Moving responsibly and safely into the future

ISO Certification 9001:2008


Whether development, production, planning or sales, all TESVOLT processes are continuously and systematically monitored and checked. TESVOLT has received "ISO Certification 9001:2008" from the TÜV Rheinland for the successful implementation of a quality management system across the entire company.

IEC 62040

Declaration of Conformity TÜV Rheinland Registration Number AK 60103558 0001

The battery management system developed by TESVOLT has been successfully certified by the TÜV Rheinland. All relevant safety tests between the battery management system and the SMA Sunny Island were executed. The test was performed according to IEC 62040-1:2008.

51,2  volt storage system

TESVOLT storage systems use a nominal voltage of 51.2 V and are classified as medium performance batteries. This ensures a high level of installation and maintenance friendliness. Batteries in this class are used in the automotive sector, for bicycles and stationary storage systems. Voltages below 60 V DC (low voltage) are regarded as non-hazardous, even for animals and children.

ZSW nail penetration test

The ZSW (Centre for Solar Energy and Hydrogen Research in Baden-Württemberg) has performed a nail penetration test on the cells used by TESVOLT. The test was passed. The tested unit did not catch fire or explode. Gas from evaporating electrolyte escapes from the cells if they are mechanically damaged. The gases occurring in the case of a short-circuit contain low concentrations of organic solvents and hydrogen fluoride acids. This case is practically impossible if the battery is not mechanically damaged.

In addition, the TESVOLT storage systems are delivered worldwide in solid and sturdy steel housings.

                                                                           Source: ZSW        

Quality "Made in Germany"

TESVOLT have their own production facilities in Germany and nearly all the components used in the production process are from German manufacturers. The battery cells used are manufactured in Asia according to stringent TESVOLT quality criteria. TESVOLT performs quality control monitoring at several stages, from the individual cells to the turnkey storage system. Each individual cell is subjected to quality control monitoring in Asia and also by external testing bodies in Germany. The tested cells are then further processed by TESVOLT and the finished storage systems are then thoroughly tested at the factory in conjunction with Sunny Island inverters. 

Battery management system (BMS)

TESVOLT uses a highly efficient, safety-oriented and certified battery management system for monitoring the individual battery cells.

The bidirectional balancing system has been developed by TESVOLT. The BMS monitors the temperature, voltage and charge state of each individual cell and controls these as a group of cells (stack). The BMS uses the individually measured parameters to determine the State of Health (SoH) and State of Charge (SoC) of each individual cell for early detection of faults and prevent damage to the cells. In addition, it allows both the defined charging of a cell in the other cells of a module and also the targeted charging of the affected cell from other cells in the stack. The BMS is constructed in a modular and flexible manner. A Master/Slave principle allows the implementation of capacities ranging from small lithium-based storage systems (10 kWh) to storage power stations at a MWh level.

Cell chemistry – Lithium-Iron-Manganese-Phosphate (LiFeMnPO4)

High-quality, high-performance prismatic cells are used for the battery. The special composition prevents thermal runaway. The BMS also prevents overheating or overcharging of the cells (double redundancy). These cells are also used in the automotive sector.

“Emergency-off button” for the fire brigade

An On/Off switch is located at the upper right edge of the battery cabinet door. Actuating this switch immediately disconnects the battery and thus also switches off the charging and consumer circuits.

Return of defective or used batteries

As a manufacturer, TESVOLT is committed to accepting the return of defective or used batteries free of charge. The materials in the batteries are recycled in a technically correct and environmentally friendly matter according to the German Batteries Act (BATTG2006/66/EEG).


SoC – State of Charge
The BMS can use the measured parameters to determine the state of charge of a single cell, or cell stack, and stop the charging process if necessary. This prevents overcharging. The software also has the same functions for monitoring the discharge process in order to prevent unnecessary discharging of the cells. The system stops discharging of the battery when a defined minimum state of charge is reached.

SoH – State of Health
Precise monitoring allows the system to detect performance differences between individual cells and thus detect damaged/defective cells. The system switches off if necessary and notifies the installer of the situation. The defective cell is identified and can be easily changed.



