An unconventional, scalable high efficiency 12V solar power system and
battery charge controller with low voltage cutout to protect the
battery. (ideal for systems of 50W or less). The most common solar
charger consists of a Schottky diode to prevent the battery from
draining into the PV panel and a shunt regulator that effectively short
circuits the panel once the battery is fully charged.
One problem with this approach is diode losses and the resulting heat.
If a 50W 12V panel supplies 4A to the battery, the Schottky diode will
drop about 0,4V across it dissipating about 1,6W of heat. This requires a
heat sink and loses power to heat. The problem is that there is no way
of reducing the volt drop, paralleling diodes may share current, but
the 0,4V will still be there. The circuit uses a MOSFET in stead of the
usual diode and the primary power loss is resistive. [Link]
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