Minimum current rating for connecting solar panels in series — what’s ideal?

Selecting Panels for Series Connection

When connecting solar panels in series, it’s essential to choose panels that have a similar voltage rating and a relatively small difference in current output. A general rule of thumb is to select panels with a voltage rating of 20-40% higher than the desired system voltage, and a current rating that differs by no more than 5-10% among the panels.

Calculating Series Current Rating

To determine the minimum current rating for the series connection, calculate 5-10% of the maximum current output of the panel with the lowest current rating in the series. For example, if you have a series of three panels with the following current ratings: 12A, 10A, and 9A, the minimum current rating would be 5-10% of 9A, which is 0.45-0.9A. In this case, it’s recommended to use a charge controller with a current rating of at least 10A to ensure reliable operation.

Practical Considerations

When sizing a solar charge controller for a series connection, consider the total system voltage and the desired charge rate. A general rule of thumb is to use a charge controller with a current rating that is 1.25-2 times the maximum current output of the panel with the lowest current rating in the series. This ensures that the charge controller can handle the peak current demand during charging, and prevents excessive heat buildup or other issues.