2pcs 12V-36V DC Voltage Protection Module Digital Low Voltage Protector Disconnect Switch Over Discharge Protection Module

Used these as a way to turn on and off a relay for my solar setup. I found without a device like this, my batteries would be drained below optimal levels which could damage the batteries. This turns off the relay so my EcoFlow stops pulling power from the batteries till the on voltage is achieved again.

Does the job

Another seller of this same item has excellent directions on the amazon page. This seller doesn't. I took off one star for directions. It looks to me like several sellers are selling the same item. The first one I got, from another seller, did not work at all. I opened the first one from this seller and it worked like a champ. And I have a spare. Every feature worked fine. When I lowered the voltage below the cutoff, it cut off great. When I raised it 2V over the cutoff, it came back on. I did not have to adjust the voltage, it was spot on to my meter out of the package. Perfect. I have a 24V LIFEPO4 battery, and it is nominally at about 26V. By 24V, there is almost nothing left in the battery, but my circuit doesn't like low voltage, so the cutoff at 24V makes a clean off, so if I forget to turn it off (yes, I did that once, with bad results), the circuit is protected. This is even higher cutoff than the battery pack bms (2.5V/cell=20V) .

The built in voltmeter is within a few hundredths of a volt to my Fluke meter. The disconnect was within 0.1v of the disconnect setting. Perfectly acceptable for a $5 part. Some have complained that the disconnect continues to drain the battery after disconnecting the load. In my application, I have a 12V SLA battery, an AC to DC power supply set at 13.5V (float voltage) and a load. I connected the power supply and load to the VIN terminals, and the battery to the VOUT terminals. This is opposite to the published diagram. When the AC voltage drops out, the load stays on until the battery voltage drops below disconnect (12v), then the relay opens and the battery is disconnected and has no parasitic load. When AC power is restored the relay closes and the battery gets charged.

Works so far ,but these things are super flimsy I don't expect them to last long! I already hot glued the coils to sturdy them up.