Uber-maker Mikey Sklar demonstrates how to charge, test, and recover a sealed 12V lead-acid battery from the dumpster, using his Power In My Pocket open source kit.
For more on microswitches, rockers, sliders, toggles, DIPs, SIPs, paddle switches, and more, check out the Encyclopedia of Electronic Components Volume 1 by Charles Platt. It’s the informative, concise, and well-organized resource that's perfect for teachers, hobbyists, engineers, and students wanting a go-to electronics quick reference.
I picked up one of these kits and have been working my way through a pile of 16 SLA batteries that were new, but left uncharged for probably 5-7 years each month a Lead Acid (LA) battery will self discharged about 2% of its charge, and after you loose 50% there is a good chance of severe sulfation! these batteries many are at 0-5v and sofar I have killed one battery by running DA PIMP on it too long and too hard, but i have recovered to atleast Quazi usable condition 2 of them. His kit is good, but as he states, it requires you to be an active part in the charging. and you need to watch his videos and monitor the temperature of the sealed lead acid batteries. I did also successfully charge up my drill which had been crudding out on me with it.