Apart from extending your battery backup time, you should also take good care of your batteries so they last longer and here are some tips:

Ensure to use the rubber battery terminal protectors to avoid dust and rusting of the terminals

Ensure your inverter setup is in a well-ventilated area to prevent heat from damaging the batteries.

Avoid overcharging and deep discharging (using the battery until empty). Go for an inverter that automatically protects your batteries against these.

Avoid leaving the battery idle for a long period without any form of charge or discharge activity.

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.

Unless your batteries are damaged, there are some techniques you could employ to significantly increase your backup time (how long the battery powers your appliances before it goes flat).

Integrate a battery equalizer

Uneven charging and discharging are reasons why you might not be getting the most out of your batteries. When you have batteries connected in series and any charges to 100%, all others stop charging even if they are just about 70% charged. When discharging, if any goes flat then all others too stop discharging even if they are still at about 70%.

This uneven charging and discharging is because of the batteries not being 100% identical (even if they are of the same brand and specs) and it builds up over time. This not only cheats you out of battery time but also could cause the batteries to wear easily due to over-charging and over-discharging

What a battery equalizer (Battery Management System) does is to ensure that the batteries are charging and discharging at the same rate so you have optimal charging and discharging.