Stanford’s Paper Battery
Carbon nanotubes have been making headlines recently with a multitude of different applications and proposed uses (including use in solar cells, cancer treatment, and space elevators). The incredibly small pieces of carbon are remarkably strong, capable of a 28,000,000:1 diameter to length ratio (meaning a one millimeter wide tube can be as long as 28 million millimeters, or 17.4 miles). Plus, they are only 1/50,000th of the width of a human hair!
Using these remarkable little tubes, Stanford University has come up with one of the most interesting applications yet - a paper battery. In a video posted on YouTube, Professor Yi Cui shows the process of cutting a piece from 8.5" by 11" paper, covering it in an ink that contains carbon nanotubes and silver nanowire. After they bake the liquid of the ink off, they dip in it an electrolyte solution that allows the chemical reaction that takes place in conventional batteries to occur. Finally, they encase it in some sort of housing and hook it up to whatever needs powering!
This video shows the process a little better than I can explain it:
To top it all off, paper batteries like these are 20% lighter than existing types of batteries that are made of mostly metal, so might be able to find great advantages in portable technologies.
Sources: BBC (via Engadget)
Tips to get the most out of your iPod Battery
One of the most common complaints about iPod is its battery life. According to Apple there are a few things that you can do to get the most out of your battery:
- The iPod's battery works best when it's at room temperature, generally near 20° C, but you can use your iPod anywhere between 0° to 35° C (about 32° to 95° F). If you have left your iPod in the cold, give it time to warm up to room temperature before using it. Otherwise, a low-battery icon may appear and the iPod will not wake from sleep. Also, you do not want to expose your iPod to extreme temperatures by leaving it in your car or exposing it to direct sun light.
- Discharge the battery completely before recharging your iPod.
- Back lighting and the equalizer use a lot of power so turn both off if you do not need to use them.
- The iPod's cache works best with average file sizes less than 9MB, so using smaller files and or compressing your files to smaller size files can also help extend your battery life.
Take a look at this link here for internal batteries for your iPod. Also check out this link for replacement and external batteries and other accessories for your iPhone.
Overcharging: The Grim Reaper of Rechargeable Battery Life
Overcharging
Overcharging is a very important thing to be wary of when charging whatever rechargeable battery you are using. When you leave a battery charging for a long period of time (overnight, for example) the battery charges up to 100%. But what happens when the battery reaches 100% in the middle of the night and is left plugged in until morning? Well, to understand what happens, you must know something a tiny bit about how a battery works.
When a rechargeable battery is in use, an electrical current is flowing from the negative cathode to the positive anode. This current is made up of electrons, extremely tiny electrical particles. As more and more electrons flow from the cathode to the anode while the battery is in use, it gradually loses its charge. This whole process is fueled by a chemical reaction that takes place within the battery.
In order to recharge the battery, the chemical reaction that produces this flow of electrons must be reversed. To do this, we use chargers that connect the battery to an electrical outlet. Over time, the reaction is reversed and charge is restored to the battery. One byproduct of this process is heat.
This leads right back to our original question... what happens when a battery is left for too long in a charger? The answer is that the heat that is produced from leaving the battery in the charger after the charging process is complete causes the chemical substances inside the battery to degrade, leaving less fuel for the chemical reaction that produces current.
Choosing Rechargeable Batteries
Weight-to-Power Ratios
One way of measuring the cost and effectiveness of a rechargeable battery is to measure its weight-to-power ratio. This measurement is exactly what it sounds like; that is, how much power a specific battery can pack into a certain amount of weight. One such way to measure weight-to-power is with watt-hours per kilogram (W-h/kg), or how many watts of energy a one kilogram battery can produce in an hour. Here are some examples using the most common types of rechargeable batteries:
- Lithium Ion (Li-ion) - 150 watt hours per kilogram
- Nickel Metal Hydride (NiMH) - 60-70 watt hours per kilogram
- Nickel Cadmium (NiCd or Nicad) - 42 watt hours per kilogram
- Lead Acid - 25 watt hours per kilogram
As you can see, lithium ion batteries have a significantly higher weight-to-power ratio than the other types of batteries out there.
Discharge
Another way to measure batteries is by their discharge. Here, when we talk about discharge, we are referring to how fast a rechargeable battery will lose its stored charge while not in use. As you might expect, different types of rechargeable batteries lose their charge at different rates, all based on their chemical composition and structure. Once again, here are some examples of how different types of batteries lose charge at different rates:
- Li-ion - 5% loss per month
- NiMH - 20% loss per month
- NiCd - 10% in the first 24 hours after recharge, followed by 10% per month after that
Again, lithium-ion batteries win out over nickel metal hydride and nickel cadmium.
So why aren't lithium ion batteries the one and only rechargeable batteries being used? Well, although nickel cadmium and nickel metal hydride batteries have a lower power-to-weight ratio and a higher discharge rate, they also are a bit tougher and therefore are more suited for things like industrial settings or use in machinery or power tools.
But what does this mean in plain English? How long is a battery going to last?
Unfortunately this is a very difficult thing to gauge. The best way to try to figure out how long a battery will last is to look at how much power you need from the battery, then look at its Amp-hours. For instance, let's say that you need to run a laptop which needs 1 Amp per hour to operate. A laptop battery that has 4 Amp-hours will power your laptop for... 4 hours! Similarly, a camera that needs 300 milliAmps per hour to work will get approximately 6 hours of use from a 1800 milliAmp-hour battery. All these numbers, however, are subject to change and don't take into account things like powering on and off or periodic use.
Now you know!