Propogate's post reminded me of a time we had a similar problem.
Turned out that we had a faulty charger.
Apparently iphones and ipads have a different voltage, so you can't interchange the chargers. Fortunately for us the cable went first.
Take you iPad to an Apple store.
Theywill replace it with the same model at a reduced cost.
The cost depends on a few things but is generally your best option.