This home is on the spectacular Coromandel east coast and has been fully off-grid since 1989.

Mains power was never an option for this remote house on a large farm on the Coromandel. Originally set up with massive second hand ex-Telecom 2000Ah flooded lead acid batteries that were already limited in capacity, the system never performed well, even when newer 1200Ah flooded cells were installed later.   The 1800 watts of solar panels were never adequate to keep such large batteries charged.   The system was upgraded to a 48V set of Narada REXC-600 2V 600Ah batteries in 2017 and the solar array has been upgraded to 5100 watts with all the old 120 watt BP panels being replaced.

The upgrade has allowed the old gas power fridge to be replaced with a modern LG inverter fridge freezer. This means there is no longer the awkward humping of huge 45kg gas bottles, let alone the expense.   A microwave and toaster can now be used as well. Hot water is provided by 3 evacuated tube solar thermal panels and a wetback boiler.

Before the upgrade a generator was used to recharge the batteries every few days in winter via the combiner’s inverter/charger but this is no longer required and hasn’t been used in over 3 years.

The solar array consists of 9 x 300 watt panels and 6 x 396 watt panels.  These are mounted in two different locations and at three different orientations and told angles to ensure maximum winter sun is caught.  Those on the garage located 40m from the house are connected to a separate MPPT controller from the house roof mounted panels.  Up to 60 amps of charge current has been seen on a sunny day in the middle of winter into the 48V battery bank which means that a 50% depleted battery bank can be recharged in full in a single sunny day in the middle of winter after several cloudy days with limited production.  Narada lead-carbon batteries do not suffer the usual sulphating that flooded or AGM lead-acid batteries suffer by sitting in a partial state of charge for extended period.  So they are ideal for off-grid solar applications where this is a common situation, particularly in winter.

Components used in this case study

9 x 300 watt solar panels
6 x 395 watt solar panels
Any Power combi 4000 watt inverter/charger
2 x Epever Tracer 6415AN 60 amp MPPT solar chargers
LG inverter fridge/freezer
800 watt microwave
1000 watt toaster
low energy flouro lights in old style BC fittings
2 laptops and cell phone chargers
electric fence unit

Approximate costings

48V bank of 24 x REXC-600 batteries with rack   $13,800
15 solar panels 300/395 watts   $6,000
2 x 60A MPPT solar controllers  $920
3000W pure sine wave inverter $1,200
Mounting rails, tilt brackets etc $1,500
Breakers, cables, switches etc $800

Total excluding appliances $24,220

Download technical documentation of the Narada REXC-600 battery here: REXC-600