Solar Panel Keeps Car Battery Topped Off Through OBD-II Port

Up until the 1980s or so, a mechanic could check for shorts in a car’s electrical system by looking for sparks while removing the battery terminal with everything turned off in the car. That stopped being possible when cars started getting always-on devices, and as [Kerry Wong] learned, these phantom loads can leave one stranded with a dead battery at the airport after returning from a long trip.

[Kerry]’s solution is simple: a solar trickle charger. Such devices are readily available commercially, of course, and generally consist of a small photovoltaic array that sits on the dashboard and a plug for the lighter socket. But as [Kerry] points out in the video below, most newer model cars no longer have lighter sockets that are wired to work without the ignition being on. So he chose to connect his solar panel directly to the OBD-II port, the spec for which calls for an always-on, fused circuit connected directly to the positive terminal of the vehicle battery. He had to hack together an adapter for the panel’s lighter plug, the insides of which are more than a little scary, and for good measure, he added a Schottky diode to prevent battery discharge through the panel. Even the weak winter sun provides 150 mA or so of trickle charge, and [Kerry] can rest assured his ride will be ready at the end of his trip.

We used to seeing [Kerry] tear down test gear and analyze unusual devices, along with the odd post mortem on nearly catastrophic failures. We’re glad nothing burst into flames with this one.

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Wireless Charging Without So Many Chargers

[Nikola Tesla] believed he could wirelessly supply power to the world, but his calculations were off. We can, in fact, supply power wirelessly and we are getting better but far from the dreams of the historical inventor. The mainstream version is the Qi chargers which are what phones use to charge when you lay them on a base. Magnetic coupling is what allows the power to move through the air. The transmitter and receiver are two halves of an air-core transformer, so the distance between the coils exponentially reduces efficiency and don’t even think of putting two phones on a single base. Well, you could but it would not do any good. [Chris Mi] at San Diego State University is working with colleagues to introduce receivers which feature a pass-through architecture so a whole stack of devices can be powered from a single base.

Efficiency across ten loads is recorded at 83.9% which is phenomenal considering the distance between each load is 6 cm. Traditional air-gap transformers are not designed for 6 cm, much less 60 cm. The trick is to include another transmitter coil alongside the receiving coil. By doing this, the coils are never more than 6 cm apart, even when the farthest unit is a long ways from the first supply. Another advantage to this configuration is that tuned groups continue to work even when a load changes in the system. For this reason, putting ten chargeables on a single system is a big deal because they don’t need to be retuned when one finishes charging.

We would love to see more of this convenient charging and hope that it catches on.

Via IEEE Spectrum.

You Should Not Try These Taser NERF Darts

For most of us, a good part of our childhood involved running around someone’s backyard (or inside the house) trying to score hits with a toy NERF gun. The fun level was high and the risk of personal injury was low. Now that we’re all mostly adults, it’s probably time to take our NERF game to the next level with some risk of serious personal harm.

In an effort to help his brother get back at him for being somewhat of a bully in their youth, [Allen Pan] gifted him with an upgraded NERF gun. Specifically, one with darts that pack a punch. Each of the “Elite” darts was equipped with a 300 V capacitor packed into the interior of the dart. New tips were 3D printed with special metal tips that allow the capacitor to discharge upon impact.

Besides the danger, there’s a good bit of science involved. Parts were scavenged from a new (and surprisingly expensive) disposable camera, and a customized circuit was constructed around the barrel of the dart gun that allows the darts to charge up when they’re loaded. It’s an impressive build that would be relatively simple to reconstruct for yourself, but it’s probably not the worst thing we’ve seen done with high voltage and a few small capacitors.

Thanks to [Itay] for the tip!

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MagSafe Power Bank From Scrap

Just a few short years ago, it was possible to find scrapped lithium batteries for free, or at least for very cheap. What most people at the time didn’t realize is that a battery with multiple cells might go bad because only one cell is bad, leaving the others ready for salvaging. Now it’s not a secret anymore, but if you can manage to get your hands on some there’s a lot of options for use. [ijsf] took a step further with this hack, taking a few cells from a Panasonic battery and wrangling them into a MagSafe-capable power bank for a Mac.

The real hack wasn’t scavenging batteries, however, it was getting the MagSafe to signal the computer to use power from the battery bank to run the computer only, and not to use any of that energy for charging the computer’s internal batteries. This is achieved by disabling the center MagSafe pin, which is the computer’s communication line to the power adapter. After that, the battery bank could be programmed to behave properly (a feat in itself for lithium batteries) and the power bank was successfully put into operation.

Not only was this hack a great guide for how to repurpose cells from a “dead” battery, it’s also an unparalleled quick reference for any work that might need a MagSafe connector. Of course, if you’re going to work with these chargers, make sure that you’re using one that isn’t a cheap clone.

A Table From Beyond Infinity

Infinity mirrors are some far-out table mods and make a great centerpiece. Instructables user [bongoboy23] took a couple steps beyond infinity when designing this incredible table tailor-made for our modern age.

Poplar and pine wood make up the framing, and red oak — stained and engraved — make for a chic exterior. Programmed with Arduino and run on a Teensy 3.1, the tabletop has 960 LEDs in forty sections. There are, four USB ports hidden behind sliding panels, as well as a two-port AC outlet and an inductive charging pad and circuit.  A hidden Adafruit TFT touchscreen display allows the user to control the table’s functions. Control is limited to changing lighting functions, but Pac-Man, Snake, and text features are still to come!

Weighing in at $850, it’s not a cheap build, but it looks amazing.

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Bitbanging Qualcomm Charge Controllers

With more and more manufacturers moving to USB-C, it seems as though the trusty USB port is getting more and more entrenched. Not that that’s a bad thing, either; having a universal standard like this is great for simplicity and interconnectability. However, if you’re still stuck with USB 2.0 ports on your now completely obsolete one-year-old phone, there’s still some hope that you can at least get rapid charging. [hugatry] was able to manipulate Qualcomm’s rapid charging protocol to enable it to work with any device.

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Smartphone Hack For Adding Magnet Power Dock

Here’s a neat hack for making a magnetic charging mount for a cell phone. We know what you’re thinking, but this is definitely not a traditional contactless charging system. Those use magnets but in a different way. This hack involves putting a couple of magnets onto the case of the cell phone, and a couple more on a charging base. You then wire these magnets into the power inputs of the USB port, and a USB cable onto the base, so putting the phone on the base magnets completes the circuit. The magnets themselves become the charging contacts.

It’s a neat idea, but makes us wonder what this will do to the compass sensor in your phone or your credit cards if they are nearby. With these caveats, it is a neat hack, and could be easily adapted. Want to make a vertical cell phone mount, or a way to attach (and charge) your cell phone to the fridge? This can be easily adapted for that.

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