Jonathan makes some excellent points re Lithium batteries.
Look, battery technology has come a long way in the past few years...for a myriad of applications, from automobiles to ultralight R/C aircraft intended for indoor (still air) flying. There are caveats for a lot of commonly used batteries. Heck, what have we learned along the way about ye olde alkaline batteries and their shortcomings of charging, long-term storage, etc., etc..
The point of discussing the potential of 'dead rail' in this hobby is to project what current...and future...batteries might do to change the hobby...for the better, hopefully. I've said it many times, but if you want to see what Lithium batteries have done to revolutionize the R/C industry, go to a full line hobby shop, the R/C counter. Chat with the folks behind the counter about what's happened...R/C airplanes, cars, ultralights, helicopters, drones, powered boats/ships, sailing vessels, construction equipment, military equipment, robotics. Ask the folks who favor the Large Scale (typ. G) branch of model railroading most commonly used outdoors...how NOT having to maintain rail condition for electrical continuity has changed their enjoyment of the hobby.
Yes, there are bad stories about batteries in most branches of the R/C hobby industry. Many of them are borne of bad assumptions, misinformation, ignoring instructions and fine print therein among the users...NOT the manufacturers. But there are a lot of positive experiences, excitement, enjoyment among those hobbyists who want to learn and be a part of this evolution.
IMHO, to dismiss the possibilities of dead rail and battery power in the future of O scale model railroading would be as embarrassing as some other famous past predictions among 'experts' about technological change/impact that has now become commonplace and necessary in our daily lives...like some guy by the name of Bill Gates in 1989:"We will never make a 32-bit operating system!"...or Ken Olsen, 1977: "There is no reason anyone would want a computer in their home!" ( It's easy to find those memorable gaffes in a few key strokes.)
Favorite quote: "There is a correlation between the creative and the screwball. So we must suffer the screwball gladly", Kingman Brewster (Former Yale University president, ambassador to Great Britain, et al.
KD