Charge Controller Test Procedure

Every device in the solar charge controller comparison ran this identical procedure on the MPPT Testbench. The goal is that anyone with comparable instruments can reproduce our numbers from the published CSVs, and that results measured months apart remain comparable.

Note

Procedure revision r1 (July 2026). Ambient is currently the unregulated lab temperature of about 24 °C; the final bench revision will regulate ambient near 30 °C to reflect tropical operating conditions. Values marked provisional may still change until the bench design is frozen.

Setup

The bench operates a star topology around the device under test (DUT):

Device	Role
ITECH IT6500D-series DC supply	Simulates the solar panel at configurable voltage/current setpoints
Prodigit 3366G electronic load	Absorbs output power in constant-current mode
HIOKI 3193-10 power analyzer	Measures input and output power simultaneously; the reference efficiency reading

Efficiency is always the HIOKI reading, P_out / P_in, sensed through isolated voltage and current inputs on both sides of the DUT. Supply and load telemetry are logged alongside but never used for the headline efficiency number.

Wiring: the HIOKI voltage sense leads connect at the DUT terminals, not at the supply or load, so cable losses are excluded from the efficiency measurement on both sides by construction. The supply’s remote sense wires also connect at the DUT input, so the supply regulates the voltage the DUT actually sees and the commanded setpoint holds at the DUT terminals regardless of cable drop. The published vin_V column records the HIOKI reading at the DUT input.

Procedure

1. Verify instruments: uv run bench identify must report all three instruments before anything else runs.
2. Configure the bench for the DUT: uv run bench setup with the device’s rated input voltage window and output current limit. Guards are set to the DUT’s published ratings; the bench rejects any sweep step that would exceed them.
3. Record conditions: ambient temperature, DUT serial or revision, firmware version if applicable, and the procedure revision (this page).
4. Warm up: run the DUT at 50 % rated load until heatsink temperature changes less than 1 °C over 5 minutes (provisional), so all points are measured at a comparable thermal state.
5. Run the 2D sweep: uv run bench sweep-vi across the envelope below: at each input voltage the output current ramps from 0 A up to the DUT’s maximum. Each point dwells until the HIOKI readings settle before it is logged.
6. Thermal guard: the sweep pauses automatically when heatsink or board temperatures approach trip limits and resumes after cooldown; guarded points are re-measured, never skipped.
7. Repeatability spot check: re-run one input-voltage line after the sweep and compare; the efficiency delta must stay within 0.1 percentage points (provisional) or the whole run is discarded and repeated.
8. Publish: the sweep CSV goes on the comparison page byte-for-byte as the bench exported it. No smoothing, no outlier removal, no unit conversion.

Sweep envelope

Parameter	Value
Input voltage	60 V up to 120 V or 150 V, clamped to the DUT’s rated window
Output current	Ramped from 0 A to the DUT’s maximum output current
Output bus	48 V nominal
Ambient	about 24 °C unregulated (30 °C regulated planned)

Devices with a smaller rating simply end their ramp earlier; the envelope is never extrapolated beyond a device’s published limits. The exact voltage lines and current step size within this envelope are recorded per run in the published CSV setpoint columns.

Data format

One CSV per device, one row per operating point:

Column	Meaning
set_vin_V, set_iout_A	Commanded setpoints
vin_V, iin_A, pin_W	Measured input voltage, current, power
vout_V, iout_A, pout_W	Measured output voltage, current, power
eff_pct	HIOKI efficiency, Pout / Pin, percent
t_heatsink_C, t_board_C	DUT temperatures

Pre-run checklist

• All three instruments respond to uv run bench identify
• HIOKI sense leads at the DUT terminals on both sides
• Supply remote sense wires connected at the DUT input
• Supply, load, and guard limits set to the DUT’s published ratings
• Ambient temperature recorded
• DUT serial/revision and firmware version recorded
• Procedure revision recorded
• Warm-up completed (heatsink drift under 1 °C over 5 minutes)
• Sweep completed without unresolved guard trips
• Repeatability spot check within 0.1 percentage points
• CSV published unmodified alongside the run conditions

Revision history

Revision	Date	Change
r1	July 2026	Initial procedure; ambient unregulated (about 24 °C)