Available power on molex chain for each connector?

[TheNaitsyrk]

Hi there,

 

Currently powering 45x fans using 5x AquaComputer Octos. I recently added 2x 240mm XE rads to my build which will require another 4 fans.

 

The thing is, all of my AquaComputer Octos are maxed out. I have fan splitters but just wanted to check before I do anything.

 

One molex chain cable (4x Molex on a cable on peripheral 6pin going into PSU)

 

How many watts can each connector take? Is it 54W per connector or 54W for the entire cable?

[mariushm]

The contacts inside the molex connectors are rated for up to 5A of current. So that would be 5A x 12v = 60w on 12v , and 5A x 5v = 25w on 5v 

The wire from the molex connectors to your power supply is rated for at least 10A of current (if AWG18 or better)

The contacts inside the connector on the power supply are usually rated for 9A of current or more (depending on the type of contacts could be 13A or even more)

 

So you have at least up to 9A of current going out the power supply through each of the two voltages, then going to the molex connectors on a cable.

 

I would just say round it up to around 100w available on 12v to ALL the molex connectors on a cable, and each individual molex connector could give up to 60w on 12v (but I'd recommend not going over 40-45w or around 3A of current)

 

The current is listed on your fans... but keep in mind that for a few seconds when the fan starts from cold and spins up, the current is much higher... I'd say a safe amount would be 2-3x more current for a few seconds until it gets up to speed.

This is good to know so you don't overdo connecting 4+ fans on a motherboard header, stuff like that, because all 4+ fans starting at same time could exceed the 1-2A rating of the fan header on motherboard. Less of an issue with molex connectors.

 

 

[TheNaitsyrk]

33 minutes ago, mariushm said:

The contacts inside the molex connectors are rated for up to 5A of current. So that would be 5A x 12v = 60w on 12v , and 5A x 5v = 25w on 5v 

The wire from the molex connectors to your power supply is rated for at least 10A of current (if AWG18 or better)

The contacts inside the connector on the power supply are usually rated for 9A of current or more (depending on the type of contacts could be 13A or even more)

 

So you have at least up to 9A of current going out the power supply through each of the two voltages, then going to the molex connectors on a cable.

 

I would just say round it up to around 100w available on 12v to ALL the molex connectors on a cable, and each individual molex connector could give up to 60w on 12v (but I'd recommend not going over 40-45w or around 3A of current)

 

The current is listed on your fans... but keep in mind that for a few seconds when the fan starts from cold and spins up, the current is much higher... I'd say a safe amount would be 2-3x more current for a few seconds until it gets up to speed.

This is good to know so you don't overdo connecting 4+ fans on a motherboard header, stuff like that, because all 4+ fans starting at same time could exceed the 1-2A rating of the fan header on motherboard. Less of an issue with molex connectors.

 

 

Each fan pulls 0.3A or 3.6W.

[tkitch]

you're pulling over 10A, and getting closer to 15A.
I wouldn't pull more from those molex cables.

[Skiiwee29]

<-- Moved to Power Supplies -->

 

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[Guest]

1 hour ago, TheNaitsyrk said:

Hi there,

 

Currently powering 45x fans using 5x AquaComputer Octos. I recently added 2x 240mm XE rads to my build which will require another 4 fans.

 

The thing is, all of my AquaComputer Octos are maxed out. I have fan splitters but just wanted to check before I do anything.

 

One molex chain cable (4x Molex on a cable on peripheral 6pin going into PSU)

 

How many watts can each connector take? Is it 54W per connector or 54W for the entire cable?

Your limitation is not going to me each Molelx or the wire, but the connector at the PSU.  The 6-pin connector only has ONE +12V terminal.  So the load of all of the fans on that cable are on that one pin.  That one pin is rated at maximum 9A.  So be careful.

 

 

[TheNaitsyrk]

On 7/1/2022 at 6:59 PM, tkitch said:

you're pulling over 10A, and getting closer to 15A.
I wouldn't pull more from those molex cables.

That's not true.

 

I have 5 Octos. Each hooked up to a separate molex chain.

 

Each Octo has 8 fans on it, except for one but let's disregard it for now.

 

8 fans x 0.3A = 2.4A per Octo.

In total yes it's 12A.

 

But as I said it's not all loaded in one cable, it's spread across 5 different ones hence why I'm just wondering if I added one fan per Octo, would it still be fine or meh? Hence why I asked for maximum wattage on each chain.

 

[tkitch]

1 hour ago, TheNaitsyrk said:

That's not true.

 

I have 5 Octos. Each hooked up to a separate molex chain.

 

Each Octo has 8 fans on it, except for one but let's disregard it for now.

 

8 fans x 0.3A = 2.4A per Octo.

In total yes it's 12A.

