Posted on 09/04/2009 11:01:57 PM PDT by djf
OK!!!
Fun stuff.... ;-(
I have an older laptop. Actually, more than one of the same model.
Battery in one of them died - well, not quite. It would still start up the charge cycle but would only go to what it says was 30% or so no matter how long I left it on charge.
Then, if I unplugged it and let it run on battery, it would run about 5 minutes and suffer a somewhat violent shutdown.
I was able to get a few more batteries from somebody who once had a boatload of these models, but none would take a charge.
So, as any good, curious, brave, adventurous FReeper would do, I decided to find out what the H is happening with all this stuff and started taking battery packs apart.
(Note how I conveniently left off the "stupid as a mule" descriptor!)
Battery is for a Gatecom.
It is rated at 11.1 volts, 6000 maH.
Internally, it is divided into three banks of three cells each. Each "pack" is three cells wired in parallel, and the three packs are put in series.
Each of the li-ion cells appears to be nominally rated at 3.7 volts. Three times 3.7 is 11.1, so I don't think I'm too far off the mark!
Oh, BTW, there is also a PCB in there for charging, temp monitoring, etc. The PCB front ends the battery to the laptop, so there is no direct connection from the cells to the computer.
Now I spoke to a friend earlier to ask him what would be a good voltage to use to try to charge a 3.7 v li-ion, and he said about 4.25, but never to exceed 5.5 or so, so I settled on a 600ma 4.5 volt power supply I have.
I disassembled the cells off the PCB and broke down the packs to individual cells.
The GOOD news is that a few of the cells still had a residual voltage to them. When I put the power supply to them, I can tell by the small voltage drop of the power supply that the cell is actually charging.
The BAD news is that the majority of the cells had zero voltage and high resistance.
I believe I will have enough good ones to rebuild the 3-cell packs, reattach the PCB, and plug er in.
Finally, I get around to the question. Are the dead cells really dead? Or are they kinda asleep with a very high resistance? I mean if they got drained TOTALLY down, are they then trash material? If I put the 4.5 to them for a while, might they internally wake up or something?
Now for any FReepers who have never tried this kind of thing or don't own a voltmeter I can only say DO NOT TRY THIS AT HOME!!! I have SEEN li-ion cells explode, and besides for the danger of fire, there are caustic chemicals etc, that can make for a very bad hair day or do a number on your rug that you will probably have to call "modern art" after it happens!
But... just thought I'd ask!!
Call the mfr. Buy a new battery pack. I would *not* mess around with notebook PC batteries for fun.
Trust me, I’m taking precautions.
I just want to know more about the internal workings and have already figured out some kind of interesting scenarios.
Die young, stay pretty! Eh?
You can run it with a 12 volt source.
I am iffy of you charging from the same source though.
Get a new battery pack if you need too.
Problem with laptop batteries, or for that matter, most Lithium-ion batteries, is that they have complex recharging circuitry embedded within the battery housing. Don’t try to change the individual cells because they can play havoc with the control circuitry, making the latter think the former is what it was designed for, and apply currents for durations that the new one might not be able to handle. What that will result in, is a violent Lithium fire.
It’s not for no reason that we don’t commonly see lithium-ion rechargeable AA’s or AAA’s as easily as we do, the other types.
Wow! According to that, it can still have a full or near full charge, but be unable to let it out due to internal resistance!
Never thought of that one.
Thanx!
Whoa!
Li-ion batts is one of the more exotic and tempermental battery chemistries out there!
Proper charging is imporant, and they *do* were out/show signs of diminished capacity!
More/a good place to start:
http://www.batteryuniversity.com/parttwo-34.htm
I gutted the pack and used the plastic shell as an electrical connector for an external 8.4 volt 2.5 amp power supply. The supply I used was a variable voltage 13 volt unit turned down to 8.4 volts. That made the supply run so hot that it required a cooling fan blowing on the regulator.
If I want to continue using the notebook, and I have a dozen good desktop units, I will have to scrounge in my junk box and build a power supply specifically for 8.4 volt output at 2.5 amps that will run for hours or days without overheating. Everything matters - transformer, rectifiers, filter caps, regulator, heat sink, cooling fan or not, etc. It all matters a great deal.
Anyway, sometimes old technology can't be sustained without going to excessive lengths to make up for parts and accessories that are no longer available. In my case, I don't have any use whatsoever for a portable computer, so my only purpose in keeping this clunker going is just to see if I can do it, a technical challenge.
Are you applying your power supply directly to the battery(ies)? I’d be concerned 1: that you aren’t charging thru the computer’s “intelligent” circuitry which would current limit and perhaps step the voltage over time, and 2: you have no apparent provision for current limiting. That’s one potential explosion/blowup hazard...the other being too-rapid gas buildup, if that issue exists in lithium batts.
I am not an expert on charging batts. One thing I can tell you, though, is when you use lithium batts on power tools, unlike NiCads, they go from working to dead in about 15 seconds. Your drill doesn’t slow down and get weaker on torque over a few minutes; the thing goes from working to “won’t turn” in almost no time.
Exactly.
Technical challenge.
GMTA.
Detailed info on how Panasonic (battery menufacturer) says their Li-ion cells should be treated (I ran across this info awhile back while doing research):
http://www.panasonic.com/industrial/battery/oem/images/pdf/panasonic_liion_charging.pdf
A Li Ion should be replaced. I know of no way to fix one.
No, no!
To the individual cells.
And not for a very long time either.
I just want to find 9 cells that will charge to the nominal 3.7 volts each, then reassemble the whole mess.
I have one of the batteries right now (I mean the whole battery, PCB and cells and everything) on a sort of “deep discharge” cycle now connected to a 12v auto lamp. Freakin lamp has been burning bright and not dimmed at all for like 2 hours now...
Wow!
I’m thinkin’ - Duct tape!
If you take that whole mess of dead batteries, and duct tape them all over your POS computer, do a little Indian electricity dance all around the living room,
when you turn her on, she should be good to go.
But, maybe not, so in that case, take the whole mess, duct tape and all, place it in the galvanized can, and give it to the garbage man’s little boy - he’ll get ‘er working jus fine!
Bump for info. I have a BUNCH of Li-ion batteries (10.8v, 4500 mAh) that I bought for a piece of equipment I use. Will go through 4 -5 of them in a day. I bought one new for $100+ as I recall. Then one off of ebay for $60 (it was dead!!).
Wandering through my local used electrical supply store they had 40 or more on the shelf for $5 each. I bought 3 to see if they were okay and they were. Went back later and got 10 more. And then another 10 more as “spares”. Only later did I realize I needed to charge them up first or they would die. So now I have 5 to 10 dead ones. (And no more $5 batteries on the store shelf!!)
From what I read about li-ion, you can charge them or not.Whatever.
But if you put them on a shelf for 5-7 years, they die. No matter what. There’s no way to prevent the internal chemistry from changing.
;o)
Dude. I would just use it while plugged before I took the battery apart. Some computers these days have more cells in them and this lets them run longer.
The more batteries are charged they’ll degrade. One day they’ll hold 97%, a few months later they might only charge to 95% and so on.
They can be recycled I think, but I think they melt them down or something.
So you have the expertise to build a good battery from several bad ones? Good for you! Maybe you should market that skill. Might be a good business there.
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