[SOLVED] Directly powering a PC with a 12v battery. Skipping the PSU

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Thwwack

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Mar 28, 2014
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10,510
Hello folks.

I am hoping for some advice.

I'm about to embark on a long vanlife adventure, and want to take my beloved desktop PC with me.

From what I understand, PC PSUs output 12v. I'm thinking I'll just directly power the PC with my house battery in the van, skipping the PSU.

Does anyone know of any problems I may encounter doing this? The only problem I can imagine would occur when the battery voltage starts to drop, but surely there is some software I can install to make the PC recognize this, and shut components down (like in a laptop).

The supply power will be fused.

Any problem identifications and software recommendations are greatly appreciated.

Cheers
Emile
 
Solution
InvalidError
Another approach would be to use four separate DC-DC converters to accommodate all of the usual supply rails. The main problem would be finding a 40-50A 12V buck-boost converter that can accommodate the 9-16V range of a car's 12V electrical system.

A likely much simpler and safer hack would be to use 12V to 170V DC-DC step-up converters and feed that to a conventional PSU the normal way, then your PC components should be about as safe as they would be on regular AC. Some universal-input PC PSUs will operate on less than 100VDC. At this point though, you have already incurred most of the losses that a high-efficiency inverter would have since the lossiest part of the process is stepping up 12V to 170V for the output bridge.
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King Dranzer said:
I don't think he has any intention of going Solar Power Route.

If OP takes Solar Power Route then he wouldn't have to spend all the time and resources trying to work it other way round.

It is on bit high out-right expenditure. But if he is regular traveler it is completely worth it.
Click to expand...
The solar reference was based on the OP's comment "It's a toyota hiace with 120AH house battery and solar DC-DC charger. Jap only model with a HUGE alternator."
 
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Thwwack said:
P.S. I realised I didn't answer your question. It's a toyota hiace with 120AH house battery and solar DC-DC charger. Jap only model with a HUGE alternator.
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Why are you even wasting your time trying to figure stuff out. When there is simple and easy and OBVIOUS answer laying in front of you.

You have to do nothing at all. Simply get the Inverter and be done with. No point in even thinking of other alternate.
 
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Thwwack said:
can you point me to a resource that will tell me which components in my system require 3.5v, 5v, and which require 12v, and give specifications for power requirements for each, by chance?
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All the pinouts are well known, no need to measure by yourself.
If you can supply these V and grounds you can make a cable with a plug that will connect straight to the mobo.
Most of the PSU is protection from overvolting and smoothing out the DC voltage that has a lot of spikes in general.
A car battery should be much more stable so you could just skip the protection stuff.

But yeah, without a lot of experience in electronics you should not even think about touching that.
https://www.smpspowersupply.com/connectors-pinouts.html
 
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COLGeek said:
I would not recommend connecting to an unregulated power source, unless the smell of burnt electronics is something you like.
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Me neither. But that's what the gambling reference is for.

The "12V DC" in a car actually ranges between 11V to as high as 15V, depending on what the vehicle is doing, the battery condition, and how well the charging regulator is working. Because of that. It's not uncommon to see car accessories rated to operate between 10.5 to 16V DC. The 2DIN entertainment system in my car actually had that stamped on it.

Most 12V devices not designed to work in a car will probably tolerate +/- 1V. Beyond that, all kinds of weird things could start to happen. The PC is one such device that requires absolutely stable power. We typically talk about adding or subtracting mere millivolts (mV) when OC'ing to maintain stability... imagine what a 1-3V bump or dip can do to a PC.
 
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USAFRet said:
@jonnyguru - Your expertise and advice requested, sir.
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Oh.. ok.

Thwwack said:
Hello folks.

I am hoping for some advice.

I'm about to embark on a long vanlife adventure, and want to take my beloved desktop PC with me.

From what I understand, PC PSUs output 12v. I'm thinking I'll just directly power the PC with my house battery in the van, skipping the PSU.

Does anyone know of any problems I may encounter doing this? The only problem I can imagine would occur when the battery voltage starts to drop, but surely there is some software I can install to make the PC recognize this, and shut components down (like in a laptop).

The supply power will be fused.

Any problem identifications and software recommendations are greatly appreciated.

Cheers
Emile
Click to expand...

Can power a PC with unregulated power. There's a reason why stuff like this exists: https://www.powerstream.com/DC-ATX-12v.htm

First off, car power is not +12V. It's 11.8V on battery and 14.1V on alternator. And the alternator typically has about 100mV of ripple and is still considered "within spec".

Some can say, "well, how come car radios, GPS's, etc. work directly off battery?" and the truth of it is, those components actually have their own DC to DC power supplies in each of them. In fact, the bulk of power supplies put out by tier 1 suppliers like Delta and Flextronics are actually the power supplies inside a car to convert battery power to clean, safe +12V.
 
