Can EG4 18KPV work as UPS for sensitive loads like computer servers?

[PConlin]

I need a high capacity UPS in the 10-12kW range to keep a rack of servers up while the backup generator starts. I recently purchased an EG4 18KPV hybrid inverter and four EG4 LL server rack batteries. This is grid connected with no solar and no grid back-feed. I am seeing a "glitch" on the critical loads when the mains go off. During the switch-over I can hear the pitch of the server cooling fans change and some computers reboot. Very disappointing.

EG4 uses the term "UPS" in their marketing literature / spec sheets and it has a so-called high speed relay built in gird-to-battery switching. The EG4 specs for the 18KPV say 10ms transfer time which is what most consumer grade 1000-2000 VA UPS are rated for so I fully expected this to work. There is a poorly documented setting on the 18KPV called "seamless switching" which sounds like what I want. I have this checked and yet the glitch remains. Current load is only about 4-5 kW so not even fully loaded, but not nothing either. I may try catching the glitch on an oscilloscope but getting the right capture trigger to see the actual "event" might be tricky.

Interestingly when the critical load is being partly powered by battery, meaning the inverter is already "on", there is no glitch when the mains go off. This "glitch" in output only occurs when load is entirely supplied by the mains and the mains fails causing the relay to switch. So maybe something slow with the inverter turn-on and/or sync? But why do they spec 10ms switching time then?

If found this thread https://diysolarforum.com/threads/online-ups-functionality.53936/ which appears to be focused on using an all-in-one inverter to provide electrical noise isolation like a double conversion UPS. I don't need noise isolation and would rather eliminate double conversion to avoid the resulting efficiency losses. What I need is a simple stand-by battery back-up UPS in the 12kW range that provides 240VAC. Feels like the 18KPV would be perfect. What I am missing?

Is anyone powering sensitive loads like computers directly with an 18KPV? 120 or 240. Without having a purpose made back-up UPS between the inverter and the computers.

 

[zanydroid]

I can't speak to what the actual transfer latency spec is, or what settings dictate it. Often there are several possible latencies depending on configuration. Hopefully you can get info from another user on the specific set of settings you need. Or aggressively tag EG4/SS accounts and work on crafting enough engagement or drama to get social media based support.

Double conversion has other advantages, like guaranteeing that you are not paralleling with/spurious exporting to grid, and allowing the AC frequency of the inverter to be modulated to control AC coupled solar. But it comes at a cost.

Would you consider something like running critical load in the minimum possible grid assist mode (like 50W from mains) and buying a chargeverter or other charger to make this up? This is basically double converting on a fraction of your load, to keep the inverter spun up. So the net efficiency is better (albeit you might be running the charger at a lower efficiency point in its operating envelope). I believe the 18k is a HF inverter so it cannot AC charge while inverting unless it has a separate set of FETs for AC charging from inverting.

Midnite Rosie supposedly has a low transfer speed, and may have a better support model for giving details since the company has a better reputation. But you have your hardware already.

 

[Ampster]

Double conversion has other advantages, like guaranteeing that you are not paralleling with/spurious exporting to grid, and allowing the AC frequency of the inverter to be modulated to control AC coupled solar. But it comes at a cost.

I don't know about my SolArk or the EG4 latency but I rememnber years ago in an Outback Radian that there was a configuration that had very little or no latency but it had much higher overhead. Perhaps that was a double conversion process like you describe. I don't think my subsequent Outback Skybox had that configuration and it was a different design.

 

[zanydroid]

I don't know about my SolArk or the EG4 latency but I rememnber years ago in an Outback Radian that there was a configuration that had very little or no latency but it had much higher overhead. Perhaps that was a double conversion process like you describe. I don't think my subsequent Outback Skybox had that configuration and it was a different design.

What was the efficiency difference?

Is the Radian a LF design? Those would have a lower theoretical turn around time from charging to inverter, I think close to zero. I am not sure if the inverter mode running in reverse is as efficient as reconfiguring the inverter fully into a charger, or vice versa.

 

[Ampster]

Is the Radian a LF design?

I think it might have been. I also did not use the charger configuration since it was simply a load shifting experiment and had no AC coupling ability at that time which was eight years ago. When I sold that home I removed it and sold it seperately.

 

[Markus_EG4]

I need a high capacity UPS in the 10-12kW range to keep a rack of servers up while the backup generator starts. I recently purchased an EG4 18KPV hybrid inverter and four EG4 LL server rack batteries. This is grid connected with no solar and no grid back-feed. I am seeing a "glitch" on the critical loads when the mains go off. During the switch-over I can hear the pitch of the server cooling fans change and some computers reboot. Very disappointing.

