UPS can not public internal battery cell status as external value or have proprietary format.
At least when I had the APC Omny-SMART 650, it was impossible to read from it to find out the battery level - the device did not report. When the battery was discharged, the signal “Battery low” was issued into the cable and the OS had 30 seconds to turn off. What about branded utility and cable, what about my homemade one.
The whole difference was that the cable itself was soldered and there was no "Made in USA" blot on it, and its parameters for the devices were many times better than those of branded hack. But the merchant for the branded shoelace requested half the price of UPS, the charge for mathematics was three times as much as the UPS table itself. Yeah, he rolled his lip, but the Wishlist will not burst?