Automatic Transfer Switch

[karlfk]

Hi all

I'm looking for a 12 volt Automatic Transfer Switch for my shed solar, so when my battery runs low it will auto switch to 240v mains, any idea on what I could use.
could some explain how they work.

cheers karl

[NEOH]

Not many details, I assume ...

You have a DC-to-AC 240 Volt Inverter that is powered from a Battery bank.
At some point the battery voltage is too low and the Inverter shuts down.
At this point you want an Auto-Transfer Switch to re-connect all LOADS to the Grid

Yes...
You connect the ATS "control" wires to the the Inverter's output
You connect the Inverter Power to ATS Input #1 ( Normal )
You connect the Grid Power to ATS Input #2 ( Back-Up )

You connect your loads to the ATS Output.

When the Inverter is OFF the loads are switched to the GRID.

The ATS switch must have the proper Voltage & Amperage rating for your loads.

[inetdog]

One very serious problem with using the Low Voltage CutOff (LVCO) of the inverter is that it is designed to protect the inverter more than the batteries, and by the time it shuts down the batteries are likely to be seriously stressed. To the point that they will not survive even a hundred cycles of that abuse.
Second potential problem is that, depending on your battery cost and utility power cost, you may be losing money as you try to save power using PV and batteries. If you want backup for unreliable utility power you should configure it so that it only uses batteries when the utility is down.
Finally, how do your loads react to the interruption of power if you let the inverter shut down to trigger switching back to utility?

[solardreamer]

Hi all

I'm looking for a 12 volt Automatic Transfer Switch for my shed solar, so when my battery runs low it will auto switch to 240v mains, any idea on what I could use.
could some explain how they work.

cheers karl

I have similar situation and what I do is use a solar charge controller that has load output that I can set the low voltage threshold for discharge disconnect to prevent over-discharging the battery. I don't like to discharge battery more than 30% DOD so I set the disconnect voltage threshold pretty high. The charge controller load output drives the inverter which in turn drives the coil of a DPDT relay that uses the inverter output (normally open input of DPDT relay) for load power when the inverter has power or the grid (normally closed input of DPDT relay) when inverter does not have power. You'll need to find DPDT relay or ATS with appropriate specs to fit your setup.

[Logan5]

You could consider a LVD from Battery mart, they have a 10 and a 15 amp pre wired with dip switches to set points and control a relay to disconnect your inverter. or much less money you can obtain a China PCB module with LCD to make your own, still controlling a relay. If you have a programmable charge controller with the Aux out, you can use that to control a relay as well.