There s a New Powerhouse in Town

Transcription

1 There s a New Powerhouse in Town By Edward R. Breneiser, WA3WSJ I ve been working on my Icom 703 Plus HFpack about two years now. I think I just found a great power source for it. I was using a good power source in the form of a Sealed Lead Acid 12V/10ah Battery. The SLA battery is cheap to purchase, works great with the 703 Plus, but has one major disadvantage it s heavy! Fast forward two years and now we see Li-ion battery technology has arrived for all to use. Not only has it arrived, but it has become the go-to battery technology. Yes, I know what you re thinking, I don t want a fire! Well, I ve been using Li-ion batteries in my Elecraft KX1 for a few years now without a single problem. Yes, I said without a single problem! Why has Li-ion battery technology been embraced so much in today s electronics? What makes Li-ion battery chemistry better than past battery chemistries? How has Li-ion battery technology addressed the safety issues that have plagued it in the past? I hope to answer these questions in this article and maybe few more. Why has Li-ion battery technology been embraced so much in today s electronics? For many years most consumer electronics used batteries that were sealed lead acid, nickel cadmium (NiCd) or nickel metal hydride (NiMH ). But there s a new kid on the block now. Here s lighter and packs a powerful bunch! For a given voltage, a lithium ion battery is smaller in size and lighter in weight than a nickel cadmium (NiCd) or nickel metal hydride (NiMH) battery. In addition, lithium ion has virtually no self-discharge. This allows a lithium ion battery to be stored for months without losing a charge. So when we compare the energy density to size and weight, Li-ion batteries come out a winner compared to the older technologies. The energy density of lithium-ion is typically twice that of the standard nickel-cadmium. There also is potential for higher energy densities. The load characteristics are reasonably good and behave similarly to nickel-cadmium in terms of discharge. The high cell voltage of 3.6 volts allows battery pack designs with only one cell. Most of today's mobile phones etc run on a single cell. A nickel-based pack would require three 1.2-volt cells connected in series. This is why many consumer electronic devices including amateur radio devices now use Li-ion batteries.

2 Take a look at the chart. You want a battery that s in the upper right-side of the chart. The lower left-side is not to good place. As you can clearly see, most of the Li-ion chemistries are in or near the upper right-side of the chart. In short, they pack more punch for size and weight! But, you also see that in the middle of this chart lies nickel metal hydride technology. NiMH chemistry batteries are considered the stepping-stone technology from SLA and NiCd batteries to Li-ionbased batteries. What makes Li-ion battery chemistry better than past battery chemistries? Lithium-ion is a low maintenance battery, an advantage that most other chemistries cannot claim. There is no memory and no scheduled cycling is required to prolong the battery's life. In addition, the self-discharge is less than half compared to nickel-cadmium, making lithiumion high energy density potential for yet higher capacities. Here are a few of the advantages of Li-ion Technology: Does not need prolonged priming when new. One regular charge is all that's needed. Relatively low self-discharge - self-discharge is less than half that of nickel-based batteries. Low Maintenance - no periodic discharge is needed; there is no memory. Specialty cells can provide very high current to applications such as power tools.

3 But, when using Li-ion batteries one must adhere to a few safety items: Requires protection circuit to maintain voltage and current within safe limits. Subject to aging, even if not in use - storage in a cool place at 40% charge reduces the aging effect. Requires the proper battery charger. Expensive to manufacture - about 40 percent higher in cost than nickel-cadmium How has Li-ion battery technology addressed the safety issues that have plagued it in the past? In the past Li-ion batteries had a bad rap compared to other battery types. Is this bad rap still true today? Well, I ll say that Li-ion batteries still have somewhat of a negative image in peoples minds, but it s changing as I type this piece! We all know of or have seen a Li-ion battery video that shows a Li-ion battery catching fire. But, are they as bad as the videos lead us to believe or not? First I must say that Li-ion battery technology has come a long way since most of those videos. Li-ion battery safety has two major innovations that have made the use of Li-ion batteries possible in many everyday electronic devices. First is the use of protection circuit boards or PCBs as part of the battery. These PCBs perform many tasks that keep a Li-ion battery safe. Some PCBs actually even balance the charge of each individual cell in the battery. Here s what the three PCBs attached to my 14.8V/7.2ah Water Bottle Battery do to keep things safe: Overcharge (>16.8V) Over discharge ( < 11.0 V) Over drain ( > 19.0 Amp) The second important safety feature added to Li-ion batteries today is the use of a polyswitch. My Li-ion battery also has one polyswitch installed to limit maximum discharging current at 7A and to protect for wrong polarity. The Polyswitch maximum current is PolySwitch devices are used to help protect against harmful over current surges. Like traditional fuses, these devices limit the flow of dangerously high current during fault conditions. The polyswitch device, however, resets after the fault is cleared and power to the circuit is removed the load.

4 The polyswitch is welded or soldered between two cells in one battery pack. Here are the specifications for the polyswitch in my battery: Specification Current Rating: 7.3A Holding Current: 20'C Tripping current: 20'C Tripping current is the maximum open circuit current. Note: The Percent of rated hold and trip current will be reduced with an increase in temperature. Here s my new power source or battery for my Icom 703 Plus HFpack. This baby is actually a bike light battery. But, it seems to works great with my Icom 703 Plus as the maximum voltage input to my radio is specified at 9.0V to 15.87V. I just charge the battery until it reads 16.0V while attached to the charger and then stop the charge. After removing the charger, the battery reads around 15.8V. This works great with my setup. I even checked the battery voltage before one operation and it was 15.8V. After operating for three hours the battery read 14.7V. I still had plenty of energy to operate for another day or two! If your rig can t take the higher voltage, just make up a cable with a few series diodes installed in the power line to drop the voltage down. You could also purchase this style battery, but in a 3-C form. This will provide 11.8V to the rig. As you have just read, the use of PCBs and poly switches have dramatically increased the safety factor when using Li-ion batteries. Can they still catch fire? Yes, you will have a fire on your hands if you improperly care for the battery or improperly use the battery. That s why I use the water bottle version as it s protected from the elements such as rain etc. It s also protected from handling abuse being inside the bottle. I feel completely safe using Li-ion batteries as do millions of people who use laptops, cell phones etc. As an amateur radio operator, you just have to select the proper battery for you and don t abuse it. Her are some links to Li-ion Water Bottle Batteries:

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