{"id":76640,"date":"2023-07-24T12:08:33","date_gmt":"2023-07-24T01:38:33","guid":{"rendered":"https:\/\/www.solarquotes.com.au\/blog\/?p=76640"},"modified":"2023-07-25T10:55:12","modified_gmt":"2023-07-25T01:25:12","slug":"how-to-measure-battery-degradation","status":"publish","type":"post","link":"https:\/\/www.solarquotes.com.au\/blog\/how-to-measure-battery-degradation\/","title":{"rendered":"Battery Degradation Part II: How To Measure It"},"content":{"rendered":"
\"dead

Image Credit: Selectronic Australia<\/p><\/div>\n

All batteries degrade over time. The battery warranty specifies the maximum degradation you can expect – typically over ten years. But how do you know how much your battery has actually degraded?<\/p>\n

<\/p>\n

Part one of this post helped you understand why and how a battery degrades<\/a> and how you can minimise degradation (TL:DR; don’t let it get too hot or cold).<\/p>\n

In this post, I’ll explain how you can measure your battery degradation and how manufacturers will measure it to verify any warranty claim. I’ll also give you some tips on choosing a robust battery for your home.<\/p>\n

How Do You Measure A Battery’s Degradation?<\/h2>\n

If there’s any suspicion about the performance or longevity of your home battery, the first step is simply observing your battery monitoring. I much prefer this way of measuring real-world performance because you can observe over time and get a really clear picture. Numbers don’t lie, and graphs are great for visualising what’s happening.<\/p>\n

Funnily enough, I don’t know of any home battery monitoring software, first or third party, that gives you a battery degradation figure. If you know of any, please let me know in the comments.<\/p>\n

It’s obvious why battery manufacturers don’t want to be transparent about battery degradation – the sad truth is the less you know, the less likely you are to make a warranty query1<\/a><\/sup>. But I’m surprised no one has made a third-party app that hooks into your battery monitoring and gives you a degradation trend. These apps are common for EV batteries<\/a>, but I can’t find any for home batteries.<\/p>\n

How To Measure Your Battery’s Degradation Using Monitoring<\/h3>\n

To measure your battery degradation – you are at the mercy of your monitoring software. In this example, I’ll look at my friend Sean’s twin Tesla Powerwall installation using only the Tesla app.<\/p>\n

I’ll start by looking for a 24-hour period where the batteries fully cycle once. Sean’s Powerwalls are set to a 15% reserve level, which means charging from 15% to 100% and vice versa makes a full cycle.<\/p>\n

July 18 looks good:<\/p>\n

\"tesla<\/p>\n

The batteries charge from 14% to 100%, adding 86% of capacity.<\/p>\n

The batteries initially discharge from 53% to 14%, losing 39%. Following a top up, they drop from 100% to 55% – losing 45%. So they discharge a total of 86%.<\/p>\n

So I’ve found a 24-hour period where the 2 Powerwalls charge up by 86% and discharge by 84%.<\/p>\n

To add 86% took 22.4 kWh of electricity. I will normalise that to 84% so it matches the discharge capacity:<\/p>\n