 

But as I said it's not all loaded in one cable, it's spread across 5 different ones hence why I'm just wondering if I added one fan per Octo, would it still be fine or meh? Hence why I asked for maximum wattage on each chain.

 

are you talking about 5 separate PSU Connections, or 1 PSU Connection, or another number?
 

5 Molex connectors on the same chain, have the limit of a single molex draw, not 5x that.

[mariushm]

13 minutes ago, tkitch said:

are you talking about 5 separate PSU Connections, or 1 PSU Connection, or another number?
 

5 Molex connectors on the same chain, have the limit of a single molex draw, not 5x that.

no,  a chain with N molex connectors will be limited by the connector on the power supply in which the chain is inserted.   If the power supply connector can do 100 watts,  and each molex connector on the chain can do 50-60 watts ... the molex connectors in total can only do 100 watts.

 

I think he means he uses 5 chains with molex connectors,  and connects one OCTO in a single molex connector on each chain.

 

Assuming 0.3A during regular use, around 0.75A at spin-up (probably too much but nice round number), you have 8 x 0.3 = 2.4A during regular use , 6A during startup.

You're nowhere close the individual molex connector limit (5A) and nowhere close to the chain's limits (9A+)

 

You could probably have two OCTO per chain, one octo per molex ... only concern is peak current when all 16 fans spin-up.

Though, there's enough thermal mass that the cable will tolerate 12-15A for a few seconds even if each fan peaks at even 1A for a few seconds at spin-up. The ratings of 9A for the psu connector and 5A for the molex are for sustained use, not a short burst value.

In the 2-5 seconds it takes for the fans to spin up, there's not enough time for the contacts in the connectors to heat up, or for the wire to get too hot and so on.

 

Once they're spinning at 0.3A average current, 16 fans would only consume around 5A or 60 watts, which can be handled by a chain of connectors and it's well within the ratings of all parts involved.

 

You can go overboard if you want,  ideally you'd do a staggered spin-up of the fans ( spin 8 fans, wait 2-3s, spin the next set of 8 fans) ... but I don't know how you'd do it. If the OCTO has an enable pin of some sort, you could implement a delayed star but otherwise it's not easy.

[tkitch]

35 minutes ago, mariushm said:

I think he means he uses 5 chains with molex connectors,  and connects one OCTO in a single molex connector on each chain.

IDK, I've never seen a PSU with 5 connectors for molex, unless you replace all of the SATA cables with molex

[mariushm]

5 minutes ago, tkitch said:

IDK, I've never seen a PSU with 5 connectors for molex, unless you replace all of the SATA cables with molex

My Seasonic X-650 has 5 peripheral/sata connectors : https://silentpcreview.com/x-650-seasonic-hits-gold/

8 sata and 5 molex across 5 chains

OK, the cables that come with the psu are mix of sata and molex and not 5 connectors per cable (max is 3 connectors per cable), but nothing stops me from going to cablemods to make custom cables for it.

Higher wattage power supplies sometimes come with more peripheral connectors though the trend these days is to have limited current on 3.3v and 5v so that's contradictory.

[TheNaitsyrk]

It's AX1600i.

 

I has 6 peripheral 6 pins. 

[TheNaitsyrk]

2 hours ago, mariushm said:

no,  a chain with N molex connectors will be limited by the connector on the power supply in which the chain is inserted.   If the power supply connector can do 100 watts,  and each molex connector on the chain can do 50-60 watts ... the molex connectors in total can only do 100 watts.

 

I think he means he uses 5 chains with molex connectors,  and connects one OCTO in a single molex connector on each chain.

 

Assuming 0.3A during regular use, around 0.75A at spin-up (probably too much but nice round number), you have 8 x 0.3 = 2.4A during regular use , 6A during startup.

You're nowhere close the individual molex connector limit (5A) and nowhere close to the chain's limits (9A+)

 

You could probably have two OCTO per chain, one octo per molex ... only concern is peak current when all 16 fans spin-up.

Though, there's enough thermal mass that the cable will tolerate 12-15A for a few seconds even if each fan peaks at even 1A for a few seconds at spin-up. The ratings of 9A for the psu connector and 5A for the molex are for sustained use, not a short burst value.

In the 2-5 seconds it takes for the fans to spin up, there's not enough time for the contacts in the connectors to heat up, or for the wire to get too hot and so on.

 

Once they're spinning at 0.3A average current, 16 fans would only consume around 5A or 60 watts, which can be handled by a chain of connectors and it's well within the ratings of all parts involved.

 

You can go overboard if you want,  ideally you'd do a staggered spin-up of the fans ( spin 8 fans, wait 2-3s, spin the next set of 8 fans) ... but I don't know how you'd do it. If the OCTO has an enable pin of some sort, you could implement a delayed star but otherwise it's not easy.

We got a winner.

 

You understood perfectly.

 

It seems as though adding just one more fan per Octo should do the trick which is amazing.