Page 19 - PS Battery Guide May 18

Battery guide For PowerSpout

Charge and discharge rates
Lithium batteries can absorb and deliver energy much faster than lead acid.
They can be fully charged or discharged in 2 hours. Lead acid batteries take
many hours and require a tapered current toward the end of charge to arrive at a
full charge.

Physical size and weight
Lithium batteries take up much less space and are easier to transport (due to
reduced weight) and install.

Safety
On the whole, Lithium batteries are likely to be safer than lead acid. Some types
that are used for mobile applications such as portable electronics and cars use a
chemistry that can be thermally unstable. (NCA and NMC types of lithium
battery have potential for thermal runaway.) But several manufactures use LFP
chemistry that has no such safety issues. Lithium batteries do not produce
explosive hydrogen and oxygen gas mixtures like lead acid.

All of the above advantages go a long way to offset the higher prices of the
Lithium battery options. A much smaller lithium battery can often do the job of a
lead acid battery much better and for much longer.

Disadvantages

Compatibility
UP to now inverters and charge controllers (PCE) have been designed for
lead acid that requires constant voltage charging with a tapering current.
Lithium batteries have different needs. They usually have an onboard
battery management system (BMS). Some makes are packaged as "drop
in replacements" for lead acid. Other such as the Tesla Powerwall can
only be used on the AC side of the power system, which makes them
unsuitable for off-grid use. Some manufacturers of off-grid inverters
(SMA, Victron etc) are working with battery manufacturers achieve
compatibility.

Cost
At present, Lithium batteries are very costly in terms of their amphour
capacities. But it is important to look at the actual energy cycling abilities
of the battery (DOD) and its cycle life along with the other advantages
listed above.

Other battery types
There are many other promising battery technologies being commercialised.
Flow batteries for example that store energy as liquid in a tank. Other batteries
based on salt water. Some are proving more successful than others. Small
companies can go bankrupt and leave users stranded. In a few years it will be
clear what these new technologies can do and the prices should be lower as
production volumes rise.

© 2018 EcoInnovation Ltd (NZ) Page 19
Last reviewed 19/6/18