Fixing laptop battery packs

I'm pissed off with buying new packs for 25 quid or whatever and then findi ng they're soon bricked by the PSU sensing circuitry just because one indiv idual cell has gone down below a certain threshold. I'd like to use a Dremm ell to whip a pack open and just replace the faulty cell in question; save a fortune. Anyone done this? Comments?
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Dunno what's inside them - ie if you can buy spare cells. However, a decent make should also have a decent life.
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On Thu, 1 Aug 2013 15:46:42 -0700 (PDT), snipped-for-privacy@virgin.net wrote:

Some smart protection chips in the packs will lock out the pack if the voltage at the chip ever drops to zero, i.e. you just replace a cell. This because Li packs can burn happily and energetically, and the chips are designed to prevent the repair you have in mind, for liability and safety reasons. If you want to this anyway, you may need to attach the chip to external voltage source while you replace the cell.
Thomas Prufer
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On Thursday 01 August 2013 23:46 snipped-for-privacy@virgin.net wrote in uk.d-i-y:

Li-Ion batteries are not safe to fix in this manner due to the risk of self ignition if they are not treated correctly.
Believe me, you do not want burning lithium in your home or car.
So no.
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Or aircraft ... :o)
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On Thu, 1 Aug 2013 15:46:42 -0700 (PDT), snipped-for-privacy@virgin.net wrote:

Ignore the pee-whinging nay-sayers - it's not that difficult.
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On 02/08/13 09:43, Grimly Curmudgeon wrote:

its not hard for nickel but its a mugs game for lithium
The answer is not to buy 25 quid packs in the first place. Pay for ones that have matched cells in them
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On 02/08/2013 09:43, Grimly Curmudgeon wrote:

£25 sounds far too cheap to be a decent laptop battery pack.

And your household insurer will laugh all the way to the bank when they find the cause of ignition as a bodged Lithium-ion battery repair.
The safety circuit is there for a reason. Li-ion cells tend to self immolate at the slightest provocation as Boeing and Sony will testify. Defeat the safety interlocks and it will work for a while until it eventually catches fire spectacularly and then all bets are off.
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On Fri, 02 Aug 2013 13:39:32 +0100, Martin Brown

Cheap and nasty lithium cells treated badly are dodgy things, but avoid the cheap shit, weed out the old ones and select decent brands with plenty of life in them after doing some discharge tests and just use the damned things with some care.
They're not a technology for numpties, sure; but be aware of the pitfalls and enjoy them for what they are - a really cheap source of useful portable power.
Here. http://budgetlightforum.com/forum/batteries/rechargeable
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Well some are thin film batteries. These tend to be the ones that catch fire. The reason the sensing circuit stops the charging is that a dodgy cell can catch fire, and the heat can cause a chain reaction making the whole lot explode. I'm sure you have seen the many pieces of security camera footage of this happening at airports and the like. Mostly, I have to say in Sony machines, unless the purveyors of such videos have it in for them. The person who told me about all this also says it was aired recently in Terror in the Skies about the investigation into the battery issues in the Boing Dream liner.
Now if some batteries do contain the cells you suppose to be there then maybe its possible, but the whole point of matching cells in Lithium batteries is to avoid one or more cells getting too hot at charge time, so be very careful I don't think laptops have built in fire extinguishers. Brian
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Fire extingushers don't work on Lithium batteries. They are basically fireworks - all the chemicals for the reaction are contained inside, and starving of oxygen, or spraying with water, or spraying with fire inhibitor will have no effect at all. You just have to wait until it's burned out, and try and stop it igniting anything else (for which a fire extinguisher might be useful if you didn't waste it all on the battery).
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On Thursday, 1 August 2013 23:46:42 UTC+1, snipped-for-privacy@virgin.net wrote:

ding they're soon bricked by the PSU sensing circuitry just because one ind ividual cell has gone down below a certain threshold. I'd like to use a Dre mmell to whip a pack open and just replace the faulty cell in question; sav e a fortune.

I'm not sure which packs your buying but perhaps the cheaper ones are rubis h so you have to buy more. (reminds me of some of those pound shop AAs) Alt hough I know more people with Apple laptops I see more people buying batter iies for their PC latops more regualry. In fact most Apple users I know of the batteries last at least 3 years. I've opened up an Apple battery and looking at the cells they were quite ex pensive to replace the high capacity ones with the same, but easy to get 's imialar' from hong kong, decide it wasn't worth the efffort. So brought ba n Apple spec from hong kong for £50, 2 1/2 years later it's still working OK.
So my main point is you get what you pay for.
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On 02/08/2013 11:04, whisky-dave wrote:

That's how long it is before they chuck the machine. The batteries have only been at 25% capacity for half that time. they don't buy new ones because they can't get the glue off the one that's glued inside the machine.
People buy new batteries for their PCs so they can have a spare, you can swap them when they are going flat on most PCs. I have three for mine and they all still work after 4-5 years.
I've

Or not as the case may be.
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On Friday, 2 August 2013 12:44:56 UTC+1, dennis@home wrote:

really.

This is the one I was referring to.
http://www.ifixit.com/Device/PowerBook_G4_Aluminum_15%22_1.67_GHz
A replaceable battery, this is the second one this computer has had.
New in 2005/6, my friend brought this in 2010 as the original user said the battery didn;t last and wanted to upgrade anyway. he usues it on a baot so charges it quite often.

Something which happens less with Apples because Apple batteries seem to ei ther have higher capacity or the computer uses less power. As an example on another friend thinkpaid which is 5 years younger I can he ar the bfan and feel teh temerature rise as the laptop is in use, thi9s doe sn;t happen to the same extent with my friend Apple labtop.
> I have three for mine

Still work yes so did my friend Powerbok battery but 30-45mins he didn;t c onsoider that to be still working as he wanted. I have a friend with a PC l abtop from 2008 it'sa thinkpad of some discription and that won;t last 10mi ns without been plugged in but as he always uses it pluged in it's not a pr oblem buit it still works doesn;t it.

exactly, maybe I could wire up one of those 50 blister packs of coin cell battries from the pound shop. That's over 150V of battery power .. bargin ; -) Actually last week I brought 100 CR2032s that's 300V H&S were informed :)
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On 01/08/2013 23:46, snipped-for-privacy@virgin.net wrote:

finding they're soon bricked by the PSU sensing circuitry just because one individual cell has gone down below a certain threshold. I'd like to use a Dremmell to whip a pack open and just replace the faulty cell in question; save a fortune.

Recent thread in uk.comp.homebuilt on hacking the battery's EEPROM
https://groups.google.com/d/msg/uk.comp.homebuilt/_2h04wG3rHs/ZC3apFFYkfEJ
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If you are having short battery life, are you sure it's not the laptop charger which is to blame? My Acer knackers batteries if they're left on charge. If you remove the battery when it's not needed they last much better.
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On 02/08/13 11:36, Dave Plowman (News) wrote:

+1
Ideal long term state for cells is half charge, for lithium.
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On Frid

Switching to "best battery life" in control panel might stop it overcharging. Seems to on Sony's. However then the CPU runs slow if the mains isn't plugged in.
rusty
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On Sun, 4 Aug 2013 02:08:03 -0700 (PDT), therustyone

I would take "best battery life" to mean "longest working time per charge" not "longest working life of the battery". The setting probably has the effect of minimising the current taken by the laptop.
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