Overview
How this machine carries the load.
A new cell site is often ready to go on air before utility power reaches it, and until it does, a temporary diesel generator runs it around the clock. 123-SG-4S82-40 does that job as a modular system of two units: the ten-panel 123-SG-4S82 solar trailer carries the site, and a standalone 40 kW diesel generator on its own trailer runs only when the sun and the battery cannot, then stops.
The solar trailer is rated for 12 kW continuous, set by its inverter, with surges to 24 kW for 10 seconds and 13 kW for 30 minutes. Its 4.6 kW array harvests 19.8 kWh on an average day into a 30.4 kWh lithium iron phosphate bank, and below 0.82 kW the generator never starts.
Above the break-even, the generator carries the load and recharges the bank together, then shuts down. At a steady 6 kW that is 6.83 engine hours a day, and the 140-gallon tank lasts 14.39 days between refuels, against 7.92 days for the same generator carrying the load alone. The lighter the site, the wider the gap: 23.32 days at 4 kW and 62.52 at 2 kW, while the generator alone still refuels every 7.92 days. Both engines are read by the same fuel rule: their own published figures, held at the lowest one below it. At a remote site every refuel is a truck, a driver and a day on the road, so the days between refuels are what make this the cost-effective way to keep the site on air.
Because the generator is a separate unit, it can be serviced or exchanged without moving the solar trailer, and the solar trailer can work alone where an engine is not permitted. Output is 120/240 V or 120/208 V at 50/60 Hz with a 5 ms transfer.
Features and benefits
- Standalone 40 kW diesel, 140-gallon tank — Refuel visits about two weeks apart at 6 kW: 14.4 days between them.
- Ten 460 W panels over a 30.4 kWh lithium bank — Light overnight loads run silent, with no engine hours.
- Two units, two trailers — Maintenance is a one-unit job, and the solar side can work alone where engines are not permitted.
- 12 kW inverter, 24 kW surge for 10 seconds — The generator is never asked to cover a start-up spike.
Performance
Performance across the load range.
Zero to 12 kW, the rated maximum.
engine hours per daydiesel, US gallons per daythe array carries the whole dayrated continuous output
| Loadcontinuous, 24 h | Solar generationthe array, per day | Battery only | Daily drawload × 24 h | After solar | Days of autonomy | Generator | Engine runsa day × each | Charge setting | Days on a tank |
|---|---|---|---|---|---|---|---|---|---|
| 0.82 kWsolar break-even | 19.8 kWh | 17.8 h / 24.92 h | 19.8 kWh | covered | indefinite | 0 h/day | none | 258 A | — |
| 2 kW | 19.8 kWh | 7.33 h / 10.27 h | 48 kWh | 28.2 kWh | 0.52 days | 1.99 h/day | 1.6 × 1.2 h | 258 A | 62.5 days |
| 4 kW | 19.8 kWh | 3.67 h / 5.13 h | 96 kWh | 76.2 kWh | 0.19 days | 4.71 h/day | 3.8 × 1.2 h | 258 A | 23.3 days |
| 6 kW | 19.8 kWh | 2.44 h / 3.42 h | 144 kWh | 124.2 kWh | 0.12 days | 6.83 h/day | 5.5 × 1.2 h | 258 A | 14.4 days |
| 8 kW | 19.8 kWh | 1.83 h / 2.57 h | 192 kWh | 172.2 kWh | 0.09 days | 8.53 h/day | 6.8 × 1.2 h | 258 A | 10.4 days |
| 10 kW | 19.8 kWh | 1.47 h / 2.05 h | 240 kWh | 220.2 kWh | 0.07 days | 9.93 h/day | 8 × 1.2 h | 258 A | 8.2 days |
| 12 kW | 19.8 kWh | 1.22 h / 1.71 h | 288 kWh | 268.2 kWh | 0.05 days | 11.09 h/day | 8.9 × 1.2 h | 258 A | 6.7 days |
Every load here runs continuously, and the day is 24 hours — daily draw is the load × 24 h, so 2 kW is 48 kWh. A load that runs an 8-hour shift draws a third of the figure shown and lasts three times as long. Battery-only hours are given at both state-of-charge settings. Solar is a daily energy offset, not an instantaneous power match — over a day it balances, within a day it is not a guarantee of cover.
The engine starts at 30% state of charge (a 70% depth of discharge) and stops at 80%, putting 15.2 kWh back into the bank on each run while it carries the load. The engine runs a day follow from that at each load.
Case study
Against the 40 kW generator running alone.
At 6 kW around the clock, its own 40 kW generator — the one telecom sites use for temporary power — would carry the site alone at 15% of its rating, 24 hours a day. 123-SG-4S82-40 runs its engine 6.8 hours a day — 72% fewer engine hours — and burns 45% less diesel: 9.2 US gallons a day against 16.8 US gallons, and 14.4 days between refuels against 7.9 days.
PDF The full engineering sheet with this case study, to print.
| Loadcontinuous, 24 h | 40 kW alonediesel a day, engine 24 h | Days on a tank40 kW alone | This systemengine hours a day | Diesel a daythis system | Days on a tankthis system | Engine hours saved | Diesel saved |
|---|---|---|---|---|---|---|---|
| 2 kW5% of the 40 kW | 16.8 gal | 7.9 days | 1.99 h | 2.1 gal | 62.5 days | 92% | 87% |
| 4 kW10% of the 40 kW | 16.8 gal | 7.9 days | 4.71 h | 5.7 gal | 23.3 days | 80% | 66% |
| 6 kW15% of the 40 kW | 16.8 gal | 7.9 days | 6.83 h | 9.2 gal | 14.4 days | 72% | 45% |
| 8 kW20% of the 40 kW | 16.8 gal | 7.9 days | 8.53 h | 12.8 gal | 10.4 days | 64% | 24% |
| 10 kW25% of the 40 kW | 16.8 gal | 7.9 days | 9.93 h | 16.3 gal | 8.2 days | 59% | 3% |
| 12 kW30% of the 40 kW | 20.2 gal | 6.6 days | 11.09 h | 19.7 gal | 6.7 days | 54% | 2% |
The 40 kW generator carries the load alone, 24 h a day with no sun and no battery, on its own 140 gallon tank (133 usable). Both engines are read by the same rule: their own published fuel figures, a straight line between them, and below the lowest published point that point’s burn — for the 40 kW, 25% of its rating. No lighter-load figure is invented for either engine. This system’s figures are the performance table above.
Size it for your site
Your load, on 123-SG-4S82-40.
Most sites swing between a low and a high. Enter both, and the hours a day spent at the high, and the figures follow your day rather than a flat worst case; add your diesel price for the fuel bill. The load is yours — nothing is assumed until you enter it, and nothing that names you is kept; the PDF button builds the engineering sheet from the figures you enter.
PDF The engineering sheet, with page two worked out for your load.
| Held flat at your high24 h at the high load | Your dayhigh and low, as entered |
|---|
Read from the performance table above: engine hours and fuel follow the day's energy, so your day is read at its average load; solar is the published daily figure; battery-only hours are the published bank at your high load. A load held for 24 hours is the worst case at that level. With no days entered it runs indefinitely; a week and a year are your day repeated, at the same sun.
Gallery
On site and on the road.
Applications