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Simple Game Boy Advance micro USB / USB-C Li-ion battery power supply aka the “CheapJuice”

Don’t be mistaken, the CleanJuice v1.1 or Retro Modding Rechargeable Battery Pack Game Boy Advance USB-C power supply are well-thought-out solutions. They’re almost “drop-in”, need minimal modifications to the GBA and keep the battery compartment intact so you can still use AAs. But they’re also relatively expensive, especially if you don’t live in the US. Just the PCB + battery and compartment lid for the CleanJuice would have cost me >50€ incl. shipping and taxes. Aaaand shipping takes time.
My GBAs shell already had some holes from previous mods, so I decided to build the “redneck” variant of the CleanJuice myself from stuff I had at hand. It is simple to make, cheap and works together with the GBA battery indicator. What you’ll need:

  • TP4056 Li-ion charger (I used the micro USB variant of this one, but there are many USB-C versions too. ~2€ in single quantities + shipping)
  • Li-ion battery (Make sure it fits the cut-out battery compartment and has an over-discharge protection circuit! I used this 1000mAh model. ~6€ + shipping).
  • 1N4001 diode (scrap box, couple of cents)
  • 2 pin power connector and wires (scrap box, couple of cents)

Open the GBA and remove the battery connectors soldered to the PCB. This needs a soldering iron with some power and some patience.

Solder the 1N4001 diode to the OUT+ connector of the charger module and connect that to the PCB where the positive side of the battery connector was (BT+). GND / OUT- goes to negative side of the battery connector (BT-).

Circuit diagram of the power supply

The diode has a forward voltage of ~0.7V. So when the battery is fully charged 4.2V – 0.7V = ~3.5V will reach the GBA. The GBA will shut itself down at about ~1.9V, meaning ~2.6V battery voltage, which would be a bit too low for the battery (a minimum of 3V or even higher would be recommended, depending on your battery). This is why you should buy a battery with over-discharge protection, which will cut the power at the specific minimum voltage for your battery. Mine cuts power at around 3.2V.

My GBAs (backlit screen, full volume) power draw is ~100 (regular game) to 200mA (demanding graphics demo on flash cart), so the diode will sink max. 0.7V * 0.2A = ~0,14W, which is about ~15-20% of the battery power going to waste. Any other switched DC-DC converter will probably work more efficiently.

I removed the battery compartment almost completely, making sure to provide enough space for the battery, charger module and the connector.

Most of the battery compartment is gone

You need to cut or file an opening into the battery compartment lid for the USB socket to stick through (or you can also get a ready-made lid that has an opening for an USB-C connector if you’re going for that nice look). I also drilled a hole into the lid where the status LEDs of the charger are and sealed it with some hot glue. This way the LEDs can be seen through the lid.

Notch in lid USB socket and status LED hole sealed with hot glue

Pro-Tip: Put some flat, polished metal (old cutter knife blade etc.) below the hole, press the lid onto it, then gently pump hot glue into the hole, put some more on top and let it cool off. When the hot glue has completely cooled off, remove the metal part. You will be left with a perfectly flat “window”.

TP4056 charger glued in with JB weld
Lid glued to battery compartment with plastic glue
Battery connected and attached to compartment with a bit of hot glue
Charger LED visible through lid (red – charging, blue – done)
Game Boy Advance running again \o/ (low power LED on)

So, does it work?! Let’s see… Power lasts for ~7 hours with a flash cart and the ST-Sound Advance demo playing chiptunes – That’s plenty. It has no problem running the most demanding graphics demos from my flash cart – Check. The low battery battery indicator lights up ~10 minutes before the GBA shuts down – Should be enough. A full charge takes ~70 minutes.

I’d call the “CheapJuice” a success. It is a bit rough ’round the edges, but was definitely fun to build and cheaper and faster that just ordering a CleanJuice, (though I do agree their solution is pretty slick).


Published by HorstBaerbel

Software developer by trade and interest, but I venture into the electronics- and diy-world from time to time.

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