Cheap Battery backup system for a 3 phase grid

[Alrc797]

Hi

I am willing to build a very cheap battery backup system for my home, only for blackouts.
What is the cheapest way to do that? Is it possible to connect 3 cheap inverter for each phase in a lead acid battery bank? Or is there any cheap option for a 3 phase inverter?
My critical devices that need to run in this emergency is different phase.
No solar system. Only the grid.
Thanks

 

[AntronX]

How much power and energy your backup needs to provide? What's the price on cheapest deep cycle (gold cart type) lead-acid batteries you can source locally?

 

[Alrc797]

The power amount should not exceed 500w (peak of 1000). The capacity of the system should be around 5.000kwh
The average price of a deep cycle battery that I can source locally here is around $100 for 12v 100a

 

[AntronX]

My critical devices that need to run in this emergency is different phase.

Your backed up device requires 3 phase power?

 

[Alrc797]

No. Max 2 phases
Ex:
1 phase: tv + wifi
2 phase: fridge (phase 1 with phase 2)
3 phase: lights

 

[AntronX]

2 phase: fridge (phase 1 with phase 2)

Why do you have fridge across 2 phases? Do you have 4 wire Y service with neutral or 3 wire delta service?

 

[Alrc797]

It is a 4 wire system. 3,phases + neutral. each phase with 110v.
The fridge is 220v (2 phase)

 

[AntronX]

That's one interesting case you got. I think you can get by with split phase inverter set to 110/220V output and wire in custom transfer switch to reconfigure your loads from 3ph to single split phase arrangement automatically.

 

[Alrc797]

That's one interesting case you got. I think you can get by with split phase inverter set to 110/220V output and wire in custom transfer switch to reconfigure your loads from 3ph to single split phase arrangement automatically.

Ok. Got it.
Is there any way to instal 3 different cheap inverter and then synchronize them in some way?
My concern is if I change the devices later between the phases.

 

[AntronX]

Is there any way to instal 3 different cheap inverter and then synchronize them in some way?

There are inverters than can be synchronized into 3phase operation but I am not immediately aware of which ones. Maybe other members here can suggest something.

 

[Alrc797]

There are inverters than can be synchronized into 3phase operation but I am not immediately aware of which ones. Maybe other members here can suggest something.

One idea that comes into my mind is to put an Variable Frequency Device (VDF) single to 3 phase used for motors to connect in my grid. Would this work?

 

[AntronX]

Would this work?

No. VFDs are made for driving motors and don't have output filtering or neutral and require high voltage DC input.

 

[SajgZi]

No. Max 2 phases
Ex:
1 phase: tv + wifi
2 phase: fridge (phase 1 with phase 2)
3 phase: lights

Do some quick math on your options here regarding your unusual phase situation:

1. buy a new fridge that's single phase
2. buy an inverter (or 3x) that can output the correct phases

You may find it cheaper to get a new fridge and 1x standard single phase inverter

 

[Alrc797]

No. VFDs are made for driving motors and don't have output filtering or neutral and require high voltage DC input.

Thank you!

 

[Alrc797]

Do some quick math on your options here regarding your unusual phase situation:

1. buy a new fridge that's single phase
2. buy an inverter (or 3x) that can output the correct phases

You may find it cheaper to get a new fridge and 1x standard single phase inverter

The 3 phases, 127v each is the standard configuration here in south Brazil, for big house. This is why I am trying to figure out some cheap solution without the need to rearrange the devices. Is there an affordable (~$200) 3 phase inverter at max 4kw? No need to be hibrid with solar panel connection.

 

[Piet_de _Pad]

Hi

I am willing to build a very cheap battery backup system for my home, only for blackouts.
What is the cheapest way to do that? Is it possible to connect 3 cheap inverter for each phase in a lead acid battery bank? Or is there any cheap option for a 3 phase inverter?
My critical devices that need to run in this emergency is different phase.
No solar system. Only the grid.
Thanks

Your lucky I developed a system like that. I have a backup for 1KWh 600W and my cost price is 500USD
Let me know if your interested