View Full Version : Lithium-ion laptop battery packs

16th Jan 2015, 10:42
I'm starting this thread to relay my concerns over Lithium-ion laptop batteries and the poor quality that I've recently encountered.

Essentially I am appalled at how easily they can be short circuited.

My trusty EEEPC laptop's batteries have effectively become useless over time so I thought I'd just refit new ones into the old battery pack. With a dremel tool I cut open the pack and removed 4 dead Li-Ion batteries. I purchased 4 new ones but they were a few millimeters oversize because they incorporated a protection circuit at one end. In my quest to remove the protection circuit from one of the batteries I accidentally short circuited it and got a huge flash out of it. Looking closer as to why this happened I noticed they ran a foil wire down one side from the anode which was only insulated from the cathode by simple cello tape, and it wasn't even straight!!! This battery was so close to causing a fire from poor insulation. I checked the other 3 batteries and they were much the same - the cello tape was crooked and if squeezing the battery in the right spot I'm sure over time it will eventually short itself.

Unfortunately, and after addressing the above issue, although my testing of these replacements was fruitful I inadvertantly managed to kill the battery pack's battery controller. So I was left with 4 new spare batteries.

What to do? I grabbed the spare laptop the one that I hate using (Win 7) and did the same with the dremel tool to open up its battery case. As I was pulling out the batteries the thing shorted itself and I saw smoke coming out of the controller. I noticed that it was the cello tape again but this time it was used on the batter controller between the cells and again was poorly applied.

As for these laptops it doesn't really matter as they were very old anyway, but the concern of using poorly applied cello tape as insulation to an energy source rated at 4 to 6 x 2200mh has me extremely concerned.

My EEEPC is beautifully manufactured and I can easily pull it to bits and put it back together again, in fact there are may How-to's on modding these laptops. But it remains appalling to see that the quality of Lithium Ion batteries and their battery packs are not to the same standard.

16th Jan 2015, 11:07
So in summary you broke open a battery pack contrary to the warnings that you should not do this and you short circuited the batteries causing a potentail hazard as well as screwing up your battery controller.

Hmmmm ... maybe the warnings are there for a purpose.

16th Jan 2015, 11:23
The protection circuit is on the negative terminal. The insulation has to be good for 3.7V, say 5V. The conductor has to be rated for 5-10 uA. Add your desired safety margin. It's never going to be seen/touched by anything in normal and most abnormal use. If the conductor DOES touch the case because someone is diddling with the cell, the PTC/CID under the positive terminal will physically rupture, if the conductor hasn't melted by then, to isolate the positive terminal from the cell.

16th Jan 2015, 12:00
... but maybe he runs a local repair shop. Not mine I hope.

Solid Rust Twotter
16th Jan 2015, 12:18
Have shed, will tinker...

Where's the problem?

16th Jan 2015, 12:26
The EEEPC I purchased in 2008 for $300, batteries long since dead but the laptop still remains good for its original purpose - the web. I'm using it now minus battery pack to write this post.

The Dell Inspiron 1420 I purchased second hand for $50 from an exec who barely used it. Besides the dead batteries it's still as new but it is a really crappy design.

Both these units could have been brought back to their former selves but the battery and battery pack design let me down.

It's no skin off my nose as I have already committed to buying a replacement a few weeks ago, just gives ye the shytes that house brand cello tape is being used as an insulator. Who would have thought.

16th Jan 2015, 12:37
house brand cello tapeAre you sure? I'd be prepared to bet it was something a little better than that. Lots of different tapes look very similar.

And as others have said, the insulation and the rest of the assembly were perfectly safe throughout its long life, and only failed when you ignored the safety instructions. Did you feel Mr Darwin looking over your shoulder?

16th Jan 2015, 12:56
"Did you feel Mr Darwin looking over your shoulder?"

Let us hope that Mr. Darwin would be standing well back. And wearing safety goggles.

16th Jan 2015, 13:13
There but for the grace of God go I. :ok:

16th Jan 2015, 13:48
With most tablets you can't even change the batteries, at least without major surgery and voiding the warranty.

16th Jan 2015, 14:16
And why would you want to stuff around with a laptop battery pack anyway?
They're cheap enough via Fleabay.

16th Jan 2015, 14:31
henry crun wrote:

Lollipop next time.

next time? My Google tablet - 2013 - just updated itself to Lollipop last night!

16th Jan 2015, 20:52
When I was flying cargo aircraft we had to watch this video on our annual refresher. Only bother to watch the first 1.30 as that's the only bit that's relative to this thread.


17th Jan 2015, 11:50
Yep, it definitely is common household cello tape.

Wasn't there a spate of laptop batteries catching fire a few years ago? Maybe the new gear is better because they have stopped asking me at the airport check-in if I have a laptop in my luggage, maybe the question they should be asking now is if I have an *old* laptop in my luggage.