Coin Cell Challenge: Jump Starting A Car

December 8, 2017 by Tom Nardi 80 Comments

Clearly a believer in the old adage, “Go Big or Go Home”, [Ted Yapo] has decided to do something that seems impossible at first glance: starting his car with a CR2477 battery. He’s done the math and it looks promising, though it’s yet to be seen if the real world will be as accommodating. At the very least, [Ted] found a video by [ElectroBOOM] claiming to have started a car with a super capacitor, so it isn’t completely without precedent.

Doing some research, [Ted] found it takes approximately 2,000 W to 3,000 W at 14 V to start the average car engine. This is obviously far in excess of what a coin cell can put out instantaneously, but the key is in the surprising amount of potential energy stored in one of these batteries. If the cell is rated for 1000 mAh at 3 V, [Ted] shows the math to find the stored energy in Joules:

According to the video by [ElectroBOOM], he was able to start his car with only 6,527 J, and [Ted] calculates it should only take about 9,000 J on the high side from his research. So as long as he can come up with a boost converter that can charge a capacitor with high enough efficiency, this one should be in the bag.

[Ted] has started putting together some early hardware, and has even posted the source code he’s using on a PIC12LF1571 to drive the converter. He notes the current charge efficiency is around half of what’s needed according to his calculations, but he does mention it was an early test and improvements can be made. Will it start? If it does, this is some awesome Heavy Lifting.

The Incredible Shrinking Coin Cell Battery Pack

December 7, 2017 by Kristina Panos 15 Comments

How’s it going with your project for the coin cell challenge? You can only use a single one, but Hackaday alum [Jeremy S Cook] has a great way to package coin cells into a sleek little power packs whether you need one, two, or even four.

[Jeremy] is building a wireless Wii nunchuk, so he needs a small battery that won’t short out or get punctured in the confines of the controller body. A single coin cell holder is already a bit bulky, and he needs to use two in series. He thought, why not try shrink wrapping them together? The only downside here is that the biggest tube that came with your average heat shrink multi-pack is probably a bit too tight to fit around them, so you might have to buy more (aw, shucks!).

After trying a few ways to make a good connection between the leads and the bare coin cell faces, [Jeremy] settled on generously stripping stranded wire and wrapping the long strands around the end to form a conductive swab. This slides in nicely between the coin cell and preshrunk tube. A little more heat will make a good connection, and some hot glue secures the wires. Click past the break for his build video and the other connection methods he tried. Have you come up with something better? Let us know in the comments.

Stray a bit further from the bench and you might come up with something like this googly eye battery holder we saw a few months ago.

Continue reading “The Incredible Shrinking Coin Cell Battery Pack” →

Coin Cell Challenge: Use Coin Cell, Win Prizes

November 29, 2017 by Brian Benchoff 74 Comments

Today, we’re calling all hackers to do the most with a single coin cell. It’s the Coin Cell Challenge, and we’re looking for everything from the most low-power electronics to a supernova in a button cell battery.

Electronics are sucking down fewer and fewer amps every year. Low power is the future, and we’re wondering how far we can push the capabilities of those tiny discs full of power. The Coin Cell Challenge is your chance to plumb the depths of what can be done with the humble coin cell.

This is a contest, and as with the tradition of the Open 7400 Logic Competition and the recent Flashing Light Prize, we want to see what the community can come up with. The idea is simple: do something cool with a single coin cell and you’ll secure your fifteen minutes of fame and win a prize.

Three Challenges

To kick this contest off, we’re opening up three challenges to all contenders to the world heavyweight champion of button cell exploits. The first, the Lifetime Award, will go to whoever can run something interesting the longest amount of time on a coin cell. The Supernova Award is the opposite – what is the most exciting thing you can do with a button cell battery, lifetime be damned? The Heavy Lifting Award will go to the project that is the most unbelievable. If you think you can’t do that with a coin cell battery — lifting a piano or starting a car, for example — odds are you probably can. We want to see it.

Prizes and Rules

All Hackaday hardware hacking challenges need prizes, and for this one, we’re rolling out the red carpet. We’re offering up cash prizes for the top coin cell hacks. There are three $500 USD cash prizes, one for each winner of the Lifetime, Supernova, and Heavy Lifting awards. We’re not stopping there, because the top twenty builds overall will each receive $100 in Tindie credit, where the winners can cash in on some artisanal electronics sold by the people who design them.

What do you have to do to get in on this action? First, you need to build something. This something must be powered by nothing more than a single coin cell battery and must include some type of electronics. We also want this to be Open Source, and you’ll need to start a project on hackaday.io. The full rules are available over here, but don’t wait — the deadline for entry is January 8th, 2018.

