My new ipad cellular air won't charge properly

Hi I bought the new Ipad Cellular air recently, I think it's great except it will not charge properly,!

For example my ipad was at 24% Battery last night at 19:45 pm so I plugged in the charger and powered down the iPad

When I awoke at 06:00 am it was only at 80% charge

Surely that is not right

Kind regards David