Li-On Cells from Laptop Battery Packs

Thread Starter

PCBoy

Joined Dec 14, 2011
26
I was wondering, could I use the cells inside battery packs as normal AA batteries?

I got an old battery pack here that doesn't hold much charge anymore and was thinking of opening it up and check if some of the cells still work and use them for my digital camera.
 

Adjuster

Joined Dec 26, 2010
2,148
Please do not open up an old battery. Lithium batteries can be dangerous if used other than intended by their maker, and even trying to take the battery apart can be dangerous.

If the battery blew up in your face, you could lose your sight, or worse. The risk is not worth it to salvage a few cells which are probably nearly useless anyhow.
 

JMac3108

Joined Aug 16, 2010
348
I can't overstate how dangerous it is to try to open up a LiIon battery pack. Lithium is volatile when exposed to air. If you were to nick or cut into a cell in some way when opening the pack, it will go up in flames.
 

R!f@@

Joined Apr 2, 2009
9,734
Does lithium really explodes ?

Cause I am making thingamabob to break open a lappy battery really soon.
 
Last edited:

bertus

Joined Apr 5, 2008
20,773
Hello,

Lithium is not to play with.

Lithium will ignite and burn in oxygen when exposed to water or water vapors.
Lithium is inflammable, and it is potentially explosive when exposed to air and especially to water, though less so than the other alkali metals.
The lithium-water reaction at normal temperatures is brisk but not violent, the hydrogen produced will not ignite on its own.
As with all alkali metals, lithium fires are difficult to extinguish, requiring dry powder fire extinguishers, specifically Class D type (see Types of extinguishing agents).
Lithium is the only metal which reacts with nitrogen under normal conditions.
This is from this wiki article:
http://en.wikipedia.org/wiki/Lithium

Bertus
 

tom66

Joined May 9, 2009
2,595
Yes, lithium ion and polymer types are -extremely- dangerous.

I have accidentally punctured a Li-Po. The reaction rapidly put the battery in flames, spewing molten lithium all around it. Luckily I was outside, and I had a bucket of water nearby. The water smothered the battery and stopped the reaction but it was still rapidly bubbling for several minutes afterwards. These batteries store a -huge- amount of energy and are NOT to be messed with.
 

CraigHB

Joined Aug 12, 2011
127
Barring all the hazards of Li-Ion cells already mentioned, you can NOT use them as replacements for AA batteries.

Laptop packs commonly use 18650 round cells which are 18mm x 65mm compared to the 14mm x 50mm of an AA battery.

Alkaline cells are nominal 1.5V where the Li-Ion cells used in a laptop battery are nominally 3.7V.

Li-Ion cells require a charging profile that's totally different from something like an AA NiMH or NiCad rechargeable cell. You need a Li-Ion charger to charge a Li-Ion cell.

If you can safely remove the cells (don't cut or puncture them), you can use them if you add the necessary protection. They need to be protected from over-current, over-discharge, and over-charge. Charging or over-current faults can result in thermal runaway which causes the cell to go up in flames spewing super-heated electrolyte. Over-discharge (draining a cell below a threshold voltage) is not dangerous, but can damage a cell irreparably.

Keep in mind that Li-Ions have shelf life as well as cycle life so even if the batteries are well within their cycle life, they may be worn out from sitting around too long. Li-Ions can drop down to less than half their original charge capacity after 300 cycles and/or 3 years, but some hold up better depending on the exact chemistry and quality.

You'd do much better to buy new round cells instead of harvesting old ones from laptop packs (you can also get flat cells). They are readily available at places like http://lighthound.com You can buy them with the necessary protection electronics built in. The laptop cells don't have any since protection is built into the laptop pack. They are not safe to use without it.
 

Audioguru

Joined Dec 20, 2007
11,249
To the Original Poster:
An alkaline battery cell is 1.6V when brand new and it quickly drops to 1.5V then to 1.1V. It slowly gets less and less.
A rechargeable Ni-Cad or Ni-MH cell is 1.4V to 1.5V when fresh out of the charger then it quickly drops to 1.2V for most of a discharge.
A rechargeable Lithium cell is 4.2V when fresh out of the charger then it slowly drops to 3V when its protection circuit disconnects its load.

See how the Lithium cells have a much higher voltage than the others?

I used the battery cells from a laptop that malfuctioned but its battery was still pretty good. I built a charger that charged each cell slowly up to 4.20V.

I powered my electric RC airplane with them. Some cells were better than others. They got pretty warm but the motor in the airplane got hotter.

I still have the cells and have not used them for 3 years. Each cell still measures 4.1V.
 

CraigHB

Joined Aug 12, 2011
127
That would be the exception, hobby applications. They use high drain LiPo (Lithium Polymer) flat cells without protection. This is the same type of cell you find in many consumer devices such as cell phones and cameras, but low drain for those applications.

You can buy LiPo cells designed to drain as much as 60C or 60 times their charge capacity. They're available within a range of maximum allowable drain rates, anywhere from 2C to 60C. You trade off charge capacity for higher drain with higher cost.

The motor controllers used in RC applications offer some protection, mainly over-discharge, but it's not practical to incorporate over-current protection. Drain rates as high as 100 Amps are not uncommon, especially for performance aircraft. It's not unusual for them to explode into flames on a severe crash if the batteries get crushed. A wiring fault can meet the same end.

Hobbyists use expensive multi-channel balancing chargers to recharge the cells. I've read stories of charging mishaps that result in flaming batteries as well. They put the batteries in a fireproof containter when charging because of that.

People who use these cells for hobby applications know the risk and take appropriate safety precautions. It's not the kind of thing you could ever expect someone to do with a consumer device. Consumer devices rely on electronic protection mechanisms.
 

tom66

Joined May 9, 2009
2,595
All of the above is completely true. I fly model aircraft and use 20C and 25C LiPolys. This is why I am highly advising Rifaa doesn't try and blow up one of these cells.
 
Did you lately notice poor performance of your notebook Li-Ion battery?. do not be balled over, this is often happening even to the most effective battery! currently days Li-Ion batteries are widely utilized in moveable devices owing to there glorious energy to weight ratio and for the rationale they're not tormented by "memory effect".
 

JMac3108

Joined Aug 16, 2010
348
Seriously .... LiIon cells are just not something a hobbyist should be playing with. Even many large companies with experienced design groups (including ones I've worked for) outsource battery pack design because they are afraid of the consequences of making a mistake with the safety and protection circuits that are required to be used with LiIon cells.

Never open a LiIon battery pack.

Never use raw LiIon cells. Only use battery packs with proper safety circuits inside.

Don't try to design a LiIon battery charger unless you are experienced and fully understand the charge profile and safety considerations.

These things will go up in flames and hurt you or someone else if not handled properly.
 
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