LiFePO4 batteries work much better in a camera than NiMH


We agree with [Zapmaker] that Canon cameras chew through nickel metal hydride batteries. But we’re not going to use Alkaline because we think it’s wasteful. His solution is to use a battery that has a higher voltage rating. What you see here is a single lithium iron phosphate cell paired with a dummy cell to increase life between charges.

The reason that NiMH batteries don’t last very long is that they’re only rated at 2.4V. It won’t take long for that voltage to drop below the camera’s cutoff threshold since they didn’t start very high to begin with. But a single LiFePO4 cell has the same form-factor but produces 3.2V and maintains voltage well through it’s discharge cycle.

The size is right, but using one cell won’t work by itself. He built a filler for the other slot which is just a wood dowel with a screw all the way through it. The point was ground down and a bit of foil added to ensure a proper connection. We’d be interested to hear back about how this performs over the long term.

Testing 30 brands of batteries

Batteries come packaged in bright blister packs emblazoned with vague guarantees such as “45% more pictures” and “five times longer lasting.” During his internship at BitBox this summer, [Thomas] decided to put those statements to the test. He tested thirty brands of batteries on a homebrew rig to find the batteries with the most power and the most bang for your buck.

The hardware [Thomas] used an STM32 microcontroller to perform two different tests: a high drain and a low drain condition. For the high drain, 1000 mA were sucked out of the batteries until the voltage reached 0.8 V. For the low drain, 200 mA were used. Data including milliwatt-hours, milliamp-hours, joules, voltage, current, power, and effective load resistance were all logged for both conditions for all 30 batteries.

Generalizing the results for both low and high drain conditions, lithium batteries were better than alkaline, which were both better than zinc AA cells. Perhaps unsurprisingly, batteries marketed as ‘long life’ and ‘extended power’ were the worst batteries for the money, but a brand-name battery – the Kodak Xtralife cells – were actually the best value for the money.

Squeezing the juice out of some AA batteries

[Ray's] breadboard power supply lets you drain the last traces of power from ‘dead’ AA batteries. Electronics that are powered off of disposable alkaline batteries have a cutoff voltage that usually leaves a fair amount of potential within. Since many municipal recycling programs don’t take the disposables (you’re just supposed to throw them in the trash!) we love the idea of squeezing them for prototyping use.

His design uses just one IC, the MCP1640, along with a handful of passive components. The chip is a boost converter with a startup voltage of just 0.65V, which means the batteries themselves – normally starting life above 1.5V – can be used until they drop to about 0.3V each.

Above you can see the kit he is selling. But it’s an open source project and the circuit is so simple we’re sure you can build your own. Add that boost converter chip to your next parts order for around $0.40.

[Ray] made a nice demo video for the device which you can see embedded after the break.

[Read more...]

Cellphone battery mouse modification

Ever wanted to increase the battery performance in your wireless mouse? [Davetech] shows you the way with this guide for converting a mouse from AA to lithium batteries. We were delighted by his hack-tacular approach that seems to have a nice little work-around at each step in the process. He grinds down the plastic battery housing that is molded into the original mouse body, then uses an old Compact Flash card connector as a set of spring terminals for a Nokia cellphone battery. This battery has more capacity and recharges faster than non-Lithium AA cells. But unfortunately the spring terminals didn’t quite reach the recessed batter contact. No problem, he just builds up solder on the battery to bridge the gap.

[Davetech] manages to fit the entire battery inside the mouse and the pointing-device still works. Your mileage may vary by model (both battery and mouse). It is necessary to take the battery out of the mouse for recharging, but since this only happen about every couple of weeks thanks to the extended capacity it’s not too much of a hassle. Perhaps someone could carry this to the next level by adding a USB port and the necessary charging circuitry?

Revive your tired Dremel battery pack

It turns out there’s nothing more than six Nickel Cadmium AA rechargeable batteries inside of that cordless Dremel battery pack. Yep, standard rechargeable AA’s that you can buy most anywhere, and now you can revive that aging battery pack by following [Stuuf's] guide. Since you’re already at it, a few more bucks will yield a real upgrade by using the superior Nickel Metal Hydride batteries which should yield around three times as much use between charging. We totally understand having a battery pack, since the shape of the case is part of the handheld tool, and it should be easy to interchange the battery as one unit. We just wish that the battery pack had been designed to have the AA cells swapped out by the user once they had reached the end of the line.

Do you have other cordless tools in need of a pick-me-up? Check out this Makita battery pack repair hack for a point in the right direction.

[Thanks Bluewraith]

Elegant wearable computer

[Jason Statham] [Martin Magnusson] wrote in to tell us about his adventure in building a wearable computer. The device in its current state is a Beagleboard running Angstrom Linux tethered to an iPhone for internet. A bluetooth keyboard allows for input, while output is displayed on monocle-ized Myvu. And last but not least, the entire setup is powered by 4 AA batteries for 3 hours of life.

Its not as small as some of the wearable computers we’ve seen before, but if you wanted to whip out your own it sure takes a lot less soldering.

Thin client as robot platform


[Extra Ketchup] has a couple Neoware thin clients and thought they would make a good robotics platform. It’s a Geode based board that came with Windows CE. He built a small Gentoo system to fit on the 130MB solid state drive. He likes the idea of using it as a platform because the board has serial, parallel, and USB support. The best part is shown above; it can run off of just 4 AA’s.