– Checklist for KIT criteria


 KIT Li-Ionen checklist

Technical features

Max. score

Li 10 - 30

Li 40 - 60

2 electro - mechanical, normally open DC relay for redundant shut/down of the battery




Overvoltage and undervoltage monitoring at a cellular level with redundant triggering of battery shut/down




Individual temperature control to each cell or

„Current Interrupt-Device (CID)“ in every cell




Reliable protection against re-starting after

Deep discharge or other significant damage




No unsecured , direct parallel connection of cells

without „Current Interrupt Device (CID)“ in each cell




Active flow control as a function of cell voltage

and cell temperature




Metallic, sealed battery case, alternatively closed metal battery cabinet




Transport tests after UN38.3 for the battery system

or for a battery module




Total points




 Table 1: KIT Li-Ionen checklist


The TESVOLT storage systems achieve a total score of over 110, which means they can be used without hesitation.

The technical features for the safety of lithium-ion storage systems listed in Table 1 by KIT (Karlsruhe Institute of Technology) gives an initial guide to evaluating safety-relevant features in a storage system. However, only a perfectly coordinated overall concept for all individual components ensures complete safety. That is why TESVOLT strives to use high-quality individual components by manufacturers with years of experience and high quality standards.


Notes on evaluating the KIT features

Technical feature 1:

“2 electro-mechanical, normally open DC relays for redundant shut-down of the battery”

From TV Li 10

TESVOLT uses 2 normally-open DC relays activated by both the battery management system (BMS) and a manual pushbutton. The BMS monitors each individual battery cell’s temperature, voltage and current. If they deviate from the standard state, the BMS opens the 2 electro-mechanical DC relays. The battery is not activated until the pushbutton is pressed and the BMS enables it.
TESVOLT GmbH also recommends using its battery systems with the Sunny Island products by SMA Solar Technology AG. If CAN bus communication between the battery and charge controller (Sunny Island) is interrupted, the charge controller shuts down automatically. Furthermore, both the Sunny Island and the BMS process the voltage, current and temperature and shut down the storage system in the event of malfunctions. Accordingly, the battery has a variety of shut-down devices for redundant shut-down.  

Technical feature 2:

“Overvoltage and undervoltage monitoring at a cellular level with redundant triggering of battery shut-down”

From TV Li 10

Voltage is monitored redundantly at a cellular level, and the battery is shut down using the procedures explained under technical feature 1 in the event of faults.

Technical feature 3:

“Individual temperature monitoring of each cell or current interrupt device (CID) in every cell”

TV Li 10-30

TESVOLT uses temperature monitoring at a cellular level.

From TV Li 40

As many cells are required, it is not possible to monitor the temperature in each individual cell. In this case, every second battery cell in a parallel set-up is equipped with a temperature sensor to allow risks from temperature increases to be detected in spite of this.

Technical feature 4:

“Reliable protection against restart after deep discharge or other significant damage to the battery”

From TV Li 10

If the battery is subjected to a deep discharge or other significant damage, both the BMS and the Sunny Island prevent the storage system being restarted.

Technical feature 5:

“No unsecured direct connection in parallel of cells without a current interrupt device (CID) in every cell”

TV Li 10-30

In the storage systems Li 10 to Li 30, the cells are not connected in parallel.

From TV Li 40

From the Li 40 storage system and above, not every cell has a current interrupt device. However, the cells self-vent in the event of overpressure, fulfilling the function of the CID.

Technical feature 6:

“Active current control as a function of cell voltage and cell temperature”

From TV Li 10

TESVOLT’s active bidirectional BMS monitors compliance of the battery parameters current, voltage and temperature with their specified working ranges.

Technical feature 7:

“Sealed metal battery housing, or sealed metal battery cabinet”

From TV Li 10

TESVOLT GmbH uses sealed metal battery cabinets for its storage systems.

Technical feature 8:

“Transport tests per UN38.3 for the battery system or for a battery module”

TV Li 10 – 40

The transport tests for 200 Ah cells were performed per UN38.3.

From TV Li 60

The transport tests for 400 Ah cells were performed per UN38.3.


Download the Security

TESVOLT Safety-Datasheet Li-Series
Kind: Overview
Language: English

TESVOLT Declaration of Security Concept
Kind: Document
Language: German

Kind: Checklist
Language: German