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Cell Phone Emergency Charger Pack using Ni-Cd Batteries

Cell Phone Emergency Charger Pack using Ni-Cd Batteries

In this post  we discuss the construction of a simple emergency charger pack using Nicket Cadmium (Ni-Cd) batteries for your cellphones and smart phones for emergency charging of your cellphone, so that next time you are never stuck on a highway with a full discharged dead cellphone battery.

Circuit Concept

It often happens, our cell phone goes into a low battery condition right in the middle of an important conversation, and even worse it happens while we are travelling or situated in some remote outdoor location where there's no charging facility available.

No matter what, this little pack will give your cell phone an immediate refill every time it tends to get flat outdoors.

We all know that at 3.7 V DC, a cell phone battery is considered to be fully charged.

For charging it at the above level a charging source needs to provide around 4 to 5 volts to the discharged cell phone battery.

Since here we are discussing an energy transfer from one battery to the other or rather from some power source to the cell phone, we need to have some sort of chargeable battery pack which would generate the required 4 volts and which could be used anytime for charging a flat cell phone simply by integrating the two together.

The above emergency battery pack can be very easily made by putting four Ni-Cd cells in series.

Let's learn how to do it.

Materials you will Require

It's not difficult, you would require four 1.2V Ni-Cd AAA penlight cells, a four cell holder assembly and a 1 Ohm 1 watt resistor.

How to Build the Cellphone Battery Bank

The above holder would generate a voltage of about 4.8V at its wire terminals with four AAA 1.2 Ni-Cd attached to within the given slots correctly.

The 1 Ohm resistor can be connected at the center of the red wire by cutting the red wire at the center and bridging the resistor terminals such that it comes in series with the red wire. The resistor should covered under a plastic tubing or sleeving.

The red and the black wires of above assembly should be terminated with a suitable cell phone charger-pin so that it can be easily inserted into the cell phone charging socket whenever required.

Now let's learn how we can charge the above emergency battery pack at home.

Ni-Cd cells can be charged safely for about 10 to 14 hours using a constant voltage charger at C/10 rate. The very useful 7805 voltage regulator IC can be used here for charging the Ni-Cd battery pack.

The following diagram shows a very simple Ni-Cd charger circuit which can be used for charging the above battery pack so that it remains in a standby position and can be taken outdoors in the form of an emergency cell phone charger unit.


About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!

61 thoughts on “Cell Phone Emergency Charger Pack using Ni-Cd Batteries”

  1. Can you help me. I live where there is no electricity grid in Brazil. For almost 4 years with the limitation of electricity by not knowing the electronics. You are looking to learn and sell in alternative alternatives, but I have the financial limit.
    Generally available from a stationary 12v / 12Ah battery and some 3.7v Lithium batteries. Fueled by a 12v / 20w solar plate, mini 12v hydroelectric generator and I’m trying to make a three-phase wind turbine and other small ones with printer motors.
    All knowledge and help are welcome.
    Do you have an email that I can share some of your knowledge and remove some doubts?

    • Marcelo, I’ll try to help you, but I would prefer discussing it here through comments so that other readers are also able to benefit from our conversation.

  2. Thank you for your attention and response.
    I experimented with a modulus xl6009 DC-Current Continuous Boost Buck Adjustable Step Up and I was able to charge a cell phone and another li-ion battery.
    I made the joule thief with a ceramic capacitor 103 and a 1k resistor at the input, a toroid (2×12 turns), TIP 31c, a diode 1N5148 and electrolytic 1000uF / 25v, but I can not even recharge another battery, even having 6v at the output .
    Could you change this setting to try loading?

    • Can you please tell what supply input did you use for the mentioned module? The module has a specilaized IC so the output will be much efficient. 12 turns is quite less…try 20 turns at least and check the response…and use 7805 IC after the 1000uF for stabilization. In my case the battery wasn’t strong enough to sustain the smartphone charging current…if possible I’ll try to use a bigger battery as the input and check the response.

      • I understand about xl6009. It adjusts output according to requirement. Right?
        I used a 3.7v and 1200mAh Lithium cell phone battery, marking 4.2v.
        My problem is to lose a little of the charge of the batteries they power.

