Most off-grid failures in the first year are installation defects, not equipment defects: a loose terminal, a reversed string, a controller left on the wrong battery profile, or an earth that was never actually connected. A structured commissioning pass catches these in an hour rather than a season later.
Before power-up
- Verify array open-circuit voltage against the controller’s maximum input at the coldest expected morning
- Check polarity of every string and every DC run
- Confirm fuses and breakers match the design, not whatever was in the van
- Inspect terminations for correct ferrules and torque; pull-test each one
- Confirm the controller is set to the right battery chemistry profile
- Verify the earth conductor is continuous and bonded at the single designated point
First power-up
- Bring the array online with the battery connected — never the other way round on most controllers
- Watch the controller report charge current within a few minutes of good sun
- Check absorption and float voltages against the battery datasheet
- Verify the low-voltage disconnect threshold is above the load’s minimum operating voltage
- Measure voltage at the load terminals under full load, not open circuit
Load testing
Run the heaviest load — the pump, the motor, the transmitter — and measure battery voltage during the surge. A drop that takes the pack below the equipment’s brownout threshold means the battery or the cabling is undersized, and it will fail in the field exactly when the site is most needed.
Enclosure and mechanical
| Item | What to check |
|---|---|
| Cable glands | Correct size, sealed, drip loops below entries |
| Enclosure seal | Gasket intact, door closes against stop, IP rating intact |
| Ventilation | Filter clean, fan (if fitted) runs on thermostat |
| Panel fixings | Torqued to spec, mounting rated for local wind |
| Conduit | Fixed at close intervals, expansion allowance on long runs |
| Labels | Every cable and breaker identified — for the next person |
Records to leave on site
A commissioning sheet with measured values is the most useful maintenance tool you can leave behind. Record:
- Array open-circuit voltage and short-circuit current per string
- Battery voltage at rest, and under full load
- Controller settings (chemistry, absorption, float, LVD)
- Daily energy estimate and measured load current
- Earth resistance if measurable
- Date, technician, and the weather at the time of measurement
Without a baseline, every later visit becomes a guess about whether the battery has degraded or the load has grown.
Handover items often missed
- Who cleans the panel, and how often
- What the site should do after a prolonged outage
- Which breaker to switch off before touching anything
- Who to call, with a phone number that is reachable
FAQ
How long should commissioning take?
For a small monitoring site, one to two hours including load testing and records. Larger repeater sites with multiple strings take longer, mostly in documentation.
What is the most common commissioning defect?
Loose or incorrect terminations, followed by a controller left on the wrong battery profile. Both are invisible until the site fails.
Do I need to measure earth resistance?
Where lightning risk is significant, yes. A visible earth rod is not proof of a low-impedance path; measure it.
We supply off-grid systems with a commissioning sheet matched to the configuration. Ask for the handover pack.