... more like 50 AH. The biggest car battery I ever dealt with was for a VW diesel, and it was only 63 AH. Had to turn a 2 horsepower starter against the 23:1 compression ratio of the engine, *and* feed the glow plugs which required more than 30 amps.
73 de Jim, N2EY ************** In the USA at least, AH ratings for car batteries are hard to find. Most of them are rated for the actual service in ways that make them difficult to assess for running a radio. Three common ratings are the "Cranking Amperes" (CA), "Cold Cranking Amperes" (CCA) and "Hot Cranking Amperes" and (HCA) indicating how many amperes the battery can deliver at some given temperatures (usually ranging from -18C to about +20C). They are seldom very useful in determining how long you can run a radio like the K2 or the K3 from it, especially at 100 watts. Perhaps the closest indicator is the "Reserve Capacity Minutes" (RCM). It's the number of minutes a battery can deliver a significant current - something like 25 amperes. Using that number one can make an educated guess about how long it can deliver current to support transmitting with a 100-watt rig, but it's not a perfectly linear curve. You can't count on multiplying the time by some factor for lower receive currents or lower transmit powers. Most car batteries are designed to deliver short bursts of energy to operate the starter and then "float" on the line while most of the electronics run off of the alternator. These batteries have a larger number of relatively thin plates to provide the greatest current flow through the electrolyte during peak demands, but the thin plates limit the time the battery can deliver the current. Deep discharge batteries designed for continuous service have fewer, thicker plates to provide more ions for more current over time, but they have a much smaller capacity to deliver high currents for a short time. Getting optimum performance is a matter of carefully matching the actual demands of the rig and how it will be used with the right battery but, typically, the "Golf Cart" or "Electric Chair" types designed to deliver nominal currents over a longer time are the most suitable for radio use. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
