Roger Lee Posted February 28, 2011 Author Report Share Posted February 28, 2011 Looks like the forward voltage on n5819, which is 1A 40V is .55V. It all depends on how much voltage you need to get to 13.9 - 14.2 volts. You could use it, but first start your engine and check the voltage at the battery and the shunt if you have a Dynon. If you only have 13.5 V or lower at those points then that diode would work. The whole key here is to get a full charge, but not go over that amount. Once installed you must do another check at the battery and shunt to make sure you're not over charging. Link to comment Share on other sites More sharing options...
chanik Posted February 28, 2011 Report Share Posted February 28, 2011 It's about the same; the 40V is just a higher reverse voltage tolerance. Usually that means maybe 0.05V higher forward voltage. It only has to handle 10mA or so so literally any diode can handle the current and any voltage above 20V is fine for reverse voltage which again is virtually all diodes. Schottkey is the guy's name but it is attached to diodes made with metal-semiconductor junctions instead of the much more common P and N doped silicon (called a PIN diode). The physics is much different resulting in the lower Vf for schottkey types. Link to comment Share on other sites More sharing options...
ozairangel Posted March 1, 2011 Report Share Posted March 1, 2011 Thankyougentlemen.............David Link to comment Share on other sites More sharing options...
Jim Posted March 1, 2011 Report Share Posted March 1, 2011 I have a bad feeling about this mod. Hanging a diode off of a connector in the engine compartment is not good engineering practice. Depending its forward voltage drop in an environment that changes temperature from 20 to +140 degrees is not good practice either. Same with not analyzing what happens if the diode fails open. Link to comment Share on other sites More sharing options...
Roger Lee Posted March 1, 2011 Author Report Share Posted March 1, 2011 I have used shrink wrap around the diode and if the diode fails it should just be a wire in between and just revert back to the original voltage. I can't imagine it being any worse on the diode than it is on all our other electronics under the cowl. You can secure the diode in place with 1-2 tie wire ties. It can't move and not on a vibration point. You know that may be my next research project, to find out what the inside cowl temps are during flight and after the flight while sitting and I know an easy way to do it. As that stupid tabloid used to say, "Inquiring minds want to know". That's actually a good idea Jim. I'll keep you informed. Link to comment Share on other sites More sharing options...
jaak Posted March 2, 2011 Report Share Posted March 2, 2011 I have a bad feeling about this mod. Hanging a diode off of a connector in the engine compartment is not good engineering practice. Depending its forward voltage drop in an environment that changes temperature from 20 to +140 degrees is not good practice either. Same with not analyzing what happens if the diode fails open. Temperature really shouldn't be a problem, these parts are rated for -65C (-85F) to +125C (+257F) (and you can get extended temperature versions). Link to comment Share on other sites More sharing options...
chanik Posted March 2, 2011 Report Share Posted March 2, 2011 I thought about this. It's very little mass so shouldn't be able to vibrate itself into a broken lead, but that would be the main risk. Shorted, you would just be back to a wire connection like before. With an open, you would have unregulated charging. Eventually the battery would have an overvoltage alarm and you would want to pull the generator to keep it form badly overcharging. After a couple hours, if you were still flying, you'd have to turn the generator back on to recharge the battery. Effectively, the pilot becomes the charge regulator. Link to comment Share on other sites More sharing options...
Jim Posted March 2, 2011 Report Share Posted March 2, 2011 Temperature really shouldn't be a problem, these parts are rated for -65C (-85F) to +125C (+257F) (and you can get extended temperature versions). Right. The problem I'm concerned with is that the forward voltage drop will change 2mv/degrees C. And that the forward voltage drop is not well specified to begin with. Link to comment Share on other sites More sharing options...
