I guess I am out of knowledge at this point, except for a couple of loose ends: * I searched for battery life under float conditions and found only this:
ROLLS OPzV GEL BATTERY INSTALLATION & CHARGING Designed and well-suited for regular cycling as well as float and backup applications, Rolls sealed OPzV GEL batteries have a low internal resistance than Flooded deep cycle models allowing quick recharge and a low self-discharge rate (2% per month). Rolls OPzV GEL batteries perform well in installations requiring frequent cycling even under extreme operating conditions and* offer more than 20-year cycle life in float applications at 25ºC (77ºF)*. https://rollsbattery.com/wp-content/uploads/2019/11/Rolls-Battery-User-Manual.pdf .* Car batteries in daily use get 4-5 years, so 20 does not surprise me for being floated at the proper, manufacturer recommended, voltage and temperature. . * If one were really lucky, the wall wart would be 13.6 and one could just float a gel battery across it or, better, a precisely regulated 13,x to exactly match the battery manufacturer's specs for float. * If the wallwart were 12v, I would consider the precise float voltage supply & putting a 12v regulator (be sure the power design, temperature, is very conservative for long life) between the battery and the appliance. Of course connectors may be a problem in either case. (I presume that this will be my last post on this.) Thanks JK On Fri, Apr 12, 2024 at 11:24 AM Keith Lofstrom <kei...@keithl.com> wrote: > On Fri, Apr 12, 2024 at 06:21:56AM -0700, jim karlock wrote: > > How about the lowest power UPS you can find and replace the little > battery > > with car battery? > > > (car battery should be the kind that doesn't require periodic watering.) > > Tried that before - car batteries eventually "sulfate", > and won't have full capacity years later, when they are > unpredictably needed. The LiFePO4 sealed batteries last > decades, and are a heck of a lot lighter. Data centers > use them, but the technology hasn't trickled down to > smaller SOHO users ... or not yet, AFAIK. > > Hence my question to the list. > > An array of smaller "lantern format" batteries can be > charged one at a time, perhaps at a bicycle-accessible > location that still has power when my home doesn't. > > BTW, I also considered replacing the 12V wall warts on > both devices with a direct feed from the 12.8V batteries. > However, the electronics in the Optical Network Terminal > may be finicky about voltage levels, and I would need to > pry open the ONT case to access the internal plug and jack. > > Thanks for the suggestion; if you've had better long-term > success with car battery UPS, tell me more. > > Keith > > -- > Keith Lofstrom kei...@keithl.com >
