"The crystals, short chains of amino acids called peptides, can store a charge..."
I am not a chemist but to this layperson it sounds more like a hyper-capacitor than a battery, which would be consistent with other capacitor technology. It would also go some way towards explaining why the waste heat doesn't cause an explosion.
Also, I did not see any explicit mention of just how much charge is stored. I understand that battery meters assume charge based on the output voltage, rather than measuring actual joules.