lasts 1.6 hrs, so plan on solar, grid or generator recharging for anything longer than an evening outage. Because the inverter cannot actually run this load in UK/EU/AU mode, treat these numbers as an energy-budget reference for a compatible inverter of the same capacity.
3. BS 7671 / IEC 60364 Breaker & Cable Sizing
IEC-based codes size protection by design current rather than a blanket 125% multiplier: Ib ≤ In ≤ Iz. At 230 V the load draws 24.0 A (the EVSE's 24 A pilot current at 230 V), so a 25 A Type B/C MCB with RCD protection applies. In the UK, BS 7671 Section 722 additionally requires a dedicated circuit and Type A or Type B RCD for EV charge points.
| One-way distance | MCB | Min. cable | Voltage drop |
|---|---|---|---|
| 7.5 m (25 ft) | 25 A | 2.5 mm² | 1.16% |
| 15 m (49 ft) | 25 A | 2.5 mm² | 2.32% |
| 22.5 m (74 ft) | 25 A | 4.0 mm² | 2.16% |
| 30 m (98 ft) | 25 A | 4.0 mm² | 2.89% |
Moving the Fox ESS EP5 Modular Hybrid from 7.5 m to 30 m away forces the conductor up from 2.5 mm² to 4.0 mm² — park the unit as close to the load as ventilation and weather protection allow.
4. Solar Array Recharge Time Breakdown
The Fox ESS EP5 Modular Hybrid accepts up to 6,500 W of photovoltaic input. Real arrays rarely deliver nameplate output, so we apply an 80% harvest factor for MPPT conversion, cell temperature and soiling, and convert hours to days using 4.5 peak-sun-hours — a conservative annual average for the US, southern Europe and Australia (UK winters can fall below 1.5).
| PV array | Real harvest | 0–100% recharge | Sun-days @ 4.5 PSH | Net with load @ 50% |
|---|---|---|---|---|
| 800 W | 640 W | 8.1 hrs | 1.8 | −2,120 W |
| 1,600 W | 1,280 W | 4.0 hrs | 0.9 | −1,480 W |
| 3,000 W | 2,400 W | 2.2 hrs | 0.5 | −360 W |
| 6,000 W | 4,800 W | 1.1 hrs | 0.2 | +2,040 W |
| 6,500 W | 5,200 W | 60 min | 0.2 | +2,440 W |
A typical 800 W portable array refills the battery in about 8.1 hrs of strong sun, while maxing out the 6,500 W input cuts that to 60 min. To fully offset the BMW i4 / iX (Flexible Fast Charger 24A) at a 50% duty cycle (2,760 W average) during daylight you need roughly 3,450 W of panels, which this unit can accept.
5. Frequently Asked Questions
Can the Fox ESS EP5 Modular Hybrid run a BMW i4 / iX (Flexible Fast Charger 24A)?
Not reliably in the UK, Europe and Australia — our verdict is "Continuous Overload". The 5,520 W running load exceeds the 5,000 W inverter. The EcoFlow Delta Pro Ultra (1 Inverter + 1 Battery) is a compatible alternative.
How many miles of range can the Fox ESS EP5 Modular Hybrid add to a BMW i4 / iX?
A full 5,180 Wh charge delivers about 4.0 kWh to the vehicle battery after inverter (85%) and on-board charger (90%) losses — roughly 14 miles at 3.5 mi/kWh. Charging at this profile is not possible on this unit without reducing current or changing voltage.
What breaker and wire size do I need to connect a BMW i4 / iX (Flexible Fast Charger 24A) to the Fox ESS EP5 Modular Hybrid?
At 230 V the load draws 24.0 A. Under BS 7671 / IEC 60364 the protective device must be at least the design current (Ib ≤ In ≤ Iz), so use a 25 A MCB with RCD protection on 2.5 mm² copper cable for runs up to 7.5 m (1.2% voltage drop). Connection: Type 2 EVSE · IEC 60309 32A Commando.
How long does it take to recharge the Fox ESS EP5 Modular Hybrid with solar panels?
With an 800 W array and an 80% real-world harvest factor, a full recharge takes about 8.1 hrs of peak sun (1.8 days at 4.5 peak-sun-hours). At its maximum 6,500 W solar input it drops to 60 min.
Methodology & safety note
Specifications come from manufacturer datasheets in our open dataset; ampacity and resistance values follow NEC Table 310.16 and Chapter 9 Table 8, and BS 7671 Appendix 4. Calculations assume copper conductors, 30 °C ambient and no bundling derating. Inverter-to-panel connections require a listed transfer switch or interlock to prevent back-feeding the grid. These results are an engineering estimate, not a substitute for a licensed electrician and local permit. See our methodology and safety disclaimer.