It might happen if the battery is nearly finished, so please re-charge the battery.
It might happen if the battery is running out, you can try to get a voltage indicator or similar to check the battery voltage to ensure it is working properly.
Well, it is hard to answer, it also depends on the mAh of your battery, but usually 45+ minutes. So, it is better for you to get more batteries so you do not need to wait.
There are number of reasons that you have not received our response for your inquiry.
Although you have sent us many emails in the past few hours. However, we are not operating 24 hours a day. So please be patient until we come back to work after the night and public holiday (Refer to our Calendar).
If you have not received response from us after many days, please try to check the Trash or Spam folder of your mail box because sometime our emails could be filtered by mail servers as Spam.
If you have difficulties in contacting us through emails, please try to print your questions out and fax to us (remember to leave your fax number for us to respond).