Once again, [Afroman] is here for you, this time breaking down electrolyte and the terminology behind batteries.
Volts and Amps are easy mode, but what about Amp hours? They’re not coulombs per second hours, because that wouldn’t make any sense. An Amp hour is a completely different
unit podcast, where a 1Ah battery can supply one amp for one hour, or two amps for 30 minutes, or 500 mA for two hours.
Okay, what if you take two batteries and put them in series? That would double the voltage, but have the same Ah rating as a single cell. Does this mean there is the same amount of energy in two batteries as what is found in a single cell? No, so we need a new unit: the Watt hour. That’s Volts times Amp hours, or more incorrectly, one joule per second hour.
Now it’s a question of the number of cells in a battery. What’s the terminology for the number of cells? S. If there are three cells in a battery, that battery has a 3S rating. You would think that C would be the best letter of the alphabet to use for this metric, but C is entirely different. Nothing here makes any sense at all.
What is C? That’s related to the number of amps a battery can discharge safely. If a 20C battery can discharge 2200mAh, it can deliver a maximum current of 44 A, with 20C times 2.2Ah being 44A.
So there you go. A complete description of something you can’t use logic and inference to reason through. Video below.
Continue reading “A Description of Maddening Battery Terminology”
You assume that you’ll be able to get parts forever… after all: The Internet. But what if you can’t justify paying the price for them? [Cristi C.] was in this situation, not wanting to fork over $30+ for a replacement PSP battery. The handheld gaming rig itself was just discontinued this year but supposedly the batteries have been out of production for some time. What you see above is the controller board from an original battery, with the cell from a camera battery.
The key is protection. The chemistry in Lithium cells of several types brings a working voltage of around 3.7V. Swapping the cells — even if they are different capacities — should work as protection circuits generally measure current, voltage, and sometimes temperature as they charge in order to know when the cell is full. With this in mind [Christi] cracked open a used Canon NB-6L type battery and grabbed the prismatic cell as a replacement for the pouch cell in the Sony S110 case (PDF). The Canon cell is enclosed in a metal case and is just a bit smaller than the pouch was. This means with careful work it fit back inside the original plastic enclosure.
On a somewhat related note, be careful when sourcing brand-x batteries. Some manufacturers implement checks for OEM equipment but there are ways around that.
If you’re wondering how to get a better signal on your cellphone, or just want to set up your own private cell network, this one is for you. It’s a GSM base station made with a BeagleBone Black and a not too expensive software defined radio board.
The key component of this build is obviously the software defined radio. [Julian] is using a USRP B200 radio for this project. It’s not cheap, but it is a very nice piece of hardware capable of doing just about anything with GNU Radio. This board is controlled by a BeagleBone Black, a pretty cheap solution that puts the total cost of the hardware somewhere around $750.
The software side of the build is mostly handled by OpenBTS, the open source project for the software part of a cell station. This controls the transceiver, makes calls and SMS, and all the backend stuff every other cell station does. OpenBTS also includes support for Asterisk, the software of choice for PBX and VoIP setups. Running this allows you to make calls and send texts with your SDR-equipped, Internet-enabled BeagleBone Black anywhere on the planet.
This tiny little scratch-built electric tricycle is a insanely powerful. Some might think you don’t need a crash helmet for testing a trike, but seeing the video after the break where [Ben Katz] is flying through a parking garage while slaloming between the support beams proves that this ride has some pep to it.
Looking through the presentation post linked above is fun, but when we started digging though the six build log posts we felt ourselves getting sucked into the project. It’s a delight every step of the way. It started with an aluminum box which will host the two rear wheels, drive train, motor, and battery. [Ben] decided to go with A123 Lithium cells, and after testing to see how many he could fit in the space available he started making choices on the motor and driver circuit. When he finally got his hands on the actual cells for the project he took on the fascinating process of constructing his own battery. Dozens of them were hot glued, then soldered together before being encased by placing them in soda bottles and hitting the plastic with a heat gun. And we haven’t even gotten into the bicycle hub-gear transmission system, disc brakes, differential, chain-drive, and motor… you see what we mean about sucking you in.
Oh, and in case you’re wondering this is not [Ben’s] first electric vehicle build. Last year he was showing off his all terrain scooter.
Continue reading “Electric tricycle build log is like hacker crack”
Most of what people call batteries are actually cells. All of the common disposable alkaline batteries from AAA to D are single cells. The exception is the 9v battery which actually has six smaller cells inside of it. [Tom] took a look inside three different batteries to see what cells they’re hiding. Since he no longer uses the batteries for their intended purposes the individual cells may find a new life inside of one of his upcoming projects.
The six volt lantern battery on the left has four cells inside of it. This is no surprise since each zinc-carbon cell is rated for 1.5V. There’s not much that can be done with the internals since each cell is made of a carbon rod and zinc electrolyte ooze (rather than being sealed in their own packages).
Moving on to the rechargeable PP3 battery in the middle he finds the 8.4V unit is made up of seven 1.2V nickel-metal hydride cells. Many of them were shot, but we’d love to see one of the intact cells powering something small like a bristlebot.
The final component is an old laptop battery. Inside are an octet of Lithium Ion cells. The majority register 0V, but a few have 0.4V left on them. This is not surprising. We’ve seen power tool packs that have a few bad cells spoil the battery. It’s possible to resurrect a battery by combining good cells from two or more dead units.
[Doctor Bass] needed to do some welding on his electric bicycle. The problem is that he’s never welded before and doesn’t have any tools for it. As you can see, that didn’t stop him. He used a bicycle battery made from reclaimed DeWalt A123 cells to power his diy welding rig.
He has a huge adjustable resistor which is responsible for limiting the current. 80 Amps seems to work the best with the welding rods he’s chosen. It is worth noting that when he shows off each part of the welder (see the clip after the break) the color of the wire used for positive and negative leads is opposite of convention. His positive wiring is black while his ground connection is red.
To get the welding under way he connects a jumper-cable-like clamp to his work piece which serves as the positive electrode. To hold the welding rod he drilled a hole in a pair of vice grip pliers and bolted on the negative lead. This way the end of the welding rod can be clamped in the vice grips while his other hand guides the tip. So far he’s still practicing, but it looks like he’s nearly ready to take on the job at hand.
Continue reading “Welding with over a hundred A123 Lithium cells”
This is a scratch-build meter for measuring the internal resistance of Lithium Polymer cells. [Bleuer Csaba] uses the LiPo cells for RC vehicles and thet take quite a beating from the motors they’re supplying. This means that he only gets about 100-200 cycles out of each cell. To figure out where one is in its life cycle you can measure the internal resistance where a rising resistance indicates greater age. [Bleuer] mentions that you can buy a meter to do this for you, but what fun is that?
Since he’s rolling his own tool he defined his own parameters for the readings. After experimenting with different loads driven for different test periods he was able to extrapolate an equation that estimates the resistance measurement. As you can see in the clip after the break, this happens very fast. All he has to do is connect the cell and press one button. The measurements are made and various data points are displayed on the quartet of 7-segment displays.
Continue reading “LiPo internal resistance measurement tool”