Page 7 - Understanding energy storage batteries

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Comparing battery technologies

Until recently lead acid batteries have been the major player in the energy storage industry, particularly for off
grid installations but they have serious limitations in terms of requiring customer maintenance and of course
they are made from toxic materials.

Recently, Tesla’s lithium-ion batteries have received a lot of
attention due to their advertised low price and excellent
marketing, however the lithium-ion batteries are now
receiving attention due to their fire risk on the release of
embodied energy. Lithium-ion batteries have a smaller
operating range than most other batteries and most won’t
operate efficiently above 35 - 40°C. Also, lithium is a toxic
material and is in limited supply and at this stage can’t be
recycled effectively.

There are other technologies on the market, such as
Redflow’s zinc bromide, Aquion’s sodium ion salt water
batteries, improved lead acid and many variations of lithium
battery. These each have advantages and disadvantages,
both in terms of performance and size.

Cycles and Depth of Discharge (DOD)

A common way of comparing batteries is by talking about
number of cycles and depth of discharge (DOD) a battery can
be drawn down to. These are very fluid figures as there are
so many variables to be taken into account.

Cycles and DOD generally have an inverse relationship the greater the depth of discharge the fewer cycles you
will get from a battery

Some of the newer batteries are claiming a large number of cycles and a large DOD but in fact these figures are
being claimed with no proof as the technologies haven’t been in the marketplace long enough to determine the
effect of real-life operating conditions. Indeed, a number of batteries have already disappeared from the
marketplace as they have not lived up to advertised operating claims.

Also there is no consistent measure of a
cycle. Some companies claim a cycle as the
amount a battery is discharged to and Some of the newer batteries are claiming a large
another cycle when it is recharged, making 2 number of cycles and a large DOD but in fact
cycles when most people would consider this these figures are being claimed with no proof. As
one cycle. A cycle can also be when a battery
is only discharged by less than 5% rather the SoNick battery isn’t a new technology their
than to the full recommended DOD meaning figures are based on fact, not guestimates.
there can be multiple cycles in a day.

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