Disconnecting the negative circuit of a car battery stops the ground connection for all vehicle circuits. This means no current flows, so the battery will not drain.
The actual process is dependent on the type of battery we are talking about. In a lead acid battery, The cell voltage will rise somewhat every time the discharge is stopped. This is due to the diffusion of the acid from the main body of electrolyte into the plates, resulting in an increased concentration in the plates.
Current will not drain through the circuit, but if you consider the battery leakage current, then yes, the battery will drain. This drain rate varies according to the battery technology (lead acid, lithium, etc.) and may or may not be big enough to impact your project.
Besides, inside the battery there is basically an acid (the density might be lower compared to a bleacher but, still an acid). A lead acid battery can be stored for at least 2 years with no electrical operation. But if you worry, you should: And, if possible, recharge it periodically (3 to 6 months).
Can a dry-charged battery be filled with acid / liquid?
Yes, this is possible. In fact we had deliveries of hundreds of dry-charged batteries and separate deliveries of the acid / liquid to fill them with. Guess who, as an apprentice, got to mix the acid to the correct SG and fill batteries. They were transported like that as the liquid is heavy and more batteries can be carried.
No current will flow through the circuit, but the battery might still self-discharge slowly, same as if neither terminal was connected. The size of something that is not connected does not matter in this context. Current will not drain through the circuit, but if you consider the battery's leakage current, then yes, the battery will drain.
Does disconnecting a negative cable stop a battery drain?
The answer is yes, it can. Disconnecting the negative cable doesn't completely stop the battery drain. It only delays it. How does that happen? And what can you do to avoid battery drain altogether? This post will reveal the surprising truth behind this widespread belief. I will also show you how to keep your battery in top shape.