Upgrading your battery bank is another way to extend your battery time. This is a costly approach but sometimes, your battery bank just is not enough. You do not necessarily have to change your entire setup or discard your current batteries, just add more batteries. The number and specs of the batteries you will need to buy depends on the specs of your current setup and what you really wish to achieve. I will give an example:
Let us say I have a 2.5 kVA; 24V inverter. This means the battery bank must equal 24V no matter how many batteries I connect. Let us say I opt for 12V 100AH batteries. I would need at least 2 connected in series so that it equals 24V (12+12).
Now, if I wish to upgrade by battery bank; I will have two main options
Buy another 2-100AH 12V battery so I have 4 100AH batteries in all
Discard my 2 100 AH 12V batteries and buy 2 200 AH 12V batteries
As you can see, upgrading my battery bank depends on my preference, I might not want to sell or give away my 100 AH batteries so I buy more and get a 4-battery rack. I might – on the other hand – not like the clutter of many batteries and opt for fewer, more powerful batteries.