A loudspeaker with a supercapacitor PCB next to it

Hackaday Prize 2023: Supercapacitors Let Solar Speaker Work In Darkness

July 8, 2023 by Robin Kearey 13 Comments

Solar panels are a great way to generate clean electricity, but require some energy storage mechanism if you also want to use their power at night. This can be a bit tricky for large solar farms that feed into the grid, which require enormous battery banks or pumped storage systems to capture a reasonable amount of energy. It’s much easier for small, handheld solar gadgets, which work just fine with a small rechargeable battery or even a big capacitor. [Jamie Matthews], for instance, built a loudspeaker that runs on solar power but can also work in the dark thanks to two supercapacitors.

The speaker’s 3D-printed case has a 60 x 90 mm² solar panel mounted at the front, which charges a pair of 400 Farad supercaps. Audio input is either through a classic 3.5 mm socket or through the analog audio feature of a USB-C socket. That same USB port can also be used to directly charge the supercaps when no sunlight is available, or to attach a Bluetooth audio receiver, which in that case will be powered by the speaker.

A speaker's passive radiator next to a solar panel — The solar panel sits right next to the passive radiator before both are covered with speaker fabric.

The speaker’s outer shell, the front bezel, and even the passive radiator are 3D-printed and spray-painted. The radiator is made of a center cap that is weighed down by a couple of M4 screws and suspended in a flexible membrane. [Jamie] used glue on all openings to ensure the box remains nearly airtight, which is required for the passive radiator to work properly. Speaker fabric is used to cover the front, including the solar panel – it’s apparently transparent enough to let a few watts of solar power through.

A salvaged three-inch Bose driver is the actual audio source. It’s driven by a TI TPA2013D1 chip, which is a 2.7 W class-D amplifier with an integrated boost converter. This enables the chip to keep a constant output power level across a wide supply voltage range – ideal for supercapacitor operation since supercaps don’t keep a constant voltage like lithium batteries do.

[Jamie] has used the speaker for more than nine months so far and has only had to charge it twice manually. It probably helps that he lives in sunny South Africa, but we’ve seen similar solar audio projects work just fine in places like Denmark. If you’re taking your boombox to the beach, a sunscreen reminder feature might also come in handy.

Hackaday Links: June 25, 2023

June 25, 2023 by Dan Maloney 15 Comments

Is it really a dystopian future if the robots are radio-controlled? That’s what came to mind reading this article on a police robot out of Singapore, complete with a breathless headline invoking Black Mirror, which is now apparently the standard by which all dystopias are to be judged. Granted, the episode with the robo-dogs was pretty terrifying, but it seems like the Singapore Police Force has a way to go before getting to that level. The bot, which has been fielded at Changi Airport after extensive testing and seems to be completely remote-controlled, is little more than a beefy telepresence robot. At 5.5 feet (1.7 meters) tall, the bot isn’t terribly imposing, although it apparently has a mast that can be jacked up another couple of feet, plus there are lights, sirens, and speakers that can get the message across. Plus cameras, of course; there are always cameras. The idea is to provide extra eyes to supplement foot patrols, plus the potential to cordon off an incident until meatspace officers arrive. The buzzword game here is weak, though; there’s no mention of AI or machine learning at all. We have a feeling that when the robots finally rise up, ones like this will be left serving the drinks.

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Homemade Scope Does Supercapacitor Experiments

April 8, 2023 by Al Williams 12 Comments

We’ve always been a little sad that supercapacitors aren’t marked with a big red S on a yellow background. Nevertheless, [DiodeGoneWild] picked up some large-value supercapacitors and used his interesting homemade oscilloscope to examine how they worked. You can watch what he is up to in his workshop in the video below.

Supercapacitors use special techniques to achieve very high capacitance values. For example, the first unit in the video is a 500 F capacitor. That’s not a typo — not microfarads or even millifarads — a full 500 Farads. With reasonable resistance, it can take a long time to charge 500F, so it is easier to see the behavior, especially with the homemade scope, which probably won’t pick up very fast signals.

For example, A 350 mA charging current takes about an hour to bring the capacitor up to 2.6 V, just under its maximum rating of 2.7 V. Supercapacitors usually have low voltage tolerance. Their high capacity makes them ideal for low-current backup applications where you might not want a rechargeable battery because of weight, heat, or problems with long-term capacity loss.

The real star of the video, though, is the cast of homemade test equipment, including the oscilloscope, a power supply, and a battery analyzer. To be fair, he also has some store-bought test gear, too, and the results seem to match well.

Supercapacitors are one of those things that you don’t need until you do. If you haven’t had a chance to play with them, check out the video or at least watch it to enjoy the homebrew gear. We usually look to [Andreas Spiess] for ESP32 advice, but he knows about supercaps, too. If you really like making as much as you can, you can make your own supercapacitors.

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Battery Engineering Hack Chat Gets Charged Up

December 16, 2022 by Tom Nardi 9 Comments

Turn the clock back a couple of decades, and the only time the average person would have given much thought to batteries was when the power would go out, and they suddenly needed to juice up their flashlight or portable radio. But today, high-capacity batteries have become part and parcel to our increasingly digital lifestyle. In fact, there’s an excellent chance the device your reading this on is currently running on battery power, or at least, is capable of it.

