Diode

[n38139]

I want to install an aux battery in my electrical system just for my
EFIS. I have the battery issue worked out but I want to put a diode in the system to isolate the battery. A friend of mine did the same thing I am going to do but I cannot find the p/n diode he used. Any of you electrical gurus know what I need?

thx

[Mike S]

I dont remember the part #, but I went with a Schotkky diode for the lower voltage drop it offered.

They are rated as to voltage, and reverse current. You need to find one that will handle the load you intend to subject it to, plus a bit extra for a safety factor---I used 50%.

Be sure to work in a heat sink into your plans, if your application is going to need it---look at the specs for each diode.

You can find many kinds of mounting for these diodes, may help fit into your particular needs.

Bob Nuchols has a simple setup shown in his Aerolectric Connection book, uses a different diode---but a lot out there flying.

Good luck.

[111RF]

For my aux battery for dual EI, I used the Shottky Diode from Perihelion Design - www.periheliondesign.com. With the optional mounting base it's a simple installation.

[Garage Guy]

Originally Posted by Mike S

They are rated as to voltage, and reverse current.

I'm guessing you meant to say "rated as to current, and reverse voltage". At least, those are the important things to look at, along with forward voltage drop at working current. (Reverse current is going to be negligibly small.)

That Schottky diode Perihelion has http://www.periheliondesign.com/powerschottkydiodes.htm is overkill to isolate an EFIS battery, but will certainly work, and probably won't even need a heat sink in that application.

--Paul

[Mike S]

Originally Posted by Garage Guy

I'm guessing you meant to say "rated as to current, and reverse voltage". At least, those are the important things to look at, along with forward voltage drop at working current. (Reverse current is going to be negligibly small.)


--Paul

Yep, my bad.

Not enough coffee at that early post.

[rocketbob]

Search for DSS2X121-0045B-ND at Digikey.

Two diodes per package, much higher current ratings, better mounting arrangement, and cheaper than the perihelion shottky. If I remember correctly when I researched this one, it also had a lower forward voltage drop.

[Rick_A]

I used the perihelion Shottky for my E-bus but I used some other sort of diode (don't remember exactly what) for my GRT Aux battery.

I use the Aux bat to initialize the GRT before start up while my Avionics bus is off. On the last few flights, the GRT "grays out" and re-initialized when I start the Engine. I'm thinking that I've blown the diode in the aux bat charging circuit. (The charging circuit connects to the Main Bus, not the Avionics Bus.)

Bottom line. I'll be getting another Shottky from Perihelion.

[Jkkinz]

B&C Specialty Products also carries them with the heat sinks

http://www.bandc.biz/index.aspx

[Garage Guy]

Originally Posted by Jkkinz

B&C Specialty Products also carries them[/url]

Those 'essential bus diodes' at B&C are regular old P-N junction silicon bridge rectifiers, where you end up using only one diode out of 4 in the bridge. Which will work too, but the much lower forward voltage drop of a Schottky is a real plus in this application IMO.

--Paul

[apatti]

To isolate my aux bat I used a Schottky Diode from Digi-Key. Their part number is 90SQ030-ND. It is rated for 9A. I am not expecting nearly that much current. No heat sink required. Looks like the forward voltage drop in the current/temp range I am using it will be <.3v.