Battery degradation

With many households already having solar PV installations many people are now looking at energy storage systems to upgrade their home energy supply.

One of the most common questions is what battery is best for my needs. There is a lack of knowledge and a great amount of misinformation in the battery storage industry. It is critical to do your own homework and not just believe what salesman / installers are telling you as they are often restrained in their knowledge by the battery brand they are trying to sell.

In an effort to compare battery technologies a company called ITP renewables, in Canberra, set up a battery test site, https://batterytestcentre.com.au/ to conduct longitudinal performance testing of conventional and emerging battery technologies. This is an Arena funded testing facility set up to independently test and compare different battery technologies under Australian conditions for both performance and longevity for a 3 year period. This testing centre was first set up with Phase 1 in 2016 then phase 2 started in 2017. Originally it was for lithium-ion batteries only but now includes other technologies.

The SoNick battery is included in round 3 which started in 2019 and to date showing excellent results. 10 Previous 6 monthly reports are available from the test centre and can be download.at http://batterytestcentre.com.au/reports/

Energy storage batteries come in a variety of different sizes and weights and each have different characteristics. Here is a comparison of the degradation after 10 years of batteries currently available in Australia with comparisons of size for a similar sized system from other battery technologies.

You can see from this image that different battery technologies have different degrees of degradation over their lifetime. You need to take this into account when deciding the best battery for your needs. If a battery seems cheaper to purchase upfront but has then degraded significantly after a couple of years and may be down to only 50 or 60 % of original capacity after 10 years this will significantly affect how much power you can draw from that battery.

This degradation is also what may make it difficult to add additional batteries to an installation after a few years. In many cases with lead acid and lithium ion batteries you may need to purchase a new system if you want to add extra capacity.