In a message dated 22/04/05 19:50:27 GMT Daylight Time, [EMAIL PROTECTED] writes:
I had a 33 Ohm resistor of 5W in stock which was only 0,3 inch, so it fits very nicely. I have mounted it on the component side of the pcb, otherwise it gets in the way of the battery! The result is very positive, it charges nicely. I have mounted a timer in line with the charging supply, an old Nokia 12V GSM supply, to avoid overcharging as I read that NiMh cells dont like that. Reply: ----------------------------------------------- Hi Dick, Yes, that method will work and is used in most simple hand held radio battery chargers to limit the charge current. However to get the best life out of NiCad and NiMh cells/batteries I have always understood that they should be charged under constant current conditions at the recommended rate given with the cells or battery. The series resistor method does limit the maximum current though may partially fall down on not providing a constant current. There are several methods of providing a constant current, the most common being to use a voltage regulator with a series resistor providing feedback. I use an earlier method with two transistors and two resistors that is easily adapted to any required constant current and will cope with a wide range of input voltages. Not sure how the charging of the KX1 is configured so your options may be limited. Contact me off the list if you need the two transistor schematic. Gross Overcharging of *any* rechargeable cell/battery is always a problem resulting in heat generation and eventual destruction of the cells unless this is limited to a charge rate of 2.5% or less of battery capacity. I had something like 400 UHF HH to maintain at an oil terminal/gas plant and apart from the operators using the radios instead of a hammer, the main problem was gross overcharging which could lead to failure of the battery in as little time as a year. Some automatic chargers received more recently were the answer to this problem, though these are even today far from being widely available. Time limiting the charge will work as long as the battery is fully discharged to start with. A partly discharged battery subjected to a full charge cycle will only dissipate the resultant continuation of charge after full charge is reached as heat. Note that all modern cellular mobile telephones are fitted with an automatic charger to get maximum recharging life from the battery. Bob, G3VVT _______________________________________________ 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
