I started looking for larger capacity batteries so we wouldn't be lifting so much packaging. Bigger batteries also allow more current to be pulled.

 

Lithium Sulfur batteries come in 2 things that are called C cells: long run, low current for clocks, and high current ones. What's confusing is that most of the low current ones are now Lithium Thionyl Chloride (look at the hazmat specs on those!)

 

SAFT makes a full line and the specs are at

http://www.saftbatteries.com/120-Techno/20-10_produit.asp?sSegment=&sSegmentLien=&sSecteurLien=§eur=&Intitule_Produit=LSH&page=2

The LO or LSH series looks like what we want. 

C Cell: http://www.fedcoelectronics.com/detail.tpl?SKU=LSH14

D Cell: http://www.fedcoelectronics.com/detail.tpl?SKU=LO26SX

 

Assuming we want to get to 7.2 volts & don't need more than an amp of current draw, C cells are the better power/weight trade off.

 

 

 

Old (but still good ) info.

 

 

For Ordering: consider getting the energizer L91. I'm not sure about the e2. The mail I got back from energizer was thoroughly unhelpful (they said chemical composition info was proprietary). They sent me here: http://data.energizer.com/. Only e2 listed is an akaline. Check out the cylindrical/photo lithium section.

 

Some battery info

 

Temperature issues:

at 35K feet, temp is -50C

at 70K feet, temp is -55C

we could potentially get to 125Kft

 

lowest temp we are likely to get to should be around –60C

 

from The Handbook of Batteries:

best performance at –80C and below:

lithium-thionyl chloride and lithium-sulfur dioxide found to have the best performance

 

Other folks (http://www.utarc.org/wiki/index.php/Amateur_Ballooning_Compendium#Batteries) recommend Energizer e2 lithium batteries

 

the E2 is a lithium/Iron Disulfide battery

weight 0.5 oz

spec sheet attachedl91.pdf, or at data.energizer.com/PDFs/l91.pdf (at least, presumably that's the spec sheet. It's what google gives back for the e2, though the sheet says it's the L91. not sure if that is google's problem or energizer's problem)

 

voltage drops to 1.4 quickly, then down to about 1.0 just over 2.5 hours. But that’s rated at 21C.

 

Question: how to determine how quickly the voltage will drop at –30C and below?

Peanut gallery answer: styrofoam cooler, datalogging multimeter, battery and some dry ice? (boiling point of C02, -78C)

 

3ric says everything stops working at 6 volts, and we can go up to 40 volts.

 

What about Solar?

solar cells work for satellites.. perhaps they'd work for this? All depends on the power requirements but if they're low enough a few PV cells and a supercap or two might fit the bill. PV cells tend to work better at lower temperatures (as opposed to chemical batteries). Here's a link to a old solar cell handbook: http://downloads.solarbotics.com/PDF/sunceramcat.pdf . The cells listed in this book tend to have a min operating temp of -40C but, again, they use PV cells in space so clearly there must exist some that operate at those lower temperatures. Also, the voltage produced by a PV cell tends to rise with falling temperature (while max current drops (but more slowly)) -- this characteristic may be useful in offsetting the voltage dropoff of a battery system in a combined battery/solar approach.

 

Here's someone's post about the e2 batteries. See: http://www.nikonians.org/cgi-bin/dcforum/dcboard.cgi?az=printer_format&om=323&forum=DCForumID38

 

Jin,

 

I'm not sure about your Li CR123A batteries as I use the Energizer e2 AA Lithiums L91. From the data spec. sheet for the AA Lithiums, the details are given as:-

Battery chemical composition: Lithium/Iron Disulfide (gel based)

Storage & operation temperature range: -40 to +60 degrees C (-40 to +140 degrees F)

Shelf Life: 10 years(+)

The equivalent to the CR123A are the Energiser e2 EL123AP (3 volts) and their data spec. sheet gives:-

Battery chemical composition: Lithium/Manganese Dioxide

Operating Temperture Range: -40 to +60 degrees C (-40 to +140 degrees F)

and the following chart for shelf life (function of temperature).

Basically, in our UK climate condition, the chart predicts a fairly stable 90% plus service even after nearly 10 years so your 2+ years will be well within the batteries' storage limits!