[Completed Project/Video] 9v battery using boost regulators, supercapacitors

[mariush]

This was a project that I wanted to do for a long time but kept delaying or working on other things.  So I decided to push myself into finalizing it by making a video tutorial out of it.  (Yeah, that worked out great, it took me about 2 weeks to record and edit it but it's done )

Below you have a series of 4 videos that go through planning, building, testing etc a 9v battery replacement using supercapacitors.

I've used a LT1037 boost regulator IC and a 25F 2.7v supercapacitor to keep my Uni-T UT61E powered logging voltage readings for more than 1 hours and 10 minutes, after charging the supercapacitor within 1 minute. With 100% surface mounted components it's possible to do even better.

If you watch the videos, I hope you won't be bothered too much by my accent and diction - English is not my native language. I will appreciate any feedback you may have.

Also, I consider myself somewhat of a beginner, so there may be some mistakes or terms not used quite properly or I may have made some incorrect assumptions in the videos... hope those won't stop you from watching the videos and pointing these things out to me and learn something out of it.


Tutorial "page" : http://www.helpedia.com/pages/Designing_and_building_a_9v_battery_replacement_using_supercapacitors

Part 1

    00:10 Introduction
    03:10 9v battery types, discharge rates
    18:30 Why are 9v batteries used in digital multimeters?
    23:00 Why supercapacitors?
    26:30 Benefits & trade-offs




Part 2 shows  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.

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



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

    00:10 Components used to build the circuit
    08:50 Building the circuit
    16:40 Correcting mistakes
    19:30 Testing the circuit using a constant current load



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.

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

[TerminalJack505]

I haven't had a chance to watch your videos yet but I'm curious: did you get the device down to the same size as a 9V battery?  Can you actually fit it in a 9V battery compartment?  If so then that's pretty cool.  Either way it's a good idea.

[mariush]

Yes, I did... kinda.   

I managed to put it inside the battery compartment and partially screw the back on, but not fully closed ... with a bit of filing down of the two vertical pcbs, it would be possible to fully close the case. It was good enough to make reliable connection to the battery terminals (if I wanted i could have soldered two wires directly but it worked as designed)

With a slightly smaller supercapacitor in diameter and trimming the vertical boards, it would fit just fine. 

When I have more time, I plan to make a fully surface mount version using Diptrace or Kicad and build some boards. No trimpot (thinking of using just a jumper to switch between let's say 5.8v and 7v, for those multimeters that have a higher low battery voltage threshold), no electrolytic capacitor, just ceramic capacitors and resistors, so would fit 2 smaller supercapacitors with no problems at all.