Reversed UPS , Mains power after low battery ?

[peter247]

Hi all, what a busy and very active forum .

At this time I'm just playing solar with a couple of 300w panels and a pair of 50ah life batteries , I want to start by powering my computers from solar (only about 40-80w , 24 hours a day ).
I want a inverter which is powered from solar most of the time , but I want something like a reversed UPS which powers on mains when my battery goes into low voltage mode.

Looking at the Victron Energy Multiplus inverters they say :-

Uninterrupted AC power (UPS function)​

In the event of a grid failure, or when shore or generator power is disconnected, the inverter within the Multi is automatically activated and takes over the supply to the connected loads. This happens so fast (less than 20 milliseconds) that computers and other electronic equipment will continue to operate without disruption.

 

[DerpsyDoodler]

As far as I can remember, the victrons will allow you to configure battery as priority, and at low volt alarm will switch to grid/generator.

I know the Samlex EVO line of inverters does/will. I own an EVO 4024. It has what's called "Online" mode. This is where batteries take priority, and the inverter operates in inverting mode even when an external AC source is detected. Once it reaches a configurable low voltage warning thresh-hold, it will seamlessly switch to grid and start charging battery. It is well-documented in the manual.

 

[peter247]

Thank you , I don't think I can get any Samlex EVO invertors in the UK , without being posted from the states .
I will have to download the manual on the Victron Energy Multiplus inverters and see if I can set to main priority .
I know Victron do a device called a filax which is a 15amp 3 position priority switch, but at £350 it isn't cheap .

NO the Victron Energy Multiplus inverters does not do battery priority only mains UPS

 

[James deGriz]

I'm in a similar boat I want to add in my fridge and freezer (total max draw is about 350W all up) into my solar generator system and they need to switch back to AC when the battery is drained. I'm renting so don't want to mess with the mains and just run extension cables. I was initially giving myself high fives when I found Renogy had a UPS function on one of their 1000W inverters (https://au.renogy.com/renogy-1000w-12v-to-230v-pure-sine-wave-inverter-with-ups-function/) which is only AUD $170. But it's AC primary, which is the reverse of what I want. After a bit of thinking I figure I can plug the AC cable into my Generator and buy an AC to DC power brick, cut off the connectors and plug this into the DC inverter. I'm pretty sure that is inefficient but I'm happy to give it a try and see. I just need to figure out what the specs for the power brick. I'm also open to other, simpler suggestions, or 'hey you're going to blow something up, try something else'. I'm also hoping this will help out with anti-islanding as there shouldn't be power flowing from the inverter back into the mains.

 

[chess-equality]

Hi all, what a busy and very active forum .

At this time I'm just playing solar with a couple of 300w panels and a pair of 50ah life batteries , I want to start by powering my computers from solar (only about 40-80w , 24 hours a day ).
I want a inverter which is powered from solar most of the time , but I want something like a reversed UPS which powers on mains when my battery goes into low voltage mode.

Looking at the Victron Energy Multiplus inverters they say :-

Uninterrupted AC power (UPS function)​

In the event of a grid failure, or when shore or generator power is disconnected, the inverter within the Multi is automatically activated and takes over the supply to the connected loads. This happens so fast (less than 20 milliseconds) that computers and other electronic equipment will continue to operate without disruption.

You should look for something like a "battery priority mode".

My SNADI 3kw inverter (inverter-charger [UPS], no MPPT) has what is known as "03 battery priority/preferred mode". It supplies load from the battery but switches to grid when battery goes low. When it switches to grid, it doesn't charge the battery. This lets you charge the battery from PV.

 

[peter247]

I'm in a similar boat I want to add in my fridge and freezer (total max draw is about 350W all up) into my solar generator system and they need to switch back to AC when the battery is drained. I'm renting so don't want to mess with the mains and just run extension cables. I was initially giving myself high fives when I found Renogy had a UPS function on one of their 1000W inverters (https://au.renogy.com/renogy-1000w-12v-to-230v-pure-sine-wave-inverter-with-ups-function/) which is only AUD $170. But it's AC primary, which is the reverse of what I want. After a bit of thinking I figure I can plug the AC cable into my Generator and buy an AC to DC power brick, cut off the connectors and plug this into the DC inverter. I'm pretty sure that is inefficient but I'm happy to give it a try and see. I just need to figure out what the specs for the power brick. I'm also open to other, simpler suggestions, or 'hey you're going to blow something up, try something else'. I'm also hoping this will help out with anti-islanding as there shouldn't be power flowing from the inverter back into the mains.