      • OK! No problem, just thought if there is need to send you some photo or circuit design. Can you do this around here?

  3. Good afternoon sir.
    Thanks for the site and tips.
    Could I use a single 1800mAh cell phone battery in a joule thief to power a cell phone via usb?
    Because I have 6 v, but I can not even charge another battery of 3.7 v and 1000 mAh?
    Please help me

  4. Sir can u give me a circuit which has output 1.5-2.0 amp and 5v to charge my 3000mah battery 2 times…please…
    Thanks in advance…

  5. Dear Sir
    I need 4200ma polymer battery charger circuit after 3 min minimum 20% quick charge
    I am try many circuit but all of circuit component very hot and burn sum time.
    I try 5V out put and 3A Charge circuit this 3 min charge OK but all component vary hot .i thing this circuit not a nap pl z.. help me
    My Email ID-giashsmart@gmail.com

  6. Sir I have 2 18650 2200mah cells I want to charge my android requiring. 5v@1amp how should I proceed any simple circuit with only 2-3 components

  7. Hello sir
    I have 3. 7 v battery i want to make a power bank can you please tell me how do i make it i also want a circuit diagram

    • Mehran, you can use it for charging all types of batteries, just make sure to switch OFF power as soon as the full charge level is reached.

  8. Hello sir the last circuit indicate as the charger…………….. bt how to know that cells are fully charged any indication for that we can add to the circuit

    • Hello Basit, you can add an LED with 1K resistor in parallel with the 5 ohm resistor…it'll stay illuminated as long as the battery is charging and will slowly shut off as it gets fully charged

  9. Thanku sir once again. I wank to ask one question sir,that is can i make solar inverter with very low budjet like 500 or 600

    • Karthick, It is possible without solar panel and battery, you can buy a cheap Chinese inverter and check how it was possible for them to make so cheaply.

  10. Thank u sir. I bought this ckt sir it is working good.but my question is how many hours i hav to charge those cells if the cells discharged

  11. hai sir i am often visiting your site it is really wonderful .i just want to ask a one doubt in this emergency circuit package which is"is the ni-cd can be rechargable or not".please reply me soon sir.

    • Hi Karthick, thanks for visiting my blog!

      yes, Ni-Cd cells are always rechargeable types, and needs to be charged when fully discharged

  12. Hi uel,
    you can make a dual adjustable power supply circuit using a LM317/LM337 ICs, Google it, you will find plenty.

    set the voltages as per your requirement and use it for the application.

  13. hi sir, do you have schematic for an adaptor for digital camera? I lost the original adaptor of my BEAC digicam and I want to make a replacement particularly with -3.7V, 0V and +3.7V output to be powered from wall socket.

  14. Please sir, if i use 1uf 25v Electrolytic capacitor, do i ignore the polarity?

    And could you kindly state how i can identify the primary and secondary side of transformer. I have got all the components for this circuit but am having a problem identifying the primary side. The transformer comes with two sets of cord: at the foot where you screw, there are two black cords and two red at the top on the opposite side.

    And is there a way of testing transformers?

    Please i would appreciate urgent reply as i am very eager to build as my first DIY project.

    • for electrolytic capacitors the positive will connect with the positive line and negative with the negative line.

      check the resistances of the respective windings…the one with higher value will be the primary for the mains input and the lower one will be the output.

  15. Sir, any other values of resistors can be used? instead of 1ohm 1w & 5ohm 1w??
    a 4.7ohm 1w can b used instead of 5? plz give any other values if so…

  16. Although not recommended you can connect them in series for charging, as parameters are not so critical with such low AH batteries.

    the input can be 12V but at 500mA.

    once fully charged it can revive a run-down 3.7V cell one time only.

  17. you may have to try bigger cells, AAA may not have the capacity of charging 1600mAH cell.

    monitor the voltage of the adapter cells while it's charging the cell phone, if it drops quickly (below (3.9V) would confirm the cells inability…..

  18. You can procure readymade 12V DC tube chokes which are designed for operating with 12V batteries, and power them through a 12V AC DC adapter, in this way you would be able to drive them with 220V AC suppy.

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