EMERGRNCY LIGHT With Mobile Phone Battery




About: Now I am a retired person, who enjoys life and making small things to pass the time keep myself busy.

There were a few Discarded Mobile Phone Batteries lying around the house, so I was thinking how to use them as they had plenty of juice left in them to run something.

This is how I could find a use for them by making an Emergency LED light.

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Step 1: Parts You Will Need.

33 LED’s of 5mm.

One LED 1 watt.

A thin PVC sheet to fix the LED’s.

An old PVC light case.

3 Discarded Mobile Phone Batteries of 3.6 volts each.

1 single pole double throw switch. (SPDT)

Wires, solder etc.

Step 2:

Fix the LED’s to the PVC sheet in 3 rows of 11 LED’s.

Check the polarity of the LED’s.

Step 3:

Wire the LED’s, Batteries, and Switch as shown in the Circuit diagram.

No resistance or Capacitor have been used in this project. 

Step 4:

All the 3 Batteries should be connected in parallel, so that the voltage remains 3.6 volts at all times.

Charging the batteries should be done separately one after the other.

Never charge the Batteries all together because they are Lithium-Ion Batteries and may EXPLODE by using unregulated battery charger voltage.

Step 5:

Your Emergency LED light is ready.

Switch ON the 1watt led or the 33 LED’s as you wish.

This light is lightweight due to the batteries and can also be used by Kids.

It will give you uninterrupted light for at least 3 hours.


Step 6: Charging the Batteries

Charging the Batteries with a Li-Ion Battery Charger.

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    44 Discussions


    7 years ago on Introduction

    I thing you can put a mini usb(type b) socket/female connector. That way you can charge the battery using the usb charger, the same one that we use to charge ipod, ipad, iphone, galaxy, etc.

    the charging process will much easier.

    Mini usb b socket.jpeg
    3 replies

    Reply 2 years ago

    The problem with that is that the cheap phone charger "bricks" only provide the 5v on the USB. If you're lucky it may also current limit to the specification's 500ma. There is no circuitry to stop the charging when the battery is fully charge. Overcharging can cause Li-Ion batteries to swell and explode. You need some circuitry to prevent the overcharge condition.


    Reply 1 year ago

    Phone batteries have all needed electronics built-in (under/over-voltage protection) so all you need to do is limit current with resistor. Not for protection of batteries (three of them in series will not see high current anyway) but without that voltage of most charger will drop under usable level. Phone have protection for that (modern phones will test on start of charging highest current without voltage drop) but batteries alone doesn't.

    5/10R 5W resistor should be ok for this example. Personally I will use 5R6 5W.


    3 years ago

    How many 1 w LED i can connect to a Nokia 3.6 V battery?

    And, How long the charge will last ?

    1 reply

    Reply 3 years ago

    One 1 watt LED -2 hours.......


    4 years ago on Introduction

    Instead of throwing away electronics junks which is not too good for our environment, It is good to see you guys recycling it.

    How about recycling these abundantly found electronics junks :

    1. In many places we come across defective 600VA UPS with 12 volt batteries

    2. portable LED lamps (Chinese Made)

    Do you guys have any idea how to recycle it, so that these cheap LEDs could be powered by not so healthy 12 volts batteries from the UPS, Also since the Charging section in the UPS are often intact, one could use this to charge the 12 Volt Batteries.


    4 years ago on Introduction

    Hey !

    1.By connecting 4 mobile batteries of 3.7 V can i get 12V or high...?

    2.how can i connect all of them in parallel to get 12V ......to use some thing....

    1 reply

    Reply 4 years ago on Introduction

    1. By connecting 4 mobile batteries of 3.7 V in series you get 14.8 volts.

    2. By connecting 4 mobile batteries in parallel you get 3.7 volts.


    5 years ago on Introduction

    Hey Dipankar ! I want to glow Led from a 12 volt Battery. How Many Led i have to use? please guide me the necessary details.

    1 reply

    5 years ago

    Hi All,
    I came across similar project that I needed to work on. I ripped off four Li-Ion (falt build) batteries from Sony NP FH100 7.2v pack, pretty similar to 3.6v mobile batteries, (except that these don't have any clothing lol).
    What I did was put all of them in parallel and used protection circuit:

    And of course as a stable power supply to above circuit I can't rely on anything but DC-DC buck converter. Its just the matter of getting all things together and connecting correctly.


    5 years ago on Introduction

    Is there anyway to charge the batteries while the light is in use, like would be possible would when the battery is inside the phone?

    1 reply