Hydrogen fuel cell

Robert Bruninga bruninga at usna.edu
Wed May 17 09:00:19 CDT 2006

For what it's woth...
We're using 112 Lithium primary "D" cells on our ANDE ham satellite.
And we have met the safety requirements for flying on the 
shuttle.  BUT the primary cells are a world of difference from the
LI-I ones since
the are the same technology as the RAM backup cells in PC's.
Meaning they are designed for very low currents for very long
time.  These D'cells when shorted only produce about 1 amp
for only a few minutes.  THeir internal resistance is 3 ohms
compared to milliohms for the LI-I cells.

We abused them every way and got no problems from shorts
to reverse charging etc.  But when we overheated them above
80C and then noticed they physically expaneded and unknown
to us, began "leaking".  We put them in a cabinet and a month
or two later came back, and everything in the cabinet was
corroded including the cabinet.  It is a corrosive GAS.  No mess,
no goo no liquid.  Anything metalic in th vicinity was ruined...

scary stuff....  Bob, WB4APR

>>> John Teller <jsteller at spottydog.us> 05/16/06 10:41 PM >>>
We're designing Li-I batteries into pretty much all the new satellites 
at Orbital.  Since these are much larger than the little ones cell 
phones use, and since these are not equipped with fuses (just another 
point of failure) they are quite dangerous.  When mistreated they don't 
so much explode, as burn very quickly.  It seems thermal runaway with 
these batteries is nearly instantaneous.  They don't like being shorted 
when fully charged, over charged or too deeply discharged.  The last 
produces an irreversible chemical change that results in thermal runaway 
should a recharge be attempted.

UL approved batteries are equipped with circuits that disconnect a cell 
that is about to be overcharged, or short it out if has been too deeply 

--- JST

Robert E.Seastrom wrote:
> Robert Stratton <bob at stratton.NET> writes:
>> All that having been said, it's probably cleaner (and safer) than some of
>> the other PEMFC companies who want you to run your cell phone off of a fuel
>> containing methanol, high molarity sulfuric acid, and peroxide.
> now *that* sounds fun!  (see below)
>> For the 10 kW and up class, there is some very spiffy solid-oxide technology
>> on the horizon.
> Does the "fun quotient" of the solid oxide technology for off-label
> uses look promising?  As many warnings as I've heard about Li-I
> technology, I have yet to see a practical demonstration of their
> "unappproved" uses.
>                                         ---Rob
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