Balance of voltage losses

Now let us evaluate voltage losses and the adequacy of the panel voltage from this point of view. There is no loss due to extreme heat because the ambient temperature does not exceed 25 °C. On the other hand, the series regulator shows a loss of 0.24 V (typical value for 12 A) and the blocking diodes behind the panels 0.5 V.

As far as ohmic losses are concerned, as the components are fairly close to each other and the currents relatively low, these should not be critical and will only depend on a good choice of wiring sections. The panels have a total power of 9 A for the three panel option and 12 A for the four panel option. Assuming the distance between the output on the junction box and the battery is 8 m, one would choose a cable of 6 mm2 section (for calculation, use the chart on Figure 5.42), which induces a loss of 6.6 mV/m for 1 A of current. Losses will thus be limited to 0.48 V for three panels and 0.63 V for four panels.

In total, the voltage losses between panels and battery will be 1.22 V (= 0.24 + 0.5 + 0.48 V) for the three panel system, and 1.37 V for the four panel system. As the STC voltage at maximum power point is 16.5 V, the battery input will be between 15.1 and 15.3 V, which is largely sufficient.

Between the battery and the regulator, if the distance is short (1-2 m), a 2 x 2.5 mm cable could be used, for example.

Updated: August 23, 2015 — 9:07 pm