Old cars 1795
The most impressive set of batteries I've seen so far, are the ones at the breaker house at Long Branch station in NJ (NJT). Nice big gen-u-ine Lucent, i.e. 'phone company' ones. Look a lot like an old removeable disk pack. Enough of them to get 120 VDC, on two fiberglbutt racks, bolted to the walls of the building. Connections between them - busbar on eash side of the terminal. Nice, thick, friendly busbar. You can check the fluids, add fluids, stick a themometer in them without popping the cover. You can SEE into them.
Old cars 1798
You might think that, but I've more than paid for the extended warranties I've put on vehicles and a heater...
Big stuff. Impressive. Lots 'o amps. Was designed by an ex AT&T guy. It's in it's own vented, instrumented, alarmed building.
It controls the breakers for the catenary on that segment of the NJ coast line (25kv, 60hz). There's like 3 or 4 of 'em there. why the apparent 'overkill' in the design? Simple - if the DC power fails (and there's a redundant backup off the AC line), they can't open any breakers there (i.e., no fault protection) and have to go upstream, which will wipe out power to the lower 1-2 of the line until they get someone there to manually pop the breakers.
The batteries are garunteed to work for 40 years. They're expected to last 70 without problems.
They've not had one of these setups fail, though they would know when it does anyway, and know what to do. I asked the EE I was discussing this with what happens if the upstream breakers fail - they go to the power company then. Theoretically, from the time of failure to the utility popping their breakers is darn fast anyway.
Old cars 1796
I bought 4 cars from them, including the van I was driving. They did lose a genuine customer, not...
Not some place where you'd want to see the $39 maintenance free specials...