One thing I've learned is when it says it is a 100 watts fridge it needs a lot more power than you would ever think , I have a 500 va / 800 va burst inverter and it will not even try to power it , but go into instant overload , So not sure how that 1000 watt inverter will fair , and also that 1000 watts inverter will most likely be 1000 va and not watts .

 

[chess-equality]

One thing I've learned is when it says it is a 100 watts fridge it needs a lot more power than you would ever think , I have a 500 va / 800 va burst inverter and it will not even try to power it , but go into instant overload , So not sure how that 1000 watt inverter will fair , and also that 1000 watts inverter will most likely be 1000 va and not watts .

We just bought a Panasonic inverter fridge (8 cu. ft.) and it is rated 85 watts, sure enough it doesn't go over 80 watts, at least when I am monitoring it. Normally 50-80 watts.

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[12VoltInstalls]

want a inverter which is powered from solar most of the time , but I want something like a reversed UPS which powers on mains when my battery goes into low voltage mode.

Many (all?) MPPSolar units have ‘zero switchover time’ as an advertised function of SBU. Even the 1012LV-MK I have does this.

 

[JoeHam]

Many inverters can prioritize solar or battery before grid.

Switchover times on quality equipment are usually less than 20 milliseconds which should not cause a problem even for things like a computer. You may see a slight flicker in a light bulb. Of course there cannot be zero time involved but it’s usually inconsequential if less than 20 milliseconds.

I know my Scheider CSW 4048 does this, it is an inverter/charger only. My computers have never had a problem. The CSW4048 specs say less than 20 milliseconds.

I believe most of the MPP Solar and Growatt all in one units (SCC, AC Charger, Inverter) do this as well.

 

[RonP]

One thing I've learned is when it says it is a 100 watts fridge it needs a lot more power than you would ever think , I have a 500 va / 800 va burst inverter and it will not even try to power it , but go into instant overload , So not sure how that 1000 watt inverter will fair , and also that 1000 watts inverter will most likely be 1000 va and not watts .

It is an interesting exercise to have a power meter like a Whatsup connected to the fridge and then to see the power draw with the door closed, with the door open (lights on) and when it goes into defrost mode or cooling modes. Mine uses 200 watts for the light bulbs in the refrigerator section which are in need of replacing with LEDs apparently. I let the Whatsup collect data for several days to get a better average load.

 

[RonP]

Many inverters can prioritize solar or battery before grid.

Switchover times on quality equipment are usually less than 20 milliseconds which should not cause a problem even for things like a computer. You may see a slight flicker in a light bulb. Of course there cannot be zero time involved but it’s usually inconsequential if less than 20 milliseconds.

I know my Scheider CSW 4048 does this, it is an inverter/charger only. My computers have never had a problem. The CSW4048 specs say less than 20 milliseconds.

I believe most of the MPP Solar and Growatt all in one units (SCC, AC Charger, Inverter) do this as well.

Growatt 3000 I have can and does do this. I have it run on the batteries down to 50% and then recharge to 99% from utility if I don't get the solar connected for recharging.

 

[dmsims]

Multiplus will do it

There is a setting in Virtual Switch called "Dedicated ignore AC input"

 

[James deGriz]

I think I found a solution. This appears to be exactly what I need, a dual ac automatic transfer switch. It will not create an Island and prioritises the solar input. My concerns are the mechanical switch and how long it will last. And the potential for it to stick back and forth is the solar is intermittent. I’m putting a delay on relay between the switch and the inverter to give it 30 mins to charge the batter and reduce the risk of this happening.

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[dmsims]

As I said before the Multiplus will do what you want, no need for that switch!

 

[Isleidyll]

You should look for something like a "battery priority mode".

My SNADI 3kw inverter (inverter-charger [UPS], no MPPT) has what is known as "03 battery priority/preferred mode". It supplies load from the battery but switches to grid when battery goes low. When it switches to grid, it doesn't charge the battery. This lets you charge the battery from

 

[Isleidyll]

You should look for something like a "battery priority mode".

My SNADI 3kw inverter (inverter-charger [UPS], no MPPT) has what is known as "03 battery priority/preferred mode". It supplies load from the battery but switches to grid when battery goes low. When it switches to grid, it doesn't charge the battery. This lets you charge the battery from PV.

I have a similar Sandi 2kw 24v. It can charge the battery in battery priority mode as long as the mains charging current is set above zero. My SNADI manual says that the charging current can be up to 40a. I assume this is at 100% setting. Make sure your cables can handle this load.