EG4 uses the term "UPS" in their marketing literature / spec sheets and it has a so-called high speed relay built in gird-to-battery switching. The EG4 specs for the 18KPV say 10ms transfer time which is what most consumer grade 1000-2000 VA UPS are rated for so I fully expected this to work. There is a poorly documented setting on the 18KPV called "seamless switching" which sounds like what I want. I have this checked and yet the glitch remains. Current load is only about 4-5 kW so not even fully loaded, but not nothing either. I may try catching the glitch on an oscilloscope but getting the right capture trigger to see the actual "event" might be tricky.

Interestingly when the critical load is being partly powered by battery, meaning the inverter is already "on", there is no glitch when the mains go off. This "glitch" in output only occurs when load is entirely supplied by the mains and the mains fails causing the relay to switch. So maybe something slow with the inverter turn-on and/or sync? But why do they spec 10ms switching time then?

If found this thread https://diysolarforum.com/threads/online-ups-functionality.53936/ which appears to be focused on using an all-in-one inverter to provide electrical noise isolation like a double conversion UPS. I don't need noise isolation and would rather eliminate double conversion to avoid the resulting efficiency losses. What I need is a simple stand-by battery back-up UPS in the 12kW range that provides 240VAC. Feels like the 18KPV would be perfect. What I am missing?

Is anyone powering sensitive loads like computers directly with an 18KPV? 120 or 240. Without having a purpose made back-up UPS between the inverter and the computers.

Can you PM me I think I can help with this problem

 

[zanydroid]

I think it might have been. I also did not use the charger configuration since it was simply a load shifting experiment and had no AC coupling ability at that time which was eight years ago. When I sold that home I removed it and sold it seperately.

How did you load shift without an AC or PV charger?

 

[SilverbackMP]

Kind of following as I have an Outback 12v 3500 watt VFX that I plan to try to repurpose for the same task. Keep some smaller servers and Synologies running in the event my main system goes down. Also have an old 3000 watt Trace that might work.

I know with the Outback, the lights would momentarily dim when the generator was shut off but no flickering and it didn’t effect the TV. So it will probably work.

Sorry for the hijack.

 

[DIYrich]

EG4 uses the term "UPS" in their marketing literature / spec sheets and it has a so-called high speed relay built in gird-to-battery switching. The EG4 specs for the 18KPV say 10ms transfer time which is what most consumer grade 1000-2000 VA UPS are rated for so I fully expected this to work. There is a poorly documented setting on the 18KPV called "seamless switching" which sounds like what I want. I have this checked and yet the glitch remains. Current load is only about 4-5 kW so not even fully loaded, but not nothing either. I may try catching the glitch on an oscilloscope but getting the right capture trigger to see the actual "event" might be tricky.

Interestingly when the critical load is being partly powered by battery, meaning the inverter is already "on", there is no glitch when the mains go off. This "glitch" in output only occurs when load is entirely supplied by the mains and the mains fails causing the relay to switch. So maybe something slow with the inverter turn-on and/or sync? But why do they spec 10ms switching time then?

Sol_ark claims a 4ms transfer time. If you can borrow one, you might want to test it.

The following can be done with a sol-ark:
Set grid support just under your base load (4kW).
Then the inverter will always be supplying ac for the amount over base load.
Hook up a chargeverter to replace the power being drawn.
Similar to double conversion, but only for the amount over base load.

 

[zanydroid]

Sol_ark claims a 4ms transfer time. If you can borrow one, you might want to test it.

The following can be done with a sol-ark:
Set grid support just under your base load (4kW).
Then the inverter will always be supplying ac for the amount over base load.
Hook up a chargeverter to replace the power being drawn.
Similar to double conversion, but only for the amount over base load.

That is basically identical to what I suggested above but I had said minimum configurable grid support. What is the reason for going just under base load? Is it to avoid browning out during the transfer? To try to use more solar? If it was to use more solar then maybe that just under base load setting should be during hours with production.

Also just under base load might end up adding up a lot over time.

 

[Samsonite801]

I need a high capacity UPS in the 10-12kW range to keep a rack of servers up while the backup generator starts. I recently purchased an EG4 18KPV hybrid inverter and four EG4 LL server rack batteries. This is grid connected with no solar and no grid back-feed. I am seeing a "glitch" on the critical loads when the mains go off. During the switch-over I can hear the pitch of the server cooling fans change and some computers reboot. Very disappointing.

EG4 uses the term "UPS" in their marketing literature / spec sheets and it has a so-called high speed relay built in gird-to-battery switching. The EG4 specs for the 18KPV say 10ms transfer time which is what most consumer grade 1000-2000 VA UPS are rated for so I fully expected this to work. There is a poorly documented setting on the 18KPV called "seamless switching" which sounds like what I want. I have this checked and yet the glitch remains. Current load is only about 4-5 kW so not even fully loaded, but not nothing either. I may try catching the glitch on an oscilloscope but getting the right capture trigger to see the actual "event" might be tricky.

