In BST High Temperature Cells, active materials are optimized to remain stable at high temperature. This technology enables the battery to maximize the storage of applied charges. At the temperature of 55°C, over 90 persant of the battery capacity can be replenished after it has been charged at 0.05C for 24 hours or at 0.1C for 16 hours. These two charging methods are widely adopted in the emergency lighting application as a single rated or combined as a two rated charged to the battery after a mains failure.
The chemicals and separator used in BST High Temperature Cell have been optimized for operating in high temperature environment. These durable materials ensure that the battery's permanent at elevated temperatures. The certificate of Endurance Test in IEC61951 1:2003 Clause 22.214.171.124 for NI CD battery by an independent laboratory has proven that BST batteries can sustain permanent overcharge at high ambient temperature.