Picture this- the year is 1990. You're on hour six of an eight hour road trip to Mount Rushmore. Tears For Fears is blaring on the radio of your Chevrolet Celebrity station wagon. Mom's driving. You've run out of Ecto-Cooler Hi-C and your stupid brother has been car sick since Sioux Falls. Playing your brand new Gameboy DMG that you got last Christmas is the only thing keeping you sane at the moment. You're about to take your high score in Tetris- 150 lines and you get to see that cutscene of the dancing Russians and Buran shuttle being launched. What a payoff! Then it happens, the screen goes dim... You can't see what you're doing. You are able to make out one last weird noise that Tetris makes when you lose. You know the one. SCreeEDEEDOooh. Then the red LED next to the screen blanks out. Your game boy is dead. You're out of batteries and there's still two hours left to drive. Welcome to hell.

Now, let me ask you a serious question: Have you ever want to put a LiPo battery into your ORIGINAL Gameboy DMG for NONSTOP GAMING EXCITEMENT?? No? Well, too bad there's no turning back now. 30 years later, I've devised a solution to this quandary that has plagued mankind for decades. After this, I'll invent the time machine so you can help your past self out on that road trip from hell by giving your childhood you THIS modded Gameboy. This amazingly incredible mod jams a LiPo in your Gameboy's backdoor with a recharging board so you never have to fuss with batteries in your beloved little handheld portable gaming system NEVER EVER AGAIN almost. The best part is that it utilizes your Gameboy's original DC jack so you can keep your Gameboy's original pristine aesthetic (no new holes in the shell) and still use your inefficient old wall charging brick that you bought at Toys 'R Us in 1991 when you first got sick of wasting batteries playing Super Mario Land. What is up with that game anyway?

Supplies

Your original Gameboy DMG that you're fed up with having to replace the batteries every week for the past 30 years.
A LiPo battery that fits in your Gameboy's battery compartment. Mine is a 3.7v 2000mah battery. This is the one I got from Adafruit.
A powerboost 500c or 1000c if you're rich.
A small tri wing screwdriver to open your game boy.
Mad soldering skillz and a soldering iron of justice, plus solder, duh
Some wire
Maybe an exacto knife. Or something sharp, I don't know. Don't cut yourself, I am not responsible.
Nothing better to do with your life.

Step 1: Prep Your Gameboy for the Operation

I'm not gonna lie, I'm giving your Gameboy 3 to 6 months to live if we don't operate STAT. That thing is about 3,000 years old in computer years. I think my toilet has more processing power. WHAT A TIME TO BE ALIVE.

Crack that Gameboy open using your tri wing screwdriver, and pull out the big white ribbon cable so you're left with two halves of a Gameboy. Set aside the screen half, we aren't even going to think about touching that.

Next, you're going to pop out the removable battery terminals. Leave the ones that are attached to the PCB, unless you really feel like wasting more time on this. There are little tabs on the terminals that you have to push in in order for them to release them from the case. Use a small flat head screwdriver to push them in. You'll figure it out. You're smart.

Step 2: Isolate the DJ Jack From the Main PCB

You're about to learn more about the Gameboy DMG than you ever wanted to know- which I assume is nothing... Other than how to pop in Dr. Mario and turn it on. BTW, I will beat you at Dr. Mario. You're terrible at it. Even if you didn't stink at Dr. Mario I would still whip you. I AM A DR MARIO GOD.

Ok, on to the surgery. There is a diode near the DJ jack on the top of the board. In the photo here, I've lifted the positive end and left the other leg in place in case I want to undo this stupid mod. This will make it more easily reversible. You can take the whole thing if you want, or if you don't care at all you could just cut the trace on the bottom of the board here to achieve the same effect.

This makes sure the Gameboy never tries to power itself from the wall and the battery at the same time. It shouldn't normally happen, but if you plug in your plug just right you could do some damage. Best to avoid that on your already-dying game machine.

Step 3: Set Gameboy to Permanent Battery Mode

Next, you're going to have to trick the Gameboy into thinking it's always in battery power source mode. That is how this mod works, ya dingus. It's always running off power through the powerboost via the battery contacts. The DC jack is just for charging your LiPo now. I guess the powerboost has passthrough too, so if you don't have battery, you can still get power from the wall power brick through the powerboost.

Anycrap, there is a switch under the DC jack that gets tripped when you plug in a jack. The switch says, Hey! Let's use WALL POWER. We don't want that to happen anymore. Solder a jumper wire between pins 3 and 4 under the DC jack to accomplish this. Check out my nasty soldering job in the photo. It might help your brain picture this, or it might disgust you.

