[Elecraft] [K3] K3 Off Grid

[WILLIS COOKE]

Paul, I have been wondering where you got your information.  It now sounds like you have been using peak currents that are designed to prove to you that you need the surge protector equipment rather than any kind of metering to predict battery life or any other type of average current or electric meter charges.  Such surges are common with power supplies with large capacitance that are turned off then on and the capacitors charge.  These have to do only with the internal resistance in the power supply and the resistance of the electrical lines and nothing to do with your battery requirements.  Your battery capacity, I would estimate to be the receive current x the required operation time x the average power x 2 x transmit duty.  Receive current should be about 0.5 amps for the K2, 1.0 for the K3 with one receiver and 2.0 with two receivers.  The average power should be about 0.3 X peak power for CW and a bit less for SB.  The duty cycle should be
 about 0.7 for a contest station calling CQ down to almost nothing for a station mostly listening to a net.  The efficiency for a battery would be best predicted by manufacturer's data, but should be high for a reasonable sized battery.  A 60 amp-hour battery is fairly small.  My station battery is rated at 122 amp hours.  A contest station calling CQ for 48 hours with a K3 using two receivers and transmitting at 100 watts should require a battery capable of 48 hours x 2 amps +48 X (100 watts/12v) x 0.7 x 0.3 = 180 amp hours or two fully charged batteries.  Of course, you would want a big amplifier, a computer, some lights and a refrigerator for food and drink, so the K3 will be the least of your worry.  If you use an ice chest and an LED light and hunt and pounce a single well charged battery should handle a CQ WW unless you want a rotary beam or an amp.  You will note that you can cut your battery requirement in half with only one receiver in
 your K3.  This estimate makes a lot of reasonable assumptions, so it would require some empirical data to be very accurate, but it shows that operating on a weekend camping trip is very reasonable because you are unlikely to call CQ all night, particularly if your XYL is along to dictate some of your activity.
 
Willis 'Cookie' Cooke, TDXS DX Chairman
K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart


________________________________
 From: Paul (N1HEL) <n1helradio at gmail.com>
To: Frank R. Oppedijk <frank at qrd.nl>; elecraft at mailman.qth.net 
Sent: Wednesday, March 5, 2014 8:43 AM
Subject: Re: [Elecraft] [K3] K3 Off Grid
 

Hmmm.  Thanks for the comments. It may be that the amperage indicator on my new main line surge protector is faulty.  I will try again, this time using a Kill-A-Watt power consumption meter on my various power strips and adding up the readings of power drawn.  More news as it happens...
-Paul, N1HEL
_________________________________

----- Original Message ----- From: "Frank R. Oppedijk" <frank at qrd.nl>
To: <elecraft at mailman.qth.net>
Sent: Wednesday, March 05, 2014 2:06 AM
Subject: Re: [Elecraft] [K3] K3 Off Grid


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