> lot?). So the load is 204w x2 x 0.30 = 122w which after an hour has > totally discharged the 110AH battery
This isn't right. The capacity of the battery in watts is 110x12 or about 1320WHr. If the load is 122w/hr the battery should be totally exhausted after about 11 hours. Of course you should never intentionally fully discharge a battery so a reasonable time of operation on battery alone would be about 7 hours. The solar panel, if in full sun and at max efficiency would generate ~120w. This is barely enough to keep up with both transmitters. Nothing left over to recharge the batteries. 73 de dave ab9ca/4 On 6/29/12 3:05 AM, Edward R. Cole wrote: > 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 > ______________________________________________________________ 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