So let’s get to know batteries better. What’s the chemical process that allows them to work? For that matter, what even is a battery in the first place?

It’s these questions, and more, that made up this week’s Battery Engineering Hack Chat with Dave Sopchak. Our last Hack Chat of 2022 ended up being one of the longest in recent memory, with the conversation starting over an hour before the scheduled kickoff and running another half hour beyond when emcee Dan Maloney officially made his closing remarks. Not bad for a topic that so often gets taken for granted.

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PSU charging an externally connected supercapacitor bank that's powering the phone. There's a current clamp on one of the wires to measure charging current, and a multimeter measuring the charging voltage.

Just How Fast Could You Charge An IPhone?

November 3, 2022 by Arya Voronova 23 Comments

An iPhone 8, now a relatively cheap model, can charge its battery fully in two hours’ time. There’s hardly ever a need for faster charging, but it’s fair to ask – how much faster could it really go? [Scotty Allen] from [Strange Parts], back after a hiatus, is back to stretching the limits of what a regular iPhone can do, and decides to start off with an exploration of battery technologies.

What people commonly encounter is that charging speed depends on the charger involved, but even one hundred chargers in parallel won’t speed up this iPhone’s charging rate, so what’s up? First off, the phone’s charger chip and the battery’s BMS will both limit charging current, so for experiment purposes, those had to be bypassed. First attempt was using a hefty DC power supply with the original cell, and, unsatisfied with the lack of fire and still relatively slow charging, [Scotty] decides to up the ante.
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Building A Spot Welder From 500 Junk Capacitors

August 20, 2022 by Dave Rowntree 5 Comments

[Kasyan TV] over on YouTube was given a pile of spare parts in reasonably large quantities, some of which were useful and allocated to specific projects, but given the given the kind of electronics they’re interested in, they couldn’t find a use for a bag of 500 or so low specification 470uF capacitors. These were not low ESR types, nor high capacitance, so unsuitable for power supply use individually. But, what about stacking them all in parallel? (video, embedded below) After a few quick calculations [Kasyan] determined that the total capacitance of all 500 should be around 0.23 Farads with an ESR of around 0.4 to 0.5 mΩ at 16V and packing a theoretical energy total of about 30 joules. That is enough to pack a punch in the right situation.

A PCB was constructed to wire 168 of the little cans in parallel, with hefty wide traces, reinforced with multiple strands of 1.8mm diameter copper wire and a big thick layer of solder over the top. Three such PCBs were wired in parallel with the same copper wire, in order to keep the total resistance as low as possible. Such a thing has a few practical uses, since the super low measured ESR of 0.6mΩ and large capacitance makes it ideal for smoothing power supplies in many applications, but could it be used to make a spot welder? Well, yes and no. When combined with one of the those cheap Chinese ‘spot welder’ controllers, it does indeed produce some welds on a LiPo cell with a thin nickel plated battery strip, but blows straight through it with little penetration. [Kasyan] found that the capacitor bank could be used in parallel with a decent LiPo cell giving a potentially ideal combination — a huge initial punch from the capacitors to blow through the strip and get the weld started and the LiPo following through with a lower (but still huge) current for a little longer to assist with the penetration into the battery terminal, finishing off the weld.

[Kaysan] goes into some measurements of the peak current delivery and the profile thereof, showing that even a pile of pretty mundane parts can, with a little care, be turned into something useful. How does such an assembly compare with a single supercapacitor? We talked about supercaps and LiPo batteries a little while ago, which was an interesting discussion, and in case you’re still interested, graphene-based hybrid supercapacitors are a thing too!

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Laser-Induced Graphene Supercapacitors From Kapton Tape

November 11, 2020 by Dan Maloney 47 Comments

From the sound of reports in the press, graphene is the miracle material that will cure all the world’s ills. It’ll make batteries better, supercharge solar panels, and revolutionize medicine. While a lot of applications for the carbon monolayer are actually out in the market already, there’s still a long way to go before the stuff is in everything, partly because graphene can be very difficult to make.

It doesn’t necessarily have to be so hard, though, as [Zachary Tong] shows us with his laser-induced graphene supercapacitors. His production method couldn’t be simpler, and chances are good you’ve got everything you need to replicate the method in your shop right now. All it takes is a 405-nm laser, a 3D-printer or CNC router, and a roll of Kapton tape. As [Zach] explains, the laser energy converts the polyimide film used as the base material of Kapton into a sort of graphene foam. This foam doesn’t have all the usual properties of monolayer graphene, but it has interesting properties of its own, like extremely high surface area and moderate conductivity.

To make his supercaps, [Zach] stuck some Kapton tape to glass slides and etched a pattern into with the laser. His pattern has closely spaced interdigitated electrodes, which when covered with a weak sulfuric acid electrolyte shows remarkably high capacitance. He played with different patterns and configurations, including stacking tape up into layers, and came up with some pretty big capacitors. As a side project, he used the same method to produce a remarkable effective Kapton-tape heating element, which could have tons of applications.

Here’s hoping that [Zach]’s quick and easy graphene method inspires further experimentation. To get you started, check out our deep-dive into Kapton and how not every miracle material lives up to its promise.

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