Automatic Garden Watering System

I've been getting into gardening recently, and now I realize I need to come up with a watering system when I'm out of town. There are several complicating factors here as well. I'm an apartment renter, so my planters are outdoors on my patio. I don't have access to a faucet outdoors, and I'd prefer not to run a hose from inside, as that would necessitate leaving the door open while I'm away. I also don't have an electrical outlet out on the patio, either, so this system needs to be battery powered. I've seen similar projects, but most of them involve pumps or electrical outlets.

I'm thinking of a basic gravity-driven system, with a big bucket/reservoir containing the water sitting on top of a chair, a solenoid valve to open/close the reservoir, a flow meter to measure the amount of water released, and an Arduino to link everything together. The planters I have are self-water EarthBoxes, if you're familiar with the name. In this case, "self-watering" just means that it has a reservoir at the bottom through which water is slowly wicked through the soil. It still needs to be refilled/watered via a watering inlet. The idea here is that I can just have a tube running from my big bucket into the water inlet without worrying about any fancy nozzles or anything like that at the end.

Does this seem feasible at first glance? Anything I should immediately reconsider? Any other thoughts are welcome as well. Thank you!

Sounds feasible. You might want to consider the plastic solenoid they offer - that brass one pulls a lot of current.