Hi all, total electricity noob here so please excuse my ignorance.
I have a 48v 5kw Growatt PV off-grid inverter and 4 x 12v 100ah gel batteries. I have been using this as a backup power supply for essentials during loadshedding since July 2022 without problems, until the fans in my inverter recently broke (and have since been repaired).
My question is: how do I determine the battery health or capacity? The installer noted that my batteries are beginning to die. Apparently they are dropping voltage when switching from the grid to the batteries. I don't know what this means and the installer speaks to me like I am an electrician. Are there ways to monitor the health of the batteries, via the inverter for example? Any helpful metrics? Note that I haven't picked up a drop in performance from a pure time point of view. They last the full 2.5 or 4.5 hours of loadshedding and always seem to have sufficient capacity even if we get shed three times a day. Our typical load on them is less than 10% though.
Keep in mind: my knowledge about this stuff is limited, so explain it to me like I am five.
Thank you!