76 Boating New Zealand
Eutectic refrigeration, extensive electronics and sharper entertainment systems
equate to a greater electrical load on a vessel. Lithium-ion (Li-on) batteries oset the
problem, but beware. Not all Li-on batteries are born equal.Li-on Standards
O
wners typically contemplate their vessel’s
batteries only when the engine fails to start- and it’s usually along the lines of “why-is-the-
bloody-thing-lat?”
here are multiple causes, but sadly, many
installations don’t meet some well-documented and speciied
data relating to charging parameters, discharge characteristics
and installation requirements.
Some of this data is detailed in manufacturers’ guidelines.
Some can be found in AUS/NZS 3004.2:2014 – the recognised
statutory standard for marine electrical installations. Yachting
New Zealand also has installation requirements within its
various categories of safety regulations.
hese regulations and recommendations all focus on safety
of the installation and, indirectly, the life of the batteries.
Until recently, lead-acid has been the major battery
technology used in boats, with more modern versions in the
form of GEL and Absorbed Glass Mat (AGM).
By their very nature lead-acid batteries generate explosive
hydrogen gas as a by-product of the charging process. In the case
of the GEL and AGM technologies this is recombined within the
battery by way of a pressure cap. he cap’s designed to release gas
under high internal pressure conditions that can be caused by
excessive charging voltages and over-temperature.
hese batteries can also go into a condition called ‘thermal
runaway’ when overcharged, or when certain faults develop
within the battery. his can be extremely dangerous, resulting
in an explosion or ire. Which is why battery standards
emphasise ventilation and physical mounting considerations.LITHIUMION
As with lead-acid batteries, there are various Li-on chemistries
with diferent characteristics. While some chemistries have a
greater energy density than others, the trade-of is lower chemical
stability. hese chemistries are typically used in the personal
electronics industries, where size and weight are paramount.
he favoured chemistry for marine applications is Lithium-
Ion-Iron-Phosphate because of its reliability and stability. It
is, in fact, one of the safest battery technologies commercially
available currently. It’s used in Enertec’s locally-manufactured
‘Juice’ range.
Li-on has many advantages – high energy density (low
weight for a given capacity), small physical size, no memory
efect, the ability to be deeply discharged without damage,
low self-discharge, rapid re-charge, long service life and no gas
release on charge or discharge.
Compared to lead-acid, it also has some notable
diferences. While it can be heavily discharged it must not
be completely lattened. Unlike lead-acid batteries, where
the individual cells within a battery will always equalise any
diference of charge, Li-on cells will not. So there is a need for
external cell balancing.
It’s also important to limit the voltage given to any cell under
charge conditions, as well as the maximum temperature any cell
can reach. Failure to do so will cause poor battery performance
and shorten its life.BOATBRIEF