The positive of battery 2 is now at 18V relative to ground because it is always 9V above its own negative terminal at equilibrium. As for a short circuit, in order to get a short circuit, I have to provide a complete circular path for current to flow through. I can do this by adding another wire between any two terminals.
By short circuit we mean an electrical short circuit, a very low resistance path between the positive and negative sides of the cell or cells. A short circuit can be inside a battery cell or external to a battery cell. There are a number of things that can cause an internal short circuit within a battery cell.
A short circuit happens when there is a low resistance path between the positive and negative terminals of a battery, allowing current to flow freely between them. This can happen if the terminals are touching each other, or if something else is connected across the terminals that have a lower resistance than the internal resistance of the battery.
Yes, a short circuit can damage a battery. A short circuit happens when there is a low resistance path between the positive and negative terminals of a battery, allowing current to flow freely between them.
A battery's positive terminal does have a positive potential. ie, a test positive charge will repel it and a test negative charge will attract it. Vice versa for negative terminal. From the paper below (Section 1.2.1), it seems abundantly clear that the battery will have positive and negative potential on respective terminals.
This is due to two main reasons: first, a short circuit in a series module can cause some cells to undergo polarity reversal (as shown in Fig. 15 C and D), potentially leading to electrode material damage, electrolyte decomposition, and gas generation, thereby accelerating battery degradation .