Keeping Electronic Gadgets Happy
Dec. 20, 2006
Even in the wilderness, humans can not seem to do without their electronic devices. We bring crucial mission electronics such as Iridium satellite phones, radios, GPS receivers, and laptop computers. We also bring electronic condiments, items such as cameras, iPods, and DVD players. With a few exceptions, most of these items are consumer grade electronics, and as such are optimized to run around normal room temperatures and at elevations not too much greater than a few thousand feet. When you compound cold temperatures with high altitude, keeping these electronics happy becomes a bit of a chore. Many will flat out die as frozen lumps of silicon chips, their battery not able to produce any sparks and their LCD displays, like in the eyes of a corps, fixed in an icy blank stare.
To keep these electronics happy, they need to be kept warm. The definition of warm is a relative measure in Antarctica. Warm is anything around -5 to 0°C. Most gadgets will work if kept within this range. To accomplish this requires a place in an inside jacket pocket, a sleeping bag (when you are in it), or hanging in the tent chimney with the stove lit. Cold electronics also act like a glass containing a frozen drink on a humid day. A thin layer of icy frost forms in a matter of seconds. If the gadget is ruggedized (like a GPS receiver), this is not a big deal and the ice will simply go away as it warms up. A gloved finger works well for scrapping the ice off the LCD display. I do not recommend this technique for a camera or a computer. Ice condensate is bad news for these items. A small plastic bag is helpful in keeping the condensing moisture away from the sensitive surfaces until it can be warmed above the frost point.
Like a fussy child, a laptop computer is a high maintenance item. Not only is it a power hog, but it has to be treated with kit gloves to keep it happy. A laptop draws about 50 watts of power, a fair amount if living in a tent in the middle of nowhere. Typical portable solar panels are rated at 30 watts, significantly less than what is required. And that 30 watts is for noon summertime Arizona desert solar fluxes (about 800 watts per square meter). Summertime Antarctic solar flux is about half that, so the maximum power from a 30 watt panel is more like 15 watts. Integrating this over a day (assuming you do not have the time to continuously rotate the solar panel so that it faces the sun) brings the daily power rate down to a paltry 7 to 8 watts. Any continuous draw over that amount will result in a brownout. The solution is to have a buffer battery that can store solar power and give it back at a higher rate (for a shorter periods of time). Such batteries are massive and typically sized for what is possible to carry for a particular expedition. It might be a small Nickel-metal hydride 12 volt battery pack rated at a few amp-hours, a motorcycle gel cell, or a full sized lead acid car battery (at -20°C, Nickel-metal hydride and gel cell (lead-acid) batteries work well, but at a reduced capacity). The bottom line to keep a laptop fed requires a fair amount of voluminous and heavy solar equipment and can only run the laptop for a few hours a day before the consumption rate causes a brownout.
Laptop computers hate to be cold. Any gadget with a mechanical hard drive will have troubles at -20°C temperatures. The oil in the hard drive bearings becomes thick, slowing the disk speed below that which will allow consistent operation. High altitude also causes problems with read-write errors for hard drives. Compound the two and you have the recipe for turning a laptop into a something in which to pound in tent stakes.
Having said all this, we do have a laptop computer that we use for logging our meteorite data. However, like a little kid who gets grumpy from a change in routine, a consistent ritual must be followed to keep it operational. First, the 30 watt solar panel-battery unit is allowed to charge the gel cell buffer battery all day (if the 60 amp-hour 12 volt gel cell battery is completely discharged, it takes 3 days with no current draw to fully charge). No parasites are allowed to suck off any juice. The laptop is stored in the tent and is typically -15 to -20°C at the day's end. It is placed in the tent chimney or tent pocket near the stove during dinner prep and after a couple of hours, is above the magic temperature of 0°C. Then and only then can it be booted up and successfully run for a few hours before the pending brownout.
If the capability of a full blown laptop is not needed, a Personal Digital Assistant or PDA is the way to go. Equipped with a wireless keyboard, these palm-sized computers can be operated in the cold with minimum fuss and allow notes and data input via a reduced but full-sized keyboard. There are slots available for downloading data from other electronics including a number of common memory cards used in digital cameras. Free from hard drives with rotating parts, they will work consistently at cold temperatures. They will readily slide into an inner pocket and after about ten minutes, will be above the freezing point and happy to operate for hours on a single charge. A 5 watt flexible solar panel is sufficient to keep several PDAs and Iridium phones charged and running. If your data needs are not excessive, a palm computer with small solar panel and buffer battery is the way to go.
