Photovoltaic panels directly charge lithium batteries

Can a commercial lithium-ion battery be integrated into a micro-PV system?

A commercial lithium-ion battery was integrated into a commercial micro-PV system. Two alternative battery coupling architectures were developed and demonstrated. The passive coupling uses a parallel electrical connection of the battery. The active coupling uses a controlled converter with MPP charging algorithm.

How does a battery charge a solar inverter?

During the first day (approx. first 8 h of data), the battery is charged (I b a t t < 0) by a part of the PV current (I P V > 0), while another part is delivered to the inverter (for which always I i n v < 0). This increases the SOC of the battery and therefore increases the voltage level of the system.

What is the difference between PV and battery voltage?

The voltages of the three components (panel b) exhibit a dynamic behavior. Through parallel electrical connection of PV and battery, PV voltage is equal to battery voltage (the slight difference originates from the diode), which in turn depends on SOC: voltage is self-similar to SOC (panel f).

What is a battery charging principle?

The principle reaches back to 1968 when first patents were filed, . It is based on matching the PV and the battery respective current and voltage behaviors. During battery charge, the system voltage increases and drives the PV towards zero current when the battery is fully charged.