Interestingly when the critical load is being partly powered by battery, meaning the inverter is already "on", there is no glitch when the mains go off. This "glitch" in output only occurs when load is entirely supplied by the mains and the mains fails causing the relay to switch. So maybe something slow with the inverter turn-on and/or sync? But why do they spec 10ms switching time then?

If found this thread https://diysolarforum.com/threads/online-ups-functionality.53936/ which appears to be focused on using an all-in-one inverter to provide electrical noise isolation like a double conversion UPS. I don't need noise isolation and would rather eliminate double conversion to avoid the resulting efficiency losses. What I need is a simple stand-by battery back-up UPS in the 12kW range that provides 240VAC. Feels like the 18KPV would be perfect. What I am missing?

Is anyone powering sensitive loads like computers directly with an 18KPV? 120 or 240. Without having a purpose made back-up UPS between the inverter and the computers.

How many servers are we trying to keep running here? Like how many watts are they together?

Just a side thought... Can you get something like an APC/Schneider rack UPS to put in between? I bought a few used ones on eBay for cheap several times in the past. This could provide a couple minutes of runtime until the 18k is stable enough to take over.

I realize you shouldn't have to do this (should be expected that the 18k can do it all because is advertised as UPS), but if you did add a rack UPS (just use it with the internal battery, may not need to add additional battery shelves). It would add another layer of protection, and be more robust for handling unplanned power outages.

I manage several rack labs at work, and we have APC UPS's at the bottom of each rack, to hold the power for a couple minutes until our building generators outside start up and are stable to bring back the AC power.

On APC's, you can also install the Powerchute software or use the free UPSmon (NUT) code on a master Linux box (with serial cable connected to the APC UPS) where it will gracefully shut down all the slaves and shut itself down (set to trigger on UPS 'Low Battery' status via serial), in case the 18k inverter has a hard failure and the batteries become exhausted in the APC UPS...

This way, the 18k would be there for the sustained long-term power outages. In this sense, the 18k would be more like the auto-start building generator, and the rack UPS would be for rack-level server safe-shutdown protection and power transition.

 

[Ampster]

Can you PM me I think I can help with this problem

Why not explain it on the forum for the benefit of other readers?

 

[Ampster]

How did you load shift without an AC or PV charger?

You use the inverter to power loads during peak times and charge batteries during off peak. I also had solar but no AC coupling so I could not use solar to charge batteries. I did not have Air Conditioning.

 

[DIYrich]

What is the reason for going just under base load? Is it to avoid browning out during the transfer? To try to use more solar? If it was to use more solar then maybe that just under base load setting should be during hours with production.

Also just under base load might end up adding up a lot over time.

The Grid Support finction is how much you want from the grid before the inverter starts supplying power. If your base load is 4.1kW, and you set it at 4.0kW, the inverter will supply 0.1kW plus whatever above that. It ensures that the inverter is always in the correct mode (dc->ac). Hopefully when the grid goes down, it is faster at ramping up production.

The chargeverter replaces the power the inverter is drawing from the batteries (hook it up before the grid input to the inverter).

It is double conversion of power in excess of base load. You eliminate the double conversion loss of base load.

Another option is to use the time of use settings, and always produce 0.1kW of power from the battery. That probably works better with the Chargeverter.

 

[zanydroid]

The Grid Support finction is how much you want from the grid before the inverter starts supplying power. If your base load is 4.1kW, and you set it at 4.0kW, the inverter will supply 0.1kW plus whatever above that. It ensures that the inverter is always in the correct mode. Hopefully when the grid goes down, it is faster at ramping up production.

The chargeverter replaces the power the inverter is drawing from the batteries (hook it up before the grid input to the inverter).

Cool thanks so it's the limit from grid, so kind of does the same as my suggestion on average, but for temporarily high demand situations the two approaches will diverge.

I guess a strong reason to favor one vs the other depends on exactly what knobs there are for grid support. If you can only configure limit from grid then what you suggest is great (I don't own a storage inverter myself I'm just theorycrafting)

It might be somewhat more efficient to use a small charger where say .5kW charging is within the sweet spot. Also it would be quieter and smaller footprint than the chargeverter. Depends on if one ever needs to scale up to chargeverter power levels

 

[DIYrich]

Cool thanks so it's the limit from grid, so kind of does the same as my suggestion on average, but for temporarily high demand situations the two approaches will diverge.

I guess a strong reason to favor one vs the other depends on exactly what knobs there are for grid support. If you can only configure limit from grid then what you suggest is great (I don't own a storage inverter myself I'm just theorycrafting)

It might be somewhat more efficient to use a small charger where say .5kW charging is within the sweet spot. Also it would be quieter and smaller footprint than the chargeverter. Depends on if one ever needs to scale up to chargeverter power levels

I edited my response when I thought of the TOU settings. That would limit double conversion to 100 watts continuous.

