Off-Grid Solar Systems & DIY Installs

What an off-grid solar system actually is

• PV array (panels wired series/parallel)
• Charge controller (usually MPPT) to charge the battery
• Battery to run night + cloudy days
• Inverter for AC loads (optional)
• Protection + switching (fuses/breakers, isolation, busbars, earthing)

Stage 1: Size it so it doesn’t annoy you

1) List loads in watt-hours per day

For each appliance: Wh/day = watts × hours/day. For cycling loads (fridges, pumps), measure with a plug-in meter if you can.

2) Choose system voltage

Higher voltage = lower amps for the same power, which usually means cheaper cable and fewer hot joints.

3) Battery capacity (usable kWh)

Pick your autonomy (days of storage). One day is fine with generator backup; two to three days is comfier.

• Usable kWh ≈ (daily load Wh × days) / 1000
• Lead-acid hates deep daily discharge; lithium needs a proper BMS and protection.

4) Solar array size (W)

• PV watts ≈ daily load Wh ÷ (peak sun hours × 0.7)
• Winter can be brutal: size for your worst month if you want fewer genny days.

Stage 2: Gear that doesn’t suck

Panels

• Used panels can be a ripper deal if you test them (Voc/Isc) before building strings.
• Minimise shading and give panels airflow underneath.

MPPT charge controller

• MPPT lets you run higher-voltage PV strings, reducing cable size and improving low-light charging.
• Size it for battery voltage and PV input limits (especially cold morning Voc rise).

Battery options (DIY reality check)

• LiFePO4: common off-grid choice, still needs correct fusing and a solid BMS.
• Upcycled EV modules (e.g. Nissan Leaf): great $/kWh, but design properly (balancing, contactors, pre-charge, monitoring).
• Lead-acid: cheap upfront, heavy, short life if you deep-cycle it hard.

Protection + wiring (this is where DIY systems win or lose)

• Use DC-rated breakers/isolators, correct fuses, busbars, proper lugs and crimping.
• Plan cable runs to minimise voltage drop; higher system voltage helps a lot.
• Earthing and surge protection matter, especially rural sites.

Stage 3: Install and commission

1. Mount panels to avoid shade and heat build-up.
2. Build PV strings that stay under controller max PV input even in cold weather.
3. Install protection and isolation on PV, controller-to-battery, battery main, and inverter feeds.
4. Connect battery to controller first, then PV, then loads.
5. Load-test and check cable temps, connectors, and inverter alarms.

Build videos worth watching

These are the quickest way to sanity-check your plan (especially protection, cable sizing, and commissioning).

DIY upgrades + symbiotic links

• Solar pumping: pump when the sun’s up and store water high (water becomes “storage”).
• Trackers: old motors can boost morning/afternoon yield.
• Water-from-air: dehumidifier hacks can make water and dry a space (energy permitting).