I have a RPi2 powered by an Adafruit Powerboost 1000 Charger and a 6600mAh 3-cell Li-ion battery.
Whenever I start the RPi2 on a normal 2A USB charger, I do notice a current draw spike at about 2-3 seconds after startup, causing the rainbow box to appear for a split second in the top-right corner of the screen. If I am not using the USB charger, but the battery and Powerboost, it causes the Pi to reboot every time it hits this spike. If I unplug the HDMI LCD display (that is also being powered by the same Powerboost) until it passes that spike, it works fine.
What is the cause of this spike?
Furthermore, could I add a capacitor to the power circuit that could provide enough juice for a split second to help get passed this spike?