Page 11 - PS Battery Guide May 18

Battery guide For PowerSpout

system that has regular excesses of energy so your battery is kept charged
up and healthy. You will also probably need a back-up generator for when
all else fails. Water can dry up and sun may not shine.)

Energy
2 days of energy usage is = 2 x 12 kWh = 24kWh
Allow for 50% depth of discharge giving 48kWh nominal of battery storage.
Divide 48,000Wh by 48V giving 1,000Ah nominal size.
Without the solar array we might opt for one day of usage giving 500Ah.
This is common solution for home using above 12kWhrs/day.

The solutions outlined below will deliver a minimum 12kWhrs of AC at most
global locations:
Good hydro > 750W
 1 string 8 x 6V 400Ah batteries
Good hydro in wet season and 21 x 270W solar PV array (5.67kW) dry season
 2 strings 8 x 6V 400Ah batteries
No hydro and 2 arrays of 21 x 270W solar PV (11.34kW)
 3 strings 8 x 6V 400Ah batteries

As solar PV is very cheap and has a long life (20-30 years) compared to the
battery bank (5-10 years) it make sense to install plenty of solar PV. Surplus can
help to heat your hot water.
As 5kW 150V MPPT regulators can cope with 21 x 270W PV panels (wired in 7
strings of 3). This is the minimum sized PV array we install these days.

Power
Maximum charge rate is 2.5kW, which is roughly 1/20 of our 48kWh battery.
Similarly the 3kW inverter (backed up by 500W hydro) will not exceed this
power draw from the battery.
In the event of a purely hydro system, a smaller battery could also work well
without exceeding the 1/10 rule.

Clearly these are very rough calculations. Your choice of battery can be guided
by them but also constrained by the available cost-effective products. For
example you may choose to use 400Ah 6V batteries. You will have the choice of
400, 800 or 1200Ah depending on the number of strings. (8 batteries per string)

© 2018 EcoInnovation Ltd (NZ) Page 11
Last reviewed 19/6/18