Solar Charge Controller Calculator: Cold Voc, Hot Vmp, MPPT, Current, and Battery Limits
Direct answer
Check PV voltage, current, controller limits, and battery charge limits with cold- and hot-temperature assumptions.
Inputs
Results
Enter or confirm the inputs to see the result.
Interpretation
This checks cold Voc against the absolute voltage limit, hot Vmp against the MPPT window, PV operating and short-circuit current against controller limits, estimated output current against the controller and battery limits, and reports the field that caused each warning or failure.
Pass, warning, and fail conditions
- Cold-corrected string Voc, hot-corrected string Vmp, MPPT-window PASS, input-current PASS, and battery charge-current PASS are separate checks.
- PASS is below the limit; WARNING is within 10% of a limit; FAIL is over the limit or has an invalid MPPT/temperature relationship. The result names the associated input chain.
Formula or method
cold string Voc = Voc × [1 + Voc coefficient × (25 − cold temperature)] × series
hot string Vmp = Vmp × [1 − Vmp coefficient × (hot temperature − 25)] × series
PV operating current = Imp × parallel; adjusted Isc = Isc × parallel × bifacial factor × (1 + margin)
estimated controller output current = (Vmp × Imp × series × parallel × efficiency) ÷ battery voltage
Assumptions and limitations
- Coefficient values are entered as positive percent per °C. Confirm the sign convention and test conditions in the module datasheet.
- The model does not replace the controller manual, array wiring design, overcurrent protection, battery charge limits, or local electrical requirements.
- A topology mismatch between an independently entered array-watt value and module Vmp/Imp values should be resolved before using the result.
Worked example
For three modules in series with 49.5 V Voc, 41.5 V Vmp, −10 °C minimum cell temperature, and 70 °C maximum cell temperature, the calculator shows cold Voc and hot Vmp separately before checking the controller window and current limits.