Advanced Battery Pack From Cell Phone




Introduction: Advanced Battery Pack From Cell Phone

About: I am a maker, builder, inventer, problem solver

Want a great use for you old phones sitting around? Sure you do. I have the perfect solution. Turn them into rechargeable battery packs.

Parts and Tools:

1. Screw driver
2. Soldering Iron
3. Multi-meter
4. Solder
5. Flux
6. Wire cutters
7. Knife or razor

Note: A battery with a protection circuit is advisable to make sure you don't discharge the battery too much.

Step 1: Find Charging Terminals

1. Take the phone battery back off
2. Take out the battery
3. Plug the charger into the phone
4. Take a multi-meter and find the positive and negative terminals

• Most phones have 2 to 4 terminals that connect to the battery and are clearly labeled.
• Most likely you will have a +, -, and T. The + is positive, the - is Negative, and the T is a temperature terminal

Step 2: Solder

Solder your wires, or plugs, onto the terminals that you found to be positive and negative. try to solder to the outside surface of the terminal (the one that makes contact with the battery). You may have to take a knife or razor and carve some of the plastic away in order to allow the battery to fit while the wires are soldered.

Step 3: Replace Battery and Back

Put battery back into the phone and use your multi-meter to test weather or not you are receiving voltage which means you are receiving current through the wires. If yes, then plug the phone charger in and see if you are able to charge the phone.

Locate where the wires are coming out of the phone and cut or drill an appropriate hole in the battery back to allow for the wires to be accessed.

Step 4: Test

Test and see if you are still getting voltage and current.

Step 5: Thoughts

This is a great little mod because it allows you to use a phone that you otherwise would not. It is great for running an Arduino mini or other small item. The best part is that it has alarm functionality, a clock, and a great battery bar. I have done many phones and have had great success.



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    51 Discussions

    I am trying to replicate it but it is not working, when I solder the wires on the connectors I lose voltage, and when I remove the wires the phone works again, is possible that the solder I use is not conductive?

    1 reply

    "Put battery back into the phone and use your multi-meter to test weather or not you are receiving current through the wires. If yes, then plug the phone charger in and see if you are able to charge the phone."

    Actually, unless you are testing the T-terminal, and not either the Positive or Negative terminals, you would be testing whether or not you are receiving current through the wires. Nice weather we're having, innit? ;~0

    Also in this case since you are checking continuity, you are checking for a potential voltage difference and not, strictly speaking a current, which - in order to test - would require a break in one arm of the circuit in which to place the ammeter or current rate (amperage) of the circuit under test - the battery and the wired connection to the terminal side you are checking - either the Red (positive wire) or the Black (negative - or Ground wire) that you have just soldered.

    It might be good to point out that measuring current is a serial operation, requiring an actual break to see the rate of flow being measured by the meter while it is being placed in a serial connection between one side of a broken wire and the other break in that same broken wire.

    Voltage, which isn't the same as current since it doesn't measure a rate of electron flow, but instead measures the potential difference between one point and another in a circuit, is a parallel operation; one test lead goes to one terminal and the other test lead goes to the other terminal: the two points in the circuit between which you are measuring the potential difference in units of Volts or fractions of volts. This difference is measured on the Volt scale and is, in this case would be by touching the Positive Terminal with the Red or Positive Test lead. The other test lead (probably Black in color) would be attached or touch the Negative terminal or circuit Ground point. You would be measuring the number of Volts of potential difference between the two sides of the circuit that make up the Battery. You can measure circuit continuity by attaching the test lead to any part, component or wire that is attached to the circuit terminal or polarity under test. This will tell one if the solder joint creates a good bond and is at the same potential at both ends of the wire being tested for continuity. Unless the wire in question being used is very thin (consequently having a high resistance that can create a potential difference like would be caused by inserting a resistor in-line with the test lead), the measurement of voltage at either wire end would be practically speaking the same.

    Sorry for being so verbose, but I thought it important to make that distinction. Voltage and current flow are principles of electricity and electronics that make their understanding crucial at a fundamental level. Many people struggle with these basic principles for years until a full comprehension is reached.



    4 replies

    It was a general statement. Current sounds better than voltage. Ohms law shows that if there is voltage (using the multi-meter) then there is current. I had faith in the intelligence of those reading the instructable to know this. Thank you for your comment though.

    "Current sounds better than voltage" ?? That's like saying "cheese" sounds better than "cat" (which, in fact, it does but that is besides the point). They are very different concepts, and only serve to confuse the reader if you mislabel them in the way you did. It does you good *not* to rely on the intelligence of the reader, especially by the people new to electronics who might mistakenly use your instructable as basis of learning. Other than that, keep up the good work!

