Are you saying that the inverter does not monitor the battery voltage and go into sell mode once the battery bank has hit some limit?

I think I have some 3 phase motor start contactors that might fit your AC side switching needs. At least one was over 100 amps rated. If interested I will dig thru my stuff and see what sizes there are. You are welcome to one if you wish to try that route. I got these from Drives Dean awhile back and my projects list has been shortened to where I doubt I will use them all anyway.

Let me know here if interested and I will contact you off board.

Much rather pass them on to someone who will use it that rot in my pile.

Tom

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it

Also, if you rely on just the timer you may run heavier than expected loads on the inverter and it will shut down before the next "grid window" and then any critical loads (like a fridge) will suffer from the outage (if you're not around to override the timer).

I've got a SmartGauge that does what you want. It can measure the battery SoC directly and can be programmed to output a relay alarm at a particular low SoC. So when the battery bank hits 50% it alarms and the relay closes/opens (it's a change-over type) and you can use this to operate an external buzzer, light or even start up a genset to charge the bank. The alarm will continue for a set time (programmable) so you are meant to set it to a time that would allow a genset to fully recharge the bank and then it will time-out and stop.

In your case, you set the alarm relay to drive a big grid change-over relay so that while the battery stays above 50%, the grid is disconnected and the inverter runs but if the wind power isn't enough to keep the SoC above your chosen set-point, the SmartGauge will alarm and connect the grid and charge the bank for some programmed number of hours (avoiding any weird cyclic behaviour).

Hopefully the wind charge controller would take care of things like topping off the battery once in a while and equalising the bank (if you've got floodies), as the SmartGauge will not connect the grid unless the bank gets critically low.

You can see more on the SmartGauge at www.smartgauge.co.uk

Maybe to avoid the bank sitting for a long time at a partial charge you could also trigger the grid relay once a week for a few hours just to make sure that the bank gets topped off at least once a week to keep the sulphate at bay.

The SmartGauge isn't cheap though (about £145 / $230). You could rig something with voltage comparators & some logic but then you'd maybe suffer from false alarms as a large load can easily drag a bank down to under 24V temporarily but as soon as you remove the load (boiling a kettle) the bank voltage rebounds and it hasn't actually discharged that much (just maybe 3-4% in reality).