"Sisu" is a word for perseverance in Finnish, a unique ability to withstand any challenges that one may face. SISU battery product line is the most recent development of Geyser Batteries, and rolling out in the next 3 years. This line has started with a specific customer case and is currently in the development phase.
SISU batteries can be operated safely for hours and hours, and be charged in a matter of a minute. Just like all of the Geyser ECRs, water-based electrolytes make SISU a safe and high-performing solution for opportunistic charging of buses and ferries, or for any other application where perseverance is required.