标签: batteries

The convenience of an untethered world of mobile phones, personal wearable devices, and the many wireless sensors and controllers in our homes comes at a price: constant attention to and management of the rechargeable batteries that power them.   There have been recent proposals for providing other means of maintaining their operation such as super-capacitors, energy harvesting of radio waves and vibrational energy from the ambient environment. But such alternatives alone will not be sufficient. To ensure a constant source of power, rechargeable batteries (currently based on lithium ion cells) will be necessary. To conserve power consumption in mobile devices, the MIPI battery interface (BIF) spec only needs a single pin (BCL) to send and receive data and commands for proper management. (Source: MIPI Alliance)   Dependent as we have been on rechargeable batteries for more than a decade, it has always puzzled me that a common device- and protocol- independent standard has not emerged.   Until relatively rechargeable battery management has have been barebones. A typical low cost relatively dumb battery scheme often consists of no more than identification resistors connected to the battery pack terminals. Alternately the pack might include a resistive temperature sensor next to the power supply connectors. The measured value of the pull-down resistor indicates the capacity and chemistry information.   There are many so-called smart battery management schemes available. But they are either company, industry, or application specific, despite the fact that they all use the same battery types, sizes, and chemistry. The problem will only get worse as we move from a world in which there are almost eight billion mobile phone users to one in which there will be tens and perhaps hundreds of billions of battery dependent wearable wireless Internet of Things devices. This does not count the already existing consumer products that require dependable battery management.   My candidate for a standard cross-platform battery management is the Battery Inferface (BIF) specification developed by the MIPI Alliance. MIPI’s 250-company membership has initially targeted BIF at mobile phone and computing devices. Although it has taken longer than I expected to be widely used in mobile devices, I have no doubt BIF it will come to dominate not only there but more broadly as well. There are two reasons for my optimism.   Within the BIF specification, a rule-based battery-charge algorithm can be triggered by either a regular charging clock tick (i.e., for one to five seconds) or by asynchronous high-priority events. (Source: MIPI Alliance)   One is that the MIPI Alliance’s BIF working group did not try to encompass every aspect of rechargeable battery management. Instead, it limited the focus to how the battery subsystem communicates with the rest of the device within which it resides, which at present is mobile phones.   But because it deals with only the hardware and software aspects of the communications interface and nothing particularly device specific, it looks like a good candidate for more power constrained wireless platforms such as wearables and other consumer IoT devices. And because it does not try to do more than is necessary (a problem with many industry standards) BIF offers the promise of also being adaptable to other battery chemistries beyond the lithium-ion currently used on mobile phones and other wireless devices.   On the hardware side, BIF is about as minimalistic as you can get, with hardware transceivers that can be implemented in as few as 1k gates using a typical non-bleeding edge CMOS process. This is small enough to be easily incorporated into either mobile phone power management ICs (PMIC) or the digital baseband ICs (BB).   Infineon’s ORIGA 3 Battery Management IC makes use of the MIPI Alliance Battery Interface (BIF) spec to protect smartphone and tablets from unexpectedly running out of power. (Source: Infineon)   Although its small gate count will make it an excellent candidate for IoTs and wearables, also counting in its favor is that the spec adds only a single wire, the battery communications line (BCL), to the two already existing power connectors, VBAT and GND, in a typical mobile phone. Over a single BCL line, the BIF communications protocol has been designed to deliver all the signaling required for a range of management functions: battery presence detection, analog battery identification, as well as a delivery of data, address and command words, inband interrupts, and power-save wake up commands.   The second reason I think BIF has what it takes to establish itself more broadly is the software management scheme the working group came up with. To manage all that functionality being sent over one pin connection, they’ve defined an algorithm that allows a developer to define a set of battery charging rules that can be stored in no more than 64k bytes of addressable RAM, ROM, or reprogrammable nonvolatile memory for each slave device in a system. In addition to some generic software drivers, this scheme allows a developer to include functions in the rules-based algorithm for host charging control is stored in a prioritized order specific to the requirements of the application.   But even with such a scheme available, there are a lot of low cost “dumb” analog batteries out there that have to be taken into account and identified. The BIF working group has taken that into account by incorporating a pull down resistor connected between the BCL and GND, allowing a BIF based battery subsystem to identify whether the battery is a smart or low cost type, as well as identify the electrical characteristics for a low cost battery.

