I know using multiple power supplies is safe, but what if??????

SherylinRM

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Ok so I have seen videos of people using two or more power supplies to hasten the charging of their batteries.
So I know it is safe if they use the same power supply.
But what if you mix and match them?

First off I understand that they would all have to be the exact same voltage. That is a given.
But if they were all different amps though.
Would this still work?

I prefer someone with actual experience if possible.

Thanks guys :)
 

wholybee

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It's fine. They don't even need to be the exact same voltage. It is quite common (yes I have done it often) to charge from an AC charger, an MPPT solar charger, and an alternator, all at the same time. All different amperage and voltages.

What happens is that once connected together all the voltages become the same, pulled down to (nearly) the battery voltage.
 

SherylinRM

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It's fine. They don't even need to be the exact same voltage. It is quite common (yes I have done it often) to charge from an AC charger, an MPPT solar charger, and an alternator, all at the same time. All different amperage and voltages.

What happens is that once connected together all the voltages become the same, pulled down to (nearly) the battery voltage.
Thanks, but I would want them to not go crazy on me and so I would have them all the same voltages.
After watching RFMans videos though. I am curious how you got around the feedback that caused stoppage of the amperage going into the batteries?

RF Man discusses load sharing in parallel power supply's and boost converters
 

wholybee

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Thanks, but I would want them to not go crazy on me and so I would have them all the same voltages.
After watching RFMans videos though. I am curious how you got around the feedback that caused stoppage of the amperage going into the batteries?

RF Man discusses load sharing in parallel power supply's and boost converters
He is describing a different situation, not one in which you are charging batteries, but one where you are using multiple supplies to supply a constant voltage to a load. In the case where you have multiple supplies and each one on its own is large enough to support the entire load, then they will not work equally-one may support the entire load. For example, you have 3 20A 12V supplies, connected in parallel to a 10A load. Only one of the supplies will be suppling the current. That only even matters because one supply will fail from use before the others, but doesn't otherwise affect operation of the load.

In the case of charging, if the charging voltage is set to 14.6V(or even if they are different, say 14.5, 14.6, and 14.7) , and the battery voltage is 12.8V, then when all paralleled together the voltage is going to be pulled down to below the 14.6V (probably close to 13V) and all the supplies are going to max themselves out (in his video he talks about pulse width getting longer. That is what will happen, but only as much as the supply is able to) suppling as much current as they can. If one supply is rated at 20A, and another rated at 10A, then that is what they will contribute. This will happen until the battery nears full charge and the battery voltage approaches 14.6V. At that time the charge current will drop off and may not be equal. But you will still be supplying the max the battery can take so it doesn't actually slow down charging. And the time period of that inequality is short, so it doesn't really shorten the life of one of the supplies.
 

Horsefly

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My thoughts were to use an ATX PS. It has 8 12 volt rails of 30 amps each.
First off, if it is ATX I would expect it has 3.3V, 5V, and 12V rails.

Secondly, I believe the amp rating of a power supply on each rail is not cumulative. That is, you probably can't pull 30A off the 12V rail at the same time you pull 30A off the 5V rail. I may be wrong though. Maybe someone else can clarify.

Third, if you use a boost converter to step up the voltage, the available current will go down. The total energy in watts (V * A) coming out cannot be more than you put in. So if you double the voltage you will have half the current. Actually, a little less than half because of the losses in the converter.
 

wholybee

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Some others have used ATX power supplies. I don't recommend it, but it seems to work. As to your configuration, I would be very surprised if you can get 80A out of the power supply. Does the PS have a total Wattage rating? What I expect is that individually any single rail can supply 30A, but not all at the same time. A power supply capable of 8x30A at 12V would be 2880W, not including the other lower voltage outputs.

Also, as Horsefly mentions, the other voltages are different rails. If the supply has multiple 12V outputs, they are may all be on the same rail. The fact is, building a quality 80A supply is not cheap. That is why they are expensive, and why an ATX power supply isn't likely a good shortcut.
 

wholybee

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I will ask again separately in case it got lost. What is the wattage of the supply?
 

Short_Shot

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My thoughts were to use an ATX PS. It has 8 12 volt rails of 30 amps each.
8x 12vdc 30 amp rails huh? 240a @ 12v you say?

You have a 3kw ATX power supply?

Got a link to this monster or have you made an error?

At any rate many of the high end units only have a single 12v rail. I had one unit back in the day that was 1x 100a 12v rail and it was a monster.


At any rate further good luck charging a 12v battery with a 12v power supply when the battery needs 13 to 14+ volts depending on what type of battery it is to fully charge.

And an atx power supply isn't variable.
 

Short_Shot

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The total is 1,200 watts.

To answer Horsefly. Every computer power supply I have worked with since the 1990's has had a 3 v 5 v and 12 v as well as 5- and 12- on them. So your point was moot. As I have no intention of using 3 volts to charge a 24 volt battery. It never occurred to me to mention it.
And doubling the voltage from 12 to 24 and halving the current from 30 times 8 to 15 times 8 is just fine with me.

As for the rails. Some computer power supplies have one rail for each voltage and some have multiple rails.

This particular one has 12 rails total. 8 just for the 12 volt section.


