Our Battery Systems – in bush and town

The old: Deep Cycle Lead Acid Batteries

For most of the last 40 years we have had batteries as a major component in our energy supply. They were the centre of our stand-alone energy system and stored power from our wind generator and solar panels. As far I am aware the current owner still has the same system. The batteries were lead acid deep cycle in series and parallel providing nominally about 800 watts of storage. They required constant (ie daily) checking and to maintain longevity of the storage the batteries had to be maintained above 30% charge. The batteries it seems had a ‘memory’ and ‘remembered’ any deep discharge which shortened their life. On the other hand the two ‘black-outs’ we had in more than 30 years were fixed in a matter of minutes.

When moving to town in 2012 our new unit was chosen partly because of the north facing (and unshaded) aspect of the roof. Four KW of panels (250w each) were installed – more than 4 times that of our bush system – and the system was designed to cover winter usage in our all-electric residence. The battery storage was replaced by feeding the extra power generated into the grid and for most of the year we provided far more electricity than we consumed – more than 4 times on average. And when we were receiving about 30 cents per kw hour (now 11c) the system was a good money earner.

And the new: bottom right corner

Since our move to town the development and economics of lithium ion batteries has been rapid and barely short of miraculous. About two years ago I started considering adding a lithium battery to our system and was waiting for the battery prices to decline. When our postcode was added to the Victoria solar rebate, we got a new quote for a small battery system. After getting the rebate it then took about 6 months to be installed. The new design was for a small 4kw battery (still four times more storage than the old ones) a hybrid inverter and two extra kw of panels on east and west facing roof.

It is not expected to that we will recover our investment in our lifetime and is a form of climate action – ‘putting your money where your mouth is’. One final improvement (if we live long enough) will be incorporating our second-hand Nissan Leaf into the system giving us another very large battery (24 KW) with vehicle to the home capacity and, if the price is right, even vehicle to the grid.