Digital cameras are other items that need some advanced thought for their successful use. There are a wide variety of high quality point and shoot digital cameras available on the market today and these work remarkably well for recording expedition images. Most of these use rechargeable lithium-ion batteries that do not do well in the cold (see discussion below). A few are powered by AA batteries, which is the way to go for use in the Antarctic field. Lithium primary batteries (non-rechargeable, also discussed below) are available in AA size that happily operate down to -40°C and thus will power these cameras with no fuss and no need for chargers and solar panels. I recommend going with a camera that takes AA batteries, thus alleviating the head aches of battery charging, even if you have the charging equipment available for other camp-based electronic devises.
Full-sized digital single lens reflex cameras can be used if one is willing to cater to their needs. We have a Canon EOS 5D along and it will work down to -25°C if the lithium-ion battery pack is removed and stored in some place warm. The camera itself is too large to fit inside of any pocket so it is left hanging on a strap exposed to what ever the elements can dish out. When an image is required, the battery is extracted from its warm spot and inserted into the cold-soaked camera and pictures are taken. As soon as the shooting is finished, the battery goes back inside the pocket. This worked but proved to be a bit of a pain since one's gloves need to be removed and your parka unzipped every time the battery is extracted from the inner pile pocket. A better way to go is to have the Canon attachment that allows 6 lithium AA (non-rechargeable) batteries to be used in place of the rechargeable lithium-ion battery, thus providing power down to -40°C. We found that even at -25°C the Canon functioned without any issues, including the autofocus lens (16 to 35 mm zoom) and the color LCD display. Use of the color LCD display was limited to conserve battery life.
Warm places are required to keep these electronics happy. To investigate this further, I attached liquid crystal thermometer strips to our cameras and PDAs so that their surface temperatures could be measured as a function of where they happened to be. These temperature strips were made for freezer compartments and cover the range from -30 to +30°C in 5 degree steps. I also used our NASA hot box, a high tech “cooler” turned into a “warmer” for storing and charging electronics.
Sitting on the floor of our Scott tents, cameras and PDAs would constantly be at -20°C. If up off the floor, perhaps in the tent pocket or on a wooden box near the stove, they would be around -5 to -10°C. If placed in a hanging net bag suspended in the chimney, they would be around +15°C as long as the stove was lit. Tent relative humidity typically runs near 90% so any cold camera or PDA immediately condenses a layer of water that quickly turns into a layer of ice. A small plastic bag helps keep things dry until they are warmed above the dew point.
When outside for a full days worth of meteorite gathering, the ambient temperatures typically ran at about -20°C with wind chill from -35 to -40°C at 50% relative humidity. An unprotected pocket-sized camera would quickly cool down to -20°C. If kept in an outside bellows-style parka pocket, it would stay at -15 to -20°C. If kept in the mid-layer pile jacket pocket (first layer under the parka and bib wind pants), the temperatures would run around -5 to +5°C. If placed in bib-wind pants outer pocket but covered by the bottom parka skirt, temperatures would run around -10 to -15°C. It was a struggle to routinely remove a camera from the mid-layer pile pocket in -40 wind chill (having had to first remove mittens or gloves and partially unzip your parka) so the camera was kept in the bib-wind pants pocket and operated at -15°C. The camera was inserted into the bib pocket with the lanyard left hanging outside so that it could be extracted without removing your mittens by simply tugging on the string. The Canon EOS 5D was too big for a pocket and simply hung by its strap on the outside of the parka and stayed a frozen block at -25°C. One quickly optimizes which pocket to keep things by taking into account the frequency and duration of the intended use.
There are two basic kinds of lithium batteries;
primary (non-rechargeable) cells that are single use only, and rechargeable cells. Both are based off of different lithium-based chemistries.
For primary cells, the lithium chemistry not only has higher energy densities than alkaline batteries, but will operate at temperatures of -40°C, a regime where most batteries simply die for lack of any sparks. The standard half-cell reaction for lithium produces 3.045 volts. Batteries based on this chemistry are rated at 3 volts and its multiples. Consumer electronics using AA or AAA 1.5 volt batteries are not compatible with the standard 3 volt lithium cell. There is a lithium chemistry based on iron sulfide that produces 1.5 volts and is made in AA and AAA sizes that make them ideal for replacement batteries common to most consumer electronics. So any consumer AA or AAA electronics powered by these lithium primary cells will at least have good power at low temperatures. There may be other complications due to inoperable LCD displays or thick grease in mechanical parts, but at least the electrical power will not be a factor. Once these primary lithium cells are expended, they are replaced with new ones, thus a sufficient supply of spare batteries are needed. Aside from their rather hefty cost, their performance is unparalleled. For expeditions to Antarctica, one simply shells out the dollars and buys the best.
