lml@lancaironline.net Mailing List Archive

<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> There is a special type of diode called a Schottky diode which can have a voltage drop as low as 0.2 volts verses the typical 0.7 volt drop of a standard silicone diode. Schottky diodes are still silicone diodes, but they dope the PN junction a little differently with various metal oxides. I recommend using the Motorola 1N5829 Power Rectifier Schottky diode for your backup battery charging application. This diode is rated at 25 Amps and 20 Volts. Here are the forward voltage drops from the chart: At 0.3 amps the diode drops 0.21V At 1 amp the diode drops 0.25V At 5 amps the diode drops 0.3V At 10 amps the diode drops 0.36V At 20 amps the diode drops 0.4V At 25 Amps the diode drops 0.44V As your battery charges and draws less current, the diode voltage drop will decrease so you will eventually get a loss of only 0.21V. In case you want to build in a little more protection you can get higher voltage ratings with the same specs. They typically cost more if you get higher voltage ratings. There is a note in small print on the data sheet that reads: "1N5831 is a Motorola Preferred Device" This means that Motorola will manufacture more of these. This may also mean that these could cost less when you order small quantities (supply and demand). Check them all out, they will all work. 1N5829 20 Volts (probably lowest cost) 1N5830 30 Volts 1N5831 40 Volts (better availability) Regards, Ed Armstrong Watsonville CA LML website: http://www.olsusa.com/Users/Mkaye/maillist.html LML Builders' Bookstore: http://www.buildersbooks.com/lancair Please send your photos and drawings to marvkaye@olsusa.com.