I am getting my Ham Radio setup for HF and have a lot of RFI noise. Part of the testing is to turn off ALL electrical circuits in my house to see if any devices in the house are causing the RFI. To do this I needed a battery to run my radio from, I have a Yaseu FT-817ND which can run from battery, but the internal battery has died and I have been running from a power supply plugged into the wall. I was going to ask some local Ham Radio operators if I could borrow a battery for testing, but I am a maker and as the better half says a pack rat. Some time ago I disassembled some laptop battery packs that were giving problems and saved the good 18650 cells for playing around with.
I had purchased some 18650 cell holders so I soldered together a small 12V battery pack.
I then plugged it in and the RFI is still there :(.