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Here is a simple circuit that closes a relay when a battery bank voltage is low and opens it when the voltage is high. Both set points are adjustable. My generator requires the start signal to be continuous, but it wouldn't work for a momentary start push button. This could also be used for many other events that are voltage dependant. I used an adjustable power supply to set the trip points. Many improvements could be made, but the simplicity works well for me. I also realize there's a typo on the design, as the is a U1 and a U3 but no U2. The 12 volt control power comes from an LM317HV, so it can be used up to 60 volts.
Here is a simple circuit that closes a relay when a battery bank voltage is low and opens it when the voltage is high
This circuit is similar to what I use to charge 12 separate banks of 16s lithium ion battery to open at 65 v and stop charging . Thank you .
Venerable 555...looks like it's being used as an R-S latch with the digital input thresholds providing the trigger setpoints. Clever circuit.
...I just can't help but wonder how small I could get a PCB with that circuit on it 🤣. Probably could fit it onto a 1.5x1.5" board (using a smaller relay as well)...