[aprssig] balloon tracker

Scott Miller scott at opentrac.org
Wed Mar 2 12:48:04 CST 2005

What brand/chemistry were you using?  Are you sure it was the batteries
freezing that killed it?

I think most of the consumer grade lithium cells are lithium/manganese
dioxide.  I looked up the specs on one of my favorites, the CR123A, and it's
rated to -40C.  Tadiran sells lithium thionyl chloride cells rated to -55C.
Haven't tried them, but they've got a good reputation.  Digi-Key carries
them - a 2.4 Ah, 3.6 V 'AA' cell is around $6 - about what the CR123A costs
me at Wal-Mart.  Weight is 17.6g, vs. 16.8g for the 1.5 Ah, 3 V CR123A.  I'm
too lazy to calculate it in watt/hours per gram.

If this had come up yesterday, I'd have added a few to my Digi-Key order for
testing.  Oh well, maybe in a week or two.


----- Original Message ----- 
From: "Jason Winningham" <jdw at eng.uah.edu>
To: "TAPR APRS Mailing List" <aprssig at lists.tapr.org>
Sent: Wednesday, March 02, 2005 10:30 AM
Subject: Re: [aprssig] balloon tracker

> On Mar 2, 2005, at 10:51 AM, Scott Miller wrote:
> > The OpenTracker reports temperature just fine in APRS mode.
> Yep.  My balloon mounted OT worked just fine right up to the point
> where the batteries froze (so much for lithiums rated to -40C; last TX
> I got was at 0C).  Later in the flight when the batteries thawed it
> started up again.
> -Jason
> kg4wsv
> _______________________________________________
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