Geeks living off the grid are hard on batteries

Many of you will remember [Mikey Sklar] from the multitude of times he’s been on hackaday. What you may not have noticed is that he is an ubergeek, living off the grid.

He has Solar PV battery bank, three electric vehicles, a shipping container loaded with battery powered tools and a small army of iRobot Roomba’s for cleaning. Getting the maximum lifetime out of a battery by removing sulfation is essential to keep expenses down.

Keeping expenses down is nearly a full time job when trying to live the homestead lifestyle. Our current culture makes it extremely difficult to survive completely on self made/grown things and bartering. They seem to be doing pretty well though. One way he can reduce his costs while still getting to enjoy some modern gadgets is to get longer life out of his batteries.  He does this by using a capacitive battery charger and desolfator that he designed and affectionately calls “Da Pimp”. He also brings in a little bit of income by selling kits!

 A capacitive charger behaves like a constant current power supply dynamically adjusting the voltage to get over the batteries internal resistance. Plus there is a pulse from the AC/DC conversion. This allows for old batteries to last longer and for dumpster dived to be used as replacements. Capacitive chargers are small, silent and super efficent (up to 60% more so than cheap transformer based chargers).

Of course, [Mikey] is a supporter of sharing information so you can also go to his site and download the schematics,bill of materials, gerber files, and files for the housing,  to build one yourself.

Scavenging from consumer electronics to make a flame-powered phone charger

[Gigafide] just finished building this flame-powered phone charger. The concept is not new. He grabbed a Peltier cooler and used the temperature differential between a flame and a heat sink to produce electricity used by the charger. If you search around here enough you’ll find plenty of candle-powered devices, and a few hacks that use a Peltier device in a bit more interesting way. But we really like his high-production value video, straightforward explanation of the concepts, and ability to source the components in consumer devices. We don’t think you’ll be disappointed by his video found after the break.

The Peltier device comes out of a USB drink chiller. It is supported by a metal stand made from electrical box covers and threaded rod. Underneath he’s using a gel fuel can used by the food industry, and above he’s got  CPU heat sink and fan. This setup puts out around 1.5V but he’ll need a boost converter to charge a phone with that. A single AA battery charger meant to power your phone in a pinch is perfect for this application.

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Prototyping a solar charger for your truck

[Bryan] got his hands on a solar panel and decided to take it on the road rather than throwing it on the roof of the house. On sunny days it will top off the car battery, letting him use his stereo in the middle of nowhere without needing to keep the engine running. Instead of buying a ready-made solution he chose to design and build his own charging circuitry.

The charger uses an Arduino, which draws its own power from the panel via a regulator. It senses the voltage level of the battery and the available juice from the panel, connecting or disconnecting it from the electrical system as necessary. The system includes a set of LED indicators, which he installed in the dashboard near the cigarette lighter. This also gave him an excuse to install a voltmeter which uses a 2.5 digit seven segment display to read out the battery voltage. You can see a brief overview after the break.

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Wireless iPod charger built from scratch

Despite the obvious use of a lot of wire, this project is actually a wireless charging system. [Jared] built it as a way to explore the concepts behind transferring power inductively. Alternating current on one of the white coils induces current on the other. This is then rectified, and regulated for use as a 5V charger. In this case it powers his iPod, but any USB device should work with the setup.

The transmitter uses the power supply from an old laptop as a source. Some filtering and a couple of MOSFETS are responsible for generating the AC current on the transmitting coil. The receiving coil feeds the bridge rectifier. In the writeup that voltage is fed to a 7805 regulator to provide a stable 5V output. However, in the video demo after the break [Jared] shows off the boost converter that he uses on his improved circuit. This way if the voltage drops due to poor alignment of the coils it will still be able to provide a steady output.

We’ve seen the same coil concept used to add wireless charging to cellphones too.

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Pros and cons of replacing tool batteries with Lithium Polymer

[HammyDude] was tired of buying replacement batteries for his power tools. He had some Lithium Polymer batteries on hand and decided to take one of his dead drills and swap out the dead power pack.

The orange battery pack you see above has a deans connector on it for use with RC vehicles. By opening up the drill housing, [HammyDude] was able to add the mating deans connector. Now the replacement easily plugs into the drill, and it even fits inside the handle body.

This battery is made up of several cells, and an inexpensive charger is capable of topping off each individually for a balanced charge. In the video after the break [HammyDude] points out that the Makita charger applies voltage to all of the cells in series. It’s incapable of balance charging so when one cell dies the battery is toast. We’ve encountered this problem with Makita tools before.

One drawback to take note of in the end of the video: this replacement doesn’t have any low voltage cut-off. Running this battery pack down too low will permanently damage it. There must be a simple circuit that could be added as a safety measure. If you know of one, drop us a tip.

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Hackaday Links: November 6th, 2011

Build details for Raspberry Pi prototype

With the launch of Raspberry Pi approaching the development team released the details about the prototypes from about five years ago. The board was originally based on an ATmega644 and built on some perfboard.

‘Zero Energy Device’ challenge

We call BS on the title of this one, but the goal of finding devices that don’t use disposable energy sources is a good thing in our book. For instance, can we get more stuff that uses long-life capacitors instead of batteries?

Command adhesive for mounting bulletin boards, etc.

This seems like a no-brainer, but we’ve been using nails to mount bulletin boards and white boards for year. The problem is, when you stick a push-pin in one side, the other side pops off of the nail. [Zhanx] is using adhesive from 3M Command Hooks to keep his stuck to the wall.

Servo-driven gripping hand

[Navic] has been hard at work on this robot hand. There’s few details but he shows it can grip objects under one pound and he’s been taking amperage measurement during testing.

Emergency cellphone charging

It might not have been an emergency this time, but [Chris] did figure out a way to charge his cellphone after the snow storm in New England knocked out his power. He connected to lantern batteries to a 7805 regulator, then patched that into a USB hub to get his phone connected. Not bad in a pinch!

Cellphone battery booster built at the checkout counter

When you’re away from home and your cellphone runs out of juice it can be a real downer. Sure, you could find a store and buy a wall charger, but wouldn’t it be more fun to build your own battery booster without using tools? [Spiritplumber] did just that, popping into a Radio Shack for the parts, then making his how-to video (embedded after the break) while standing at the checkout counter. You can see he hust set his camera on top of the battery display case and got to work.

He’s using four D cell batteries to provide 6 volts of power. Assuming your phone charges at 5 volts this is going to be just a bit too high, even though there’s some tolerance with most phones. To overcome that obstacle he added a diode to the circuit, taking advantage of the 0.7 volt drop that it brings to the mix. Grab a plug adapter for your model and then just hand twist the connections. [Spiritplumber] admits it would be better to solder these, but in a bind you can get away with it. We looked up some prices for this method and we figure this would cost around $18 (batteries included) depending on the price of the plug adapter for your phone.

Of course if you’re just looking for a way to charge your phone without paying consumer prices there are ways of accomplishing that as well.

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