Bob,
Polarity is correct as written. 

Should be more than enough soda for that amount of water. 

One thing I might try would be to wire brush a spot in the rebar where your
connections are to make sure they are connecting well.

Are you getting any bubbles?

One other thing I have heard( but not experienced) is that on some chargers
there is a safety which won’t allow them to charge unless there is something
drawing amperage. Some advocated putting a battery in the circuit to start the
draw, or finding a charger without that safety feature. I don’t know if this
applies to yours or not.

Sent from my iPhone
Brent Kinsey