54VDC and 48VDC are roughly the same thing in telco land. E.g. I hooked up a Juniper MX960 last week with "-48 VDC Nominal" power supplies. The operating voltag

54VDC and 48VDC are roughly the same thing in telco land. E.g. I hooked up a Juniper MX960 last week with "-48 VDC Nominal" power supplies. The operating voltage range is -40 to -72VDC. A "48V" rectifier will output 54VDC to the power bus (feeding batteries and systems) since it's battery float voltage. If the rectifier goes offline (loss of AC power) the batteries will power the bus keeping systems online. I'm curious what the actual difference in practice is between Facebook's 54VDC and Google's 48VDC.