FoxESS CQ7-M 7.02kWh HV Master Module Heated energy storage

FoxESS CQ7-M 7.02 kWh HV Master Module Heated Energy Storage System

The FoxESS CQ7-M is a high-voltage (HV) lithium iron phosphate (LFP) battery module that serves as the master module of the CQ7 series—it controls the entire battery stack and communicates with the inverter. It does not operate on its own: together with the 7.02 kWh CQ7-S slave modules, it forms a modular energy storage system, scalable from 14.04 kWh up to 98.28 kWh. Typical applications include residential and smaller C&I PV systems connected to FoxESS hybrid inverters.

FoxESS CQ7-M 7.02 kWh HV Master Module Heated Energy Storage System

The FoxESS CQ7-M is a high-voltage (HV) lithium iron phosphate (LFP) battery module that serves as the master module of the CQ7 series—it controls the entire battery stack and communicates with the inverter. It does not operate on its own: together with the 7.02 kWh CQ7-S slave modules, it forms a modular energy storage system, scalable from 14.04 kWh up to 98.28 kWh. Typical applications include residential and smaller C&I PV systems connected to FoxESS hybrid inverters.

What is it used for?

We primarily recommend it as an energy storage solution for residential solar systems, where the household’s daytime PV generation is stored for evening consumption, and where off-grid (backup) operation is also required. Thanks to its 14-module scalability, it is also suitable for smaller commercial and industrial (C&I) installations—such as office buildings, small factory halls, and agricultural facilities—for peak shaving and self-consumption optimization. It can also be integrated into microgrids, where continuous availability is critical.

How does it work?

The CQ7-M is the “brain” of the stack: it contains the BMS, the communication interface, and a 6-LED display that indicates the system status. You simply connect the CQ7-S slave modules (plug-and-play daisy-chain), and the master module handles the entire array’s cell balancing, thermal management, and communication with the hybrid inverter via the CAN bus. Based on this, the inverter decides when to charge from the PV or the grid and when to supply energy to consumers. Due to the 90% DoD, approximately 6.3 kWh of the nominal 7.02 kWh is actually usable—a particularly good ratio on the market.

Technical and system-level advantages

The module works exclusively with FoxESS HV-compatible hybrid inverters (e.g., H1, H3, AIO series) – it cannot be connected to inverters from other manufacturers. The operating voltage range is between 104–920 V depending on the stack size, which requires an HV architecture: the benefits of this include lower current, thinner cabling, and higher system efficiency (>95% round-trip). Thanks to its LFP chemistry, it is thermally stable, features a built-in fire protection function, and, with IP65 protection, is suitable for both outdoor and indoor installation. With an operating temperature range of -10 to +55°C and an optional warm-up function (down to -25°C), it operates reliably year-round under Hungarian weather conditions.

Differences

The difference between the CQ7-M and the CQ7-S is clear: the M is the master (controller) module, and the S is the slave (expansion) module. A stack requires exactly one CQ7-M, to which 1–13 CQ7-S units can be added. If you are installing a new storage system, you must start with the CQ7-M—the CQ7-S cannot be started on its own. Compared to other FoxESS series (e.g., ECS, low-voltage units), the CQ7 offers better scalability with higher capacity and voltage, but requires an HV inverter.

Important to know

The module is not compatible on its own, either as a standalone system or as an AC-coupled solution—it works exclusively with CQ7-S modules and the FoxESS HV hybrid inverter. If your existing installation uses an inverter from another manufacturer, this storage unit will not be compatible. The maximum installation altitude of 3,000 m above sea level is not a limitation under domestic conditions. It is the right choice if you are planning a new FoxESS system or if your existing FoxESS HV inverter is already prepared to accommodate the CQ7 series.

SOLARKIT Reviews

We recommend the CQ7-M to installers and end-users who are considering a FoxESS ecosystem and want a storage system that can be flexibly expanded in the long term. The plug-and-play installation significantly speeds up the process—assembling a 3-4 module stack takes considerably less time than commissioning a traditional rack-mounted system. At the residential level, 2–4 modules (14–28 kWh) typically cover the daily energy needs of an average Hungarian household; for small businesses, 6–10 modules are recommended. If you haven’t decided on an inverter manufacturer yet, choose the inverter first—the CQ7 is only a good choice if you’re building the entire system on FoxESS.