I just tried injecting some DC voltage into a 5 V wall-wart power supply (100-240 VAC, switch mode), suitable for powering a small computer like a Raspberry Pi.
The supply did nothing until the input reached 30.2 VDC and then it switched on and operated normally, only drawing 20 mA (it is rated at 2 amps output). Once it was on, the input voltage could drop back but once it got below 25 VDC the output started dropping below 5 V, and the input current increased up to 60 mA before it switched off due to too low an input voltage.
However even at 30 VDC input, the device would shut off (and switch back on a second later) if you tried to draw anything more than a few mA through it, even though it's rated to deliver 2 A. I was surprised it worked at all as low as 30 V, but clearly it needs a higher voltage to deliver any sort of useful current.
Since my bench power supply only goes up to 30 V, next I tried a 96 V battery pack, and I had much more success with this. This time the device drew closer to 50 mA with minimal load, and it increased to 80 mA (at 96 V) when successfully delivering 5 VDC @ 1 A.
As a bonus this device also appears to be isolated, as there was less than 1 V potential between GND and either terminal on the 96 V battery bank.
So for me, it looks like I don't have to find an expensive power supply that can convert 96 VDC to 5 VDC to run an RPi for monitoring my battery bank, I can just use an ordinary wall wart to do the job.