Regal 42SC Owner's Manual page 274

If the battery is not completely charged, but still adequate
to crank the engine over, you may see a reading closer to
12 volts.
2. If the battery shows less voltage or will not charge
up completely it's time to use a hydrometer. This device
checks the proportions of sulfuric acid and water in the
electrolyte which is a precise indication of the level of
charge. Check all cells. If the readings are below 75%
charge the battery. If the electrolyte level is too low to
read with a hydrometer, add distilled water only (tap wa-
ter will eventually ruin a battery's capacity) to any cells in
which the electrolyte isn't touching the bottom of the fi ll
port. Do not overfi ll any cells.
Take another hydrometer reading the following day after
the boat has been run and the distilled water has had an
opportunity to mix.
If the level of electrolyte is very low, suspect that your
yacht's charging system may be generating too high a volt-
age. The maximum voltage you should see across the bat-
tery terminals with the engine running as read by a volt-
meter well above idle is 14.6 volts.
3. Check both positive and negative terminal hardware
for tightness. Loose connections are known to discharge
a battery very quickly.
4. Make sure all terminals are clean. As discussed earlier,
a battery cleaner tool along with a toothbrush should be
used to clean both the positive and negative terminals.
Use a small amount of baking soda and water. Remove
any acid residue from the terminal area and battery top
with a damp cloth. Be sure to wear plastic gloves and eye
protection. See the illustration.
Install anti-corrosion protection to the posts before
reinstalling the terminals. This lubricant is available as a
paste or spray type and can be found at most marina or
auto supply stores.
Be sure to reinstall any red (+) battery (anti-short)
boots.
Cosmetic Care & Maintenance
Use an old toothbrush and baking soda to clean terminals Use an old toothbrush and baking soda to clean terminals
29
BAKING SODA
AND WATER
CLEANING
SOLUTION
Use a battery tool to clean connectors and terminals Use a battery tool to clean connectors and terminals