Price
These were recovered from EV battery modules. These are VERY EXPENSIVE online. If you have any project that needs a high current relay this is your chance to save some money.
Make a cheap 30a BMS into a 500a BMS. This will work for batteries in the 9-36v range so perfect for Lifepo4 and Lithium Ion 4s-8s. Wire your BMS like normal except the C- that goes to your charge and discharge will go to the black wire on this relay. The red wire on this relay will go to the positive of the battery. When the BMS is on it will trigger this 500a relay on. When it detects a problem the BMS will shut off and trigger the 500a relay to shut off. Now your main positive wire for charge and discharge will go right to the battery positive and the 500a relay will go in line with your main negative wire. You will want to add a fuse in line as well to protect from an external short or fault that is not battery related. Let's say a charge controller breaks and causes a short, you need a fuse to protect your battery from that. We have great high amp fuses for cheap and you can also find them on Ebay too. Do not use this with a BMS without adding a fuse because you never know what equipment could fail. Chargers, charge controllers, and inverters can fail and you need to protect the battery against that.
The relay can handle up to 500 amps and works up to 900vdc but the trigger wires work between 9-36v which is perfect for all 12v and 24v systems.
If you use a solar charge controller to charge a 12v or 24v battery this is perfect. Connect one of these to the output of the solar charge controller and if it ever fails and shorts this will disconnect the circuit before it does damage to your batteries.
There are many reasons and applications for using these relays and there is no need to spend hundreds of dollars on them when we have them here for a small fraction of the price.