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.

Good buy

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) .

Does the job

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.

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.

One thing which is not clear is the relay connects the input to the output, so it is not for a connection where the "output" just turns on or off. But you can link the output directly to a big relay. I do need to put it in a nice case though. I'm using it in my F250. While I doubt my personal electronics will kill the battery, I really don't want everything on all the time. With the engine going (including remote start), I get 14.2v. When I shut off it drops to 13.5 then slowly goes to around 12.5. This makes it easy to give a short time until it shuts off, about 5 seconds after the engine shuts off when it hits 13v, but disconnecting that jumps back to 13.4-.5V, so the turn on threshold also helps. I can do electrical engineering, and wiring to use various indicators and run them through, but it is trivial to cut a short 12V plug extension and put this board between Programming is also easy. Press the left button and hold it to set the disconnect voltage, then use the left to go up and right to go down - holding them in will start a fast count up or down. You have to disconnect power to store the value (it will store the current value on the display any time power is off) Then use the right button to set the voltage above the cutoff to turn back on. In my case, I used 13.0 and 0.6 so it shuts off below 13.0v (the display stays on) and turns back on above 13.6v.

If you intend to use this to prevent battery from over discharged, this product is not what you're looking for. The relay would cut the power off at set voltage. However, the circuit will continuously drain your battery till it's over discharged.