• Ian

Lead Acid to Lithium batteries for off grid

Updated: Feb 14

We woke up one day to find our power system completely failed. The inverter, which converts DC to 240V AC, has a low voltage light blinking. The voltage has dropped to a point where the system shut down. Our battery has failed. We knew it was coming since we had been testing the batteries but now we are confronted with the reality.

Living in the bush can often involve living without any connection to the electricity network, supplying your own power, running 'off grid'. It is a wonderful feeling to be independent and seemingly 'green' however the reality is you need to manage the power system yourself. One reality of living off grid is the eventual failure of the battery system. All batteries have a life span and will eventually fail.

Batteries

Our system is around 8 years old. The battery bank is made up of a bank of 12 flooded lead acid batteries or cells, which was the most common type of battery at that time. Each battery or cell has a voltage of a little over 2V, when combined makes up 24V (2V x 12). These cells are large, six pairs of these will fill an area of two washing machines with each pair weighing nearly 100kg, totaling almost 600kg.


We were always told if one cell fails you have to replace the all of the cells. This is not exactly correct as we found after contacting suppliers. It is not recommended as it may affect all the other batteries and so cause problems with these but it is possible. It may give you an additional few months or even years by replacing the individual cells but each cell retailed at about $1000 so this could get expensive as each of the other cells does eventually fail. Batteries have a definite life span, although no one will say how long that it. "It depends" is the usual answer from suppliers when you ask. If you treat them well maybe 10 years but cells fail for lots of seemingly unknown reasons.

Batteries are one of the most expensive and important parts of an off grid system. Our original battery bank cost over $8000 eight years ago. These were the flooded lead acid batteries where you have to top up the water level regularly. Later models of lead acid batteries are often gel and so have less maintenance.

Suppliers

We started our journey by getting quotes from several suppliers in our region, northern NSW.

The current system was supplied by a nearby supplier, Rainbow Power from Nimbin, so these people were the first we contacted. They confirmed that the batteries were failing and we talked about replacing the bank. They also did mention replacing the failing battery, which was a surprise to us given we had always been told you shouldn't do this, even by Rainbow Power years earlier.

When we got quotes we were surprised by the variation in amounts, ranging from $8000 to $14000 for essentially the same gel lead acid battery. Rainbow Power was the only supplier that had any other battery other than lead acid. They quoted $12000 for a lithium battery replacement, installed. The other suppliers either dismissed lithium or were honest enough to say they didn't know enough about them.