Muriatic acid is hydrochloric acid, not sulferic. It can be quite potent with high concentrations, but it vents very easily as gas. Sulferic acid sticks around. Of course it is my dad who is the chemist and is really into batteries, not I.
BTW there is a rechargeable battery type based on iron that is a "forever" battery. Typically used in remote locations like mountain tops and such. A low energy density, but are rated in some cases for over 100 years of constant cycle.
http://www.nickel-iron-battery.com/
