Do I need a special Hydrometer to test deep cycle batteries.?

Question

I have been told that I cannot use the same type of hydrometer for testing deep cycle batteries as the one I use for testing car batteries.

Answer 1

Car batteries usually are acid batteries.

Deep Cycle is usually required only on alkaline batteries.

When this two electrolytes are mixed together you can have very violent reactions, and even a few drops of one can dramatically damage the other type of battery.

Using the same hydrometer for both batteries, first of all, would be dangerous, second would damage the batteries, and lastly would be useless because the range of density is totally different.

What do you think you should do?