About: I am an Electrical Engineer. I love to harvest Solar Energy and make things by recycling old stuff. I believe, IF YOU TRY YOU MIGHT, IF YOU DON'T YOU WON'T.

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[ Solar Power Bank ]

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

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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.

Update : DIY Solar Power Bank

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.

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.

Tools :

You needs only few basic tools for disassemble the battery pack

1.Screw Driver

2.Wire cutter

3.Nose Pliers


Safety Equipments :

1. Gloves

2. Goggles

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.

Hope my tutorial is helpful.If you like it,vote for me.

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216 Discussions

is there any way to charge laptop which is required 19v dc 3.42Amp.its possible to charge laptop with boost converter.?or some other boost


Please give the battery connection diagram if i use all six batteries for power bank.

Discharged lithium batteries aren't dangerous in an of themselves with a caveat. If a Lithium battery drops below 2v don't recharge it, it can be dangerous afterward.

Basically when a battery drops below 2v it dissolves some of the metal inside, and when you re-charge it after that the dissolved metal can short inside the battery. That can make the battery dangerous (fire/explosion).

Some people find 3v a safer (e.g. use 3v in what I said above), but personnally I think thats overly cautios.

So, if I have an old laptop I haven't used for years it would be dangerous to use the batteries?

No, its still safe to harvest the "good" batteries from inside the pack; many of the individual batteries may be quick good. Once you get the individual batteries out, just toss the ones that are below the voltage previously discussed.

Reason: The whole "pack" may show dead because the circuitry in the "pack" detects a couple bad batteries it cuts off that/those sections; so a couple of bad batteries can make the "overall pack" dead. But for using the individual batteries inside in other projects, you may still have luck.

I've personally harvested a dead pack from a Sony laptop and gotten 8 good batteries from 9 originally in the pack; they were even fully charged when I pulled them out. That 9th battery just shorted in the pack and the circuit killed the entire thing.

If they have some charge and you chop into them with an axe, maybe (there's fun youtube video's about that).

If they are completely dead, no. Just don't recharge the dead ones.

how do i recognise the positive from the negative terminal

Hey, just thinking here, I have a few power backs from dollarama that should take 18650 batteries, but I've got better 18650 batteries in my battery box, so is it worth trying to rip apart the ones I've got? They only cost me $4 Canadian.

hello, i have 6 laptop battery cells, but i cant seem to find how much current they take, and im kinda scared charging more than 0.7 amps, but i saw that it's charging very slowly, like 1V in 2h. Well, basically i would like to know how much current it can handle is there any way to test it? they used to be dead, but i revived them with a DC power unit....

2 replies

If you have the casing from where you got the batteries, than you can calculate how many amps they have. Typically, they have from 2 to 2.2amp per cell. Voltage is always 3.6-3.7.

Since you revived them, there is no tell how many amps they can hold now. Maybe they can hold the same as before or less. Are you charging them with proper charger, i mean charger that was made for charging li-ion?

Yes, i have a proper charger that was made for charging li-ion, li-po, ni-cd and ni-mh batteries. it can charge up to 5 amps, and now, when im reading my comment, i thought of charging to 4.2v and discharging them to 3.7v at 1 amp and calculate how many milli amp hours it would be and then just calculate it to amps.

Looked around Ebay a bit.

Power bank case in a color other than pink: $1.02+
Supply your own battery, around 3,000 mAh.

5,600 mAh Power Bank, Complete: $0.99

I understand recycling, reusing, and all that jazz; but maybe find something else to do with your batteries?

3 replies

You mean, a complete powerbank with batteries cost less than a dollar? Good luck drawing out more than 1amp out from it, because it has fake batteries that are hollow inside and can't even go as high as 2.2amp per cell. Buy them, cut them, and see if I was wrong :)

With the above hack, you get real batteries, which would cost you around 3-4 bucks per cell, for a lot cheaper. Laptop batteries are the real deal unless you buy a counterfeit, but that one won't last long anyway.

Noname powerbank from China - good choice if you want to test your luck against fire and explosion in your own home, or test your device against fire or explosion. :) Great price for "care free" life! :)

Yeah, whatever I saw was either a typo in the price or a scam.

If he would use 2 or 3 cells and made the circuit for charging in and out by himself then it would be much more efficient.

Sir...I want to make this.Please reply can we use AA batteries to make this Power bank because 18650 batteries are very expensive....

3 replies

My problem is how do i recharge the disassembled Lion Batteries or i have to charge them indibidually with direct charger?

You can buy a charger that can take more than 1 battery to charge. Or just charge them individually