When online classes started because of the lockdown, I had to quickly install a solar inverter. I thought I had done enough research and made several mistakes. I bought a Luminous 750 solar inverter. It can handle only 320 watts of AC loads. I also bought an ordinary inverter battery because solar batteries were expensive and not easily available. I thought I could run two fans for an entire night with a 100-AH lead-acid battery. It was too late when I realised that a 100-AH battery can only be discharged up to 50 AH.
I bought the solar panels (₹13,000) and inverter (₹4000) online at really cheap rates. The battery was ₹10,000. The solar cables, DC SPD and other materials brought the total to around ₹30,000.
I have 375 watts of solar panels. They charge the battery in about two hours. For the rest of the day, the panel output is an excess and would have been wasted as heat by the inverter. I run some AC loads on the inverter during this time and this (solar) power is free. (The AC input cord of the inverter is plugged in to an extension box that is in turn plugged in to to a wall socket. It is not switched on. It is used only to provide the mains earth connection for the inverter and its AC output.) At night, I would consume battery power for one hour around dinner time. After this, I would switch off the inverter for the night. The inverter battery is a tubular battery but I do not deep-discharge it as it were a solar tubular battery.
I installed three-pin sockets in several rooms and connected them with dedicated cable conduits from the AC output of the inverter. When I had to switch off the inverter, I had to manually unplug the devices from the new inverter-powered sockets and plug them to old mains-powered sockets.
Belatedly, I added a 1000-watt inverter with a built-in 100-AH lithium battery to my solar power installation. I bought the lithium-battery-based inverter form Stalwart Solar for ₹25,000. This is a one-box system that includes the inverter, charger, UPS and lithium battery. It does not have a solar charger input. I charge it using the solar inverter. (If I had known better, I would have bought Stalwart Solar's 1000-watt solar inverter with built-in 100-AH lithium battery for only ₹30,000 and reduced my system size.) Now, I am able to use all 100 AHs of the lithium battery instead of only 50 AHs of the lead-acid battery.
The AC input cord of the solar inverter is plugged in to an extension box (red) for the mains connection. The lithium inverter is connected to the AC output of the solar inverter. I crafted a two-socket extension box (white) to connect to the AC output of the lithium inverter. The AC loads are now connected to this extension box. When the solar inverter is switched on, I am limited by its 400-VA load limit so I use it only for charging the lithium inverter. At night, I switch off the solar inverter and run the AC loads using the lithium inverter. It can handle 1000 watts but I do not push it beyond 200 watts. On a bright sunny day, the lead-acid battery gets charged in two or three hours. After that, all solar power is used to charge the lithium battery and power my AC loads. The lead-acid battery is unlikely to get cycled much now. Its life will increase but I will have to deep-discharge it once a month. I will also have to temporarily remove the lithium inverter during rainy season and use it sparingly during that time.