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Thread: Advice for rebuilding cell phone battery

  1. #1
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    Default Advice for rebuilding cell phone battery

    I got around to taking apart my nokia phone battery to upgrade it with new nicads, nickle metals, alklines or lithums. THe part number is bkl-25 4.8volts. Guess that voltage thing limits me to 4.8 volts?

    It looks like 4 aa cells in two rows of two hooked in series. THe two outer contacts are hooked to the battery terminals directly, the inner terminals, one to a diode red/white clear one and the other inner terminal to a resistor to the same side of the battery as the outer terminal.

    Basically the battery does not hold a charge and when it did, use was limited to 8 hour standby and a 3 minute call or 3 15 minute calls from the off position before the low alarm went off.

    I bought a higher cap battery from an online store, but it was a mini nickle metal and the results are just a bit better. I want to upgrade it since the battery thing is large enough for aa cells to something I could leave and use as needed. I normally do not receive calls and use it for outgoing. The idea was to use the lithum aa cells mentioned here. When they die or are used up, just replace them. The thing that holds the cells pops right open with a knife. It wasnt glued, welded or sealed in any way.

    Thanks for the suggestions.

  2. #2

    Default Re: Advice for rebuilding cell phone battery

    get 4 2500nimh AAs for about $10 and recharge them when needed.
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  3. #3
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    Default Re: Advice for rebuilding cell phone battery

    I think I forgot to mention then are all soldered, shrinked wrapped together. I think I could put in a battery holder, heck I wouldnt mind hacking it up to accept one with access from the rear.

    I hadnt quite thought out how I would go about replacing them. If I did the replacement of nicads, I would try to do the same work and use the stock charger. If i did the lithum aas I would likely do the same so it can be stock looking.

    Not sure rat shack sells a a 4aa battery holder that holds them in two rows vs one row.

  4. #4

    Default Re: Advice for rebuilding cell phone battery

    haven't seen a 2x2 battery holder but the standard charger that comes with the phone would probably charge nimh but you would need to monitor it so you don't overcharge them thus reducing their life.
    You could try a pair of 2AA holders to see if they fit or chop off one end of each and tape them inside of the case if there is enough room for them and the springs.
    I have some cheap 1200mah nimh AAs if they would be enough I could send you
    They were originally 4/5AAs I soldered brass extenders on to make them standard AA length and if needed you could saw off part of the extenders to fit but then they wouldn't fit in a standard charger without help.
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  5. #5

    Default Re: Advice for rebuilding cell phone battery

    Quote Originally Posted by cobb
    Basically the battery does not hold a charge and when it did, use was limited to 8 hour standby and a 3 minute call or 3 15 minute calls from the off position before the low alarm went off.
    You might want to see if your plan will allow you to upgrade your phone.
    It sounds like you have an old analog phone or are always in an analog mode.

    The batery on my phone will not hold anything AA size and gives me 10 or more days on standby and several hours of talk when in digital mode.

    PS If your phone normally lasts in standby for a fairly long time but the time is a lot shorter every once in a while it's because it has lost a digital signal and goes full strength and/or analog trying to find it again.

    PPS I rarely use my cell phone and even with a good plan was paying about fifty cents a minute (based on my actual use.) I switched to Trac-phone, the only pay as you go plan that I've found that does not have hidden daily charges. If interested e-mail me and I'll tell you the dark side of the service.

  6. #6
    Flashaholic* BatteryCharger's Avatar
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    Default Re: Advice for rebuilding cell phone battery

    You can probably buy a new battery on ebay for around a buck.
    I got a fever and the only prescription is more cowbell.

  7. #7
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    Default Re: Advice for rebuilding cell phone battery

    lynx, thanks, think I will go to rat shack and get the high cap nicads with 2 2 double a holders and machine/file one or the other to make them fit. I really do not feel comfortable soldering batteries, shrink wrap, etc. This way wouldnt have to worry about the higher voltage of nickle metal batteries ruining anything.

    batterycharger, I got the nickle metal one from batterystation for 15 bucks. I dont think its their fault, think its the analog thing of the phone. This is an old prepaid phone, not sure i would trust an ebay battery unless i ruin the case andneed another one to make this mod work.

    Mike, its an old analog prepaid trac phone. It was my uncles who died 3 years ago. It had a few hundred minutes on it and I adopted it. Works fine, but as I have used it battery life started to go and the tower location changed. I use to get full signal at work, now just 1 or 2 bars. I do not think it has a digital mode.

    300 minutes is more than enough for me a year when I renew it online and get for a year service for a hundred bucks. I do not think you can transfer minutes from one phone to another or I would do so.

    Wish me luck. I tried to hack an old motorola 550 flip phone battery, but it just came apart in pieces when I tried to pop it open. Believe it used 6 aa cells in series with lots of glue.

  8. #8

    Default Re: Advice for rebuilding cell phone battery

    Trac-phone is pretty good about transferring minutes and the old number.
    It can be a pain to type in all the numbers required but they are helpful and almost any phone call to them with a problem will get you an additional 10 minutes.
    They have two $19.95 phones now - about $25.00 delivered with 40 minutes and a coupon book.
    I've had zero problems and my friend Hank was about to kill me but he bought when the lights went out in Florida. H'e happy now.

  9. #9
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    Default Re: Advice for rebuilding cell phone battery

    Thanks Mike. Will look into that. I have a newer nokia phone that I used down to 3 minutes a few years ago and just keep plugging it in every so often to charge it up. It is "newer" and seems to have pretty good battery life. I think I can talk over an hour with a few hours standby or leave it on standby for 2 days before the low battery alarm goes off.