The rechargeable lithium cells are called lithium-ion batteries. These operate at 3.7 volts or its multiples and are specifically designed into the particular electronic device, thus primary cells may not be directly used as a replacement. Lithium-ion batteries have a remarkable charge capacity based off of a lithium-cobalt complex, can be recharged hundreds of times, and are cheaper and more convenient than feeding your device with a constant stream of primary cells. Lithium-ion technology has taken over consumer electronics to the point where it can now be difficult to find a devise that operates off of standard AA or AAA batteries.
The problem with lithium-ion batteries is that they do not operate below 0°C. If you have cold soaked batteries and electronics, they simply will not run with lithium-ion chemistry. If one looks at the discharge curves for lithium-ion batteries, they will grudgingly squeak out some power with a significant decrease in capacity at temperatures as low as -10°C (for brief periods of time), however, they can not be charged unless the battery temperature is above 0°C. This is why the manufacturers give the lowest operating temperature of 0°C even though it is possible to use them in discharge mode below this point. If one understands these boundaries, they can be used in discharge mode to -10°C so long as they are charged above zero.
Lithium-ion batteries are fussy to charge and thus typically come with "smart chargers" and sometimes even have "smart chips" built directly into the battery pack. These "smarts" monitor and regulate current and voltage while keeping an eye on the temperature. If anything is out of limits, they shut down the charging, and sometimes, permanently shut down the battery pack. Gone are the simple days of hooking a battery up to some generous supply of voltage and walking away. For lithium-ion batteries, the charger will not charge if the temperature is hovering around 0°C (these chargers either directly measure the battery temperature or measure the air temperature). For use in Antarctica, this feature can be annoying. It is heart breaking to have your discharged batteries hooked up to the charger for hours, only to find that they were just sitting there waiting to warm up. This typically happens during the field work day when your spare set of batteries are left in the (-20°C) tent to charge. Another feature of these smart battery packs is if the lithium-ion battery voltage falls significantly below its normal operating range, the smart chip built into the battery can permanently disconnect the output terminals and the battery pack becomes useless. This can serendipitously happen if the battery pack is kept warm, discharged to the low end of its limit, and then allowed to get really cold. A battery pack in this state is useless and most likely, not recoverable while in the field.
Understanding these technical details is essential to keep your electronic operable. Like understanding how to tweak the governor on a go cart to make it go faster, it is possible to warp the charge/discharge cycles to extract extra cold weather performance at the expense of battery lifetime. With a little bit of electronic doctoring, the temperature sensing circuit on the charger can be disconnected. This allows the batteries to be recharged when the temperatures are dancing around zero, a condition that often happens in your tent. If you find yourself with a once working battery pack that suffered a sudden death, it may be time to perform some miracle healing which in the long run will lead to ruin, but in the short term will breath new life into the carcass. We had a nominal 8 volt lithium-ion battery pack for an HDTV video camera that simply would not charge. We did a little electrical surgery in the field, bi-passing it's built in voltage safeguards, and directly charged it with 12 volts. According to all the technical specifications, this is a real no no. We ultimately destroyed this battery;
however, we were able to shoot another 60 minutes of video. Considering our location and the value of the video, the trade was worth it. As is often the case, if you understand the rules, you can selectively break them, particularly if you are willing to live with the consequences.
For keeping electronics powered under Antarctic field conditions, it is best to bring devices that use AA or AAA batteries and feed them lithium primary cells. If this can not be, then one must cater to the temperature demands of rechargeable lithium-ion technology, along with having solar panels, buffer battery packs, and chargers to keep them energized.
Intrinsic human behavior ultimately impacts how these devices are used in the wilderness. Even though we would be submerged in awe-inspiring beauty, natural displays of wonder so foreign to your city-honed intuition that it would make you forget your place in space and time, the intrinsic laziness of human beings would still prevail. If your camera was not readily available, if you had to remove gloves, unzip layers, thus extracting and or assembling your apparatus, the required effort to take a picture was often times simply too much. The moment would forever be lost. Only if your camera was readily available from a simple lanyard tug would every possible moment be preserved. Such is the nature of human behavior when surrounded by harsh beauty.
Sanyo temperature data for their single cell 3.4 volt lithium-ion rechargeable battery.
Energizer L91 primary lithium cell temperature data showing operation at -20°C.
Discuss this post
0Comments about this post
- A Poem for Saturday: One Planet is Not Enough
- From the Diary of a Space Zucchini: The Frontier
- From the Diary of a Space Zucchini: Preparing for Departure
- A (New) Moon is Born
- From the Diary of a Space Zucchini: Gardener's Spacesuit
- From the Diary of a Space Zucchini: Baby on Board!
- With Warm Regards
- Stray Light
- From the Diary of a Space Zucchini: Happy Sprout Day!
- From the Diary of a Space Zucchini - What Do Dragons Eat?