Important Information About Batteries

Lithium cells and LiFePO₄ (LFP) batteries are a reusable source of electrical energy. They can also be used as a replacement for other types of accumulators if the total voltage and maximum current are set correctly, as compared to lead-acid batteries (SLA, VRLA) and nickel-cadmium (NiCd, NiMH) batteries they have different operating characteristics.

I. Potential Risks

► Risk of short circuit and fire

Even partially charged cells contain a large amount of electrical energy which, in the event of a short circuit, can overheat and damage electrical wiring and cause electric sparks or arcs. A short circuit can also cause overheating of the lithium cell itself, which may lead to the release of hazardous gases and, under certain conditions, to fire or explosion. Battery storage systems with a total capacity over 2 kWh must always be placed in a separate fire compartment and ventilated to prevent gas accumulation.

► Danger of injury from direct current

When a larger number of cells and batteries are connected in series, the risk of electric shock from direct current increases. Do not touch uninsulated electrical conductors or other live components.

► Risks related to chemical substances

Lithium cells and batteries do not contain corrosive substances or acids. However, they do contain chemical substances that may affect the human body and can cause chemical reactions. When handling cells and batteries, the following rules must therefore be observed:

• Eye protection – use suitable safety goggles to protect your eyes from chemical substances.
• Skin protection – use protective clothing and gloves. Prevent physical contact of chemicals released from a damaged battery with your skin.
• Avoid inhalation – overcharging, short circuit or mechanical damage may generate toxic gases released from the lithium cell, which may cause temporary or permanent health problems.

In case of an accident, evacuate all persons from the area where the gas could spread.

II. Important Information for the End User

Battery systems may only be assembled, installed and commissioned by a person with the appropriate electrical qualification and sufficient knowledge of LFP batteries and related technologies.

Battery systems may only be used by persons who have been properly trained and informed about the use of lithium cells and batteries. Information and training are provided by the installation company or the final seller. Appropriate project documentation must always be available for the installation and operation of the battery.

III. Rules for Transport, Use and Storage of Lithium Cells

Lithium cells are transported as dangerous goods under ADR regulations. Always transport them in accordance with the applicable regulations and in appropriate packaging.

► Storage and transport of cells

Cells may only be stored in their original packaging. When stored in other packaging or stacked, deformation of the cells may occur and there is a risk of fire or chemical leakage.

Cell terminals and packaging must not be welded, soldered, dismantled, repaired or mechanically modified.

Battery cells must not be enclosed in housings that block the safety valves. The housings must be ventilated to prevent gas overpressure.

► Protection of cells against adverse environmental conditions

Cells must be protected especially against:

• Water vapour, fog and direct or condensing water
• Frost and temperatures above 40 °C
• Vibrations, shocks, puncture and pressure
• Direct sunlight and pulsating heat
• Aggressive gases and vapours
• Improper installation
• Biological pests

► Self-discharge

Most LFP batteries and cells have very low self-discharge, which allows them to be stored for long periods. The typical self-discharge curve is specified in the cell datasheet.

During long-term storage (months), the self-discharge of the cells should be monitored and, if necessary, the cells should be recharged.

It is not recommended to store cells long-term if they have been charged to 100% immediately beforehand. In such cases, it is recommended to reduce the initial state of charge to approximately 90%.

IV. Initial Charging

New LFP/LFYP cells are supplied partially charged from the factory. Before first use, individual cells must be charged to full capacity uniformly across the entire assembly. Initial charging should be performed at a current of optimally 0.3C (ratio of current in A to capacity C) up to the voltage specified in the technical datasheet (typically 3.65 V). Initial and subsequent charging must always be performed with the cells mechanically compressed according to the manufacturer's specification (in a "compression box"). Battery capacity stabilises during the first several cycles.

V. Operational Charging of LFP Cells and Batteries

Always carefully monitor and do not exceed the maximum permitted charging voltage and current specified for the cell or battery and observe the prescribed operating temperature. Failure to comply results in irreversible damage and loss of warranty.

Maximum and operating values are specified in the product documentation.

Cells must not be maintained long-term at voltages higher than 3.40 V (floating mode). After reaching the maximum charging voltage, charging must be stopped until discharge occurs. If no subsequent discharge occurs, the cell voltage will gradually decrease on its own to a value close to the nominal level.

Cells/batteries have no memory effect and can be charged and discharged at any time. Repeated short charge/discharge cycles do not affect battery lifetime.

To increase cell lifetime and system stability, it is recommended not to use the maximum permitted charge limit of the cell and to set the maximum operating limit, for example, to approximately 3.45 V (compared to a limit of, for example, 3.65 V, the loss of available capacity is negligible).

If the cells/batteries are in use (i.e., connected to an inverter, etc.), we recommend charging them to 100% capacity at least once every 30 days. This prevents the loss of actual capacity and performance over time due to imbalance and incorrect calibration.

VI. Operational Discharging of LiFePO₄ Cells / Batteries

It is always necessary to carefully check and comply with the minimum operating voltage and the maximum discharge current according to the cell or battery specification, and to observe the prescribed operating temperature. Failure to comply with the specified values will result in irreversible damage to the cell/battery and the warranty will become void.

