The first specs we look at when choosing a cellphone are the battery life numbers. We know that eventually we’re going to see performance loss, and [Dr. West] wanted to see if there’s a way to delay the inevitable. What he found is that ambient temperature affects the battery throughout its life. He set out to build a phone chiller to slow the degradation of the battery.
The research that he points to shows that at room temperature, a Lithium battery will lose 20% of its capacity each year. This seems like a dubious number so do share links to studies that state otherwise in the comments. Whether that 20% is right or not, the point is that cooling the battery will preserve it. With that in mind, [Dr. West] put together a pod that uses a peltier cooler and a heat sink to host his Blackberry while he sleeps. He figures he can reduce the capacity lost per year from 20% down to 14%. This of course comes at the expense of running that cooler every night (in addition to charging the phone when it needs it). But perhaps this solution will spark an idea that leads to a better one.
We’ve noticed that wireless routers pump out a bunch of heat. [Jernej Kranjec] wanted to make sure that he didn’t fry it once he started adding more load to his router using OpenWRT. What he came up with is the idea of using an old CPU as a passive heat sink. He applied a bit of thermal paste to the center and some super glue to the corners. You can see the finished product is an old AMD chip adhered “dead bug” style to the stock processor. We’d bet it’s not very efficient compared to an aluminum or copper heat sink, but it normally would have no help in shedding those extra degrees.
What you see above is a generator that converts heat to electricity. [Reukpower’s] thermoelectric lamp is one of those hacks that makes you scratch your head even though you understand why it should work. The heart of the system uses a Peltier cool, just like the thermoelectric solar generator. When there is a temperature differential from one side of the Peltier to the other a small current is generated.
In this case a candle heats one side and a heat sink cools the other. The tiny voltage picked up from the Peltier’s contacts is then boosted using a joule thief. We’ve seen LEDs powered with a joule thief before, benefiting from their own low power consumption. In this case, the boost circuit is scavenged from an emergency phone charger and probably achieves higher efficiency than if he had built it himself.
The need to conduct laboratory-style experiments runs deep in some people. [Freddyman] built an apparatus to test out several commercial and homemade thermal pastes, including the DIY diamond thermal grease we reported on last month. He setup each experiment in the middle of an air conditioned room, ran the heat sink fan for 30 minutes to equalize the temperature, then turned on the DIY heat generator that the paste and heat sink were connected to. He’s got a lot of data from tests he ran with the eight thermal conductors; air (using no paste), Arctic Silver 5, Ceramique, Dow thermal fluid, pure silicone oil, silicone and diamond slurry, Dow fluid with diamonds, and the Inventgeek.com remake.
One of the big problems with DIY paste is the air bubbles that are introduced into the slurry as you mix in the diamonds. All of the homemade pastes except one were put in a vacuum chamber in an attempt to remove tiny bubbles. The one that wasn’t put in the vacuum performed the worst of all the thermal conductors. In all cases, the commercially available products performed quite well while the DIY solutions delivered mixed results.