Almost every power station can charge from solar panels: 116 of the 121 ranked here publish a solar input rating, up to 5,800 W. Two numbers on the spec sheet decide which panels work and how fast they charge: the maximum solar input in watts and the input voltage range.
Maximum solar input
This is the most power the station will take from panels. Panels connected beyond it won’t hurt the station (it only draws what it can use), but the extra panel capacity is wasted at midday.
In practice panels rarely produce their full rated wattage. Sun angle, heat, haze and dust all cut output, so many owners connect somewhat more panel wattage than the input rating to fill it for more of the day, as long as the voltage stays within limits.
Input voltage
The voltage range is a hard limit. Below the minimum, the station won’t charge; above the maximum, it can be damaged. Spec sheets give it as a range such as “12-60V” or “11-60V”.
To match a range, wire panels:
- In series (positive of one panel to negative of the next): voltages add, current stays the same. This is how you reach a high-voltage input.
- In parallel (positives together, negatives together): currents add, voltage stays the same. This keeps the voltage down for a low-voltage input, but needs a station whose input current limit can take it.
Use the panel’s open-circuit voltage (Voc) from its label when you add up a series string, not its lower working voltage. The station must stay safe at Voc.
Cold weather raises voltage
A panel’s voltage rises as it gets colder. Cold, bright mornings produce the highest voltages a solar array will ever see. The US electrical code requires installers to work out the maximum voltage at the lowest expected temperature for that reason. One worked example: a panel rated 45.5 V Voc reaches about 52.7 V at −23 °C (−9 °F). Leave a margin below the station’s maximum input voltage, or a series string that is fine in summer could exceed it on a winter morning.
MPPT
Most stations have an MPPT (maximum power point tracking) charge controller built in. It continually adjusts the load on the panels to pull the most power they can give under the current light and temperature. That’s why a station can make use of a wide voltage range.
How the rankings use it
Solar input is one of the eight factors in how we rank, scored as solar watts relative to the battery’s capacity: how quickly the sun can refill it. See the solar charging ranking.
Sources
- Wikipedia, Maximum power point tracking: what an MPPT controller does.
- Solar Permit Solutions, NEC 690.7 solar voltage limits: cold raising panel voltage, the lowest-temperature calculation and the 45.5 V worked example.
- Solar input ratings and voltage ranges: each product’s manufacturer specifications, linked from its page.