The minimum operating voltage and maximum discharge current for individual cells and batteries are specified in the product's technical documentation.

When the minimum operating voltage is reached, discharging must be stopped and must not continue until the cell or battery is again within the operating range.

Cells or batteries discharged in this way must not be stored; they should be recharged, at least partially, as soon as possible.

To increase cell lifetime and system stability, it is recommended not to use the lowest permissible discharge limit of the cell and to set the minimum operating limit, for example, to approximately 3.0 V (compared to a limit of, for example, 2.5 V, the loss of available capacity is negligible).

VII. Charging and Discharging at Non-Standard Temperatures

Recommended operating temperature for LiFePO₄ cells is +5 °C to +40 °C.

Electrical properties change below +5 °C and above +40 °C. In general, you should expect changes in operating voltage, charging and discharging current values, and a reduction in capacity. LFP cells must not be charged if their temperature is below freezing (0 °C).

VIII. Assembly of Cells into a Battery

Cells can be connected in parallel (this increases capacity), in series (this increases voltage), or in a series-parallel combination (this increases both voltage and capacity). When connecting cells, use only original cell connectors and mounting hardware (they ensure the correct cross-section and mechanical flexibility).

A battery may be assembled only from cells that have been initially charged (balanced to the same voltage). It is also recommended to check other parameters (capacity, internal resistance, self-discharge), which should be the same for all cells.

Just before connecting, carefully clean the contact surfaces with sandpaper with a grit size of approximately 200. Oxidation of terminals is a natural process; it does not depend on the production date, does not change the properties of the cells, and has no effect on their function or lifetime.

Tighten the screws using the torque specified for the individual cells.

During battery operation, regular maintenance must be carried out, especially:

• Check and tighten all screw connections
• Balance the battery cells (equalize them to the maximum voltage)
• Check the functionality of the BMS, especially protection limits U_min and U_max per cell

Special attention should be paid to the battery during approximately the first 50 operating cycles.

Series-parallel connection of cells in a battery is not recommended, mainly for the following reasons:

• Risk of contact resistance in more complex interconnections
• Risk of uneven load distribution among cells in a parallel group
• More difficult identification of a faulty cell in the battery
• Dangerous energy flows within a parallel group in case of failure or malfunction of one cell

To achieve the required battery capacity, it is recommended to use only series connections of individual cells with appropriate capacity that are available for standard installations.

For larger battery systems, it is recommended to connect single-cell series strings to a common busbar. Each string should be equipped with its own BMS module, which communicates with a higher-level control system for the entire assembly.

Cells with different usage history and age must not be combined within one battery system.

Operation of battery cells and systems is recommended under supervision or with continuous monitoring using a protective and control system (BMS). Protect the battery cells from overcharging and from excessive (impermissible) discharge.

IX. Use of BMS (Battery Management System)

When LFP cells are connected into a battery (a series of cells), it is necessary to use a system that monitors the condition of each cell (electrical voltage, temperature, etc.) and ensures that the battery is disconnected when limit values are reached.

For checking proper operation and for possible warranty claims, it is necessary to continuously monitor the cells and the battery, which is another function of the BMS.

If a fault or improper operation occurs in any cell, that cell (or the battery) must be taken out of service.

X. Warranty

Unless stated otherwise, standard warranty conditions apply to the cells and batteries.

Before you start using the cells/batteries, always carefully read all documentation and manuals, and make sure you are trained by the installation company on how to use the entire system. If you do not have sufficient professional qualifications, do not fully understand the system, or are unsure, do not perform any modifications, repairs, or maintenance. Always leave such work to a professional installation company.

When making a warranty claim, it is necessary to prove – e.g. by using BMS records or other relevant records (such as inverter operation logs) – that the cells/batteries have been operated in compliance with all operating conditions over a long period of time.

Recommendations – When using cells/batteries, it is advisable to have the following documentation for each installation:

• A block diagram of the actual wiring of your entire installation
• A list of all components used
• Photo documentation of the entire installation
• Record and store operational data (e.g. from the BMS)
• Regularly service and check your system (request a Service contract)
• Keep invoices, manuals, and service records

WARNING: Most BMS systems have their own standby power consumption, which can discharge the cell below the minimum allowed voltage. If you use such a system, it is necessary to charge the cells regularly.

WARNING: Do not rely on a single method of protection against overcharging or over-discharging. Always use two independent forms of protection (most commonly protection for individual cells and protection for the total voltage).

Battery and Cell Recycling – Information Required by Law

• Method of collection or recycling of batteries:
  The place of collection and recycling is the seller's registered office at the time the contract is concluded.
• Possible negative effects of materials used in batteries and accumulators on the environment and human health:
  Batteries and accumulators contain chemical substances that have a negative impact on the environment and human health. Overcharging, short-circuiting, or mechanical damage may cause the formation and release of toxic hydrogen fluoride (HF) from the battery cell. If LFP cells are used in an enclosed space in the presence of people, appropriate protection must be provided for these persons in case of an accident and the release of HF.
• Graphic symbol for recycling and collection and the purpose of labels:
  
• Do not dispose of batteries in mixed municipal waste or in fire, do not incinerate them, and do not dispose of them in landfills. Batteries must be handed over to a recycling center or a designated battery collection point.