Going off-grid slowly: a DIY project

14-11-30 3 Batt charger inverter

Stan Baker dreams of ditching his energy company and going off-grid. He explains how he aims to achieve this, one step at a time.

The well-documented ‘gold plating’ of the poles and wires networks has meant rising service fees for consumers despite falling demand for delivered energy. My own electricity bills reflected this and caused me to seriously consider leaving the grid altogether. A further consideration was the increasingly disruptive weather being experienced around the country resulting in power outages caused by high winds and electrical storms. When attempting to be energy independent, however, the problem is the high cost of the batteries and other equipment necessary to generate and deliver electricity.

Being something of a DIY type, I considered what bits I had sitting around in my garage and what expertise I might have that could be relevant. A passion over the years for converting hybrid cars to plug-in hybrids meant I had a reasonable understanding of lithium batteries, including the management electronics needed to ensure their longevity. I also had a 1.5 kW, 12 VDC Latronics inverter acquired years earlier for some long-forgotten project. Naturally, I had the usual nerdy stuff such as miscellaneous electronic parts as well as some understanding of microcontrollers.

In effect, I had much of what was needed to deliver 240 VAC off-grid, but with one question unanswered: where was the input energy to come from?

First attempts

My house has a flexible pricing plan from Origin that provides cheaper electricity between 11 pm and 7am. This meant I had a lower cost source of electricity for charging the batteries, at least for initial trialling. So, about six months ago I put together a simple system using lithium iron phosphate (LiFePO4) batteries from an electric vehicle conversion that were down to around 50% of their original capacity and therefore unsuited for vehicular use.

The battery charger was a simple linear unit that used toroidal transformers. I had my fuse box modified so that the lights in the house could be powered either from the inverter or directly from the mains.

The original system was not particularly efficient and I estimated I was losing around 50% of the incoming energy, mainly due to the battery charger. However, it did keep my lights going during most nights and encouraged me to consider a more sophisticated battery storage system.

Read the full article in ReNew 131.

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