I replace the old cells from my battery as well, but when I charge the battery it charges really fast, and later it discharges at almost the same speed.
I put new 18650 with "2400ma" each, and the other cells were 1800ma. I wondering if the circuit doesn't like this higher amount of amps in the battery.

How can I fix this?!?!

I am using a apple powerbook G4 with Leopard in it. I have 2gb of ram... (just in case someone wondered)

Thanks!!!

My previous message said to discharge the battery before hooking it up. This should not be done with a lithium battery. You should leave the batteries charged up and then connect them carefully as to avoid shorting anything out.

Once my project was completed the charging light on my notebook computer indicated everything was ok. So I published the previous article. It was not OK. When I disconnected the external charging circuit the computer shut down immediately.

I tried to charge the lithium batteries with an external charger and series resisters to limit the charge rate. The batteries appear to have an internal short and they will not charge up. Either an irreversible chemical change has occurred or a disabling circuit in the battery has activated.

All I am left with is a good control circuit for future battery repairs.

Yes, I would still encourage battery repair but you really need to know what you are doing.

Please note the following information from Wikipedia and I would advise reading the full article at Wikipedia.

Li-ion batteries are not as durable as nickel metal hydride or nickel-cadmium designs, and can be extremely dangerous if mistreated. They may explode if overheated or if charged to an excessively high voltage. Furthermore, they may be irreversibly damaged if discharged below a certain voltage. To reduce these risks, li-ion batteries generally contain a small circuit that shuts down the battery when discharged below a certain threshold (typically 3 V) or charged above a certain limit (typically 4.2 V).
This circuit prevents deep discharge in normal use. However, when stored for long periods, the small current drawn by the protection circuitry may deeply drain the battery. Some applications attempt to recover deeply discharged cells by slow-charging them.
Furthermore, this circuit adds to the cost of lithium-ion batteries, which is usually higher than that of comparable-capacity NiMH or NiCD batteries.

This article has been incouraging and resulted in saving me a lot of money.

Before ordering new batteries you need to know if the batteries are bad or if it is the battery module electronics. If the batteries are very old and have gradually decreased in power then they should be replaced. If the problem occurred abruptly you may have one bad cell or a bad electronics chip in the battery pack.

Take a volt meter and check the voltage at each cell level of each parallel set of batteries. If one cell is shorted it will drain the voltage in all cells that are wired in parallel to it. If each of the 3 sets of series connections have about 4 volts each then there is a good chance the electronic circuitry is bad. It would be of no value to replace the batteries unless you have the right electronic circuitry that works for your battery pack and your computer. You do not want to blow out the charging circuitry of your computer.

My battery pack went bad abruptly and the computer will not accept it. Each bank of cells shows the same 4 volts. The battery pack will light up some bright automobile 12 volt brake light bulbs for a long time.

There is nothing wrong with putting the lamps on the battery and draining it completely. Then you can try recharging it again in the computer. This may reset the electronics and reestablish operation with the computer. This did not work with mine.

While draining a battery with about 12 volts you can easily see if one of the 3 sections discharges faster than another by measuring the voltage at each cell level. If there is an open battery in any section, that section or that battery voltage will drop faster. That is because the current going through each series section is equal and a bad section will discharge faster.

I will not replace the electronics unless I have a complete electrical schematic of the existing and the new electronic module. I must know they are compatible. Keep in mind that some electronic modules will last longer than others. The manufactures of computer batteries use sufficient technology to dissuade all but the most ambitious techies.

My old computer battery (3 years old) still runs the computer but the batteries are very weak. So I put the new batteries from the defective battery module in the older battery pack. This worked fine. Keep in mind I completely discharge the batteries before doing this. I do not want to hook the battery wires up in the wrong order or short things out.

The wire routing was different but the electrical connections were the same as viewed on an electronic schematic.

I test the battery before sealing the case and have not decided what type of glue to use. I want to be able to break it apart in the future if I need the electronics, the case or the batteries.

Now I need another spare battery. I have found the IBM $185 battery is good for 6.5 hours in my T41p notebook.(When new) The $80 online purchase from Comptick.com is good for about 4.5 hours when new. This is with the same purchase rating specifications. The main concern is the short life span of the electronic module in the Comptick.com battery pack. I have no idea where to get a good battery other than IBM and that may not be a sure thing for a replacement battery.

I have a pack with cells that look the same, but the strange thing is, there is nothing on the net about the markings...

I have the in a red-translucent wrapping, with a big "B" on one side, and arond the other side it says: HJMFHHR
Now that's not a lot of information..

I tried to measure them, but all I get is 18 diameter and 62 in length. 18620 does not exist according to google..

The pack as 4 parallel cells, 8 in total.

It's rated 4000mA and 14.8v, now using that information, I think they should be 3.7v each, and have about 500mA, right?
If I just could find some cells that match the size.. What would cells with 2400mA do to the controller?
I guess it'd fry and have me cook potatoes on it..

How right is my direction?

Sorry for trying to resurrect an old post in here..

I'm a student in Computer Engineering, so things like this to me are a learning experience. I'll have to look at doing this to my laptop as it only has 56% of its original battery life.

I would get about 3hr 20mins, now I get about 1hr 45mins. Doesn't even last me a whole class and many don't have plugs.

What! Come on you guys. One of the things that makes us geeks is our need and want to figure out how things work. This is a great tutorial, thanks for sharing. I am shocked to see how simple it is, +1 to Knowledge.

Ridshack

Thanks for the How-To. I found it interesting, and had no idea I could do this on my own.

I've done exactly this process, however, you missed one large problem, the memory chip in the battery may (as it was in my case) be saying that the battery is too old to repair. Does anyone have any thoughts on that problem? I've thought of hacking it, but I'm rather a noob at hacking in that manner.

Great article...

This isn't just about $100 but it is more about being eco-friendly and even more...u had the fun of learing the trade..

What the commenter before me doesn't realize is that some of these laptops have lost their worth and wouldn't pull more than $300 - $400 on ebay. It's not viable to spend %25-30 of your laptops worth to replace the batteries. Now if it were a spanking new $2000 laptop by opinion would be different, but then it would probably be covered by a warranty still.

This is an awesome howto that shows just how easily these can be replaced, thanks!