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jonnyguru said:
Oh.. ok.



Can power a PC with unregulated power. There's a reason why stuff like this exists: https://www.powerstream.com/DC-ATX-12v.htm

First off, car power is not +12V. It's 11.8V on battery and 14.1V on alternator. And the alternator typically has about 100mV of ripple and is still considered "within spec".

Some can say, "well, how come car radios, GPS's, etc. work directly off battery?" and the truth of it is, those components actually have their own DC to DC power supplies in each of them. In fact, the bulk of power supplies put out by tier 1 suppliers like Delta and Flextronics are actually the power supplies inside a car to convert battery power to clean, safe +12V.
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That can be handled even using regular DC-AC Inverter. But is doing that safe for 600-800W setups. Or are there any direct 600-800W DC-DC PSUs.
 
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King Dranzer said:
That can be handled even using regular DC-AC Inverter. But is doing that safe for 600-800W setups. Or are there any direct 600-800W DC-DC PSUs.
Click to expand...

Yeah... You could do that too. I actually have this massive inverter I bought from Walmart that can power electric power tools from the car (when connected directly to the battery with the car running, of course). Seems to be ok. But I have the rest of the stuff in the car off (no radio, A/C, etc.)

I mean.... you have to take into consideration a few things. And that brings up a good point.

What's the current rating of the car's alternator? Newer cars are over 100A because of ICE, heated seats, etc. American trucks are upwards of 200+ Amps. So that should be fine. But you also have to consider how much power everything else in the car needs. I mean... there's a reason they put those size alternators in those cars. 😀

Of course, you could always do what people do when they have massive stereo systems in their car and upgrade the alternator. Does Phoenix Gold still make alternators? LOL! I'm showing my age.
 
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So, to sum up:

There are multiple ways to power a desktop level PC from a vehicle.
Vehicle specific PSU, power inverter, Intel NUC or Beelink type system, high perf laptop...

But NOT simply from the vehicle battery direct to the PC motherboard.
Correct?
 
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jonnyguru said:
Yeah... You could do that too. I actually have this massive inverter I bought from Walmart that can power electric power tools from the car (when connected directly to the battery with the car running, of course). Seems to be ok. But I have the rest of the stuff in the car off (no radio, A/C, etc.)

I mean.... you have to take into consideration a few things. And that brings up a good point.

What's the current rating of the car's alternator? Newer cars are over 100A because of ICE, heated seats, etc. American trucks are upwards of 200+ Amps. So that should be fine. But you also have to consider how much power everything else in the car needs. I mean... there's a reason they put those size alternators in those cars. 😀

Of course, you could always do what people do when they have massive stereo systems in their car and upgrade the alternator. Does Phoenix Gold still make alternators? LOL! I'm showing my age.
Click to expand...
Yeah man that was my First Question to OP. What Capacity is his Battery and Alternator Setup. His Answer was
Thwwack said:
P.S. I realised I didn't answer your question. It's a toyota hiace with 120AH house battery and solar DC-DC charger. Jap only model with a HUGE alternator.
Click to expand...
So I was like okay that with any Engine weighing up of 2.2L was paired with Hefty Alternator out of the Factory.
 
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USAFRet said:
So, to sum up:

There are multiple ways to power a desktop level PC from a vehicle.
Vehicle specific PSU, power inverter, Intel NUC or Beelink type system, high perf laptop...

But NOT simply from the vehicle battery direct to the PC motherboard.
Correct?
Click to expand...
Nope unless the Motherboard itself is Modified to Function using Straight 12v and only dependent on that. Answer is No it is not possible.
 
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USAFRet said:
Can you build your own "power supply"?
Well, it can be done. I don't know if YOU can do it, but, in theory, it could be done.

Buy a current PSU.
Obtain the engineering and design docs.
Recreate it, in a different box.
Poof...your own system.

Which works exactly as the one you bought does.

(try this with throwaway computer parts. Don't use your good PC on the first (or tenth) attempt)
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TerryLaze said:
All the pinouts are well known, no need to measure by yourself.
If you can supply these V and grounds you can make a cable with a plug that will connect straight to the mobo.
Most of the PSU is protection from overvolting and smoothing out the DC voltage that has a lot of spikes in general.
A car battery should be much more stable so you could just skip the protection stuff.

But yeah, without a lot of experience in electronics you should not even think about touching that.
https://www.smpspowersupply.com/connectors-pinouts.html
Click to expand...
polyal said:
PLEASE keep everybody posted on your mission...esp me.. cant wait to see what
transpires♪♪
Click to expand...


