Question Power Supply with 4 x 12v rails to power an electrically adjustable car seat ?

[.ESC.]

i have an old hiper type-m 630w psu that has 4 x 12v rails that can do 18a each and i want to power an electrically adjustable car seat with it without the heating element, is it possible to join these rails together into 1 high amp 12v output, i wouldnt be putting a heavy load on them i just need 30a for the seat as that was what it was in the car, ill be connecting all the 12v wires coming out of the psu into 1 and all the ground wires into 1.

 

[Ralston18]

This PSU?

http://www.xoxide.com/hyper-type-m-630w-black.html

What are the electrical specs for the car seat motor(s)?

Do you have an electrical schematic for your plan?

All in favor of DIY and repurposing things etc..

However, the proposed application needs much more detail and explanation.

 

[.ESC.]

yes thats the psu and all i know is that the seat was on a 30a fuse in the car, i cant get to the motors in the seat to see if they have any information on them as theyre all tucked away inside the seat, also for the schematic there isnt really much to it, i just looked up the pinout of an atx psu and i was gonna cut all the wires off of the connectors and bunch up all the 12v wires and the ground wires and have them as a positive and negative as the seat only has a positive and negative to connect to, if you think you could find something for how much power the seat needs its from a 2012 volkswagen passat with the high spec interior

 

[bill001g]

From what I can tell that power supply also has a 28amp 12v output. That maybe your best option it is close enough to 30 amps. The power supply should have a internal fuse or protection circuit if you try to draw more than 28 amps.

If this was a some electronics then I would say combining the 18amp outputs would be risky but for something that will tolerate dirty power like a motor it is less of a issue.

So it has been a while since I look into this in depth so things might have changed. Years ago when they talked rails it was almost as though they put multiple 12volt power supplies in 1 box. There never was the issue of plugging say 2 power cables into the motherboard or video card they tended to only have 1.
Now days it is common for the motherboard or video card to take multiple power connectors. You really don't want those coming from different power supplies.....even though I have seen people using multiple external power supplies which is the same problem. There can be very slight differences in the voltage regulation between the different power supplies which can harm sensitive equipment.

What you see lately when they talk rails is not really the same concept. There is really only 1 main circuit for regulation. What they do is in run it though multiple different protection circuits. So they would say run 2 20 amp circuits rather than 1 40 amp one. If you connected connectors from both to a single device it would still have 40 amps combines since it should pull equally.

 

[.ESC.]

i've just wired it all up and it works amazingly, thanks for the help people, ill let you know if i have any future issues with it, i wired 2 of the 18amp rails to the seat, the psu i have doesnt have a 12v 28amp output it has a 5v 28amp though, its only got 4x12v 18amp so i thought just 2 of them would do the job and it does.

 

[bill001g]

Never did the math before you update. Something is screwy with the ratings. 4 18 amp 12 volt connections would be 864 watts which is massively above the 630 and it ignores the other voltages like 5 volt and -12 volt etc.
But you are still likely nowhere near even the 630 with your application.

 

[arif1752002m4a1]

As I have Designed Some SMPS and Have a lot of experience here..
I can conclude that, This PSU is actually Generating Single 12V rail... Then Output is sensed through 4 different Shunt resistors to make 4 different rail.. while Origin is same 12V rail.. So yes you can connect them in parallel...

But as I can see its Minor Rail Rating which is 30Amps.. means its actually a Group Regulated Power supply.. which is actually a big problem...

Group Regulated PSU = GPSU
see these GPSUs are not good in maintaining steady output voltage across all rails.. specially under unbalanced mode.. means one rail is loaded while other are not.. which can cause high voltage in unloaded Rails... and PSU safety triggers... and your PSU will turn off....

if your PSU is actually a GPSU.. then drop the Idea.. get a modern DC-DC labeled PSU.. where PSU only generates 12V.. and Independently regulates 5v and 3.3v.. so no matter what king of Cross rail Load you put on these Modern PSUs.. they will maintain very steady output voltage,.. and hence can be loaded with any king of load...