[One (M7) General] Shan89:
Here some info.

Charging :

No matter which charger you use phone it self won't allow more then 1a even if charger can do more , this is for safety reasons.

Charging time :

HTC one supports fast charge from Qualcomm but htc disabled it due to preserving longer battery life since we can't access the battery.

My phone usually takes around 2 / 2:20 hrs to charge from 20 to 100%. Screen off , if you're using the phone it'll charge much slower , turning the phone off won't really benefit you much faster charging , don't expect more then 5/10% faster charging.

How long will battery last in one :

Here's my rough calculation :

The battery in one is supposed to last around 1000 cycles.

1cycle = 0/100% charge , 50/100 = half cycle , 0/20 or 50/70 ( doesn't matter ) = 1/5 cycle.

How long will battery last ... well roughly everyones battery on xda even huge time flashers / gamers should last 1 year , if you calculate like this , 3 full charges per day ( 0/100% ) will last you 1 year without wearing battery at all , then we can expect 10% loss , but take this in consideration , if you charge phone 3x in a day fully discharged charged it'll take 9 hrs roughly to do 3 full charges and battery will last minimum 3 hrs screen time even if you were able to play 2 heavy games in the dame time so in total 18 hrs charges discharges , pretty much impossible to do in 1 day unless you really have that much time , no life , no needs for food etc it'll still last 1 year minimum.

Heavy user ( not super heavy like above ) will most likely charge 2 full charges per day so he's battery will last minimum a almost 2 years.

Average consumer charges phone once daily which would be 365 cycles in 1 year so you can say their battery will easily last 2.5 years +

Light user charges once in 2/3 days so battery will last 4/5 years before it losses any power.

LASTLY , us on XDA tend to change phones every now and then , usualy once per year so you have nothing to worry about HTC One battery !

Things you should never ever do !

- never discharge to 0%

- never game or super heavy use phone on charger

These 2 are the worst things you can possibly do to your phone.

Proper healthy charging :

Don't let your battery go under 20% , and charge it when you can ( I don't mean to charge it from 90/100 % lol ).

Healthy battery should last :

Average 16/20 hrs with heavy / moderate usage and 5+ hrs screen time ( I'll post pics of my average battery life bellow btw I'm heavy user and flashing literally every 2 days my phone. )

Deep sleep

Results before I put it on charger

This was 3/4g usage the whole time no wifi at all with average brightness 30/50/70%

If you're hard core gamer and playing heavy 3d games like a8 your battery should give you from 100% to 20% around 3:30 hrs play time , if playing daily 1hr you should lose average 15/25% per hr , I personally can play a8 for 4:20.

Important things for battery life and imo most important thing for good battery life / screen time is the deep sleep !

Example :

I lose average 1/2% per 10 hrs deep sleep , if a person with bad deep sleep ( wakelocks ) loses 10 % ( those guys consider this as good idle drain which is wrong ) for example : person who loses 10% and I lose 1/2 % I'll get out from 8 % which i didn't lose in deep sleep 40 mins of screen time average in 20hrs on battery person with 20% drain in 20 hrs will have 0 screen time and 80% on battery while I'll have same ammount of time on battery with 1hr 20/30 mins screen time.

Simple app for good deep sleep is greenify.

Hope this helps and answers some questions.