Designing and building a 9v battery replacement using supercapacitors

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Introduction

In this video tutorial, a 9v battery replacement circuit is planned, designed and built.

By using supercapacitors and a boost switching regulator, a "battery" which can power a digital multimeter for over one hour and can be recharged within one minute to the maximum capacity is created.

Description

Part 1 of 4

Part 1 of this video tutorial introduces the viewer to the reasons why the author of this tutorial wants to design and build such a battery replacement.

Several types of classic 9v batteries are described, showing how many hours of life they would provide to an average digital multimeter and comparing their efficiency from a price point of view.

The reasons why a 9v battery is used in a digital multimeter are presented and supercapacitors are introduced as a potential replacement for such bulky, inefficient (when it comes to providing energy to digital multimeters) batteries.

Supercapacitors are not ideal replacements though - several advantages and disadvantages are presented, along with possible "fixes" or "improvements" that alleviate some of the disadvantages.

  1. 00:10 Introduction
  2. 03:10 9v battery types, discharge rates
  3. 18:30 Why are 9v batteries used in digital multimeters?
  4. 23:00 Why supercapacitors?
  5. 26:30 Benefits & trade-offs
Part 2 of 4


Part 2 shows viewers how to select a boost switching regulator that would be most suitable for creating such battery replacement, one that would be able to take out as much energy from the surpercapacitors, generating the higher voltage digital multimeters expect, with a reasonably good efficiency.

Several factors that influence the selection of a boost regulator are explained: availability, package type, price, extra components required to complete the circuit being just a few of them.

Once a boost switching regulator is selected, the datasheet is browsed and the application circuit presented in the datasheet is altered to be more suitable for the footprint of a 9v battery.

The modified circuit is then re-created in the free circuit simulator software LTSpice IV, the basic simulation showing the efficiency and the limitations of the boost regulator in regard to minimum voltage required to obtain the desired output voltage and current.

  1. 00:10 Selecting a DC-DC boost switching regulator
  2. 06:00 Things to look for when deciding on a DC-DC boost switching regulator
  3. 14:00 LT1037 datasheet and application circuit
  4. 24:00 Adapting datasheet application circuit for the 9v battery footprint
  5. 28:00 Simulating the circuit using LTSpice IV


Part 3 of 4

In Part 3, the circuit is actually built. After a brief presentation of the components needed for the circuit, changes to the planned circuit are explained.

As the circuit is finalized, mistakes are detected and corrected and everything is ready to be tested using a home-made constant current load.

  1. 00:10 Components used to build the circuit
  2. 08:50 Building the circuit
  3. 16:40 Correcting mistakes
  4. 19:30 Testing the circuit using a constant current load
Part 4 of 4


Part 4 goes through selecting a linear regulator suitable for charging the supercapacitor at a safe maximum current, and building such regulator from scratch.

After the custom charger is built and tested, some suggestions for improving and refining the built battery design are made and conclusions are drawn.

The project is considered successful, after it was able to keep the digital multimeter powered for over one hour and ten minutes, using a single 25F 2.7v supercapacitor.

  1. 00:10 Selecting a suitable linear regulator IC, options for limiting charging current
  2. 14:50 Presenting and testing built custom charger
  3. 20:20 Problems experienced, changes made to planned design, suggestions and improvement suggestions
  4. 26:45 Conclusions