My stir plate is pretty much the same as yours. I bought one of those variable voltage ac plugs (I'm sure that there is a proper name) and a fan with three speeds. I'm running @ 9V with the fan set to Low I think. I'm using the 1 inch stir bar from morebeer in a 1000ml erlenmeyer.
I think that 3.7 might be a little bit too low. You might want to go for at least 6V. That's just my opinion, but it kind of smells like my asshole.