    I am now just on the fence. I may go ahead and buy the larger cap nicads and battery holders and see if the run time is any better. If it is by a few days or some significant amount, I may just continue to use the older phone. It its same or little bit more, will return the nicads and swap the minutes like you suggested.

    Guess I am spoiled with the old motorola 550 flip phone I had with the duracell extra cap lithion battery. Man, that was one big combination to stick into any pocket. You had to wear it in front and put a chain on it as it will pop off from time to time.

  10. #10
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    Default Re: Advice for rebuilding cell phone battery

    You can always put lithiums in there with a volt regulation/protection circut for maximum runtime?

  11. #11
    Flashaholic* snakebite's Avatar
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    Default Re: Advice for rebuilding cell phone battery

    sounds like my old nokia 638
    back then the stock pack was 700mah.
    i got some 1500's and rebuilt it.made a big difference.the old cells were pretty well worn out after 2 years anyway.

    i am always looking for old radios and tv sets.tube stuff.ham gear.i repair all the above.
    email me for more info. SPAMMERS WILL BE PUNISHED!

  12. #12
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    Default Re: Advice for rebuilding cell phone battery

    Excuse my ignorance guys, turns out nickle metal batteries too are 1.2 volts fully charged like nicads. I thought they were 1.5.

    I bought a pack of 2000mah from rat shack for 20 bucks for a 4 pack. After looking online, found i can get some up to 2600 mah and cheaper. Also found the stock battery on a website was 1200mah. I decided I wanted at least 2400 or double the stock battery capacity. I returned the batteries to rat shack and found 2500mah ones at sams club 8 of them, with charger and 4 aaas 850 mah for 25 bucks. I then headed back to rat shack for some shrink wrap as the battery holders were not going to work since both deremels I have died. THink brush problems. So, got home, see the shrink wrap is a hair too small to fit over the end of the cells.

    So, thats where I am at. Guess i could do the electrical tape thing, wanted to be a bit professional with out any loose connections. Looks like the batteries in the pack are connected with little strips with two small punctures like they were tapped into the cell tip or tail. I hate to solder and screw anything up with the heat and all.

    How should I go from here? Where is a good cheap place online or store to get shrink wrap? THink heating the shrink wrap will make it stretch?

  13. #13

    Default Re: Advice for rebuilding cell phone battery

    Soldering is fine as long as you clean/sand and pretin the wires. I would just tape the batteries together if you are going to hide them in the plastic case as shrink wrap doesn't give any more functionality to cells that are already encased.
    Under loads nimh are superior to alkaline as they start off at 1.5v but quickly sag below 1.4v while nimh hot off the charger start at 1.4v and spend most of their life between 1.2 and 1.3 volts which averages out higher than alkalines under heavier loads.
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  14. #14
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    Default Re: Advice for rebuilding cell phone battery

    Thanks. Hey, how do you solder these things? Is a low power gun better than high? 15 watts vs 100 watts? Just tap it til the solder flows like you solder in general?

    I am about ready to pull the trigger. Got a 100 watt gun, wire, solder, electric tape, heat shrink and an open weekend to do it uninterrupted.

  15. #15

    Default Re: Advice for rebuilding cell phone battery

    You can use a 100 watt gun and get on/off fast.... personally I prefer using about 40-60 watts as you can find irons that are less hefty at those wattages and it gives you a little more time to get things straight without overheating the battery too much.
    With a 100 watt gun I would prep the battery and pretin the wires put the battery in something to hold it in place so you can get on off fairly fast.
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  16. #16
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    Default Re: Advice for rebuilding cell phone battery

    THanks. I generally pulse the trigger like a semi auto gun to kind of hazardly regulate the temp. Sure its fun to hold the trigger and watch the end glow red, but that got old real quick.

  17. #17
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    Default Re: Advice for rebuilding cell phone battery

    I did it. I bought a few 4 packs of 2500 milliamphour batteries from walmart and sanded the tips and soldered them in. All connections were great, it fit in the cassette, it works fine.

    THe problem is, when I go to charge it, nothing happens. Normally when I plug in the ac adapter it beeps and the charger icon flashes to charge or stays motionless if it is charged.

    Well? What do you guys think went wrong?

  18. #18
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    Default Re: Advice for rebuilding cell phone battery

    Anyone? Think the internal resistance is different from going from nicads to nickle metals? Its making contact, just the phone will not recharge with the rebuilt pack on it. It will trigger the charge mode flipping packs from another poorly performing one.

  19. #19

    Default Re: Advice for rebuilding cell phone battery

    I think you have a bad connection somewhere. try getting a few clipleads and pins and connect them up bypassing the plugs/sockets as much as possible.
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  20. #20
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    Default Re: Advice for rebuilding cell phone battery

    No luck. I transferred the minutes to yet another tracfone and going to leave it on and see if its dead if it will recharge or how long it lasts.

  21. #21
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    Default Re: Advice for rebuilding cell phone battery

    Well, I ran it dead and it still wouldnt trip the charger. I decided to take back the 4 aas I put in it and give the phone its fate. Amazing how quickly it snapped when I bent it over the counter. Who knew it has a 1/4 inch aluminum plate in the middle between the phone and battery?

  22. #22
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    Default Re: Advice for rebuilding cell phone battery

    Incase anyone is interested, I took apart the slim nickle metal that I bought a year ago for my phone. Turns out it has small square gum shaped batteries in it. Going to hang on to that incase can use it in the future. I assumed it has small tripple A or AAAA cells in it.

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