This project came about because my old NiMh Xbox360 pack with its unfeasibly large claims of battery capacity stopped working entirely. It never lasted more than a couple of hours to start with, and I thought it might be time to upgrade it to Lithium.
As most gadgets ship with lithium batteries nowadays, it's fair to say most electronics tinkerers have a few laying around from dismantled items that had failed too spectacularly to be repaired.
- Lithium batteries can be highly dangerous and cause fires if pierced, short-circuited, overcharged, overdischarged, overheated or abused in any way.
- Triple check any wiring before connecting the battery.
- Please ensure that you understand and accept the risks before attempting this project, as I cannot take any liability for mistakes made if you choose to follow this guide.
To perform the upgrade, the parts you will need:
- A lithium charger IC.
- A SOT-23 breakout board to mount your charger IC on.
- Assorted wires.
- A silicon diode with at least 1A rating, such as 1N4001.
- A 2k2 0805 surface mount resistor, more about this later.
- 2x 0805 1uF surface mount capacitors (not essential but recommended).
- A lithium cell that will fit inside your battery pack, with room to spare.
- Some EVA foam or similar to ensure the new battery is a snug fit.
- A soldering iron with a fine tip and temperature control.
- Precision tweezers.
- Hot glue gun
- A spudger - ideally the metal kind. You may get away with a small flat screwdriver if you're careful.
- Optional Safety Pie Dish (thank bigclivedotcom for the idea) to throw any hazardous/burning bits in a hurry.
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Step 1: Open the Case & Assess the Innards
If you have the same model of battery pack as me, you'll find that there is a thin line of glue around the edge. Gently pry the top housing open from the bottom, you'll need to do this all the way around both sides and you will hear it 'click' as the glue gives way. The top should separate easily once all the glue has been sheared.
Unfortunately with my battery pack the cells had leaked so the corrosion must be cleaned off the contacts. Submerge them in cheap diet cola overnight - the phosphoric acid should remove any traces of corrosion. Weak hydrochloric acid would do a similar thing if you have it.
The charger circuit for the NiMh cells was nothing more than a diode and a resistor, with nothing to prevent overcharging! In addition, there was a 3mm LED with resistor - you can save this for later or change the LED to a different colour if you feel like it.
Step 2: Desolder the Needed Parts
You will need to retain the LED, small resistor and the DC jack, being careful to remember/write down which of the pins on the connector is positive (hint: the middle pin is almost always positive).
Additionally if you don't have a new diode to hand, you may use the one in the package provided that you check it with a multimeter on the diode setting and it has a drop of at least 0.6V.
Dispose of the old dead NiMh cells preferably at a recycling point.
Step 3: Find a Suitable Battery
I went through my collection of lithium batteries before settling on a 500mAh 902030 cell.
A little about lithium cell sizes / part numbers for those that aren't familiar:
- The first two digits are the depth, in 0.1mm steps, so mine was 9mm thick.
- The second pair of digits are the width in 1mm steps, so mine was 20mm wide.
- The third pair of digits are the length, so mine was 30mm long.
It's important that you choose a cell with a protection circuit on, this should go some way to protecting the cell (+your house, +your fingers) if you manage to short circuit this during the build. A small narrow PCB next to where the wires come out indicate that it has protection.
Step 4: Modify the Case to Fit the Battery
As the original used 2 AA cells, and the new battery is rectangular it's necessary to trim out some of the central separator. After trimming with both a knife and nibbling away at it with wire cutters, I was still left with a raised section. As the height of my battery was much less than the case, it wasn't really an issue - a few simple pieces of EVA foam were enough to ensure the battery sits flat.
Step 5: Solder the Battery Charger IC
The battery charger should be fitted securely and inspected (tip: smartphone cameras make excellent magnifying glasses to inspect your solder joints).
I won't go into SMD soldering here, but observe all the usual stuff such as tip temperature below 350C and plenty of flux. Give it all a clean with some IPA afterwards to keep it shiny.
Step 6: Work Out Your Charging Rate
Depending on what charger chip and battery you've chosen, you'll now need to set the charge current. Most of the generic 5 pin Chinese parts (ME4064A, HX6001, TP4065, XT4054, LTH7, XC5071... many more, just go through the PMIC - Battery Management section on LCSC.com and search for 5 pin devices), seem to have the same setting method. I'll demonstrate the method I used with my ME4064A but please ensure your IC is compatible.
First of all you'll need your battery capacity. I chose a 500mA battery, and it's good practice to ensure that the charge current does not exceed the capacity (known as charging at 1C).
To set the charger current, you connect a resistor between the Prog pin and ground.The ME4064A datasheet states the formula to work out the charge current (Ibat) is:
(1 / Rprog) * 1100
Let's try 3k3: (1/3300) * 1100 = 0.333A, too low.
Try again with 2k2: (1/2200) * 1100 = 0.5A, perfect so we just need a 2k2 resistor.,
Step 7: Solder the PCB
Attach the cathode of your diode to the positive contact, and a black wire to the negative contact. Make sure you don't solder this too close to the edge, as it needs to fit comfortably into the housing.
Connect the opposite end of this black wire to the negative pin of the DC jack, keeping the existing wire in place (this will go to your PCB).
On the PCB fit the 2k2 0805 package resistor from PROG to the unused pin, and the 1uF 0805 capacitor from VCC to the unused pin also (we will later connect this unused pin to ground). The other 1uF capacitor fit between the BAT pin and ground as shown in the image above.
Fit the ground link for the two centre pins on the opposite side of the board.
Fit your LED on two short leads to the VCC and CHRG pins (note that the cathode/black wire of your LED goes to the CHRG pin).
Step 8: Fit & Glue Battery Contacts
You may need to remove the foam padding whilst you slot the contacts back in the end of the battery pack.
Check they're well aligned and glue both sides of them with hot glue to ensure that when the spring contacts in the controller press against them, they can't come loose.
Push your DC jack back into the three guide ribs. No need to glue this as the lid will keep it in place.
Step 9: Wiring and Test
Attach the VCC to the red wire of the DC jack, attach the ground black wire from the DC jack to the ground wire you soldered on the underside of the board.
Solder the battery+ to the BAT pin, and the battery- to the ground pin on the PCB. Also solder the anode of your diode to a short length of red wire, and connect this to the BAT pin.
Check your connections a couple more times, and plug in the DC Jack to check everything is working. All being well you'll get a green charging light, and around 500mA current drawn (less if your battery is almost full). Use a meter to ensure you have around 3.5V on the output (4.2V battery, with 0.7V diode voltage drop).
Step 10: Pack Out and Reassemble
Cut some more EVA foam blocks to ensure that the battery and circuit stays in place.
Fit the spring release mechanism back into the housing.
Clip the lid back on, ensuring the LED and DC jack line up correctly with the holes. Now you should test in your XBOX remote before applying glue to seal the housing.
Step 11: FAQs
- Q.Why did you only use a 500mA battery? A. The next size up I had was 1500mA, which would not fit.
- Q.Why is the diode needed? A. The XBOX remote is expecting to see a voltage between 2.2V and 3.5V. A fully charged lithium battery is 4.2V which could potentially damage your remote. The diode was used to drop the voltage to a safe level.
- Q.How long will it take to charge? Using the setup I had, it will start to charge at 500mA from empty then taper off as the battery is nearly full. I would expect around an hour and a half to two hours. You'll know it's complete because the light will go out.
If you have any further questions I haven't covered feel free to post a comment.
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