When your phone needs charging, it switches itself off....you connect a supply and it automatically "sees" it and commences recharging....does this for hundreds of cycles.
So, WHY is the "screamliner's" system so pi55-poor that it won't stop an over-discharge but instead converts it to a disposable?
I think this was covered in either this or one of the other (five?) threads.
In an emergency you don't want your battery to shut down just to save itself from the scrap heap.
Imagine this scenario.
Full inflight electrical supply failure (doesn't matter why-lets call it fuel starvation so no APU either. The Airtransat A330 gliding into the Azores springs to mind.)
The main bat kicks in while the RAT drops and spins up.
The a/c lands safely due to excellent pilot skills
but on the roll out as the RAT winds down due to lack of airspeed, the brakes are being powered by the main battery. The battery monitoring system at this point senses a low charge state and shuts the battery down. Pilots get a black screen, microsoft windows icon, the words "hibernating" flash on the PFD and a little yellow box pops up and says "please connect external power or change to a new battery".
Meanwhile, the poor chaps at the front end are smashing their feet through the brake pedals as the end of the runway looms at about 140kts.
OK I'm being facetious, and you could argue that a simple logic based on air/ground, airspeed, wheel speed etc should be incorporated to stop that.
Maybe it was suggested and dismissed as unnecessary expense/weight/design complication. Who knows?