Introduction: How to Add a Rechargable Battery to Multimeter [HAcked]!!

Multimeter is a very good tool when you're an electronics enthusiast or a professional but it a very tedious task to change the battery, and sometimes if you left it turned on quite a long time (you just drank too much and forgot to turn off the meter :) and bam the cell is flat and you are trying to fix the multimillion dollar project and now you have to search for a damn 9v battery in order to get it running. No worries today i am going to show you how to add a rechargeable battery to your multimeter.And also you would learn to make a boost converter from scratch which can aslo be used as a power bank.

Step 1: Gather Your Supplies(nothing Special :)

We need common parts which can be sourced from nearby electronics stores or from old circuit bords:)

  • A multimeter of course
  • A power bank board
  • 1/2 watt led or less
  • push switches
  • enameled copper wire 24awg
  • N channel mosfet (low rds)
  • npn generic transistor
  • resistors
    1. 150Ohms x1
    2. 3.3k x1
  • cell phone battery 3.7v at lest 3.7Wh
  • micro usb breakoout (iused the port from cell phone:)

if you wish to prepare this project in modular way then you'll need

  • A multimeter of course
  • tp4056 charge controller
  • common low current boost converter
  • lm317
  • 15ohms resistor
  • common spst switches x2

Step 2: Tools

Nothing special here basic electronics tools

Step 3: The Plan (Schemtics)

We'll be using a boost converter in combination with a charge controller and discharge protection. The led can be connected to the either the power bank board or using an lm317 circuit we can achieve the desired results.The resistor on the board can be change in order to get the desired current.

Step 4: Prepare the Boost Converter

This is a very simple boost converter build upon a pair of transistors this circuit has a high efficiency and a very little leakage but if you want ,you can simply buy a ready made boost converter but still

Few words about the boot converter:-

If you intended to use this circuit as for a power bank then make sure the main transistor Q1 mosfet can supply the current and if the rds is low it is not need to be kept under a radiator.If the circuit doesnt work then try changing the primary connections of the transformer. And also change the zener to 3.3v.Ihave used this circuit and below 1amps there is no need of radiator

Step 5: Care for Your Battery (charge Controller and Over Discharge Protection )

I used a power bank circuit as it has constant current charge controller and over discharge protection.But you can use a tp4056 charge controller.

Step 6: Leds Who Don't Love Those

You can change the resistor to get the current if you are using a power bank.Else you can make the lm317 circuit.

Step 7: Wiring & Cable Management (A LOT:)

Be careful and use hot glue as much as possible not tp short anything and when working with bare batteries, they can short and cause fire.

Step 8: Testing and Closing All Up

You have to spend a lot of time in making adjustments so that your device fits nicely in your case.

Step 9: Results and a Few Words

Check the link below for a further demonstration of the device.This device has a very good efiiciency buu keep in mind that my design don't have over discharge protection as i bypassed it but at full charge it would run for about 24 hours as per my experience and you would probable notice it and if not my circuit will draw every single juice out of it as it can run even in volages below 3V.

My design is far from perfect but it is a good way to make such a device comparing the long term shipping time of the online good ,you can make something from your own hands and it brings you experince and you learn something new.

have a nice day!