iPhone 6 battery drain fast
Once they start to go, they go fast.
Mine went from 'perfectly fine all day' to 'need to carry a charger with you' in about a month.



Switch it into Low Power mode for now, ring Apple &amp; arrange to take it to an Apple Store or for them to collect it.
Battery change takes 2 hours if you take it in or 3 days by post. [They say it can take longer but that's direct experience.]

Do it soon because the low price battery replacement offer ends in September, so I've heard.

You must release it from Find my iPhone before they will accept it.
Safest is to fully back it up &amp; erase it before handing it over.
If you have a spare iPhone, restore it from that backup &amp; drop the SIM into it for the duration.