When I returned home from work a few nights ago, I discovered my wife (Gina The Gorgeous) happily working on our Christmas decorations. As part of this extravaganza, Gina was activating some battery-powered garlands festooned with LEDs that she was planning on draping around our front door (well, if the truth be told, she was planning on having yours truly drape these little rascals around our front door).   I don’t know how Gina found these garlands in our loft (I thought I'd hidden them better than that). I was also somewhat surprised to discover that she had located and ravaged my emergency supply of D-type batteries -- the ones intended for lanterns and radios in the case of a power outage (fortunately I have a super-secret reserve emergency supply of batteries that Gina doesn’t know about -- at least I don’t think she does -- plus I now have my precious my trusty emergency generator ).   The thing was that Gina ended up surrounded by a bunch of old D-type cells from the last time we used these garlands. A lot of people simply discard their old batteries in the trash, but this is an incredibly bad idea (it's also illegal in most places). It's hard to pin this sort of thing down, but if you perform a quick Google while no one is looking, you will find estimates of around 3 billion batteries being discarded in the United States each year. Many of these little scamps find their way into landfills or incinerators, thereby releasing all sorts of unpleasant substances -- including mercury, lead, cadmium, nickel, and other metals -- into the environment.   The problem is that a lot of people simply don’t know where to take their old batteries. Also, most people are inherently lazy incredibly busy and don’t feel they have the time to deal with things appropriately. The end result is that -- even though people may know that it's wrong and feel bad about it -- they often discard their old batteries in the trash.   This is sad, because there are lots of places for you to take your old batteries. For example, Call2Recycle is a non-profit organization that collects and recycles batteries at no cost for municipalities, businesses, and consumers in the United States and Canada. I just checked online, and they have 12 locations close to me, including Lowes, Home Depot, and Radio Shack. Personally, I typically drop my old batteries off at my local Batteries Plus Bulbs store. These stores, which are located all over the place, boast that they can supply more than 45,000 different types of batteries and light bulbs for all one's personal, business, or commercial needs. (My local store is located at 6290 University Drive, NW, Huntsville, Alabama -- if you happen to live around here, feel free to drop in and say "Hi" to them.)   Having said all of this, we all know that there are still going to be people who cannot be bothered to take their old batteries to a recycling facility. They may shrug their shoulders and grimace a little, but they will still toss their old batteries into the trash. What we need to do is make things easy for them to do the right thing.   When I came into my office this morning, for example, I stuck a "Battery Recycling Station" sign on a cardboard box, which I then placed next to the coffee machine in the kitchen. Just to get the ball rolling (and to make sure everyone got the idea), I pre-populated the box with the old D-type cells from our Christmas garlands.     Whenever this box starts to fill up, I'll empty it into a carrier bag and transport all of the batteries down to my local Batteries Plus Bulbs store for recycling.   The box has only been there a couple of hours, but already several people in the building have dropped by my office or sent me emails saying that they think this is a wonderful idea and that they will be bringing their old batteries into the office henceforth. I now have the warm glow that comes with knowing I'm doing my little bit to help out (or maybe I'm coming down with a cold).   So, what say you? How do you dispose of your batteries? Even if you do dispose of them appropriately, what about your workmates? All of which leads me to the big question: What do you think about mounting your very own battery recycling program in your workplace?

