Great! You have a laptop. It came with a battery. That battery life now SUCKS or fails. You are looking for a cheap way of bringing it back to life. Here's how.

DISCLAIMER: Working with Lithium-Ion batteries is not for the inexperienced. Misuse of these batteries will result in fire, damage to your electronic equipment (laptop) or personal harm through direct electric shock. This instructable will do its best to inform you about hazards and avoid risk, however not every situation can be pre-planned.

What do you need:

1) A dead / dying battery that you don't really care about.

2) New Lithium-ion cells (6 if your battery is a 6 cell, 9 if a 9 cell, 8 if 8 etc.). I got 9 for $3ea from a trusted supplier.

3) Equipment

Solder and an iron (30 [Watt] or higher) or a spot welder
Things to open a glued battery case (Screwdriver, Sharp Blade etc.)
Sandpaper (80-120 grit) and strong glue
Voltmeter (digital multi meter) to test the electrical connection

Important Notes for non-Dell Laptops

Some batteries contain an electronic indicator which tracks the battery lifespan (EEPROM). This may limit the new battery cells from fully charging, and in fact provide no advantage compared to the replaced cells. Do some investigation into your laptop model to check if this is the case.

Aside: Epilog VIIContest Entry

This instructable was entered into the Epilog Contest VII which features a laser cutting system. I have a large number of Nafion membranes in the electrochemical laboratory that I work in which I would like to cut into complex shapes for testing in a proton membrane exchange fuel cell (PEMFC). More interestingly, I'm involved in creating foldable shapes such that the proton exchange can occur in a cross-plane instead of a through-plane translation. Following demonstration of this novel shape design, further integration of nanomaterials to enhance cross-plane conduction may lead to the best performance experienced in fuel cell technology, all possible by a highly accurate and adaptable membrane cutting instrument. Thanks!

Step 1: Opening Your Battery

!!! BE CAREFUL !!! Attempt to open it on a ceramic or concrete surface, and have a bucket of sand or fire-extinguisher nearby just in case. Safety Info.

Steps: (Note this part can be tricky, take your time):

1. The battery case is typically glued shut, as well as containing little interlocking plastic pieces. Use a sharp knife to cut along the edges of the battery case and work your way up around it a little. Do NOT cut deeply as that may pierce the batteries behind the case.

2. Once it is a little bit loose, the best way I found was to insert a screwdriver, and twist it such that the plastic is forced apart. I heard many 'cracking' sounds from the glue binding breaking and could see the frame coming apart.

3. Continue around the entire edge of the case until it is able to be completely opened.

4. If you can, test the electronics with the Voltmeter (DMM) to ensure that nothing was broken (the Dell battery has built in LED lights that worked as well).

Step 2: Checking the Design

Great. You got your battery out. Now you have to make sure that you can put it back together.

Steps:

1. Determine where the connections on the Battery are.

2. Create a schematic layout that contains all the important information about the battery configuration.

3. VERY IMPORTANT! Make a layout which shows the directionality of the terminals (positive and negative) for the internal components. You do not want to screw this up later or you will fry your charging circuit board.

Step 3: Removing the Old Batteries

Be careful. The electronic design is really hard to make on your own, so don't break it. NEVER cut through the protective casing on the batteries! The entire outer case is negatively charged, so it becomes much easier to short circuit if the casing is damaged.

Steps:

1. Use a sharp blade to work between the metal contact and the battery terminal. You can either 'saw' or 'twist' to cut through the spot-welded contact. Most batteries are also glued to each other, however this is a cheap glue that will readily come apart with hand strength and doesn't damage the casing.

2. This may take some time, so patience is required to do this for the contacts of each battery on both ends. If you are using a metal blade, avoid contact with other batteries as you are cutting so that you don't short-circuit (it will make sparks).

3. Once all the batteries are removed, it is likely that all your contacts are pretty mangled (bent out of shape). I used a small clamp to press them all flat again.

Step 4: Soldering in New Batteries

The heat from the soldering iron is not high enough to cause damage to the batteries, however it is still hot enough to burn you, burn the electronics, melt the plastic casing etc. Be cautious with where the tip is at all times.

NOTE: If you have access to a spot welder it would be optimal to weld the contact pads with the battery terminals. The steps below are for the average Joe with a soldering iron.

Steps:

1. I found it useful to first glue together the new batteries. I used industrial strength glue, and did it in a well-ventilated area with gloves on to avoid any skin contact.

2. Heat up your soldering iron. Start by tinning (applying a blob of solder) to all of the contacts for the positive terminals according to the battery diagram you made earlier.

3. The batteries should be well glued by now, so to make the solder stick better, use sandpaper to roughen up the positive terminals. You can optionally roughen the negative terminals as well.

4. The contact pads typically have a small hole, use this to insert the solder tip, and directly melt the pre-tinned solder so that it is in contact with the positive terminal. When it is melted, try to remove the tip while keeping pressure so that the contact between the electrical pad and the terminal is good. I did this by drawing the tip sideways from the point of contact (ie. maintaining a force keeping the pad in contact but removing the heat source so the solder hardens).

5. Repeat step 4 for all the positive terminals of the cells.

6. Make sure that any separator between electrical contacts is properly in-place.

Optional: You can solder the negative terminals as well, however I found that this would make the battery more 'bulky' lengthwise, so I ended up keeping the negative terminals solder-free and using the case-compression to have contact with all the negative pads.

Step 5: Putting It Back Together

Note: I was able to test right away (using the built in LEDs) that the batteries are electrically connected to the circuit after soldering. If your battery doesn't have this, use the DMM to make sure that a voltage differential of about 11-14 [Volts] exists between the positive and negative terminal of the electronic circuit. Don't measure current!

Steps:

1. Attempt to fit the batteries into the case.

2. Adjust, resolder, squeeze etc. as needed until the pack fits in - be careful that the electronics fits back into the exact slots it came from.

3. Snap the two-halves of the original pack back together. Apply pressure as needed, no glue required (just in case - haha what a pun).

Step 6: Charging and Testing

!! Very Important !! Charge your new battery pack on a non-flammable surface, keep an extinguisher nearby and be prepared in the event that your battery management system (BMS) was damaged and might overcharge your pack.

Steps:

1. Double check (via DMM or indicator lights) that the electronics is properly configured.

2. Plug in your battery to a laptop which can charge it. I recommend this software to monitor the battery.

3. Let the charging circuit run for 8-12 hours.

4. Disconnect your laptop power source, and completely discharge the battery.

5. Repeat steps 3-4 at least 2 times (leveling the new pack).

6. Enjoy / test your new battery.

Personal Tests: My original battery, though listed at ~3500 mWh would only give about 30 minutes of battery life before abruptly decaying from ~60% to 5%. The new battery, currently listed at 4690 mWh (not fully optimized still) was tested by running an HD video (Ice Age 4) and a youtube video (10hr video) while playing audio at full screen brightness, high performance. It ran for just over 2.5 hours before being drained (approximately a 6x improvement).

:) Hope all went well!