 

[PConlin]

How many servers are we trying to keep running here? Like how many watts are they together?

Just a side thought... Can you get something like an APC/Schneider rack UPS to put in between? I bought a few used ones on eBay for cheap several times in the past. This could provide a couple minutes of runtime until the 18k is stable enough to take over.

I realize you shouldn't have to do this (should be expected that the 18k can do it all because is advertised as UPS), but if you did add a rack UPS (just use it with the internal battery, may not need to add additional battery shelves). It would add another layer of protection, and be more robust for handling unplanned power outages.

I manage several rack labs at work, and we have APC UPS's at the bottom of each rack, to hold the power for a couple minutes until our building generators outside start up and are stable to bring back the AC power.

On APC's, you can also install the Powerchute software or use the free UPSmon code on a master Linux box (with serial cable connected to the APC UPS) where it will gracefully shut down all the slaves and shut itself down (set to trigger on 'Low Battery' status), in case the 18k inverter has a hard failure and the batteries become exhausted in the APC UPS...

This way, the 18k would be there for the sustained long-term power outages. In this sense, the 18k would be more like the auto-start building generator, and the rack UPS would be for rack-level server safe-shutdown protection and power transition.

10 to 12 kW of 240VAC is what we need for the two servers. This is not a typo. We have a generator so the 18KPV only needs to last long enough for it to start. If we had APC UPS as you suggest then we wouldn't need the 18KPV! If the 18KPV is not suitable as a UPS for a server then it shouldn't be marketed as one. Many users might be having power quality problems during the 18KPV switch-over and not know it. Or maybe it is only us due to this one unit, our configuration or something else we are doing wrong. This is why I am asking for feedback from 18KPV users. Would also like to hear from Sol-Ark users if they are powering sensitive critical loads like computers as maybe they work better/different. The Sol-Ark does quote a 5ms switch over vs 10ms EG4. I wonder if one number is too simplistic for this spec. Is there actually a "curve" involved where it takes time to ramp up the inverter and this spec should either show this curve or provide a couple of data points to show current availability vs time. Total speculation on my part here.

 

[DIYrich]

Cool thanks so it's the limit from grid, so kind of does the same as my suggestion on average, but for temporarily high demand situations the two approaches will diverge.

My response clarified what grid support does. It doesn't add a fixed amount, like you posted. It let's the grid do up to the fixed amount. Very helpful if you are rural and have amp limited service, or peaking charge. Grid Support adds to the grid above the limit. Similar to telling the inverter how much power it can take from a generator.

 

[DIYrich]

10 to 12 kW of 240VAC is what we need for the two servers. This is not a typo. We have a generator so the 18KPV only needs to last long enough for it to start. If we had APC UPS as you suggest then we wouldn't need the 18KPV! If the 18KPV is not suitable as a UPS for a server then it shouldn't be marketed as one. Many users might be having power quality problems during the 18KPV switch-over and not know it. Or maybe it is only us due to this one unit, our configuration or something else we are doing wrong. This is why I am asking for feedback from 18KPV users. Would also like to hear from Sol-Ark users if they are powering sensitive critical loads like computers as maybe they work better/different. The Sol-Ark does quote a 5ms switch over vs 10ms EG4. I wonder if one number is too simplistic for this spec. Is there actually a "curve" involved where it takes time to ramp up the inverter and this spec should either show this curve or provide a couple of data points to show current availability vs time. Total speculation on my part here.

I'm guessing the 4ms is the worst case to:
Detect a grid down (timing is within on quarter of a cycle).
Isolate from the grid.
Switch inverter from charging batteries to supplying power.

The quality of you server power supplies, and the % load on the power supplies is a factor on how well they respond. The power supplies have capacitors to rectify the ac to dc. The larger the capacitor, the longer it can ride through.

You could use charge controller to charge the battery, and power the servers with direct dc power. that would be the most efficient, and give you 0ms transfer time. Also eliminates any THD from the generator, or other noise/spikes on the ac line.

Get a 12v charge controller with 12 lifep04 battery.
Use something like this to power the server directly.
24pin DC ATX PSU 12V DC Input DC 12V 150 watt Pico PSU ATX High Mini-ITX Power Supply with Adapter Board ATX Switch PSU Car Auto for Computer Mainboard and car/Motorcycle https://a.co/d/fHD6ufZ

 

[zanydroid]

My response clarified what grid support does. It doesn't add a fixed amount, like you posted. It let's the grid do up to the fixed amount. Very helpful if you are rural and have amp limited service, or peaking charge. Grid Support adds to the grid above the limit. Similar to telling the inverter how much power it can take from a generator.

What I meant is my 100W fixed is like your grid support set to Baseline -100W.

If you always consume Baseline then both draw 100W

You have to squint a lot for the two to be equivalent but the intent is similar