Testing Lithium Cells For Use With A Hybrid Car

June 29, 2012 by Mike Szczys 7 Comments

[Mikey] got a real deal on some A123 Pouch Cells. These are large Lithium cells that tolerate 100A discharge and 50A recharge currents, with 20 AH of life off of one charge. He’s been doing a bunch of testing to find out if the cells can go into an expandable battery pack and be made for use with hybrid cars.

We just looked in on a battery tester used for solar power car arrays. This is a similar situation except [Mikey] is focusing on the test data, rather than the apparatus. The link above is a collection of his notes from testing. Start reading at the bottom of the page up to get the chronology right. He starts to zero in on the most efficient charging methods. Immediately he’s hit with a big need for cooling as the cells take no time to pass 100 degree Fahrenheit. He continues testing with heat sink and fan, and even brings a thermal imaging camera to help with the design.

[Thanks Chris]

Recycle Lithium Cells By Building Custom Flashlights

May 14, 2012 by Mike Szczys 30 Comments

This isn’t a brightest flashlight in the world type of hack (but it does manage to push about 1000 lumens). [Stephen Webb] is finding a use for leftover parts by building his own simple LED flashlights. As you can see, he uses PVC parts available at any hardware or home store. These are a good choice; they’re cheap, light weight, resilient, designed to be water tight, they easily thread together and have connectors that reduce the diameter of the fittings.

The electronics use standard size cylindrical Lithium cells. These are found in many types of Laptop and Power Tool batteries. Often when one of those battery packs bites the dust it’s an issue of one or more bad cells. [Stephen] desolders the cells, and reuses the good ones in this project.

We didn’t see any mention of a recharging technique. Does anyone have any advice on how to top these cells off if they’re not in their original power pack form?

From The Readers: Low Battery Cutoff Solutions

December 1, 2011 by Mike Szczys 25 Comments

We got a lot of really great feedback about low battery cutoff options in the comments section of Monday’s replacement battery post. To refresh your memory, some power tool batteries were replaced by Lithium Polymer units which can be damaged if drained too low before recharging. We had thought that many Lithium cells had cutoff circuitry these days. The consensus is that these batteries didn’t because they’re for RC applications where weight is an issue. But we did get a ton of people sending in commercially available drop-in solutions, mostly from RC hobby outlets, so search around for those if you’re interested.

[Christopher] sent us a link to the cutoff circuit he built for his bike light. You can see the schematic for it above (direct link). He sourced an ATtiny45 to drive a MOSFET which disconnects the battery when it gets too low. This would be easy to adapt to other uses, but note that there’s a voltage regulator involved as well as a few other passives… not a difficult solution but also not all that simple.

This same concept can be adapted. A few commentors mentioned using a transistor (or MOSFET) with the base driven by a voltage divider including a zener diode. This way the voltage rating of the diode would effectively shut off the gate when that threshold was reached.

We also enjoyed reading about [Bill’s] human-controlled cutoff circuit. It also uses a zener diode, but this time in series with a resistor and and LED patched into the trigger of the tool. The LED will shine brightly when the battery is in good shape. It will dim near the end, and fail to light when the critical limit has been reached. Just make sure you’re paying attention and you’re in good shape.

Feel The Hum Of Electricity Between Your Legs

August 10, 2011 by Mike Szczys 21 Comments

Here’s a little eye candy for motorcycle enthusiasts everywhere. This is the newest iteration of [Julian’s] electric motorcycle. He obviously knows what he’s doing because everything fits into the frame in a way that is still very pleasing to the eye. But this is actually slimmed down from the original design. If you take a look a back at some of his older posts you’ll see that the four relatively small lithium batteries are a new addition.

The frame was designed to hold four lead-acid batteries. Those things really take up a lot of space and add considerable weight to the vehicle. His recent upgrade was also accompanied by a re-gearing that allows him to reach higher speeds (although he doesn’t say what the top speed actually is). You can’t really see it above, but [Julian] included a wooden insert where the tank on a gasoline motorcycle would have been. It houses control switches as well as a 48V voltmeter. It’s a fantastic finishing touch like the cherry on a sundae.

Who Knew Thinkpad Batteries Require A Jump Start?

August 1, 2011 by Mike Szczys 59 Comments

Lithium battery packs reaching the end of their life usually have a lot of kick left in them. That’s because they’re made up of multiple cells and it only takes the failure of one to bork the entire battery. One of the most interesting examples we’ve heard of this is in the Toyota Prius, but that’s a story for another time. In this case, [Mika] wanted to resurrect the battery from his IBM Thinkpad T40. He identified the offending cell and replaced it, but couldn’t get any juice out of the battery after the repair.

He was measuring 0V on the output, but could measure the cells instead of the control circuitry and was getting over 11V. Clearly, the control circuit wasn’t allowing an output. We completely understand the concept here (think about that really bad press about exploding laptop batteries). It seems there’s a lockout mechanism when the control circuit loses power. [Mika] managed to get past this by shorting voltage into the control circuit, a method he likes in the video after the break to jump starting a car.

We’ve seen similar cell replacement for power tools, like a Dremel or a Makita drill.

Continue reading “Who Knew Thinkpad Batteries Require A Jump Start?” →

PVC Boombox Is Not A Potato Cannon

June 16, 2011 by Brian Benchoff 14 Comments

After [Luke] built a suitcase mini-ITX rig for LAN parties he was left with one problem: he didn’t have any speakers and he didn’t want to use headphones. Not wanting to do something boring like a USB-powered speaker setup, he built a PVC Boombox.

Built around 3 inch PVC pipe, the boombox houses an off the shelf 15 W amplifier, bluetooth receiver, and charge controller. [Luke] found a deal on a dozen 1400mAh lithium ion batteries and despite the standard, “if you don’t know what you’re doing, don’t use lithium” trope commonly given as advice, he forged ahead anyway. [Luke] picked up a power converter that charges the batteries and provides some protection. The batteries are charged though wall power with a transformer and a huge cap scrounged from an ATX power supply.

[Luke] is pretty pleased with his boombox. Not only does it put out some decent quality sound, the battery life should be tremendous. It’s not a ground-up build, but we think it’s a pretty nice project. [Luke] will be taking the ‘boomtube’ to the Detroit Maker Faire next month, so if you see him make sure to say hi.

Cellphone Battery Mouse Modification

April 19, 2011 by Mike Szczys 23 Comments

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?