Safety

Nilar Hydride® batteries are based on a mature technology that has been used commercially for over 25 years for a variety of applications including consumer products, electric vehicles, hybrid electric vehicles, and stationary power applications. The introduction of batteries into cars are now driving the safety regulations both for vehicles and other battery applications, such as energy storage.

 

The main safety benefits of Nilar batteries

  • Battery system with water based, non-flammable electrolyte(1). No risk of spontaneous fire or explosion.
  • No risk of short circuit generation even under low temperature charging as observed in other solutions: No risk of spontaneous release of energy, rapid temperature increase with fire and explosion as potential consequences.
  • Electrodes contained in Nilar modules cannot ignite or react spontaneously: No risk of heat propagation between modules under normal operation and rest periods(2).

A significant part of the Battery Management System (BMS) functionality is to keep the battery from stages, which may affect reliability and safety. This mainly concerns the prevention of overcharge, over-temperature and short circuits.

But even in the case of BMS failing or malfunction, Nilar batteries show a high degree of passive safety under abusive treatment(3):

Overcharge
The Nilar systems can manage an overcharge with 0,2C for 5 hours, or with 1C for 30 minutes without venting. During overcharging with higher current over longer periods of time, the maximum pressure limit of 5,5 bar might be exceeded and, consequently, the safety vents could open, releasing gas.

Over-discharge and reversal
Over-discharge of modules down to 0 V is not critical for safety since it does not cause a pressure nor a temperature increase. However, it does damage the battery beyond use and should be avoided. Continuous reversal can lead to an internal pressure build-up, activating the safety valves and causing a gas release. Any associated temperature increase will be modest and non-critical.

Short circuit
To prevent short circuit, Nilar has installed fuses on both the positive and negative side of each string.

External heat / fire
If an external fire would occur near the battery bank, the fire should be extinguished by CO2, in the same way as a corresponding electronics fire. If the fire is not extinguished, the heat will eventually cause the Nilar batteries to ventilate. This scenario should be addressed in the same way as a corresponding fire in a lead-acid battery installation.

(1)Electrode materials in Hydride batteries (NiMH) are chemically stable when in contact with the electrolyte. There are no heat generating reactions taking place between the electrode materials and the electrolyte and no solid electrolyte interface is needed to protect the electrolyte from electrode materials. This can be compared to chemistries containing highly flammable organic electrolyte. If the organic electrolyte is catching fire, explosive and poisonous gases are released.

(2) Propagation is a dangerous phenomenon that can occur in batteries based on other chemistries, where one cell that has run into thermal runaway can spread the heat to other cells, in that way initiating thermal runaway in other cells and causing a cascade effect.

(3) Several battery chemistries require a very strict safety region when it comes to upper voltage limits, temperature limits and current limits. If you pass the set limits you enter the safety critical region where thermal runaway can be triggered by internal short circuits and/ or external heat. For
example, during deep discharge or overcharge.

Transport

One of the advantages with Nilar battery packs, as compared with many other battery types, is that UN approved packaging and marking is not required for transport by sea, road, rail and air. No dangerous goods documentation is required when transporting Nilar battery packs by road or rail. Nilar batteries are also certified for transport via road, rail, sea or air, without the need for heavy and expensive explosion-proof containers.

A dangerous goods declaration is required if batteries are transported by sea in quantities of over 100 kg in one transport unit. Nilar battery packs are then defined as
dangerous goods, class 9. UN number and Proper Shipping Name are UN 3496 and Batteries, Nickel-Metal Hydride respectively.

Transportation of Nilar systems is easy to manage, since the IMDG Code provisions do not apply on Hydride batteries (NiMH) contained in or packed with equipment, according to Special Provision 963.

 

 

An Air Waybill or similar is required if batteries are transported by air. Nilar battery packs are not classified as dangerous goods and belong to the entry “Batteries, dry” in the list of dangerous goods in IATA (no UN number). If an Air Waybill is used, the words ”Not Restricted” and the Special Provision number (A123) must be included in the description of the substance on the Air Waybill, according to IATA-DGR.

For several other battery chemistries, heavy regulations apply for all modes of transport, especially regarding transport by air. For those classified as fully regulated dangerous goods, strict regulations and even training courses may be required for the personnel involved in the transportation.

Standards:
• Transport UN38.3 Test T1 Altitude & Test T3 Vibration
• Transport ADR-S SP238 Test A