Page 13 - PS Battery Guide May 18

Battery guide For PowerSpout

Battery types

Lead Acid
Lead-acid batteries are made from plates of lead and of lead oxide in a solution of
sulphuric acid. While the discharging and recharging of lead acid batteries is a
reversible process all lead acid batteries lose health when not charged. The
plates are converted to sulphate that may be difficult to convert back into acid if
left for too long. For maximum life expectancy you should try to keep them well
charged whenever possible. With a hydro turbine working 24 hours per day this
is relatively easy to achieve.

When cycling a lead acid battery you should try to work between 50% and 80%
charged most of the time. Try to avoid discharging below 50% or leaving the
battery like that. Charging above 80% is good for the battery so you should try to
charge it 100% from time to time, but it is not necessary every day and it tends
to take time and use a lot of water. In reality, as you will not know the percentage
state of charge, you should try to keep the voltage above the nominal level and to
charge at the maximum allowable voltage for an extended period once a month
or so. This can be done by calling for an "equalising charge" on your controller.

Some low cost controllers do not have an "equalising charge" setting. In such
cases you can set the Absorb = Float = Recommend EQ voltage(up to 62V for 48v
FLA batteries) and once the voltage gets to EQ let it continue for 2 hours then
return your settings to normal.

Lead acid has been the most popular type of battery for off-grid use, because
they are well understood and affordable. Other options mentioned below are
likely to be used increasingly in the future due to their various advantages. The
landscape is changing rapidly at this time, but lead acid is still the most likely
choice for an off-grid system.

FLA batteries are likely to remain if you have a decent hydro resource so that
your battery bank is full most of the time. The new emerging technologies of
advanced lead (with nano carbon) and lithium have the advantage in application
of high cycling.

Different suppliers and users will use different terms to describe battery types,
so it is easy to get confused. Do not relay on generic terms but always check the
details of the product specification to see whether it is suitable for your needs.

Remember that sales staff earn more margin when they sell you a high price
battery bank and their experience if often limited to solar PV systems and not
system that include hydro turbines.

© 2018 EcoInnovation Ltd (NZ) Page 13
Last reviewed 19/6/18