We’re excited to see what the community comes up with, and who will find a production coin cell that’s the size of a dinner plate. This is going to be a great contest with overheating coin cells and tiny bits of metal flying across the room. This is going to be a contest filled with blinkies and wireless devices that run for far, far too long. Someone is going to misread the rules and tape together a meter tall pile of coin cells. It’s going to be awesome, so start your project now.

Hackaday Prize Entry: A PCB To Emulate Coin Cells

September 18, 2017 by Donald Papp 43 Comments

The Coin Cell Emulator CR2016/CR2032 by [bobricius] homes in on a problem some hardware developers don’t realize they have: when working on hardware powered by the near-ubiquitous CR2016 or CR2032 format 3V coin cells, power can be a bit troublesome. Either the device is kept fed with coin cells as needed during development, or the developer installs some breakout wires to provide power from a more convenient source.

[bobricius]’s solution to all this is a small PCB designed to be inserted into most coin cell holders just like the cell itself. It integrates a micro USB connector with a 3V regulator for using USB as an external power source. The board also provides points for attaching alligator clips, should one wish to conveniently measure current consumption. It’s a tool with a purpose, and cleverly uses the physical shape of the PCB itself as an integral part of the function, much like another of [bobricius]’s projects: the Charlieplexed 7-segment LED display.

$1 Coin Cell Charger

January 17, 2014 by James Hobson 46 Comments

Sure, coin cells usually last a long time — but do you really want to buy new ones and throw the old ones out? The LiR2032 coin cell is a rechargeable lithium battery, for which you can build a charger at around $1.

The 5 minute hack starts with a TP4056 lithium charging circuit, which is a great DIY board designed to charge high-capacity cells at about 1A. Luckily, it is pretty easy to modify the board to charge lower capacity batteries. It’s just a matter of replacing resistor R4, and a little bit of soldering! Continue reading “$1 Coin Cell Charger” →

Coin Cell Battery Charger

March 28, 2012 by Mike Szczys 19 Comments

[Jay Kickliter] built his own coin cell battery recharger. This won’t work on the vast majority of coin cells as they are manufactured as disposable parts. But there are rechargeable options out there with model numbers that start with LR instead of CR. In this case he tailored the charging circuit around MCP73832 IC and chose components best suited for charging his 110 mAh LR2450. But we believe all of the LR options out there are rated for 3.6V so altering his design for use with different models should be a breeze.

We’ve been unhappy with the use of disposable coin cell batteries for some time. Sure, in a real-time clock where the cell might last 6-8 years this is not very wasteful. But in an Apple TV remote that gets a lot of use, we hate the choice of a disposable battery. All of our less-hip remotes which use AA or AAA have NiMH rechargeables in them and have used the same pair for year and years. So we’re happy to see this charger project come along.

Now the bad news. We looked around and indeed you can find LR2032; a rechargeable replacement for the CR2032. But the capacity rating falls way flat. The model we looked at boasts only 50 mAh while the disposable CR2032 offers something along the lines of 240 mAh. Hopefully this will change as battery tech evolves.

Insert Coin (Cell) To Play LedCade

May 6, 2019 by Roger Cheng 3 Comments

In this era of 4K UHD game console graphics and controllers packed full of buttons, triggers, and joysticks, it’s good to occasionally take a step back from the leading edge. Take a breath and remind ourselves that we don’t always need all those pixels and buttons to have some fun. The LedCade is a μ (micro) arcade game cabinet built by [bobricius] for just this kind of minimalist gaming.

Using just three buttons for input and an 8×8 LED matrix for output, the LedCade can nevertheless play ten different games representing classic genres of retro arcade gaming. And in a brilliant implementation of classic hardware hacking humor, a player starts their game by inserting not a monetary coin but a CR2032 coin cell battery.

Behind the screen is a piezo speaker for appropriately vintage game sounds, and an ATmega328 with Arduino code orchestrating the fun. [bobricius] is well practiced at integrating all of these components as a result of developing an earlier project, the single board game console. This time around, the printed circuit board goes beyond being the backbone, the PCB sheet is broken apart and reformed as the enclosure. With classic arcade cabinet proportions, at a far smaller scale.

If single player minimalist gaming isn’t your thing, check out this head-to-head gaming action on 8×8 LED arrays. Or if you prefer your minimalist gaming hardware to be paper-thin, put all the parts on a flexible circuit as the Arduflexboy does.