"Marc Ramsey" wrote in message
om...
Bill Daniels wrote:
OK, so what would be wrong with using a 9V lithium smoke detector
battery
that lasts 5 times longer than an alkaline? I use one of these as a
backup
on my Borgelt B40 and I've never had to replace it.

The EDS likely has an internal power supervisor which is monitoring the
battery voltage, and triggers an alarm when the amount of remaining run
time drops below a threshold. The discharge profile for lithium
batteries is different from alkaline, the alarm may be triggered too
early, or too late...

Marc

Good observation. Here's a bit of further research.

When I normalize and replot the discharge data as voltage vs. % life instead
of V vs. hours, the shape of the discharge curve of lithium seems to be
identical to alkaline.
__________________________________________________ __________________________
_
Mountain High says this about the Low Battery Warning:

The EDS model D-1 unit continuously monitors the condition of the battery
during operation. The unit flashes the red LED once every two seconds to
warn that the battery has dropped to about 6 volts. The unit will, however,
continue to operate properly for about four (4) hours @ 25° C after the
indicator starts to flash. It will flash the red LED once per second to warn
that the battery has dropped to about 5
volts and should then be replaced ASAP. The EDS model D1 will operate for 60
to 80 hours with a fresh alkaline battery under normal operation. However,
because a very small amount of current (»1 µa.) is drawn by the unit while
turned off, the battery life is about 4 to 6 months. Therefore, during long
term storage the battery should be removed. Once the battery drops below 5
volts the unit will stop
operating and the red LED will remain on.
__________________________________________________ __________________________
__

Of course this suggests the low-voltage warning will come on with 4 - 5
times as much life remaining in a lithium 9V but that's not necessarily a
bad thing. If the warning came on one hour after launching for a 1000k
attempt, I might feel comfortable continuing the flight with lithium but not
with alkaline.

The above EDS alkaline battery life data is not especially comforting. A 4
hour margin after the low battery warning could cut short a long flight.
(If you even noticed the blinking red LED) If the alkaline battery is cold,
the margin could be even less. Lithium batteries are advertised to have
greater cold performance compared to alkaline.

At $6 for a lithium 9V vs. $2.50 for alkaline, lithium seems to be a really
good buy for any device that uses a standard 9V battery. The EDS manual
warns to be very careful with the battery wires when changing the battery so
doing so less often seems like a good idea too.

As for the idea that lithium batteries catch fire; if that were true, it
would be absurd in the extreme to use one in a smoke detector, yet that's
both the government and industry recommendation. The manufacturer's data
says that in the case of a dead short the battery will not exceed 90C. I
assume these 9V lithium's are not especially prone to catch fire.

Bill Daniels