The 1500mah chip should work safely for the battery as long as it is capable of charging and maintaining larger and/or more cells then the stock battery has. My guess is that it probably is one of those chips that works with a wide range of lithium cells since it would be cheaper to get those in bulk then one specifically for the 1500mah battery.

 

One more thing...Looking at the pictures of the OP it seems to me that the battery already has some kind of chip to protect it from a shortcircuit, overloading it, etc. Do we still need a chip from an official battery? I know I would have to open an official battery to get connector anyway. Just asking.

Edit: I saw the video and it seem the chip is necessary.
Edit 2: I opened a 1500mah official battery and ordered a 2500mah battery (a 7*44*69mm one) from China. I'll post some photos and comments in 2/3 weeks.

 

How did you do this? I just looked in settings and saw nothing about screen brightness or rumble for the Wii U pad.

 

The protection chip inside the cell - if it has one at all (which, for the aluminium-shelled rectangular one, is usually visible under the yellow tape) is just that: it may disconnect (more or less permanently) power in case of overcharge, overdischarge, overcurrent, multiple of the above, or maybe none in case it's fake....

The one in a "consumer" battery may or may not do the above things, but it could also have a thermometer (for charge limiting), supply static information (serial number, ideal capacity, etc), dynamic information (wear-adjusted capacity, cycle count, more accurate remaining % and time calculations than possible by measuring voltage alone...)

All previous Nintendo products (including the whole 3DS series) took the simplistic approach with a simple resistive thermometer at best, but 4 pins point at some "smartness" (not that it wouldn't be achievable with 3!)

 

If you have a car jumper that you can plug into, or a generator...just plug in tv and wii u


So it finally died in middle of mario kart, played about 30 mins when the red light started flashing. It took 6 hours to fully charge

 

Seems like a lot of effort for so minor gains in battery life. I mean, the official extended battery is 2550 mAh and doesn't require mangling the shell.

 

You should get all types of heads for screw drivers, mainly the phillips in #00, and #000, got the triwing later after a naive young me destroyed a prestine laptop only to find out I needed to reseat the ram. I broke off the keyboard in a desperate attempt to pry it open using a standard house flat head. I regret it so bad that before I touch a repair I make sure I have the right heads and have seen a teardown article or video of the item.

 

I finished my project. As I said above, I used a 2,500mah-battery. The gamepad switches on correctly and right now I´m charging it. A couple of pictures:

 

Bad news. I played two hours in a row (2h and 5') with brightness set at level 3 and the orange light lit on the Wii U gamepad. I hoped it would last longer . I've just ordered this 5,000mah-battery. I think it will fit perfectly in the battery compartment. I will post again in a month or a month and a half.

 

Yep, even though I didn't said it before, I know that 5,000mah is not going to be the real capacity of that battery. If it was only real 3,000mah, it would stilll be a good option as it is pretty cheap and (I think) it will fit inside the gamepad battery compartment. We´ll know (I'll post it) in a month or so.