Detailed Description

Maximum Power Point Tracking, MPPT

The MPPT (Maximum Power Point Tracking) can ensure the solar panel output power maintains

at its maximum under different loads and sunlight, maximizing the conversion efficiency. We can

identify the short circuit current I

SC

and the open circuit voltage V

OC

from the cross points of the I/V

curve (green) with x and y axis respectively. The I

SC

and V

OC

grow larger with the illumination

increasing. With the output voltage V

PANEL

growing, the output current I

PANEL

gradually decreases and

then jumps down after crosses a special point V

MP

, the maximum power voltage. By multiplying the

voltage and current, which obviously results in power, and take the output voltage as the x axis, we

obtain the P/V curve (blue). The output power P

PANEL

reaches its peak when the output voltage is at

V

MP

. Although the maximum power increases with illumination, the V

MP

changes little. Therefore, we

may approximately take the V

MP

as a constant for a specific solar panel under different illumination.

IV/PV characteristic curve of a typical solar panel (picture from Linear Technology)

Inspired by the observation above, the LTC3652 solar power management IC (employed by this

module) maximizes the output power by keeping the output voltage at the vicinity of V

MP

, which is

also called constant voltage MPPT algorithm. Benefited from this feature, the module has a better

conversion efficiency compared to common solar battery charger.

Solar Panel Selection

Users can plug in any kinds of solar panel (monocrystal, polycrystal, thin flim) as long as the open

circuit voltage within 7V~30V. Taking the size, weight, price of the panel and the 2A maximum

charge current of the module all these factors into consideration, it is recommended to connect a

solar panel with no more than 20W to the SOLAR IN terminal.

The input voltage of SOLAR IN SHOULD NOT exceed 30V, or the module may be permanently 

damaged.