In a message dated 03/06/05 04:10:11 GMT Daylight Time, [EMAIL PROTECTED] writes:
Given the size and weight of batteries, I had hoped to use a 36 Ah battery, and then recharge it with solar power. But it seems that these batteries charge rather slowly, and that might not be possible. For example, I think it is powerportstore.com that has a 1.2 amp flexible solar panel recharger that puts out approximately 5.6 - 7 Ah per day. The solar panel is about $ 500.00. The general size/weight and price is ok, but it doesn't appear that such output would be sufficient to fully recharge a big battery. Reply: ------------------------------ The problem of recharging the battery from the 1.2A solar panel (about 16 -18W capacity) is related to the solar panel being rather lacking in capacity and would not do much more than delay the battery being run down considering the drain of a K2/100 on TX. It all depends on the TX to RX ratio used with the K2/100 and the mode of usage to how long the battery will last. RX is no problem with the K2 as that is in the 0.25A range, but the 100W on TX can draw something in the region of 20A at full output. However a 1.2A solar panel would be very usable with a basic K2 which has much lower TX current requirements of usually 2.0 to 2.5A at 13.8V. Even with this a charging controller would probably not be needed as the battery would provide much of the needed voltage regulation. A diode would be needed in series with the solar panel to prevent the battery discharging back into the panel when the solar insolation is insufficient to provide any charge. This diode is provided internally with most of the larger solar panels. For use with a K2/100 a much larger solar charging capacity would be better, probably in the 55W range (4A at 13.8V) or higher together with a suitable charge controller to prevent any possible over charging of the battery and consequent over voltage being applied to the K2/100. With the solar powered communications systems I was involved with from 1981 to 2002, these initially used multiple 55W panels (approx 3ft x 1ft) with individual controllers on each to provide the charging for the battery plant. Later 15kW systems used 200 x 75w panels (approx 4ft x 1.5ft each panel) and switched the solar panels in banks controlled by an intelligent charger system. A matter of balancing the required charging voltage with the amount of panels on line. This was needed to provide for the current drain of the comms systems and allow for days when the sun did not appear, where the available charging current would be insufficient to balance the 24 hr drain. With the latter systems running a microwave site it was normal to see 120A or greater charge current at 54 to 58V when the battery plant was in the morning full charge cycle. Bob, G3VVT _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
