Connect an inverter to the mains

[DD86]

Might be a question for Crossy.

Is it in principle possible to connect an inverter directly to the mains and If not what do I need to make such a connection?

There are probably more snakes in the grass then I can think of and how do emergency power generators do it?

Thanks

[carlyai]

On 3/24/2025 at 7:17 PM, DD86 said:

Might be a question for Crossy.

Is it in principle possible to connect an inverter directly to the mains and If not what do I need to make such a connection?

There are probably more snakes in the grass then I can think of and how do emergency power generators do it?

Thanks

[Crossy]

Generally, for both your inverter and a generator you will need a transfer-switch, it is vital that you never have both your inverter/generator and the mains connected together (unless the inverter is a grid-tie type).

 

If you have a hybrid inverter like @carlyai shows it has its own internal transfer arrangements, but an external switch is always handy as a backup if you need to service the inverter.

 

@DD86 What is your actual goal in life for this setup?

[DD86]

Thanks for replies.

Wouldn't actually call it a goal in life. I am 'researching' an alternative solution to a UPS. Household UPS only provides like 15 mins of operation time on the PC. When I added a couple more identicall batteries to my UPS it worked for a short while till the UPS stopped switching.

One simple solution for me would be to have my critical equipment connected seperately to an inverter, running all the time or only plugged in when needed.

 

[Crossy]

How much power (Watts/VA) do you need and for how long?

 

There are certainly UPS units that can take external batteries but they tend to be the more expensive variety.

 

Or, you could use a solar hybrid inverter without solar panels and just a battery pack. The world is your oyster then 🙂

[DD86]

Yes, a 2000 Watt inverter on batteries would suffice; in fact double of what I need.

During last earth quake we had a power outage for 2 hours.

 

[Crossy]

Something like this https://www.lazada.co.th/products/powmr-2kw-12v-20-150vdc-pv-bulit-140a-mppt-solar-charger-controller-2-i5482290007-s23263269028.html coupled to a 12V 250Ah ish LiFePO4 battery would be more than wonderful (maybe 2 x 100Ah would be cheaper).

 

 

[DD86]

Good idea when my application fails. Thank you.

[steven100]

just buy a UPS on Shopee ,,,,  no messing around and it arrives at your door,  plug it in... that's it, why bother with making your own.   ???

[sometimewoodworker]

4 hours ago, DD86 said:

Thanks for replies.

Wouldn't actually call it a goal in life. I am 'researching' an alternative solution to a UPS. Household UPS only provides like 15 mins of operation time on the PC. When I added a couple more identicall batteries to my UPS it worked for a short while till the UPS stopped switching.

One simple solution for me would be to have my critical equipment connected seperately to an inverter, running all the time or only plugged in when needed.

 

That is what we do. The main router and security CCV cameras are powered by our UPS. We have 24v 50Ah batteries powering it, it is trivial to add more capacity (though not cheap), we have had power cuts lasting more than 4 hours, I did not check the level of charge but suspect 8 hours with the current system will be no problem. We had baby UPS’s before but this small industrial one is likely bulletproof.

 

 

NB the guarantee is 24 month’s on site. I have used this once at about 20 months on a previous CyberPower UPS 

[ExpatOilWorker]

2 hours ago, Crossy said:

Something like this https://www.lazada.co.th/products/powmr-2kw-12v-20-150vdc-pv-bulit-140a-mppt-solar-charger-controller-2-i5482290007-s23263269028.html coupled to a 12V 250Ah ish LiFePO4 battery would be more than wonderful (maybe 2 x 100Ah would be cheaper).

 

 

Very interesting solution. 

What is the difference between the two mains out?

The 6.2 kW unit is rated foe 48V DC batteries and listed together with a 12.8V battery.  Are you suppose to connect 4 batteries in series?

That will give 51.2V, close enough to 48V?

Wouldn't it be better to connect a 5 kWh LVTOPSUN battery, it isn't that much more expensive.