People install battery systems for many reasons and likewise people choose battery technologies for various reasons.
For many years people have used lead acid batteries as a known battery technology, particularly in off grid installations. A battery of choice has often been used Telecom batteries which are replaced regularly from telecom installations that need guaranteed UPS (uninterrupted power supply) capabilities. As these batteries are often sold at a vastly reduced cost it is economical for off-grid households to add a large number of batteries to an off-grid system to allow for reduced capacity of the batteries.
Unfortunately, for lead acid battery systems the battery system operates at the capacity of the weakest battery so you are unable to use new lead acid batteries in older systems and would need to replace the whole bank of batteries when more capacity is needed.
Lead acid batteries are well known for having a “falling off the cliff reputation” and degrading very suddenly and quickly, often with no warning. This happens particularly often in cold or hot weather. Coincidentally this is often when batteries are needed the most for heating and cooling. At the same time, most people who live off grid have learnt to manage their electricity usage to only use what is available and to use a generator when batteries are unavailable.
This article pointed out the importance of when purchasing an energy storage battery that it is fit for the purpose that you want it to provide.
Just like many people don’t initially realise that solar arrays don’t operate if the power is disconnected, battery storage systems don’t always work either.
This is fine if you just want a battery energy storage system to provide some load sharing but if you want power when the grid is disconnected the battery has to be capable of being used in an off-grid situation and it has to be wired to allow for this. This usually means the battery inverter is wired in before your solar inverter so that the complete battery and solar PV energy system can operate independently from the grid.
The type and size of your battery system is also important and how much of a battery systems capacity is actually useable. With lead acid and AGM batteries, generally only 30 – 50% of the batteries capacity is useable which means you will need a larger system capacity overall. Also as lead acid and AGM batteries tend to degrade over time and with use this needs to be taken into account when sizing your energy storage system.