We put Czech AMVOLT battery storage systems for 35–300 kWh installations to the test. How did they fare?

We enter a smaller sheet-metal bending production hall in Uhříněves, near Prague, in full operation. Machines are running everywhere and employees are working at full capacity. We find a spacious technical room where a visually and physically unmissable yellow tower literally rises to the 3.5m-high ceiling. It is a Czech AMVOLT battery storage system, specifically 3 AMVOLT 50 kWh LV Modules with a total capacity of 150 kWh. In this installation, the storage system stores surplus energy from PV, serves as backup for company operations and optimises electricity costs. In this article, we take a closer look at the AMVOLT 35 and 50 kWh LV Modules.

AMVOLT is formally a division of Czech company GWL GROUP a.s., which has been involved in LiFePO₄ battery cells for 15 years and is one of Europe’s largest distributors of these cells. In 2016, GWL co-owner Michal Klečka joined forces with Pavel Podruh to create the first prototype of an AMVOLT storage system for the award-winning Czech Self-Sufficient House project, featuring an open architecture and a concept enabling the repair of individual equipment components. According to the founders themselves, AMVOLT’s mission is to help Europe build a more secure energy system by reducing dependence on Asian energy products. AMVOLT is a Czech manufacturer of European modular battery storage systems, ranging from small, compact units (5 - 14 kWh) to large high-voltage BESS systems in the MWh range. In the middle of this range are the AMVOLT 35 and 50 kWh LV Modules, scalable from 35 - 300 kWh.

Basic description of the AMVOLT 35 kWh and 50 kWh LV Modules

AMVOLT’s technical philosophy is to assemble structurally open storage systems in Czechia from individual battery cells and replaceable standardised components. This also accounts for the visual difference between AMVOLT Modules and other products in this category. According to the manufacturer, the open design should significantly extend the service life of the entire storage system compared with the closed battery boxes and drawers commonly used today. AMVOLT LV Modules are deliberately designed to allow customers to expand, modify or service them in any way in the future, down to the level of individual components.

AMVOLT Modules are robust, scalable low-voltage battery storage systems up to 60 V, with output of up to 108 kW. The Modules offer customers a complete solution in a compact, modular, industrial form for indoor installation or as part of a containerised option. All components except the cells (i.e. contactors, relays, BMS, protection circuits...) are manufactured in the EU and the US. Thanks to its own stock of almost 15 MWh of LFP cells, standard Module delivery times are up to 4 weeks from a binding order, according to Petr Hrubý, head of AMVOLT’s technical department.

Each AMVOLT LV Module is designed for 16 Winston WB-LYP700AHA 3.3 V, 700 Ah LiFePO₄ cells with a nominal voltage of 48 V, or 16 Winston WB-LYP1000AHC 3.3 V, 1000 Ah LiFePO₄ cells with a nominal voltage of 48 V and ČSN EN 62619 certification. Any number of AMVOLT LV Modules can be installed in a technical room (or container), stacked or placed side by side depending on available space and customer requirements. The Modules can also be designed in customer-specific dimensions to meet particular space requirements outside the standardised sizes, as in the installation we visited in Uhříněves (see below).

Each AMVOLT LV Module is typically fitted with a switchgear cabinet (DC distribution board) including a BMS, emergency disconnect, fuses and auxiliary relays. The BMS automatically disconnects the emergency contactor if the limit values for the voltage of any cell, temperature or battery output are exceeded, or in the event of electrolyte/aerosol leakage from a cell. AMVOLT LV Modules are intended for direct connection of inverters, MPPT controllers, chargers or other devices compatible with system voltages from 45 V to 60 V. Discharge, overcharge or fault indication is provided via status contacts. Closed contacts indicate normal operating status, while open contacts indicate that charging or discharging has been terminated.

AMVOLT LV Module variants and dimensions

Battery cells and the rationale for their use

All AMVOLT battery storage systems use industrial LFP (LiFePO₄) prismatic cells from the globally proven Winston brand. Winston LFP cells are highly safe and long-lasting, non-flammable and non-explosive. Typical cell lifetime is up to 8,000 cycles, although the cells can still be used without problems for many more years afterwards.

Inverter compatibility and communication

AMVOLT LV Modules are compatible with any inverter that supports battery voltage between 45 and 58 V. It must also be able to stop charging based on a specific battery voltage (55–56 V) or a change in the status of a voltage-free contact, and stop discharging when a specific voltage is reached (48 V) or based on a change in the status of a voltage-free contact. These two voltage-free status contacts for stopping charging and discharging can have any configuration, i.e. either NC (normally closed) or NO (normally open).

With AMVOLT battery storage systems, the manufacturer as standard supplies and recommends Multiplus I, Multiplus II or Quattro inverters from Victron Energy, which are currently 100% compatible and tested. AMVOLT LV Modules can discharge and charge at a maximum output of 108 kW across almost the entire capacity range (i.e. up to 3 C). However, for maximum service life, we recommend using a current of no more than 1 C. According to Petr Hrubý, AMVOLT can supply the battery storage system alone at the customer’s request, but still recommends Victron Quattro inverters as the most suitable option.

BMS and communication

AMVOLT LV Modules have an integrated, proprietary BMS manufactured in Czechia. It is deliberately not connected to any foreign cloud service, for security reasons, but allows remote control and monitoring through direct access via a firewall fully controlled by the customer. No one other than persons authorised by the customer can remotely shut down, switch off, control or monitor the equipment. The AMVOLT BMS is highly secure: its software source code is open source on GitHub, eliminating any backdoor threats. The AMVOLT BMS can also be easily replaced with another BMS at any time in the future.

The basic AMVOLT BMS and integrated DC contactor protect the batteries against excessive discharge, overcharging, overheating or imbalance. The integrated Victron Smart Shunt then uses the VE-Direct interface to transmit battery SoC %, current and voltage data to the higher-level Victron system.

Technical differences between AMVOLT LV Modules and other systems

We see a certain disadvantage of AMVOLT LV Modules compared with competing products in the longer time needed for on-site installation, as they are not serially manufactured and the storage system is therefore always assembled directly at the installation site.

AMVOLT LV Module prices and warranty terms

AMVOLT offers a 12-year warranty in Czechia for its LV Modules covering the mechanical structure and manufacturing defects in the cells, 5 years for the BMS + inverters, and 2 years for other components (EZS, EPS). The manufacturer states a battery operating lifetime of 60% SOH ≥ 8,000 cycles, with regular service inspections and use at 0.5C; 70% DOD; 25°C.

While the investment cost of a similar battery is slightly higher (around 10%) than purchasing a ready-made boxed solution from Asia, when the expected service life and the ability to service, expand or otherwise modify the entire storage system are taken into account, the cost per stored and withdrawn kWh is better than for commonly available mass-market products.