    Yeah, this point has already been made and cleared up. If I would not have corrected the problem then maybe your point would have been welcome, but with new information and taking the constructive criticism to heart I fixed the issue. That has to at lease keep someone from making the same point, made earlier, right? Thank you for your comment though.

    Are you certain the (low voltage) protection circuit is in the battery and not the phone? The the older phones I had were not built this way.

    If you discharge the battery from these wires does the protection circuit isolate the battery at around 2.7-3.0 volts?

    3 replies

    Every phone I used had a lithium battery with a protection circuit in the batery. I am sure that not all batteries do. I would advise making sure yours does.

    You really should have mentioned that IN BOLD in the instructable because there is a definite risk of damage or even fire if this is done to unprotected cells.

    I prefer to add a high power LED to the phone instead to make it a floodlight because the LED will stop conducting when battery voltage drops below the LED forward voltage which is always 2.(something)V for a white LED.

    How are you getting the time on a phone that is no longer being used as one? The time is updated by the service and I would never want to pay for an extra phone.

    1 reply

    Nope, time is updated with or without service. You can always set it yourself if you are capable of navigating the menu.

    Well constructed, sequentially-accurate instructions. I would change the title as non-tech's may wonder, "What do I need an Advanced Battery Pack for AND what does it do? Also, you are missing an ingredients, tools, etc. list at the beginning or the show: crucial for me.

    1 reply

    Added parts and tools. I discussed what you could do with an advanced battery pack on the last step. You can read it if you would like to.

    would it work to essentially use this method (or the linked charging board from user ErkinO - thanks) to have multiple batteries in parallel or series to have more storage? My thinking is that I am planning to build a solar panel with the purpose of charging a battery for powering LED lights and USB power charging in a tree house. I do have a handful of old cell batteries and would love to be able to use them for this somehow, instead of a 12 volt sealed motorcycle battery. A single 3-5 volt cell battery won't amount to much, but taking the power in series would add them up (right???)... but how could they all be charged together? Series? Parallel?

    2 replies


    Firstly, I have no idea what ErkinO made. Secondly, using this method, you would connect the batteries, and consequently charge them in parallel with the main phone battery. Thirdly, parallel Li-on(phone chemistry) battery packs aren't popular due to their low voltage, but that requires the explanation that batteries connected in parallel will add Amp Hours to your battery pack, and connecting them in serial will add voltage.

    I opened an extended laptop battery once, and found 9 cells in a formation that connected them in 3s, in parallel to multiply mAH, and then connected these 3, now large capacity packs in serial to multiply voltage. A cell phone battery is a single cell

    LATE DISCLAIMER: be careful. MOST phones will successfully turn off if the battery gets too hot. The ones that fail at this step, explode. Also, extra dangerous, if you connect another battery to your charging leads of another phone in the manner expected from this, you'll be circumventing the phone's ability to read battery temperature, making an explosion that much more likely. On top of this, it is HIGHLY UN-ADVISABLE to use batteries of different mAH rating as they will discharge at different rates. This causes the lowest rated battery to start charging from the others in the array, increasing it's heat generation; Even worse, when the batteries are connected in serial, the weakest one will charge backwards, and destroy that cell, as well as bring the voltage down considerably, if not completely.

    This really isn't meant to scare anyone, but inform you of the dangers involved; In fact, I encourage this kind of experimentation.

    Thanks... excellent information and warnings. I'm not scared but now thoughtfully aware and likely to not push my luck with exploding Li-on batteries.

    I wonder, are most phones generally capable of charging to any other phone battery, like some older phone charging a larger capacity battery, or even for that matter and power pack that would be normally charged via UPS. Of course, then I'm still guessing the voltage of the power packs is too low to do anything with a strip of LED, but it's a thought.

    My guess is that upcycling end of life cell batteries is likely a low ROI anyway, since they are already lacking an ability to hold much charge.

    I really like this idea. As I think you said, it's a great use for something that normally would be sitting in a drawer. But dude... Honestly...You get caught with this on your person, backpack or purse... A cell phone with wires sticking out of it... You just got yourself a short stay in an undisclosed, unmarked secret holding facility with sleep deprivation and questions being launched at you from a voice coming from behind a one way glass window. Compliments of our "friends" at Homeland Security! "Lucy, you got some 'splaining to do"!!! ... Then again, maybe I'm just watching too much of 'The Blacklist' lately! ;-) .