FastEddieB Posted March 2, 2011 Report Share Posted March 2, 2011 You know that may be my next research project, to find out what the inside cowl temps are during flight and after the flight while sitting and I know an easy way to do it. As that stupid tabloid used to say, "Inquiring minds want to know". That's actually a good idea Jim. I'll keep you informed. One of the pre-installation steps for installing the SoftStart module is to verify that temps at the install location are within the unit's parameters. They provided temp-sensitive stickers: I'm sure there are other ways, but that's one! BTW, my Sky Arrow shows about 13.5v to 13.7v on my Garmin 496, which I assume is an accurate measurement of "bus" voltage. My panel-mounted voltmeter shows about 15v, which I assume is just wrong: Link to comment Share on other sites More sharing options...
chanik Posted March 2, 2011 Report Share Posted March 2, 2011 I didn't know the 496 displayed system voltage; that's interesting. I wouldn't worry much about the diode thermal response. Over a 110F increase, you're talking about only 1/10th of a volt drop. Incidentaly, the ducati drops system voltage as the regulator heats up. -4mV/C drop is correct for charge voltage as a function of battery temperature but the ducati gets much hotter than the battery so is a poor proxy to determine proper system voltage. The -2.2mV/C diode drop with heat adds to this compensation Link to comment Share on other sites More sharing options...
FastEddieB Posted March 2, 2011 Report Share Posted March 2, 2011 I didn't know the 496 displayed system voltage; that's interesting. On most pages you can hit "menu" and customize fields. Voltage is just one of many options, and worthwhile having displayed on at least one screen, IMHO. Link to comment Share on other sites More sharing options...
Roger Lee Posted March 2, 2011 Author Report Share Posted March 2, 2011 I learn something new every day. One day I'll be able to finally pass my 6th. grade test and move on. Link to comment Share on other sites More sharing options...
Runtoeat Posted March 3, 2011 Report Share Posted March 3, 2011 Some data FYI. My latest flight showed voltage of 13.75 volts. I have steam gages so basically only my Garmin 495 running and the red ACL beacon on. This voltage reading includes compensation for my voltmeter reading .25 volt low for "true" voltage at the battery terminals. I always seem to have strong starts during cold weather after long flights and my charger doesn't go into a charge mode when I put the plane away after my flights. I believe that my charger will go into a 14.1 volt charge when it senses battery voltage below 13.7. My charger will go into the 14.1 charge if I pull the battery main breaker and turn the system on without engine running. I don't think I'll change anything in my charging system. Link to comment Share on other sites More sharing options...
chanik Posted March 3, 2011 Report Share Posted March 3, 2011 I would leave it alone. 13.7V is close enough. Do you have the standard Ducati regulator? It does not do step regulation. My theory is that the Ducatis slump low as they heat up so the voltage droop is more a problem with Dynon panels and such. The things get alarmingly hot, in fact. There have been other threads talking about serial failures of these things where they did not have good cooling or heat sinking. Link to comment Share on other sites More sharing options...
Runtoeat Posted March 3, 2011 Report Share Posted March 3, 2011 Hi Kurt. I've got a Ducati regulator. Interesting about these regulators heating up. I'll have to check that out. I failed to mention the Garmin radio (com only) and xponder, and my autopilot also drawing current. Some time ago I laid some fingers on the small side portion of the radio (or xponder?) that pokes out of the panel and one of these (both?) were pretty hot. There's got to be a fairly good current draw to provide this heat. Add in Dynon panels and equipment and maybe a 2nd radio and I imagine that this may put the Ducati over the top. Thanks for your insight and comments regarding the electronics. Glad to hear you agree with me leaving things "as is". Link to comment Share on other sites More sharing options...
Roger Lee Posted December 18, 2011 Author Report Share Posted December 18, 2011 Kurt, How would you know if the little diode quick working or burnt out? Link to comment Share on other sites More sharing options...
chanik Posted December 18, 2011 Report Share Posted December 18, 2011 It can't really burn out since there is little current through it to the control input, but if it did overheat alot, then it would act like a short and you would have the same performance as with a wire. A more liley failure would be if it disconnected. Then the regulator would always drive full power into the battery and not try to regulate. You would notice the battery start to overvoltage and would then have to pull the breaker to shutoff the regulator. You could turn it back on if the battery then went low after a couple hours. Basically the pilot would have to control the regulator manually Link to comment Share on other sites More sharing options...
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