What is the significance of a battery charging hulk and how is it used?

Question

From The Encyclopedia of the Arab-Israeli Conflict [4 volumes]: A Political, Social, and Military History 1st Edition by Spencer C. Tucker. ISBN 978-1851098415

From page 961:

Syria acquired three Romeo-class submarines from the Soviet Union during 1985-1986. An older Whiskey-class was also transferred to Syria in 1986 but to server as a battery-charging hulk to support the Romeo boats.

Obviously, the Whiskey class submarine was not acquired to serve in a combat role alongside the Romeo class submarines.

What is meany by "battery charging hulk"? Is there a need for additional charging capacity in some circumstances? Is the vessel able to move under its own power? Are the electrical systems of the two classes compatible? Are they any vessels produced explicitly as battery charging vessels?

Answer 1

The old naval term 'hulk' is applied to vessels that are no longer in sea service but still perform some support role in port. So in the case of a "battery charging hulk", it's used to provide additional battery charging facilities for the other diesel-electric submarines. In most cases, hulks are stripped of any items that are not essential to their new role and are not, therefore, sea-worthy.

In a diesel-electric submarine, the batteries are used to power the ship while it's submerged. These are usually charged by the diesel engines when it's on the surface. However, there may be circumstances where the submarine is unable to fully charge these batteries in the normal course of its activities when returning to port and it's unable/undesirable to run its own diesel engines to recharge them. So the hulk uses its own batteries to re-charge the Romeo-class submarines.

I would think it's unlikely that there were any purpose-built vessels of this nature. If you were intending to manufacture a separate facility to do this, it would make more sense just to install the diesel generators and the batteries in a building on land - it would have more room, be easier to maintain, easier to cool and cheaper to build. The only reason for going along the hulk route is that you extend the life of some equipment that you already have (or, in this case, are able to purchase cheaply).

According to the wikipedia entry for the Whiskey-class, Cuba also obtained a vessel to serve as a battery charging hulk for their own (Foxtrot-class) submarines.