This topic has become a complex mine field.

A couple of years ago, it was simple, you installed 100 amp/hr FLA deep cycle batteries and just added more depending on the backup period required, so long as you understood series ( voltage) and parallel for (current) connections, you could configure what ever system you required.

Then gel and AGM were the next best thing, thanks to bad inverter setup configuration and lack of temperature monitoring, these batteries were being replaced under warranty faster than the supplier could reject them. People are still being conned into fitting these types of batteries, which not only cost a lot for what they offer, they have a slow charge rate, when dealing with stage 4 load shedding becomes a huge problem. Enough bashing FLA. They served a purpose at the time, there options which can break your life savings account or lead you into silly things like second bonds etc.

Then the lithium battery popped up, will it be the future, who knows, technology moves at such a rate, 5 years is regarded as a lifetime, why would you want to blow your whole life saving or extend your bond for another 10 years just to keep a few lights on, maybe return on investment ?