Thanks to COVID-19 my regular commuter (2010 Fit) sat outside for about 3 weeks with no driving. I just went out to start it and it barely turned over two times before not starting. I though no sweat I will just jump it and drive around to recharge, or better yet since I have time pull it out and stick it on a charger/tender.. But when I opened the hood it looked like this.. What is the blueish stuff? It is like super fine grain sand that is loose (will fall away loosely if I poke it). And worse I couldn't turn the nut on the negative terminal clamp to loosen it no matter how hard I tried to wrench it..

Is the battery likely toast? (it is ~6 years old).. Any tips for getting the nut loosened?

 

Some penetrating oil on the nut that tightens the terminal clamp will help. Let it soak for a little bit before wrenching. You are likely due for a new battery.

 

That’s copper and lead sulfate. Usually caused by small leaks around the terminals and exacerbated by charge conditions. Not extremely dangerous (don’t handle it with bare hands or eat it though).

On top of the correct advise about using penetrating oil to loosen them and getting a new battery, you need to scrub those terminals real good with a wire brush and inspect them carefully. If they look like they’re delaminating or crumbling, they need replaced.

edit: I’d also pull back the red cap and check each of those nut terminals just to make sure there isn’t any built up under there also

 

There is more to this story that I want to hear.

 

Wait on the penetrating oil. First, scrub with a wire brush and a solution of baking soda and water. I'm no chemist, but that is what I would do. If you use the baking soda+water, you don't have to be aggressive. After you have cleared most, if not all, of the powdery stuff, then see how the bolts and nuts look.

 

They also sell a stuff to clean battery terminals, at least here in Canada. Could be found at Canadian Tire. Really helps!