Best way to clean flux off my battery replacement job?

What i am about to say will be a bit generalized, so do some reading if you are not sure about it.

Circuit boards are a lot more resilient then people make them out to be.
As long as there are not parts on it that are sensitive to liquid, you can just douse them in Alcohol and scrub them with a small brush just like you would clean your dirty dishes.

Batteries, buzzers, switches, certain connectors, parts that are easily bend are examples of things that might be problematic.
Common sense and a bit of experience tell you what parts to be aware of.

Years ago i bought a 2 gallon jug of ethanol.
Io clean my boards i just put them in a shallow tray, pour a good swig of the stuff on it and let it soak for a while.
Then i just brush the whole thing vigorously with an old toothbrush.
You might want to get a proper ESD brush if you are worried about ESD though.

You can even just put them in the sink and use soap with distilled water to clean old and grimy boards.
I wash them with ethanol to get them quickly dry after that and blast them with a bit of heat.

/r/AskElectronics Thread Parent