Battery Safety

Battery CCA Ratings for Gasoline Engines

Engine Size . . . . . . . . . . . . . . . . . .CCA Rating Four-cylinder engine . . . . . . . . . . . . . . . . . . . . .450 CCA Six-cylinder engine . . . . . . . . . . . . . . . . . . . . . .550 CCA Small V8 (350-cubic-inch, 5.7-liter) . . . . . . . . . .650 CCA Large V8 (454-cubic-inch, 7.4-liter) . . . . . . . . . .700 CCA

theoretically require twice as much amperage capacity as the figures above! When in doubt, consult the engine builder for the exact specification.

Again, if you have a cruiser with a lot of auxiliary equipment, you’ll need a battery bank comprised of deep-cycle batteries. Use the amp-hour-per-day formula above to calculate the total amp- hour capacity.

Battery Safety

Safety considerations around lead-acid batteries are often not taken seriously. During my career, I’ve seen two batteries explode, covering workers with acid. In one instance we were able to flush away the acid so that the worker escaped injury. What was his mistake? He left a 1⁄2-inch wrench on top of a battery, and it had come in contact with both the positive and negative terminals.

In the other instance, the victim was permanently scarred. His error? He disconnected a battery charger from a battery without first turning off the charger. The resulting spark ignited the hydrogen gas that had built up around the battery.

In a third, less-dangerous instance, a battery simply exploded and coated the main saloon of a friend’s liveaboard cruiser with battery acid—curtains, carpets, furniture, everything. I’m not sure what caused that one, but I think he was attempting to charge a battery with low electrolyte. Fortunately, no one was on board at the time of the explosion so there were no injuries.

Battery acid is dangerous. Battery safety rules are simple but must be followed.

Thoroughly ventilate the area around batteries.

Highly explosive hydrogen gas, which can be ignited with the smallest spark or cigarette ash, is being produced when charging a battery.

Don’t put tools on top of a battery when working in the area. Metal tools can cause a short between the two terminals and will literally weld themselves to the battery. The least you can expect is a spectacular spark that could easily cause an explosion or serious burns. Also, wearing jewelry when working around batteries is risky, for the same obvious reasons.

When connecting or disconnecting battery terminals, always disconnect the negative terminal first and hook it up last. This sequence minimizes the chance that a spark can jump the gap between the battery post and the cable-end terminal as you hook it up.

Don’t smoke. If you must smoke, don’t do it around batteries.

Batteries are heavy. Use the carrying handles provided on good marine batteries and get help if you need it. If your battery doesn’t have carrying handles, borrow a special battery-carrying strap, as shown in figure 5-3, and use it.

Don’t overfill wet-cell batteries. The excess electrolyte will boil out as the battery charges, leaving an acid film all over the battery and everything in the surrounding area. Figure 5-4 shows the proper level to which each cell should be filled. When the level is correct and you look down into the cell, you should see a fish-eye staring back at you.

Never attempt to recharge a frozen battery; it will probably explode. A frozen battery must be completely thawed before any attempt is made to restore it. Odds are that it’s dead anyway.

Never attempt to charge a battery that has electrolyte levels that are below the top of the battery plates. On sealed batteries with a charge-indicating “eye,” various colors are used to indicate the state of charge. Depending on the manufacturer, one of the colors will indicate electrolyte loss. This battery

Fig. 5-3. Battery carrying strap in use. This type of strap assembly will only work for smaller group 24 and 27 batteries. Larger batteries all have carrying handles attached, and should be handled by two people.

Fig. 5-4. Correct battery cell fill level.

Cell opening with cap removed, showing correct fill level

Electrolyte

Cell plates should not be charged, but replaced. Sealed batteries should have a sticker on the top explaining the color codes.

Keep batteries in a properly designed box secured to prevent battery movement in rough seas. Make sure that all cable connections are tight and permanent. No alligator clips or twisted-on connections are allowed.

Keep batteries clean and free from corrosion and any moisture or oily film on the battery top. This is not only a safety consideration but also a great way to increase the life of your batteries.

Know which battery terminal is positive and which is negative. This is important for the connect-anddisconnect procedures described above. It will also prevent damage to polarity-sensitive equipment like

GPS and radar.

Battery terminals should be marked with a plus (+) or minus ( ) sign, or the positive terminal may be marked with red paint. With a post-type battery, the positive terminal is always slightly larger in diameter than the negative. Don’t believe the cable colors. Lots of people replace cables with whatever color cable is available at the time they needed a new one. Be absolutely certain you know which is the positive and which is the ground (negative) cable.

Remember, battery electrolyte is sulfuric acid. It will burn through shirts, pants, shoes, wood, most metals, and your skin. Anything exposed to battery electrolyte should be thoroughly flushed and immediately rinsed in fresh water. Even then, your favorite jeans or T-shirt will probably end up with a souvenir set of holes after the first wash.

Battery Location

A major part of battery safety is directly related to the way batteries are installed in your boat. Our friends at the ABYC have addressed this issue in section E-10 of the Recommended Standards. They list three acceptable possibilities for battery installation.