BATTERIES
Many times while on a survey or after a survey questions are asked about why something is written up about batteries, or their installation. Hopefully this short article will assist with the question, and hopefully keep some of the problems from occurring. Quite frankly this is one of the areas where the most problems are discovered.
I have come to the conclusion that this happens because people simply don't understand some simple things. Things like what physically happens to my batteries if I hit a really big wave? Are they secure or are they going to bounce up, or slide against a fuel tank or fuel line. When I am working in the engine compartment what happens if I drop a wrench on the battery. Ever seen a battery explode? I have witnessed this on two different occasions, it not pretty, plastic and electrolyte all over the place. People install automotive battery chargers inside an engine compartment, while not understanding the sparks that occur inside the charger when it turns on and off, over and over while you are not at the boat monitoring for fuel leaks. I have seen lights dim more than one time when some of these chargers are turned on. There just seems to be no end. Hopefully a series of white papers on different subjects will make for better boats.
Most questions about battery correct installation is covered by ABYC in sections 10.1 -- 10.8.3 reading this document will cost you as you must be a member and purchase the document. But surveyors live by these documents every day, here are the basics.
Electrolyte
Batteries must be mounted to contain any electrolyte which may leak from the batteries. In most cases this means a tray under the battery, or a battery box. They can also be in a custom designed battery compartment.
Batteries must be secure
Attempt to move the battery, if it moves more than 1 inch in any direction with a force of 90# applied or a force greater than 2 times the weight of the battery it is not secure. Basically the battery must be strapped down or other means must be employed to secure it.
Mounting
Batteries must not be mounted directly below battery chargers or inverters. They may not be mounted below or above a fuel tank. They may not be mounted within 12" of a fuel line unless the fuel line is electrically insulated.
Safe Connections
The POS + terminal on the battery must be protected against accidental contact with any DC grounds. This can be accomplished by installing an insulating cover on the POS+ terminal usually the Red Rubber Boots we see, or the lid on a battery box.
Protection of LOADS
To put it simply a battery can deliver enough current to start a fire anywhere on the boat a short circuit develops. The only thing stopping this is to place over-current protectors (fuses/circuit breakers) at critical points in the system. Their purpose is to open if too much current is drawn and prevent fires. For NON-MOTOR over current protection. The rating must not exceed 150% of the ampacity of its supply conductor, meaning that if the conductor is rated for 10 amps the fuse must be at a maximum of 15 amps. There must be a fuse or breaker within 7" of the battery on the lead going from the battery to the DC panel (exception to the 150% rule). The fuse or breaker must not exceed the total combined current rating of the DC panel, IE: add up all of the breakers on the panel. In fact there must be a fuse on all conductors leaving the battery within 7" with one exception, the heavy lead going to the starter (cranking).
Chargers
Chargers must be marine rated. In other words get rid of all automotive chargers. The charger lead must be protected with a fuse or circuit breaker within 7" of the battery the fuse must not exceed the output of the charger. If the manufactures plate on the charger does not state it is internally protected, there must also be a fuse within 7" of the charger.
Battery Switches
Anytime a battery or a battery bank exceeds 800 CCA (cold cranking amps) a battery switch must be installed as close as possible to the battery.
Additional Info
| BATTERY SIZES AND VOLTAGE | ||
| Size | Capacity (AMP HOURS) | Voltage |
| U1 | 34-40 | 12 Volts |
| GROUP 24 | 70-85 | 12 Volts |
| GROUP 27 | 85-105 | 12 Volts |
| GROUP 31 | 95-125 | 12 Volts |
| 4D | 180-215 | 12 Volts |
| 8D | 225-255 | 12 Volts |
| GOLF & T-105 | 180-220 | 6 Volts |
| L-16 | 340-415 | 6 Volts |
Battery Charge Capacities
For years I compared battery charts from different battery manufactures, very seldom did their information match. Knowing that they should always match I finally reverted to an old chemistry book. There I found a chart containing specific gravity relative to temperature. Suddenly it all became very clear, the manufacturers were all telling the truth, they never included the battery temperature their chart was created with. The results is this Battery Chart it is very accurate. While the top of the chart indicates "No charge or load for 6 hours" I have found that turning off any chargers and placing a load on the battery for one to two minutes removes the surface charge then testing according to the chart can proceed. Download this chart have it laminated at your local office supply store and mount it next to your batteries. I have also found that obtaining stick on temperature tape and mounting it on the battery is a quick reference to the battery temperature.
Summary
There are two issues at hand here. The first being SAFETY, are you and everyone aboard your vessel safe from fires and explosions. The second issue has to do with the safety of the vessel, or will it burn while you are not onboard taking out your neighbors and their boat. SAFE BOATING.. Fred
Copyright Fred Moore, 2004,2005,2006,2007 All content
