24v VS 48v UPS inverter efficiency?

[HKPolice]

Sorry if this is too basic of a question, but I was trying to calculate runtime on my APC SUA2200 UPS and couldn't find any info on how efficient typical sinewave inverters in UPSes are. The only actual measurement I found is from a youtube user that converted his APC Smart-UPS 1500 into a full time inverter and measured an efficiency of 84% @ ~840w but that UPS uses 24v battery packs.

The SUA2200 model accepts 48v input and I've added an extra bank of external batteries so the APC runtime chart no longer applies. Would a higher DC input voltage be more efficient? Standard 120v 60Hz North american output. My logic tells me that it should be easier to convert 48v DC than 24v DC to 120Hz AC but I'm not sure and googling yielded no efficiency charts.

Thanks in advance for any help!

[Rerouter]

there are a large number of parameters that govern it, if the unit was mainly designed for 24V it is slightly more likely to run more efficiently at that voltage, as they would have picked the peak efficiency off of that base model design,

[Psi]

Why not just time it until it stops with a known load current.
Trying to calculate the run-time will likely produce a wildly inaccurate result.
As others have said, there are so many variables to take into consideration for the theory to produce something close to reality.

All things being equal yes, a 48V inverter will be more efficient than a 24V inverter because the current is less at 48V.
Less current = less wasted heat in the switching transistors and conductors.

UPS efficiency is usually in the range of 75-87%.
Being a reputable brand (APC) and given that the 24V version is 84% i would expect 48V to be around 86%. But its really just an educated guess.

[dfmischler]

If you really need to know then you will have to measure it.

Be careful adding batteries.  Are you sure the charging circuit can handle the increased load if all the batteries were discharged to whatever level shuts down the inverter?  Also beware of the possible increase in charging time from the discharged state to being ready to operate at full run time again.  The most effective, proven uses for a UPS are to bridge the gap between utility power loss and generator startup, or to allow a clean shutdown.

[Zero999]

All things being equal yes, a 48V inverter will be more efficient than a 24V inverter because the current is less at 48V.
Less current = less wasted heat in the switching transistors and conductors.

Yes, I agree, a higher input voltage would give a greater efficiency and is why higher voltages are often used for UPS's.