About a week or so ago, Max (the Magnificent) and I were talking about the electronic projects we are currently working on and comparing them to the ones we did when we were kids. I happened to mention one project that I created when I was 10 years old. This project made my dad so proud that he showed it to all his friends. When Max heard about it, he asked me to write it up to share it with other members of the EETimes community, so here we go...   This all happened back in 1965. Perhaps the best way to start is to describe what my project did and how it appeared to outside observers. First, there was a small cardboard box with holes in it that looked like a microphone. This was mounted on the wall next to the closed door of my bedroom. When I walked up to this box and said "open" into it, the door quickly opened and I stepped into the room. I then turned around and faced the people outside the room as the door closed slowly behind me.   Now, given that this was 49 years ago when there were no microcontrollers and such, and given the simple and inexpensive components that were available to the average 10 year old at that time, can you figure out how this was achieved? When you've pondered this for a while, continue to the next page for a detailed explanation. Take a look at the drawing below. The system involved nails, screw-eyes, both heavy and thin rubber bands, string, thumb tacks, paperclips, wire, paper, cardboard, D-size batteries, a permanent magnet, and tape.     Opening the door For the part that opens the door, heavy rubber bands were strung together with one end tied to a paper clip and the other end tied to the doorknob inside the room.   The bedroom had an interior wall that was against the hinged side of the door and also perpendicular to it, and this is where a headless nail went. This nail was placed into the wall near the floor at an angle that pointed up to where the knob would be when the door was fully open.   The paperclip at the end of the heavy rubber bands was slipped over this nail. With the door closed, the paperclip griped the nail due to the steep angle of the bands. As the door opened, however, the angle of the bands increased to the point where the paperclip slipped off the nail, thereby stopping the bands from pulling.   Closing the door The next step was to make the door close. At the top of the door was another string of very thin rubber bands. Using thumb tacks, one end of this string was attached to the top of the door, the other end was attached to the door jam. This band was much weaker than the opening-band, thereby giving the door a much slower closing speed.   Latching the door Now onto the door latch. Two screw eyes were installed adjacent to the door striker plate. These held a nail that was used to keep the door closed. Having a string tied around its head, the nail slid inside the screw eyes such that when the string was tugged, the nail moved so as to release the door.   The other end of the string was tied to a permanent magnet, which served to tug the string whenever the magnet fell. In order to get the magnet to fall when I wanted it to, I needed it to stick to something and then release as required.   The solution was an electromagnet, which I constructed using wire wrapped around a nail. In the absence of any current flowing through the electromagnet's coil, the magnet stuck to the nail inside the electromagnet. The electromagnet's orientation was such that, when it was activated, its north pole faced the north pole of the permanent magnet.   Thus, activating the electromagnet repelled the permanent magnet causing it to fall, thereby pulling the nail out of the two screw eyes. Once the nail had been pulled out of the two screw eyes, the heavy rubber bands would cause the door to open as described earlier.   The master control switch Powering the electromagnet was two D batteries taped in series, with wires also taped on to the ends. To finish out the design, there was a rather clever switch to turn it all on. This switch was made out of cardboard, fine wire, a thumb tack, a paperclip, some paper, and some tape.   A very fine wire was made by stripping down one strand of a bundle, which was then connected to a paperclip and taped to a small piece of paper, thereby forming one contact of a switch. The use of fine wire was required to keep the weight of the wire low and to keep the paper flexible.   The other contact of the switch was just a thumb tack, which was pushed into the wall where the paperclip could bang up against it. A piece of cardboard was used as a spacer to hold the paper away from the wall, thereby providing an air gap for the open contacts.   To finish the switch, a cardboard box with air holes was placed over it for looks. The switch worked because the letter 'P' in the word "Open" provided a puff of air that blew the paper such that the paperclip and thumb tack contacted each other.   So there you have it. Saying "Open" into the box caused the contacts to close, which caused the permanent magnet to fall, which pulled the string, which slid the nail out of the screw eyes to release the door. At this point the heavy rubber bands caused the door to open quickly. When the door was fully open, the heavy bands were released, thereby allowing the thin bands to slowly pull the door closed.   The final challenge One pretty bad operating gotcha to all this is that my brother would have to be inside the room to get it set up for the demo. I never got around to designing a way to get it set up from outside the room, partly because my dad didn't want me to mess the room up too much and partly because it would have gotten way more complicated.   Would you care to take up the challenge? Remembering that I was only 10 at the time, and keeping in mind the limitations in technology available to me, do you have any ideas as to how I could have arranged things so this system could be set up from outside the room?   Ivan Cowie Chief Engineer MaxVision