Step 4: Confession Time and the Power(NO)boost

I have to admit... as I was farting around with this mod, I fried the boosting circuit on my powerboost 1000c. I thought all was lost, but, LO, the charging circuit still works. The serendipitous thing is that the Gameboy can run off the paltry 3.7-4.2v that my LiPo battery was giving out, so I don't even need the boosting circuit! The Gameboy operates on 5v, so it has the voltage boosting inside itself already, making the powerboost "booster" kind of redundant, but whatever, we're doing this.

WHEN YOU PREP YOUR WIRES, MAKE SURE YOU LEAVE ENOUGH LENGTH OF WIRE. The powerboost is going to sit in the battery compartment underneath the battery. You will thread your wire through hole near the positive battery terminal and into the innards of the Gameboy. You should leave enough wire to reach the top of the Gameboy from the powerboost. You can trim as needed from there.

For my 1000c, I wired the EN pin to GND because I ruined the boosting circuit anyway. I just wanted to make sure it was all the way off.

**NOTE** There is an error in the powerboost 1000c photo. The BAT wire should be on the Vs (or Vsh) pin. Nothing should be on the BAT pin. The Vs (or Vsh) pin provides power from the wall if the battery is not in, otherwise it provides power from the battery. The BAT pin is the battery input. You don't want that. I am dumb for doing that. Sorry.

For the 500c, you will want to solder wires to the USB, GND, EN, GND, 5V, and GND pins. I didn't jump EN to GND on this board because I'm going to show you how to use the boost feature in this mod with that one since I haven't destroyed it yet.

Step 5: Almost There... Wiring Up the Gameboy

Now that your soldering iron is hot, it's time to hook up the powerboost to the Gameboy's PCB and finish the job. You're hungry and it's almost nap time, so make sure to work quickly and recklessly so you're done sooner.

If you're not utilizing the boosting circuit on your powerboost, solder as follows:

USB from the powerboost to pin 2 beneath the DC jack
GND from the powerboost to pin 1 beneath the DC jack
Vsh from the powerboost to the (+) battery terminal (the one without the spring if you somehow haven't figured this out yet)
GND from the powerboost to the (-) battery terminal (obviously the one with the spring).
EN on the powerboost to any GND point on the powerboost (disables the boosting circuit)

If you want to use the boosting circuit on your powerboost do the following:

Cut the trace at the switch in the above photo. The reason for this is that when you turn your Gameboy off under normal circumstances, the switch isolates the battery circuit so they don't discharge while your Gameboy is off. Well, guess what, the EN pin on the powerboost is going to do this job now. Get lost, old Gameboy circuit, you're no longer needed around here.

*** NOTE: WHEN YOU CUT THAT TRACE, MAKE SURE YOU DO SO THOROUGHLY OR YOUR POWERBOOST WON'T OUTPUT THE BOOSTED CURRENT. PEOPLE, I CAN'T STRESS THIS ENOUGH. If you have a multimeter, hook up the battery, turn the Gameboy OFF and make sure there's no current flowing through the two pins on the OFF side of the switch. (The two pins to the left of my screwdriver in the photo).

Make sure that battery is not in the Gameboy and now you may solder your final solderings.

EN pin from the powerboost to the solder joint to the left of my screwdriver in the photo
GND pin from the powerboost to the solder join just to the left of THAT pin

Step 6: YOU ARE DONE ENJOY

Time to pop in your battery. I find that if I put the powerboost with the topside down I can easily fit the battery on top of it with room to spare in the battery compartment. Figure it out. You made it this far. Congrats.

If your Gameboy is off and the battery is plugged in, the blue LED should NOT be lit up on your powerboost. If it is, that means you are boosting power for no reason. You are wasting your battery, dumdum. Go back and follow my instructions again. This time PAY ATTENTION.

Plug in your wall charger- does the yellow LED on your power bust turn on? Good, that means you wired the charging circuit correctly. You get an A for this part. If the green LED is on instead, it means your battery is at FULL POWER! This is just as well. Bonus points for you.

Now, unplug your wall charger and turn the Gameboy on under LiPo BATTERY POWER (tm). The blue LED should turn on (ONLY if you utilized the boosting circuit in your mod).

And.. OH, look at that! IT"S TETRIS. Oh, OH OH. Look again, is that a WORLD RECORD?! I'm a state champ Tetris player. True story. You can ask anyone.