Charge controller sizing check

Cold Voc against the maximum input voltage, hot Vmp against the minimum, and array current and power against the charge limit.

Design aid, not a substitute for the controller manual, the adopted code or your AHJ. The module, site and array values below are invented. Controller limits in the presets are copied from the manufacturer pages named under the results. It checks one controller input and one array. It does not model shade, mismatch or the controller's own losses.

Examples (invented 400 W module, 48 V bank):

Module (STC datasheet values)

Voc (V) Vmp (V) Isc (A) Imp (A) Pmax (W) Voc coefficient (%/°C) Vmp coefficient (%/°C; assumed if the sheet prints none)

Array on this controller input

Modules per string Strings in parallel Charge voltage of the battery (V)

Site (cell temperature)

Coldest cell temperature (°C) Hottest cell temperature (°C)

Controller limits (from the manual or datasheet)

Maximum PV voltage (V) Start-up: fixed minimum PV voltage (V, 0 if none) Start-up: volts above battery (V, 0 if none) Running: fixed minimum PV voltage (V, 0 if none) Running: volts above battery (V, 0 if none) Maximum charge current (A) Nominal PV power (W; blank if not printed) Maximum PV short-circuit current (A; blank if not printed) Maximum PV operating current (A; blank if not printed)

Check	Your array	Limit	Result

Method: voltage at cell temperature T = value at STC x (1 + coefficient x (T - 25)). Cold Voc and the start-up check use the string; the start-up check uses Voc at the hottest cell temperature. Estimated charge current = array STC power divided by the charge voltage, with no controller losses, which is a ceiling. A controller may limit input power instead of failing, so read the maker's wording. Preset limits: Victron SmartSolar MPPT 150/70 manual (specifications table and footnotes, no date printed); Morningstar TriStar MPPT 600V product page (last modified 8 October 2026) and datasheet (Revision 04/2016.SP); Victron Multi RS19 Solar datasheet (230 V model, no date printed). Decimal commas are accepted. Write 1000 or 1,000 for a thousand; 1.000 is rejected as ambiguous.