3Pcs 3S Battery Protection Board 3S 10A 18650 Lithium Battery Protection Board 12.6V with Charge Balance Overcharge Overdischarge Overcurrent Protection

Here's a 3s 10A balancing BMS on Amazon Plenty more over on AliX for 1/3 the price. I'm no expert on batteries, but I use a balancing BMS whenever the batteries are permanently installed and not used with an external balancing charger.