[One (M8) Q&A, Help & Troubleshooting] doublehp:
Smartphones always sucked about battery.

My solution is clear and simple: add more batteries.

For HTC Sensation, I bought two additionnal batteries, glued them on the back, and soldered wires from the external ones, to the internal batt. It's complicated because, thick wires prevent the phone from closing properly, and bend the screen; thin wires will produce a voltage diff, and in the end you just loose any possible interest. But still, the autonomy of my phone was hugely increased; not by 3, but by more than 2. Plus, when you drain a lower current from a battery, you can extract more total energy; so, with thick wires, the resulting autonomy should be greater than x3.

I decided to not open my M8; adding wires inside may be a hell any way (or not, I don't know; if it provides easy access to battery, or has official pins for wireless charger, it may be very easy). Fact is, I won't proceed the same way. I paid everything, but did not receive items yet.

I won't glue all this directly on my phone. I bought a hard case:

http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&item=261497955110

http://www.hobbyking.com/hobbyking/store/__18560__Turnigy_5000mAh_1S_20C_Lipoly_Single_Cell_.html

5000 mAh battery; it's 20C, so, hugely over powerfull; too big (in volume). Battery could be physically smaller if it had a lower discharge current. This battery is the max size that can fit behind the M8 below the cam (after folding the contact side). Glue it along a side. Not in the middle.

Protect it with

http://www.dx.com/p/charge-discharg...hargeable-li-ion-batteries-17-4mm-1-9mm-26112

http://www.dx.com/p/produino-usb-12...tage-step-up-boost-module-green-silver-291598

Now, pump up to the phone. Do not use a classic cable; see below for the cable I use to plug on the phone. Do not use the big USB A plug of this item for the phone; solder your wire below the plug, and keep this USB-A plug available for other uses, like, suplying external disk, recharging your USB ear-set ... recharging your other phone. Glue this near the camera. It will rarely be used.

http://www.dx.com/p/mp1405-5v-1a-lithium-battery-charging-board-blue-black-219454

This board used to be available with mini USB. Since all phone now use micro, we need the charger to have a micro plug; so that, you can recharge the lot with a legacy phone charger. Glue this down side, near the phones USB plug, so that it remains easily accessible, and will work ... almost like the phone itself.

http://www.dx.com/p/bonatech-diy-mp3-toggle-switch-mk12c02-micro-switch-silver-black-100pcs-303570

insert micro switched at strategic places (probably between protective circuit, and battery). These ones are low rated; but I will try them. 1A switches are hugely bigger, and we are short of room. I hope I ordered the right ref. You want a bi-stable switch. Ideally rated 1.5A+

Now, the real smart stuff:

http://www.dx.com/p/positive-qi-wir...arger-receiver-for-micro-usb-cellphone-312818

stick on the back. Cut the cable. Solder output of the pad to the input of charger. Solder the USB plug to the booster. Maybe I took the wrong polarity; triple check what you want.

At this point, your phone can be recharged by just laying on the table. It has triple autonomy, and as you will never manipulate the USB plugs any more, you have no chance to damage them. And the USB plug of the wireless pad is designed for this: live permanently inside the phone, and be so thin that it will not grow out of the phone: even if the phone falls down just on the bottom side, the chock will not break the male plug inside the female plug; will not damage the phone plug (broke several phones by ... bad manipulation during charge).

Now, features:

- http://www.dx.com/p/2-in-1-usb-2-0-to-micro-usb-otg-sd-tf-memory-card-reader-white-32gb-285865

- http://www.ebay.fr/itm/Protecteur-de-Ecran-Verre-Trempe-pour-HTC-ONE-M8-Glass-M8-/360941939081 (pretends to be 0.3mm thick, is actually 0.65mm)

- http://www.amazon.fr/dp/B00GD9RECO/ref=pe_386181_37038081_TE_3p_dp_1

- http://www.ebay.fr/itm/Cable-adapta...e-pour-tel-HTC-/380915009738?var=650261925297

- http://www.dx.com/p/5-in-1-micro-us...ion-kit-11-pin-micro-usb-adapter-black-257780

- http://www.dx.com/p/0-3-4-digit-3-5-20v-0-3a-cccc-white-black-multi-colored-326315#.U73aMtePul1

- micro sim cutters and adapters

With hard case, battery, and circuits, the phone surface did not change at all. Only thinkness and weight changed. Grown from 9 to 21mm. Depends if you cound the wireless stuff (did not receive and mount all of this yet). So, yes, heavier, thicker ... but ... lasts 3 times more, and can even supply other devices. And if organised properly, all this fits below the cam. And fits the waterproof bag with everything (I work in heavy dust environment).

I don't know yet if this set allows to recharge Iphones (not Ipad, i am sure of that, 1.2A is not enough), but the M8 can use up to 1.5A on this booster. If Iphones fail, and you need them, then, there is a fix. Buy a 1A iphone car charger for $2, dismount it, a grab the circuit sending signal to data lines, and insert it in the garbage.