This might be a dumb question, but I'm struggling to find any info.

If I get something like this: https://www.geewiz.co.za/load-shedding-solutions/190129-axpert-type-pure-sine-1000va-inverter-trolley-1x-100ah-lithium-battery-6-hour-battery-life-kit-1000w-50a-pwm-solar-with-lithium-battery-3000-cycles.html

Is this good enough to run a PC on directly without the PC switching off? I heard that inverters have a longer transfer time/switch over than a UPS. This particular one seems to be 10-20ms.

Is it normal to supplement an inverter with a UPS to not have the PC switch off during the switch over to battery?

23 minutes ago, Splat said:

This might be a dumb question, but I'm struggling to find any info.

If I get something like this: https://www.geewiz.co.za/load-shedding-solutions/190129-axpert-type-pure-sine-1000va-inverter-trolley-1x-100ah-lithium-battery-6-hour-battery-life-kit-1000w-50a-pwm-solar-with-lithium-battery-3000-cycles.html

Is this good enough to run a PC on directly without the PC switching off? I heard that inverters have a longer transfer time/switch over than a UPS. This particular one seems to be 10-20ms.

Is it normal to supplement an inverter with a UPS to not have the PC switch off during the switch over to battery?

Hi @Splat thats always a good question. With my Axpert MKS3 and MAX7. 2 it really works as UPS. Yes i see a small dip in my led lights, but pc is uninterruptably supplied.

But even so, it depends how mission critical the pc feed needs to be. Remember your inverter has to brave the elements of all sorts of load conditions, so if you trip the inverter from an overload  from the garage compressor, you loose the pc feed. 

 

It also depends on the hold up time of the PC power supply itself, i.e. as they age the caps deteriorate over time. With a good quality new PSU 20ms is normally not an issue, dependent obviously on the current load on that PSU when the power is interrupted. An old PSU may end up not having any hold up time in which case the PC will shut down immediately

Okay great. Thank you so much for the information!

I looked up this "hold up time" for my PSU, I didn't know that was a thing, but it seems to show 24.9ms

I'm pretty sure it'll work then! So I think it'll be a good idea that for the first few loadsheddings I'll make sure I'm not doing anything important on the PC and test to see if it holds on and that will tell me if I need an extra UPS or not. Don't really want to spend an extra R2k if I don't need it.

Awesome, thanks!

As said, the age of the PSU and the load will determine the real hold up time. 

Brings us to the interesting concept of running a PC off a 12V battery, i.e. no need for a PSU
And this may be a pet project for an electronics guru like @BritishRacingGreen 😉
https://superuser.com/questions/1675060/can-a-desktop-computer-run-off-of-a-dc-battery-directly

4 hours ago, zsde said:

Brings us to the interesting concept of running a PC off a 12V battery, i.e. no need for a PSU
And this may be a pet project for an electronics guru like @BritishRacingGreen 😉
https://superuser.com/questions/1675060/can-a-desktop-computer-run-off-of-a-dc-battery-directly

You don't run it without PSU. You just need to change to a suitable 12V input PSU. Something like this:

https://www.amazon.com/Output-Computer-Connect-Suitable-Mini-ITX/dp/B07TY121LT

12 minutes ago, PowerUser said:

You just need to change to a suitable 12V input PSU

That would work on a low power PC, i.e. with an APU. A full powered PC with a discrete GPU would kill it.

5 hours ago, zsde said:

Brings us to the interesting concept of running a PC off a 12V battery, i.e. no need for a PSU
And this may be a pet project for an electronics guru like @BritishRacingGreen 😉
https://superuser.com/questions/1675060

5 hours ago, zsde said:

Brings us to the interesting concept of running a PC off a 12V battery, i.e. no need for a PSU
And this may be a pet project for an electronics guru like @BritishRacingGreen 😉
https://superuser.com/questions/1675060/can-a-desktop-computer-run-off-of-a-dc-battery-directly

 

Interesting, the 12v and 5v rails will need some high power converters,  given that nowadays the pci 12v rating is huge for graphics. If you consider that you will require anything upwards from 450 watts for these rails, it will be quite a costly effort. 

Then you havent addressed the monitor issue. Yes, you get 12vdc monitor but that will be an expensive replacement. 

I think a small capacity UPS in tandem with the inverter supply will be best. 

Edited January 22, 20233 yr by BritishRacingGreen

16 minutes ago, zsde said:

That would work on a low power PC, i.e. with an APU. A full powered PC with a discrete GPU would kill it.

Then you need to get one of those:

https://www.powerstream.com/DC-PC-12V.htm

I just posted the first link as an example of what's needed. You will have to find one which provides suitable power for your application. 

