Those charging docks tend to be awful, I know because I bought one in the past and it was a complete waste of money.
The batteries aren't going to live long, the charge lasts less than what you'd expect (because they don't have the mAh they tell you most of the time) and worst of all, the mechanism to charge the batteries was incredibly flimsy, being basically two wires that needed direct contact with the tiny metallic squares in the batteries, and were pushed inside the charger so the wiimote "rests" on the dock... But that's not what usually happened.
The wires would lose contact continuously, they wouldn't let the wiimotes be in a good position because they'd be pushing the wiimote away. So you were basically having to pay attention to it to see if it was working or not. Not to mention, the docks can fall over from the weight from the wiimotes as they're basically empty inside and weigh nothing (that depends on the model, though).
If that's the one you're looking to get, I'd say forget it, they're not worth it at all. Normal rechargeable batteries are a far better investment, even without going for the ones from big brands it's going to be better.