[Elecraft] K2/100 Emergency field battery

[Tom Hammond NØSS]

Tim:

>I would like to hear anyone's recommendation for a battery to be used in
>the field that could power the K2/100 on moderate emergency
>communications traffic for 3 days if solar recharging was not available.
>I realize that "moderate" is extremely subjective, but I think you get
>the idea. I'm obviously not talking about a backpacking item. Any help,
>particularly from those with emergency field experience would be most
>appreciated.

In the past (about 18-20 years ago) I used a Deep-Cycle RV-type (or Marine) 
battery to power a solid state rig. Kept it on a regular automotive-type 
charger (Schauer, 25A Automatic Charger) all the time, and monitored the 
electrolyte levels on a monthly (maybe bi-monthly) basis.

When off the charger, the battery allowed me to run the rig for well over 
48 hours before it really started to show signs of degradation in the 
terminal voltage. When ON the charger, the charger loafed along, just 
supplying 'top-off' charge 99.9% of the time, but when in use, the charger 
went up to about 18A of charge during key-down times and then (almost) 
immediately dropped back to about a 5A to 7A charge rate until it could 
replace enough of the lost charge that the 'top-off' voltage had again been 
reached. At which point the charger went into what I call 'pulse' mode, 
only periodically supplying a 1A (or so) pulse charge, just to maintain the 
topped-off charge. I NEVER(!) ever experienced any problem with AC ripple 
(hum) from the charger... apparently the battery was more than up to the 
task of acting as a big fat filter for the charging pulses.

Unfortunately, it's been long enough ago that I no longer recall the actual 
Ampere-Hour rating of the Deep-Cycle battery, but it was moderately 
heavy-duty. After having used the battery/charger combo for probably 4-5 
years, I finally killed the battery by taking if off the charger for an 
extended period of time (over a year) when I no longer had a 12VDC powered 
rig. The battery self-discharged, sulfated up, and eventually developed a 
short between several plates, thus rendering itself un-recoverable by any 
means available to me at the time.

I have no real-life experience with gelled-electrolyte batteries, so will 
leave those comments to someone with such knowledge.

73,

Tom Hammond   N0SS