Off-Grid Solar Balance-of-System Equipment Guide

Select deep-cycle storage designed for repeated charge and discharge; automotive starting batteries are unsuitable.

Specify nominal voltage, rated capacity, usable capacity, allowable DoD, cycle life and operating temperature.

Confirm maximum continuous and surge charge/discharge current against inverter and array requirements.

Provide BMS protection and compatible communications for lithium systems.

Provide ventilation and safe access where battery chemistry can release gas.

Install stable racks or enclosures with terminal protection, clearances and environmental protection.

Verify maximum PV open-circuit voltage at the lowest expected module temperature.

Verify operating voltage, input current and short-circuit current against controller limits.

Select MPPT or PWM technology according to system voltage, array arrangement, efficiency and budget.

Configure charging voltage, current limit, absorption, float and equalization only as required by the battery.

Use battery temperature sensing where the battery manufacturer requires compensation.

Confirm low-voltage disconnect or load-control behavior if the controller supplies DC loads.

Match nominal DC input voltage and operating range to the battery bank.

Select continuous output power for simultaneous loads, not the sum of every appliance in the building.

Confirm starting surge power and duration for motor and compressor loads.

Verify output voltage, frequency, waveform quality and neutral/earthing arrangement.

Check standby consumption, low-voltage cut-off, overload protection and restart behavior.

For inverter-chargers, document transfer behavior, generator input limits and charging settings.

Size conductors for ampacity, ambient temperature, grouping, installation method and protection rating.

Check voltage drop separately for PV strings, controller-to-battery, battery-to-inverter and AC circuits.

Keep high-current battery cables short, mechanically protected and correctly terminated.

Use compatible PV connectors and avoid mixed connector types unless specifically approved.

Support cables, protect entries with glands and keep routes away from sharp edges and water traps.

Identify positive, negative, neutral, phase and protective conductors consistently.

Use DC-rated isolators and protective devices on DC circuits.

Place battery overcurrent protection close to the battery positive connection where practical.

Coordinate fuse or breaker rating with conductor capacity and equipment maximum protection limits.

Provide AC input, output and essential-load distribution protection as applicable.

Ensure isolation points are accessible, labelled and shown on the SLD.

Do not use protective devices to interrupt currents above their rated voltage or breaking capacity.

Bond module frames, mounting structure, equipment enclosures and distribution boards as designed.

Document the DC and AC earthing arrangement, including any neutral-earth bond provided by the inverter.

Use surge protective devices selected for the circuit type and system voltage.

Keep SPD earth conductors short and direct.

Assess lightning exposure and provide external lightning protection where required.

Record earth continuity and earth-electrode test results where applicable.

Monitor battery voltage, current, state of charge and alarms.

Record PV generation, load consumption and inverter operating state.

Use battery shunt measurement where accurate charge counting is required.

Set customer-visible warnings for low charge, overload, high temperature and communication faults.

Protect remote monitoring accounts and update connected equipment securely.

Keep commissioning baseline readings for future comparison.