nope. i'm afraid that's not going to work very well.
<tacky_metaphor>think of voltage like water pressure. your battery is the same voltage as your charger so no current will flow.</tacky_metaphor>
as for current, generally 10% of the mAh rating in mA for around 12 hours is a good figure.
so you would want 200mA.
if your charger says "250mA" on the plate on the bottom of it then that will be the maximum current it can supply (with out blue smoke).
that doesn't mean it will supply that much.
try this thread: http://www.societyofrobots.com/robotforum/index.php?topic=319.0
there are a few other posts on this forum about charging batteries so try searching here. your questions have probably been answered allready.