LVD for Inverter Supply

[haycord]

Hello. I am going to try to help a neighbor that already has sort of a piecemeal system that needs some serious TLC. They are on a very tight budget (he is a retired Vietnam era Green Beret) so I'm going to do my best to help pro bono. To begin:

They have one 1000W 12V Solar Array split into two 500W Arrays, two 40A PWM Controllers, a common 600AH AGM Battery bank, and a 3000W PWM Inverter (connected to the Battery bank). Fusing, cable sizing, etc., looks okay at first glance. One (of several) concerns is how to auto-disconnect that giganic Inverter before it sucks the guts out of the battery bank. It has a built in fixed alarm at 10.5V and a disconnect at 9.5V, neither of which are of any benefit obviously. I am cautioning them about limiting the Inverter Load to less than 1000W regardless of its 3000W rating. They know zero about the care and feeding of what they have so I'll be helping with that along the way.

To my first question: I'm not able to find a programmable LVD that can handle the supply current to the Inverter. I'm thinking of building one with a Powerwerx LVD-35 driving a (Amazon of course) '12V Continuous Duty Relay, Relay 250A, 5 Pin Starter Relay, SPDT High Current High Power On/Off Control Relay, Split Charge Heavy Duty Relay Switch, Coil 1.8 Watts'

Am I making this more difficult than it should be? Thanks for your help.

 

[time2roll]

Much easier to switch the 120v loads off. Then it is just the idle draw of a couple amps. Small 12v voltage controlled relay module could control a transfer switch style relay.

12v control relay example: https://www.ebay.com/itm/276081283108.

Relay would control something like this:

https://www.automationdirect.com/ad...ers/electro-mechanical_relays/ad-pr40-2c-120a

 

[haycord]

Thanks time2roll. After some research I'm surprised that many better quality Inverters likewise disconnect at a fixed 9.5V. That leaves the AGM Battery user without protection! Sure quality batteries with integral BMS take care of themselves but many people don't want to put that kind of money in the system. Still scratching my head why this is not a bigger concern with a ready solution...

 

[scrubjaysnest]

Education and training is another key. Once had to design an interlock on a system due to lack of training on the operators part.