What is the reason for the 6,000mAh battery in Wireless Charger for Model 3?
The 6,000mAh battery in the Wireless Charger is necessary to compensate for circuitry losses through the wireless system. The battery charges in the charging system and then uses that power and the power from the USB ports to output a full 7.5W to the wireless coils. Without the internal battery, the wireless charger would only output about 4W to the wireless coils.
Note: this information is only applicable to Model 3 owners operating on any Tesla firmware versions before V9. Along with the V9 update came an increase in the output of the USB ports in the front console. With some design tweaks in the Generation 2 Wireless Charger, we were able to leverage the increased output so that the integrated 6,000mAh was no longer necessary in order to achieve the full 7.5W output on each side of the charging pad. Generation 2 Wireless Chargers do not include the battery unit with the charging pad.