CoasterCycles makes a pedicab with a 750 W electrical assist motor. The battery, a 48 V, 11 Ah (1/2 kWh) Lithium Ion Polymer is typically charged over night at about 2 A, or 100 W and lasts about 4 hours under normal use. We made a 150 W solar panel to charge the battery during day time operation in order to extend the battery life for the entirety of the day (if it’s sunny).
We discovered that the battery charging port is not protected with either a fuse or a diode from catastrophically discharging. We inserted two 3A rectifier (400 V) diodes in the battery as shown below. Consequently, the battery can no longer discharge via the charging port. This will make the battery safer, will prevent the battery from discharging through the solar panels when there is no sunlight, and will also lower the maximum voltage on the battery from 54.6 V to about 54.0 V. This decrease in voltage will negligibly decrease the amount of power held in the batter because of the steepness of the State of Charge curve at this voltage.
Dissected panel, used to figure out wiring
Diagram of one 50 Watt solar panel and wiring, 32 panels wired in series, each rated 2.5 A and .6 V
Donette has opened a successful $800 KickStarter Campaign to pay for the physical upgrade. Please visit the campaign and see the updates at the bottom for more pictures.