I have recently replaced my desi UPS (700 Watts) with an APC Smart UPS 1500 VA (980 watts) which is working perfectly. But there is one question in my mind. Unlike the previous UPS, in the present one the cooling fan does not stop after the battery is fully charged. In the desi unit, the cooling fan and the humming noise used to stop, after the battery was fully charged. But in the APC unit, the cooling fan and the humming noise continues even when the battery is fully charged.
My question is that whether it is a part of built in feature of the APC unit or it reflects some malfunctioning in the new unit?