The online estimation of the state-of-charge (SOC) of Li-ion battery using the adaptive Lyapunov-based observer is an attractive proposition due to the ensured stability. adaptability and reduced computing requirement. However. the observer requires the presence of the persistent excitation (PE) to guarantee the convergence of the battery model parameters to their correct values. https://www.roneverhart.com/Under-Armour-Hustle-5-0-TEAM-Backpack/