Last autumn, my neigtbor have put kind of grease, vaseline like, to my battery poles and attaches, saying that it would prevent corrosion (scude my english, I'm fench). Now, when I charge my battery (9.02 VDC) for 15 minutes, it start but do not hold its charge? Is this grease did not made a proper contact and whith time have deplete the power of my battery? Thanks for answering me.
There is a grease called "dielectric" grease. It is used on electronics to avoid corrosion, water, salt, and other contaminants. It will NOT hurt your battery in any way. If your neighbor used a different type of grease, there may be an issue, but it is not very likely. With the amount of time that has passed, the battery has likely failed. Have the battery tested.