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I am building a Bluetooth speaker and will have two power options running into a DPDT Switch. One side of the switch will go to an 11.1 volt 2200 milliamp battery which will be regulated to 12v. The other side of the switch will go to an AC adapter receptacle. This will give me the option to run off the battery or a 12v AC adapter but neither at the same time. The battery will be charged separately off a different circuit receptacle.
My question is would it be a good idea to put a diode on the positive battery line running to the DPDT in case the switch ever failed while running off of AC? This would be a safety measure since I know LiPos can be dangerous and I wouldn't want power going back into the battery from the AC adapter source. If this is a good idea what type of diode should I get and would it only go on the positive side and before or after my regulator before going into the switch?