Few months ago my Dell laptop battery did not work.Whenever I unplug it from main AC supply,the laptop switched off immediately.After few days of frustration, I replaced the battery and kept the dead one (as per my laptop message) for tinkering.I was curious what I would find inside it.Then I go through several blogs and forum to get some ideas.I got lot of things from http://www.candlepowerforums.com/.
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Then I took apart the battery and charged them by using a good charger.By luck I found 4 batteries are in good condition. I used this battery to make a descent power bank.It really works fine for me.I thought I'd share the info to all.So that any one reuse it without throwing it in to the dust bin.
In this tutorial I will show you, how to harvest the 18650 battery from any of the old laptop battery pack you might have. Most of the time, laptop battery packs go bad when just one or few cells in the pack are dead. The protection circuit in the charging board cuts out the entire pack as a necessary protective measure for the user. There are still a few good cells though.At last I will show you how you can make a power bank by reusing these salvaged batteries.
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Disclaimer: Please note that you are taking apart battery packs in this tutorial which is expressly discouraged by the manufacturer as this is potentially a very hazardous process. I cannot be held responsible for any loss of property, damage, or loss of life if it comes to that. This tutorial was written for those who have knowledge on rechargeable lithium ion technology.Please do not attempt this if you are novice. Stay Safe.
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Step 1: Gather the Tools and Parts
Old Laptop Battery:
If you do not have,you can ask to your friend or relatives.
You can also find it from any computer repairing stores.
Power Bank Case:
You can buy it from eBay.
You needs only few basic tools for disassemble the battery pack
Safety Equipments :
Step 2: Open the Battery
First identify the weak spot somewhere along the seams, and pry until the pack pops open.I carefully insert a screwdriver blade and twist to separate. Some packs pop right open, some (like this one) take a little more effort. Because the packs are usually ultrasonic welded along the seams, with added double sided tape.
If having trouble finding a weak spot along the seams, use a dremel saw or cutting disk to cut through an angle - not along the seams, or you risk damaging cells. Be careful during doing this process.
Safety: When doing anything with bare li ion cells, it's wise to have a fireproof container nearby, along with a bucket of sand. If a cell starts heating up and/or smoking, quickly throw it in the container and dump the sand on it. Sand is the only reliable way of dealing with a lithium fire; water and most fire extinguishers won't do squat.
Step 3: Pull the Cells
Pull the cell assembly out of the pack.
They are normally held in by double sided tape or connected using metal tabs.
Safety : Be very careful when removing the cell assembly. Try not to bend the tabs as they could meet and short, resulting in a fire or explosion.
Step 4: Separate the Charging Circuit
Then carefully cut the tabs/ wires that are connected to the charging circuit and between the cells using a Wire Cutter.After separating the chairing board I kept it for future tinkering.
Safety: Avoid contacting two separate metal tabs if you are unsure about polarity.
Step 5: Separate the Cells
I found 6 18650 Li Ion batteries manufactured by Samsung.The capacity was 2200mAh.
The two batteries are wired in parallel, and 3 parallel packs are connected in series for the desired voltage and mAh.
Then separate the individual cells.
First twist each parallel group and separate them by using a cutter.
Step 6: Remove the Tabs
Twist the solder tabs off by using a nose pliers.If you want to build a pack with the harvested cells, you might want to keep the tabs instead of twisting them off, as it makes soldering a lot easier and safer.
After the tabs are pulled off, gently dremel the weld points until the surface is flat.
Keep all the removed tabs and taps inside a tray.Then dispose it in a safe place.
Safety: Be very careful when separating the individual batteries. The welded tabs are extremely sharp, especially when they are cut or torn.I wounded my finger during this process.
Step 7: Identify the Good Cells
1. Measure cell voltage. if it's less than 2.5v, throw it away.
2. Charge the cell. if it gets hot during charging, throw it away.
3. Measure cell voltage off the charger. verify it's between 4.1 and 4.2v.
4. Wait for 30 minutes
5. Measure cell voltage. if it's fallen less than 4v, throw it away. Otherwise record the voltage.
6. Store cell for 3+ days in cool, dry place.
7. Measure cell voltage. if cell voltage has fallen more than 0.1v from the recorded voltage, throw it away.
Any cell that hasn't been thrown away by doing the above test is considered to be good one.
I kept all the good cells inside the 18650 battery storage box.
Step 8: Make the Power Bank
Buy a Power Bank USB 18650 Battery Charger Case.
I bought the Power Bank casing and charging board from eBay.
Insert the battery inside the slot provided in the case.
The positive terminal of the battery should be towards the charging board.Sometimes polarity is marked inside the case.
Safety: Be sure you are inserting the battery with right polarity( if the charging board do not have reverse polarity protection).I did the mistake and fried my charging board instantly.
Then put it for charging by using the USB cable provided in the packet.
Attach the key chain with the case.
Finally the power bank is ready for use.
Step 9: Test the Power Bank
After charging I test the USB output voltage by using my CHARGER Doctor.
The output voltage is 5.06V which is good for smart phones,Tablet or any other gadgets.
Then used my another battery capacity tester to check the capacity.
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