The issue with building your own power supply is that a lot of companies who supposedly 'specialise' in psu manufacture can't actually manage to manufacture a decent quality psu.

At that they have full on production facilities, I don't see much hope for a ghetto backyard garage manufacture at all.

Your best best, decent laptop and an external gpu in casing, both run off 12v in theory and should be doable.
 
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madmatt30 said:
The issue with building your own power supply is that a lot of companies who supposedly 'specialise' in psu manufacture can't actually manage to manufacture a decent quality psu.

At that they have full on production facilities, I don't see much hope for a ghetto backyard garage manufacture at all.

Your best best, decent laptop and an external gpu in casing, both run off 12v in theory and should be doable.
Click to expand...
He can Run Regular PC too no problem. All he needs is Inverter. But Depending on Usage it may or May not be a Feasible issue. We all have been discussing about creating PSU and stuff but missed the main point. He said he will be living in the Van while Traveling. The First Thing I recommend is Amping up His Battery. The Stock Battery that comes with VAN is good for Regular usage but not for his kind of usage as he will be halting time to time and in that Period if he needs to Find Alternate Power Source. Otherwise No matter how Good the Alternator be the Battery would not have enough charge to support basic Equipment of Van over halt for Hours unless he plans to keep the Van running that entire Time. So if OP manages to solve that issue. He can pretty much carry Entire PC having High end Components with him.
 
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USAFRet said:
You missed the initial premise.
Bypass the desktop PSU completely....🙁
Click to expand...
Yeah probably because he thought Running PC using Inverter would be Much heavier than Running it direct and probably won't work due to Limitations of Power output from Battery and Alternator. But From the Model of Van he listed as I said above he shouldn't worry about the Power Efficiency as he will more than enough Power for all the other Components on the VAN even after Powering his PC. So yeah his initial reason to worry about efficiency was no more feasible. Unless OP wants do that just as Holiday Project he can but no point trying to go that route as there other more feasible alternates which are easy to work and simple.
 
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King Dranzer said:
Yeah probably because he thought Running PC using Inverter would be Much heavier than Running it direct and probably won't work due to Limitations of Power output from Battery and Alternator. But From the Model of Van he listed as I said above he shouldn't worry about the Power Efficiency as he will more than enough Power for all the other Components on the VAN even after Powering his PC. So yeah his initial reason to worry about efficiency was no more feasible. Unless OP wants do that just as Holiday Project he can but no point trying to go that route as there other more feasible alternates which are easy to work and simple.
Click to expand...
"From what I understand, PC PSUs output 12v. I'm thinking I'll just directly power the PC with my house battery in the van, skipping the PSU. "

The PSU delivers more than a simple 12v direct to the motherboard.
You need to split it into 12, 5, 3.3....
In effect, building your own "PSU".
 
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USAFRet said:
You missed the initial premise.
Bypass the desktop PSU completely....🙁
Click to expand...
Yes Bypassing Desktop PSU is interesting Project. I guess Some one most probably would have already tried it and we can find it if we search enough through the Internet. If not would be Interesting to try it. But In this specific case. OP can use his PC with nod additional Mods needed. To the Internals or PSU.
 
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USAFRet said:
"From what I understand, PC PSUs output 12v. I'm thinking I'll just directly power the PC with my house battery in the van, skipping the PSU. "

The PSU delivers more than a simple 12v direct to the motherboard.
You need to split it into 12, 5, 3.3....
In effect, building your own "PSU".
Click to expand...
Yes Sir. Exactly that would be an Interesting Project. No argument there. I have seen People Build PCs into their Vans and Cars. But all of them did it the old way. No one tried to go this route. At-least I have not come across any one who did that yet on You-tube or on TV. So yeah if some one already did I need to find how they managed to Bypass the PSU. If not hope some one Does it in Future.
 
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Some great info here everyone, thanks. Think my question has been answered well enough for me to not spend the time investigating at this stage (busy with other elements of the build). When I next find a few thrift store components, I'll hook them up to a variable power supply and see what it takes to get malfunctions and report back. Might take me a few months to get around to this but when I do, I'll let you all know my findings.

Funny how passionate people got about this topic. Speaks to our love for our components. :)

Just for the sake of clarity:

I have a laptop, have a pure sine wave inverter, have a solar setup. I was purely looking for a viable way to take my PC with me.

Seems like a good option is @jonnyguru 's 12v psu, thanks jonnyguru.

I'm betting there are many creative ways to make this setup work:

Some ideas I will try sometime when I have more time:

1. Investigate laptop circuitry/firmware and how they deal with battery management and voltage drop. I'm betting there are components you can graft from a laptop etc.

2. Test components on the variable power supply.

--

It's been good spitballing this with you all here. Cheers Tomshardware community!
 
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