A lot of effects need a lot of power or rather a lot of power feeds. I can actually drive all my effects on one 200mA BOSS wallvart, they dont need more juice but they still need one cord each. But I also need 12V regulated DC to some pedals. I solved this by getting a 12V 1000 mAh DC wallvart and feed this regulator to get two 9V and one 12V outlest delivering enough to supply all pedals with. I Also remembered that I had a 12V led battery in case I wanted to use battery power (1.3 mAh lasts many hours) The thought was to c entralize the power feed and to be able to shift between battery and high voltage. This way I can feed a lot of effects on one rechargeable battery or high voltage. The voltmeter is just there to alert me when the battery is running dry.