Pecron F5000LFP We own this
This calculator’s worked example is the unit we own. Manufacturer published limits on each of two inputs: 180V, 25A, 3,200W (2x XT60/XT60i at 3200W each, 30-180V).
MPPT wiring
Solar string sizing calculator
Series count is a cold-weather voltage problem. Parallel count is a current problem. Three or more strings add a fuse problem. The tables below are static HTML for one documented panel and controller pair.
Three limits decide a wiring plan. Series count is capped by panel open-circuit voltage in the cold — Voc rises as temperature falls, so an array sized from the 25°C datasheet number can overvolt the controller in winter. Parallel count is capped by the input's current limit. And once you run three or more parallel strings, the others can backfeed a faulted string, which requires in-line fuses if(strings − 1) × Isc × 1.25 exceeds the module's maximum series fuse rating.
Worked example: a SunPower SPR-E20-330-COM (330W,64.9V Voc, 6.52A Isc) into aPecron F5000LFP (180V / 25A /3,200W per input).
What is a watt-hour?
A watt-hour (Wh) is stored energy: watts × hours. A 1,000Wh pack can theoretically supply 100W for 10 hours, or 50W for 20 hours. Real runtime is shorter once you count inverter loss and idle draw.
Hours below are estimates from capacity ÷ labeled average watts. They are not first-hand measurements of an appliance we ran. The pack size in the table is a published watt-hour rating, not a runtime we measured.
| Labeled average load | Estimated hours |
|---|---|
| 50W average | 102 h |
| 100W average | 51 h |
| 150W average | 34 h |
Why cold matters more than heat
Open-circuit voltage climbs as panels get colder. For this panel the coefficient is -0.1766 V/°C (SunPower E-Series E20-330-COM datasheet), so a string that measures safe on a warm afternoon can exceed the controller's ceiling on a clear winter morning — the worst case is a cold, bright, no-load moment right at sunrise.
| Cell temp | 1 panel | 2 in series | 3 in series |
|---|---|---|---|
| 40°C | 62.3V | 124.5V | 186.8V ✗ |
| 25°C | 64.9V | 129.8V | 194.7V ✗ |
| 0°C | 69.3V | 138.6V | 207.9V ✗ |
| -20°C | 72.8V | 145.7V | 218.5V ✗ |
| -40°C | 76.4V | 152.8V | 229.1V ✗ |
Three in series fails at every temperature in this table, including a hot 40°C day. It is not a cold-weather edge case — it simply does not fit. Two in series would need roughly −117°C to breach the limit, so it is safe anywhere on Earth.
Every wiring option, checked
| Wiring | Panels | Cold Voc | Current | Watts | Verdict |
|---|---|---|---|---|---|
| 1S × 1P | 1 | 76V | 6.5A | 330W | OK |
| 1S × 2P | 2 | 76V | 13.0A | 660W | OK |
| 1S × 3P | 3 | 76V | 19.6A | 990W | Fuses required |
| 1S × 4P | 4 | 76V | 26.1A | 1,320W | Over current limit |
| 2S × 1P | 2 | 153V | 6.5A | 660W | OK |
| 2S × 2P | 4 | 153V | 13.0A | 1,320W | OK |
| 2S × 3P | 6 | 153V | 19.6A | 1,980W | Fuses required |
| 2S × 4P | 8 | 153V | 26.1A | 2,640W | Over current limit |
| 3S × 1P | 3 | 229V | 6.5A | 990W | Over voltage limit |
| 3S × 2P | 6 | 229V | 13.0A | 1,980W | Over voltage limit |
| 3S × 3P | 9 | 229V | 19.6A | 2,970W | Over voltage limit |
| 3S × 4P | 12 | 229V | 26.1A | 3,960W | Over voltage limit |
| 4S × 1P | 4 | 306V | 6.5A | 1,320W | Over voltage limit |
| 4S × 2P | 8 | 306V | 13.0A | 2,640W | Over voltage limit |
| 4S × 3P | 12 | 306V | 19.6A | 3,960W | Over voltage limit |
| 4S × 4P | 16 | 306V | 26.1A | 5,280W | Over voltage limit |
Try your own numbers
The tables above are the complete answer for this panel and this power station without JavaScript. Use the fields below for any other combination. The form is progressive enhancement only.