It's worth pointing out that these rechargeable batteries really are sealed; they won't drip mysterious and terrible chemicals. In particular, although the name "lead-acid" conjures up images of husky car batteries with corroded terminals and leaking acid, the sealed types really are clean batteries: You can run them in any position, they don't drip or ooze, and they're generally well-behaved. In our experience you can design them into real electronic instruments without fear of your circuit boards dissolving into a white crusty plague, or the bottom of your expensive enclosure becoming awash with foul-smelling bilge juices.