Challenging iBook Battery Pack Rebuild Question

1. Jef Atkinson - 3 June 2004

   here's a challenge for the electronic minded...

   i would really like to rebuild my 14" iBook's battery pack... i've opened it up and it has Eight, 3.7 volt sony lithium ion cells. They are rated 1350mAh. universal size/name of the cells are: CGR18650

   http://www.techfreakz.org/pcgabp52/?slide=21

   The Question: can I put in Eight 2000mAh and have it not screw up the iBook??? or is it best to put in Six 2000mAh cells and have it still work?

   lastly, how dangerous is it to work with lithium ion cells? is the risk of explosion low, medium or high? hummm...

   jef

2. Chong Woo Paig - 4 June 2004

   I don't know about the specifics of the battery, but I heard that Li-Ion batteries can completely melt down if not properly adjusted/connected.

3. Kirk Strauser - 4 June 2004

   Before you get too much farther, read:

   http://www.laptopbattery.net/laptopbatteries_refurb.html

   This article is hosted on a website that specializes in selling new laptop batteries, so consider the source of the information, but it raises several very valid points. In a nutshell, don't bother unless you can get a set of extremely closely matched cells.

   Kirk Strauser
   The Strauser Group
   Open. Solutions. Simple.
   http://www.strausergroup.com/

4. Jef Atkinson - 4 June 2004

   yeah, i'm already past the matched cells portion... CGR18650 is the correct cell... so that info really doesn't matter... i guess i'm wondering if having more power will harm the ibook... i know in digital cameras using higher mAh batteries they simply last longer... my thinking is the ibook is the same, but does anyone know for sure?

   thanks!

   jef

5. Jef Atkinson - 4 June 2004

   here's a challenge for the electronic minded...

   i would really like to rebuild my 14" iBook's battery pack... i've opened it up and it has Eight, 3.7 volt sony lithium ion cells. They are rated at 1350mAh. universal size/name of the cells are: CGR18650

   http://www.techfreakz.org/pcgabp52/?slide=21

   The Question: can I put in Eight 2000mAh and have it not screw up the iBook??? or is it best to put in Six 2000mAh cells and have it still work?

   lastly, how dangerous is it to work with lithium ion cells? is the risk of explosion low, medium or high? hummm...

   jef

6. Adrian W - 4 June 2004

   I have sucessfully rebuilt old Powerbook Duo battery packs with higher capacity cells (NiMH). The voltage is the important thing to retain; so you are going to need to replace the 8 cells with 8 cells (assuming that they are the same physical size and are rated at 3.7v).

   I don't know what the inside of your battery pack looks like, but assuming it's like the ones I've worked with the cells and connections will be crammed in there! This opens up the possibility of inadvertently creating a short circuit, so you have to be very careful to use the little pieces of plastic/card to keep the contacts separate. A frying battery pack is scary - and if it is inside your computer at the time it's rather expensive!

   Adrian

7. Adrian W - 4 June 2004

   You are correct ... an analogy would be that your Mac can run a bigger capacity hard drive ...

   Think of voltage as the pressure being exerted ... obviously you don't want to increase or decrease the pressure so keep voltage the same. Think of amp hours (or milliamp hours) as the quantity of electricty which can be supplied at that given voltage ... the more the better.

   Adrian

8. John Johnson - 4 June 2004

   From the bare cell standpoint, you need the same number of Volts to get it to work. Capacity is irrelevant. Of course, depending upon the charge controller, you may or may not get access to the extra capacity. I honestly know nothing about how the charge controller on these packs works, so can't tell you more.

   You may get more mileage asking in sci.chem.electrochem.battery. There are some real experts over there.

   lastly, how dangerous is it to work with lithium ion cells? is the risk of explosion low, medium or high? hummm...

   I cannot assess the risk of fire or explosion under given circumstances, which is one of the reasons why I don't mess with those things. It certainly depends on how safely you work, and the condition of the cells. The risk of explosion is real, as is the risk of fire. Both are a result of the Lithium, which may be present in elemental form inside a fully-discharged cell, as I understand things.

   Again, maybe someone in the battery chemistry newsgroup can offer more specific info. I would recommend against undertaking the effort, but then I've already admitted to ignorance in the area. In any case, be safe.

   Later,
   John

   johajohn@indianahoosiers.edu

   'indiana' is a noun. Leave only the noun between @ and .edu to reply

9. Matthew Russotto - 4 June 2004

   It is best to put in eight 1350mAh cells. The battery pack contains charge control circuitry which is matched to the cells. It might work properly with 2000mAh cells, but on the other hand it might not.

   Six cells isn't going to work; the voltage will be wrong.

10. Jef Atkinson - 4 June 2004

    okay! that's the info i needed... i keep seeing where it will work with 8 2000mAh and i see another note posted here that explains it like a larger hard drive. But 6 cells won't work, that's 50% of what i was after.

    i will let everyone know how it turns out.

    thanks!

    jef

11. Jef Atkinson - 4 June 2004

    Adrian -

    thanks for the additional info, i guess i'm going to go for the higher capacity cells and wear my rubber gloves/goggles and connect them up (slowly)

    a rather colorful thread of what needs to be done is here:

    http://www.lemley.net/pcga-bp51/pcg_c1_thread_20030323.html

    again, i'll post what happens.

    and to the person that googled and posted the "don't do it" info from laptopsforless, there is a comment on the above link that says that company isn't telling the full truth... see below...

    i know this isn't a normal "repair" but the batteries are just there waiting to be replaced... i gotta do it!

    jef

    Wrong --->

    For these batteries to charge and discharge correctly, they all have to have the same internal impedance (if your DC theory is bit rusty, impedance is a fancy word for resistance, generally used for pulsating or AC current).

    For this reason manufacturers go trough(sic) extensive cell testing to match together thousands of cells with the same impedance. Once they have - lets say - a lot of 10000 pieces all at 0.2 Ohms, they will design a charging circuit that is specially adjusted for that specific lot. Then they will assemble the battery packs and study the next lot that might be tested at 0.3 Ohms. The charging circuit will need to be adjusted again, for the different impedance. ____________________________________________________________

    If nothing else, you gotta respect his command of Ohm's Law!

    I know I'm ain't exactly a genius myself, but guys like this just make me (sic)

    --Dave

    What? You want more? Hookay...

    http://www.laptopsforless.com/norefurbs.html

12. Kirk Strauser - 4 June 2004

    At 2004-06-04T22:20:27Z, Jef Atkinson <ja@life.net> writes:

    and to the person that googled and posted the "don't do it" info from laptopsforless, there is a comment on the above link that says that company isn't telling the full truth... see below...

    Well, I told you to consider the source. :-)

    Still, his information is essentially correct. I'm not an electrical engineer - my degree only included physics and microelectronics - but please keep his warnings in mind when you get started.

    Good luck, and wear gloves.

    Kirk Strauser
    The Strauser Group
    Open. Solutions. Simple.
    http://www.strausergroup.com/