Since upgrading our solar charge controller to a MPPT model we lost the facility for the charge controller to shut down the inverter when the battery voltage dropped too low. This resulted in a few days when the battery voltage dropped to a very low level and risked damaging the batteries.
To solve this we made a low voltage cut-off circuit using a MAX8212 micropower voltage detector with a 60A rated mosfet to switch the inverter on and off when the battery voltage reaches a set level.
The PCB layout and schematic are available to download in Diptrace format.
Download PDF schematic.
The etched PCB with the tracks covered in a layer of solder.
Testing the circuit with a 21W 12V bulb
The completed project in a Diecast box with heatsink fitted to the top.
The values used on the circuit below give a turn off voltage of 12.4V and turn on again at 12.7V on the input side.
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