Batteries have been seen as both the saviour and Achilles heel of renewable energy. Turning night into day!
Battery technology isn't new either.

The oldest known battery like object is from 2000 years ago, made with a ceramic pot with a tube of copper and a rod of iron. It's called the Baghdad battery, as it was found in Iraq, though there are lots of guesses as to its real function.

The word battery was coined in 1748 by Benjamin Franklin who was working on a system of charged glass plates, probably while sitting bored in meetings about the foundation of the United States. The first true practical battery was invented by Alessandro Volta in 1800, and rechargeable Lead Acid batteries came along in 1859.

Given the importance of energy to the whole of human civilisation and the universe, we have been working pretty hard on improving them ever since. There were all sorts of innovations in structure, additives, and processes, but ultimately the fundamental chemistry was identical for the next 150 years.

For the vast majority of Rainbow Power Company's history, the dominant battery technology/chemistry was Lead and Acid. First as flooded wet cells, then later as sealed gel cells.

That's all changing now, at least we think it is. Some of the society-wide transformations we have seen from the mobile phone revolution is now making its way to home energy storage.

Enter Lithium-ion batteries with their higher energy density, significantly larger depth of discharge, but unfortunately also a significantly higher price. Or at least that's how it would appear at first glance.

The Australian-made Powerplus lithium-ion battery comes with a $3990 price tag for a 3.3kWh 48V block, which is $1,209 per kWh. In comparison, Trojan flooded lead acid battery retails for $650 for a 255Ah 12V set (3.06kWh). This makes their $/kWh figure $650/3.06kWh=212$/kWh.

So with lithium at $1209/kWh and flooded lead acid at $212/kWh, the choice seems obvious for many people. However that is not accounting for possibly the most important factors when choosing a battery, that being recommended depth of discharge and cycle life.

Lead acid vs Lithium-ion graph

With lithium, you can fully discharge the battery, which means when you buy 3.3kWh, you can use 3.3kWh. With flooded lead acid, the recommended depth of discharge is 50%, although less than this is better, so when you buy 3.06kWh in our example, you're only getting 1.53kWh usable.

To make matters worse, the cycle life of the flooded battery is significantly lower than for lithium. When you discharge a Powerplus lithium-ion battery to a realistic 75% every time, you can expect the battery to last 5000 cycles, or 13.7 years if you assume one cycle per day. Discharging the Trojan flooded battery to the same 75% every day means you can expect it to last around 1000 cycles, or 2.7 years at a cycle per day. So for the same size and same depth of discharge, a lithium-ion battery will last around 5 times longer than a flooded lead acid. Consequently, the heavier price tag makes a lot of sense.

In addition to the much deeper depth of discharge and cycle life, lithium-ion batteries are also a lot easier to store and to maintain. Due to their higher energy density, they are about 3 times lighter than lead acid and take about half the space. You also won't need to refill any fluid or equalise them, which makes them a good hassle-free solution for most people.

Whether lithium-ion batteries will cripple the industry or pave the way for more cost effective storage is pretty much a moot point; If ever there were a time to turn our weakness and vulnerability into strength and security, the time is now. Let RPC help you take the bull by the horns and invest in solar and renewables.

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