i know the apc 1400xl units which are 24vdc front end units will readily accept 28.8vdc
and the apc 2200 and 2200xl which are 48 volt front end, have no issues at up to 57.6vdc
those i have tested so far, i have a apc 3000 or it might be the 3000xl which also is 48volt
but i haven't tested it as of yet but i don't expect it to have any issues at up to 57.6volts either.
it would appear that they have a pretty wide range of input voltages, they seem to stay operational
all the way down to about 20% under nominal as well while carrying heavy loads and starting heavy loads.
another thing not generally known is there surge capacity, most think that these ups systems have very limited surge
capability, and the documentation supports this assumption at maybe 110% of full load.
when connected to a relatively large battery bank the surge capability goes up dramatically, to nearly 175% of the rated
full load, and they are able to carry this during starting for right at about 3 seconds. that is not bad in my opinion. that is about max
for the surge capacity that can be counted on most of the time, 150% for 3 seconds is very reliable and can be counted on.
the units are designed to cover the overload for what appears to be approx 3 seconds before they kick offline without damage or blown
internal fuses.
it would appear surge rating is more a function of voltage droop of the relatively small capacity internal battery pack that these
units are typically supplied with, than any deficiency of the inverters or its design. it would also appear to me that these units are very well designed, are reliable and very long lived. The sinewave looks exceptional on an oscope as well, looking cleaner than my utility power here at the house at up to about full load, where the steps that form the sinewave start to appear on the scope.
interestingly the little apc 700 which is 700va or 450watts is also a 24volt unit, it can also take the 28.8vdc (i almost forgot these little guys)
they produce an extremely nice looking sinewave as well. only issue i have seen with them is their relatively poor efficiency of around 80%
across the load scale. but they are cheap in surplus! i bought a stack of them for 5 bucks each, so for the money if one doesn't mind the lower efficiency they deliver clean power for around 11cents a watt, and they are built just as good as their big brothers except they don't use a fan and rely on convection cooling. that is either a plus or a minus i guess depending on how you look at it.
bob g
