The 25th Chaos communication Congress is underway in Berlin. one of the first talks we dropped in on was script’s Solar-powering your Geek Gear. While there are quite a few portable solar products on the market, we haven’t seen much in the way of real world experience until now.
script selected a four segment folding solar panel after some research. He pointed out that solar is currently a lot more of a necessity technology than money saving considering that the panels can be very expensive. For connectors, he recommended ones that were safe, polarized, and tough to short, like the RIA connect 230 series he used. a lot of of the device plugs were easily purchasable, but some had to be salvaged from old AC adapters. A crucial component of his setup was the adjustable voltage regulator. It’s based on the LTC3780 buck-boost controller which is 98% efficient and can be adjusted from 4V to 25V.
script covered some of the problems he ran into in use. The first was an Nokia that refused to charge until a resistor was added to minimize the current delivered. less sensitive devices like portable peltier fridges will work without any issue. For laptop use, he ran into problems with demand spikes killing the power delivery. He added a large cap usually used in car audio systems to make power delivery a lot more consistent. Laptops can consume as little as 15W during normal use, but when they’re charging the battery, the draw can jump to 50W. On his ThinkPad, he was able to turn off charging to stop this. He monitored the performance of the panel by building a kill A Watt style device using an ATmega8 to measure current and voltage and log it to EEPROM.
In conclusion, script stated that he was delighted with his experience, but that it was still impractical to use the portable panel in anything other than direct sunlight.
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