Sony Corp exhibited a cordless speaker system and mobile phone chargers powered by its direct methanol fuel cells (DMFC) at the International Hydrogen & Fuel Cell Expo (FC Expo 2009) taking place from Feb 25 to 27.
They all employed unique designs, containing fuel methanol in a see-through tank.
Sony used a Li-ion secondary battery to compensate for the low outputs of small DMFCs, allowing mobile devices to cope with steep current peaks.
In the prototypes exhibited this time, a DMFC powers a device while its output is from 550 to 600mW. And the Li-ion secondary battery supplements power when the output becomes larger. When the device uses less than 550mW, the DMFC's excess power is used to charge the Li-ion secondary battery.
The DMFC showcased this time is the same as announced before, Sony said (See related article). In the cordless speaker system, four fuel cells and a Li-ion battery are embedded in a speaker. A 270cc methanol tank is prominently located under the DMFCs. The company set LEDs under this tank to illuminate the methanol in various colors.
This speaker can be used for a year without refilling the tank if it is used to view DVDs for about two to three hours on weekends, for example. Up to 2W is powered by the four 550 to 600mW DMFCs. The maximum output of the speaker is about 10W. When the output exceeds 2W, the Li-ion secondary battery will supply power.
Sony said more speakers can become cordless using DMFCs as their power supply. Audio data can now be wirelessly transmitted to the speakers. But speakers have not become cordless yet. Power is still supplied from their AC adapters attached to outlets. There are some speakers that use Li-ion secondary batteries and claim to be "cordless," but they only last several hours per charge.
In contrast, by using DMFCs, it becomes possible to run a device without adding fuel for a year. Users can freely lay out a 5.1ch speaker system, for example.
The mobile device chargers, on the other hand, are charged via USB connection. Sony presented two chargers this time. One is equipped with a 10cc methanol tank, which is equivalent to a power capacity of 13.7Wh when combined with a 3.7Wh Li-ion battery. It can charge a 3.4 to 4Wh mobile phone a few times a week.
The other comes with a 100cc methanol tank and allows 25 power charges through each of its two USB ports for about a month.