@pma1612 could be a bad battery. Could also be that your logicboard has a fault which the charging IC etc. If you want to start with the battery and want to do it yourself use [guide|47287|this guide]. The battery is available at places [product|IF276-007-2|like this.]
Check with a USB ammeter if your iPad even attempts to charge. Check your cable/charger and port as well to make sure that all that functions as it is supposed to.