I can think of one reason to avoid charging every time external power is applied -- external batteries. If you are running from 14V LiFePo batteries on the trail, you don't want to charge the internal NiMH batteries at the same time.
wunder, K6WRU On Jan 30, 2013, at 11:22 AM, Rich Heineck wrote: > During charge at 200mA, the NiMH batteries can typically reach 1.5V each, for > 12V total. Add in the extra voltage for path resistance, isolation diode, > and charging regulator overhead, you get up over 13.5V, which is why the > recommended voltage is 13.8V. Charging at lower supply voltages would have > required a switching boost regulator which then gets into problems of space, > RFI, and cost. It is possible to put some charge into a depleted set of > batteries from a lower supply voltage but they just won't be able to get > fully charged. > > Because the battery holders will hold any kind of AA cell, we opted for > safety and charge reliability when it came to selection of how the charger > operates. With 8 NiMH cells in series, the influence of things like > temperature, cell condition, and other factors make automatic detection of > full charge at moderate charging currents unreliable. A timed charge may not > be elegant, but it's the approach recommended by the major battery > manufacturers when not doing a fast, smart charge. And the latter requires > much higher current and was just not feasible in the KX3 due to safety, power > requirements, heat, RFI, and a few other things. > > Hopefully this helps explain a bit why the charger operates as it does. > > 73, > Rich AC7MA > > > > > On 01/30/2013 10:33 AM, Alan Davenport wrote: >> Your questions are valid. I asked the same ones myself. I'm also >> disappointed in the charger. I also found that it is very fussy about input >> voltage. I run my 12v rigs in my shack off deep cycle marine batteries which >> I keep topped off with a high end marine smart charger (ironic!) When the >> smart charger shuts down because the batteries are topped off the charger in >> the KX3 refuses to charge its batteries while stating "input voltage too >> low". There is nothing wrong with my shack batteries. This issue (input >> voltage too low) occurred even when the shack batteries were brand new. (I >> had replaced them all just prior to hurricane Sandy.) >> I'm sorry Elecraft. All your other gear it a grand slam home run. This >> charger is just a bloop single. >> 73 de Al, W2GZN >> >> ________________________________ >> From: "[email protected]" <[email protected]> >> To: [email protected] >> Sent: Tuesday, January 29, 2013 5:53 PM >> Subject: [Elecraft] KX3 Smarter Charger >> I don't claim to know about battery charging but why can't the charger >> stop when the batteries get to "X" volts and start charging when the total >> battery voltage drops below "Y" volts, would this feedback system add to the >> cost of the charger. I bought a "smart charger" at Harbor Freight for $5.99 >> the red light goes green when the batteries ( 4 NiMH) are fully charged and >> when you put depleted batteries in it it blinks red. Why can't the charger >> in the KX3 be totally transparent? load and forget. I found the whole >> charging instructions confusing after an initial 16 hour charge do I >> occasionally give it a 4 hour charge or what ? do I want a lot of hot >> batteries in there? >> >> K6CG >> ______________________________________________________________ >> 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 >> > > ______________________________________________________________ > 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 -- Walter Underwood [email protected] ______________________________________________________________ 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
