Designing streering diodes

[ahmedragia21]

Hi All,

If I have main source from a forklift which is 9-30DC and would like to connect it with a battery to steering diodes, how would one choose the steering diodes?
The maximum current that I would draw is 5A, so I need a very high power diode, and a very high power rated resistors correct ?

 

[MikeMl]

Sketch a circuit of what you are trying to do.

 

[ahmedragia21]

Just a normal steering diodes that are used to switch the supply on power failure.

 

[kubeek]

Yeah, right, everybody knows what you´re talking about.

 

[ahmedragia21]

here is what I mean guys

https://www.electro-tech-online.com/attachments/1-png.69957/

 

[ChrisP58]

That circuit is more popularly known as a 'diode OR' Meaning that the load is powered from input A or B, (or C or D) depending on which voltage source is the highest.

As for choosing the diodes, there are two basic criteria. Peak reverse voltage, and continuous operating current. You want to choose parts with a good amount of safety margin. For 5A at 30V, operation I would pick, at the very least, a 40V, 10amp part. Specifically I would use an MBR1045, because I already have them on my shelf. It is a 45V, 10 amp Schottky diode. The choice of a Schottky diode versus a standard diode is that it has a lower forward voltage, and therefore will generate less heat.


More on voltage selection: You said that this is for use on a forklift. If there is a lot of electrical noise and/or inductances that generate high voltage transients, you may need even higher voltage diodes to prevent their failure. That can only be assessed by studying the total installation.