Look at energy instead of power. You have a 120AH solar panel to a 110AH battery. What is your load? Two 100w transmitters running 12v at 17a dc load (204w load to the battery for each radio). Your Tx/Rx duty cycle is probably = 30% during FD (are you calling CQ FD CQ FD a lot?). So the load is 204w x2 x 0.30 = 122w which after an hour has totally discharged the 110AH battery if were not being charged by the solar panel. With solar charging at 120AH you still have a negative energy equation (so maybe it takes a couple hours operation to discharge the battery).
It sounds as only one battery was used for two radios. A better solution would be separate batteries very close to the radios. Still the 120AH solar charging system is undersized to maintain the batteries very long. So lower RF power to 50w (as has been suggested) to lower dc load. Also increase dc wiring size to lower ohmic losses. Battery boosters will give a little more voltage at the end of battery life, but at the expense of battery current (no free lunch). I ran 20w psk-31 one FD using a single 60w solar panel and a 100AH diehard marine battery and was able to run about 6-hours. Of course psk-31 is keydown in transmit. The radio was a FT-847 so I do not know its efficiency running at 20w RF. The Rx and digital ckts probably consumed 3-4 amps continuously, and transmitter probably 50w at 50% efficiency for another 4 amps. So say it was 7 amps in transmit (7x12= 84w). I did not call CQ extensively but instead searched and pounced so most of the time was Rx so Tx/Rx duty cycle was probably 10%. Overall the load was probably 48w per hour so the 60w solar panel should hold the battery charge long-term. Things rarely run exactly according to theory. In my former job I maintained two remote repeater sites that were run on solar-charged batteries in summer and on alkaline batteries in winter (system auto-switched when solar battery voltage dropped to 10.5v). The solar system was two 60w solar panels feeding two 100AH deep-cycle batteries; winter was a 10,800 AH air-activated alkaline battery bank (90 1.5v cells in 10cell banks). Each 1.5v battery was rated at 1200AH. The site was operated in a stby status 99% of the time with only the UHF control radios activated full-time. We got three years life between battery replacements (helicopter only access). With new batteries the site had a 30-day operational status. Repeaters were 30w and there were more than one at each site. 73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-? DUBUS Magazine USA Rep [email protected] "Kits made by KL7UW" http://www.kl7uw.com/kits.htm ====================================== ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