So back to my original question then.
"My thoughts were to use an ATX PS. It has 8 12 volt rails of 30 amps each. Attach each of those to a step up converter [the best I could find was 10 amp ones]. That would give me about 80 amps for charging instead of the anemic 10 amps I have now.
So if I understand you correctly. I would not need to do any modifications beyond setting up the voltages. Correct?"
You do not have 8x 30a outputs if you have a 1200 watt power supply.
 

Short_Shot

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No mistake. I can read.
Antec 1,200 watt power supply I said. Not 3kw as you have said.
I never said an ATX ps was variable.
I also never said I am charging a 12 volt battery.
Why all the lies and BS?
I think blocking you is the solution to your BS.
If you only have 1200w then you do not have 8x 30 amp outputs. Period. That's simply not possible.

What are you charging then? Your first post explicitly stated "charging a battery".

Do you have a 10 volt battery?

Nothing about what I said was a lie or BS at all.

You can call it BS all you want but I've built a couple dozen high end rigs, and modified several atx power supplies for misc projects.
 

Short_Shot

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Since I'm not experienced what I'll say is that I definitely don't know about the antec high current pro power supply which states 8x 12vdc rails @ 30a.

And I definitely don't know that while each rail is capable of a maximum of 30a individually you CANNOT use all 8 of them at 30a simultaneously.

You will never get more than 1200w out of this 1200 watt antec high current pay supply.

You can run a maximum of 3 rails close to 30a, or 2 at 30a and one at a bit less, but no matter what it'll never exceed 1200w.

Antec High Current Pro HCP-1200 1200W
+3.3V@25A, +5V@25A, +12V1@30A, +12V2@30A, +12V3@30A, +12V4@30A, +12V5@30A, +12V6@30A, +12V7@30A, +12V8@30A, -12V@0.5A, +5VSB@4.0A

So subtract all the wattage of everything that's not 12v and that's what's left for the 8x 12v rails.

Divide that wattage up and distribute it among the 12v rails as you see fit, so long as each rail doesn't exceed 30a.

You'll find pretty quickly that you do not have 8x 30a sources of power.

Edit: forgive the automatic email linking. That's the forum.
 

wholybee

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The total is 1,200 watts.
8 12V rails, each supporting 30A would be 2880W. The math doesn't add up. The only way that power supply can be 1200W is if the 12V outputs share a supply. They can not all be 30A. Simple math.

It *might* be possible to get 10A from all of them like you propose, but don't count on it. Lifepo4 cells are not cheap. Don't risk them to save time with a cheap hack of the wrong type of supply.
 

Short_Shot

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8 12V rails, each supporting 30A would be 2880W. The math doesn't add up. The only way that power supply can be 1200W is if the 12V outputs share a single rail. Simple math.
The power supply offers a maximum of 30a on them. This depends on whether that is even available within the 1200w limit.

You can run 1 at 30a, or perhaps 3 at 30a, but the more of them you hook up the less total power there is to share around.

I used to run a similar one with a power budget like that. It's pretty neat, but they're fairly expensive for very little gain.

Usually you see something like 50a on one rail and 30a on another and that's it, or some combination of numbers.
 

Short_Shot

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But I'm probably blocked now so this person can't see any of the inconvenient truth.

It MIGHT support the 80a in total on those rails but I don't know the details about that exact unit OP has and it might not even have 960w available to the 12v outputs.
 

wholybee

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If you only have 1200w then you do not have 8x 30 amp outputs. Period. That's simply not possible.

What are you charging then? Your first post explicitly stated "charging a battery".

Do you have a 10 volt battery?

Nothing about what I said was a lie or BS at all.

You can call it BS all you want but I've built a couple dozen high end rigs, and modified several atx power supplies for misc projects.
He was going to use cheap 10A voltage boosters, hoping for a total of around 80A. Which *might* work with 1200W. But I highly advise against it.
 

Short_Shot

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Also I fail to see how that's "back to the original question" when that specific detail wasn't posted until comment number 10 half an hour ago.

So it was absolutely not made clear then OP blew up about it.
 

Short_Shot

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I can only go by what it says on the label. My guess is that each rail is capable of doing that much. Just not all at the same time is all.
Because on top of those you also have the 3 and 5 volt sections.

It has 8 12 volt rails at 30 amps each.
One +5 rail at 25 amps, one 3,3 v at 25 amps, one -12 volt at 0.5 amps and one -5 volt at 4 amps.
But the continuous total allowed is 1188 watts or 99 amps before things start tripping and shutting down.
Ok so that is what it says on the label.
Along with its name "ANTEC High Current Pro switching power supply 1200watt"

So if anyone has issues then take it up with Antec.
I didn't make this PS and I had no say in the matter at all.

Now maybe we can get back to the questions and answers?
Or not.
That's what I was answering before you went off the handle about information you didn't originally supply at the start of the thread lmao.

IF you can get 960w out of the 12v outputs then yeah. Go for it.

If it wasn't to spend that much money on converters its your wallet. You can just buy a 100 amp adjustable power supply for $90 though rather than 8x 10a converters which might be a couple dollars less for way more work.

Just need to find one with a slightly larger adjustment range. This one is only 5%. My 30a one I can adjust all the way to 14v.
 

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Short_Shot

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Also 10 amp boosters are not cheap where I live. Minimum $25 and up.

If you know of better ones then please link me. Thanks :)
8x $25 you are in $200.

If you can find this (or similar) on ebay you'll possibly save money buying an actual lithium charger.
 

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Short_Shot

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Ope this is even cheaper and perfect for the job of covering through absorption charge.
 

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