Just to also confirm - can you run an online UPS of say 1000W in line with this type of inverter to cater for that switch-over time?  However just getting a better/new PSU is probably cheaper

3 minutes ago, Douw G. Gerber said:

However just getting a better/new PSU is probably cheaper

The new/better PSU is no guarantee. Their tests may have valid hold up times but they don't really tell you under what load. That data is most probably under "idle" conditions. If you wish to ensure no interruption a small UPS is really the ideal solution.

On 2023/01/22 at 2:01 PM, Splat said:

Okay great. Thank you so much for the information!

I looked up this "hold up time" for my PSU, I didn't know that was a thing, but it seems to show 24.9ms

I'm pretty sure it'll work then! So I think it'll be a good idea that for the first few loadsheddings I'll make sure I'm not doing anything important on the PC and test to see if it holds on and that will tell me if I need an extra UPS or not. Don't really want to spend an extra R2k if I don't need it.

Awesome, thanks!

hi there mate - please can you share a link to this site where you got the image from?

 

3 minutes ago, zsde said:

The new/better PSU is no guarantee. Their tests may have valid hold up times but they don't really tell you under what load. That data is most probably under "idle" conditions. If you wish to ensure no interruption a small UPS is really the ideal solution.

Seem like they do state the load for Antec at least:

Another interesting point I just read on Tom's Hardware is that 16ms is the minimum spec for ATX.  Wonder how few PSU's comply.

18 hours ago, Douw G. Gerber said:

hi there mate - please can you share a link to this site where you got the image from?

 

Sorry I only saw the question now, I found it on this page:

https://www.techpowerup.com/review/super-flower-leadex-iii-argb-gold-650-w/8.html

 

I would like to comment on running PCs from 12V.  Firstly, let's tackle laptops.  Laptops normally need 19VDC, but some use 18 or 15VDC.  You can buy 12V laptop chargers that replace your 230V laptop charger.  There are some models that can run from 230VAC and 12VDC.  DO NOT BUY THESE.  I brought one and one look inside convinced me not to even try using it.  The build quality and circuit design is pathetic to say the least (!)  For instance, the battery input has no local smoothing capacitor, thus sending high current switching noise all along the battery wires, acting as huge antenas for EMI/RFI radiation.

However, you can buy a boost converter such as this one: https://www.communica.co.za/products/bmt-dc-dc-booster-12-35vout-150w?variant=31667841040457 for less than R 100.  They are of excellent quality.  Before getting my inverter, I used to run my laptop from such a device.  After 2 hours of operation, the heatsink stays ice-cold.  I really have a hard time registering any increase in temperature.

Many monitors and some of the smaller TVs also use a laptop-sized external power supply.  These tend to also run mostly from 19VDC.   So you can use the same boost regulator to power monitors/TVs.  The biggest headache is to obtain the correct DC plug, as there are many different shapes and sizes.  I had to revert to buying a cheap replacement power supply, just to strip off the DC lead.

I myself brought a 21" Mecer monitor which can actually run from 12VDC.  Many years ago, I also brought a cheap Sinotec TV, again for load shedding purposes - where I could run straight from a 12V battery.  The higher supply voltage of a float-charged SLA battery, of around 13.85V should not be a problem for a 12VDC specced device.

Desktop PCs are a problem.  I would not fiddle and replace the ATX PSU.  I went a different route.  If you want/need a desktop, buy yourself one of these miniPCs.  They are normally the size of a paving brick.  Lenovo, HP, Dell, etc. all make these.  Because of their small size, there is not enough room for a mains operated PSU and they are fitted with a DC socket.  Again, most (but not all) run from around 19VDC using laptop-type power supplies.  You can buy an older 2nd/3rd generation i3 or i5 second hand for about 3K or you can pick up the latest shiny, new, i7.

Remember that just about all electronics operate inherently at low voltages of 12 / 5 / 3.3 / 1.8 volts.  It is totally silly to take 12/24/48VDC, convert it to 230VAC just to down-convert it back to 5V to charge your phone, or power your laptop, or even drive a LED light.  An Axpert inverter has an idle consumption of between 35 and 50W.  It would drain a 2.75KWh lithium battery 100% in less than 4 days, by doing nothing else but keeping itself warm.

The boost regulators have a wide input voltage range, normally 8V to about 32V.  There is a preset potentiometer that allows you to adjust the output voltage, typically from 15 to 30V or thereabouts, but being a boost regulator, the input voltage must always be lower than the required output voltage.  Communica has even sold a 600W boost regulator that can create up to 80VDC output.  I brought one of these to play with.  I paid approx R 230.  Sadly, these have been out of stock for more than a year now.