The experience of many boat owners, if not most, is that short battery life and dead batteries are a chronic problem.
I will discuss why this is so and what you can do to eliminate this problem.
There are three primary reasons why battery problems occur:
- Poor quality of batteries or inadequate battery power
- Faulty installation
- Faulty charging systems
Damages Caused by Faulty DC Systems
Any or a combination of faults in a DC electrical system can cause serious damage to electrical components. Engine starting motors in boats
are so infrequently used that they should never have to be replaced and yet engine starting motor failures are a constant source of trouble.
The reason is either poor quality batteries, improperly maintained DC systems or substandard wiring. High resistance in electrical systems,
combined with low voltage is deadly to electric motors, especially DC motors which run on only 12 volts. If you're having a problem with electric
motor failures of any kind, chances are (unless the damage is caused by water leaks) the problem is related to problems with the system itself.
Quality and Capacity
It is very common for the builders of small to midsize boats to supply both low quality batteries and batteries that are of insufficient capacity to
supply the needs of the DC electrical equipment on board. Unlike nickel-cadmium batteries, which need to be completely discharged occasionally,
lead-acid batteries become damaged when heavily discharged. Allow a battery system to become partially discharged and it becomes seriously weakened and
never again will return to its original, full-charge rate.
For this reason, it is important not to allow battery systems to become depleted. But this is nearly impossible when the total ampere/hour
capacity just barely meets the total demand, for the batteries are constantly being over-taxed.
For example, it is very common to find 28 footers with a gang of electrical equipment on board, including an AC/DC refrigerator, that is
equipped with only a pair of 60 A.H. car batteries. Even though it probably says something like "auto-marine" on them, automotive
batteries are discernible by their thin, cheap plastic casings.
Auto electric repair shops tell us that these days that the quality of automotive batteries has declined substantially. One of the primary
cut backs in quality is the size and quality of the lead plates that generate the electricity. These thin, low-quality plates not only don't
last as long as better quality units, but also very quickly begin to experience a falloff in the total amount of power they can generate.
This, in turn, taxes the battery even more, thereby shortening its life span.
In other words, what are being passed off as "marine" batteries are really car batteries that are not suitable for marine use.
True marine batteries are distinguishable by both their heavy plastic casings and their substantially greater weight. They
weigh considerably more because the lead plates will be close to twice as thick as automotive batteries. Because plates corrode in the process
of generating electricity, plate size and thickness is the criteria for quality. Generally speaking, the thicker the plate, the longer it will
last.
Proper Installation
Some boat owners complain that even when they purchase top quality batteries, they still don't seem to last long. This is usually because
of faulty installation or poor maintenance. Whether you're using gel cells or standard lead-acid batteries, they still have to be maintained.
Here's a short list of common life-shortening factors.
- Batteries must be kept clean and dry. If the top surface of the battery gets dirty or wet, a small flow
of electricity will flow between the terminals as the water creates a conductive path. If installed in a location where water can drip onto
them, this can cause the batteries to discharge fairly rapidly.
- When boats bounce around, the electrolyte fluid in lead-acid batteries will spill out through the tops.
This creates an excellent electrical path for stray current and can lead to rapid discharge. Clean battery tops with a damp sponge or rag, then
wipe dry with a paper towel. This should be done at least biannually.
- Batteries must not be sitting on a wet or damp surface. To understand the importance of this, just take
a fully charged battery and set it on an apparently dry concrete floor. It will discharge right through the casing in about a week.
Even the plastic casing is not a total isolator. Surveyors frequently find batteries sitting
directly in the bilge water, or on a deck that gets wet from water leaks above. Or, the batteries are mounted in boxes that, one way or another,
collect water.
- Wire splices. Particularly on smaller boats where much of the wiring will get wet from leaks and spray,
if the electrical system has had alterations and additions that utilize butt connectors, these devices, when they get wet, particularly with salt
water, are very good at leaking current.
- Wiring exposed to bilge water. Very often we find battery cables laying directly on the bottom of the
hull. So, too, do we find wiring laying on the bottom, often running through pockets of accumulated water such as outboard of the hull
stringers. Be assured that these wires are leaking current to some degree.
- Batteries located in an inaccessible location. This is a very common problem. If the owner has to stand on his head or crawl on
his belly to reach the batteries, they're not likely to get serviced. To make matters worse, it’s going to cost a lot more to
pay someone to get them in and out of that tight hole. Most builders will put the batteries right next to the engines so that they can
save the cost of long cables. Consider relocating your batteries to a more convenient location if they're in a place where they
can't be reached or get wet. Ultimately, it will save you a lot more than the cost of moving them.
- Cheap battery boxes. You know, those red-and-white jobs with that impossible belt buckle that goes over
the top to hold it in place. With our hectic way of life these days, who's going to wrangle with these little monsters to service the batteries?
Most boat owners don't, and there's the problem. These things retail for less than $20 and aren't worth a nickel. Depending on size, good
quality battery boxes cost $50-$100 and they're well worth the cost when you think about replacing three or four hundred dollars worth of
batteries every two years.
- Be sure that the battery box has a hole in the bottom that will let water drain out. Rinse out the
bottoms of the boxes occasionally with fresh water to remove spilled acid. What small amount of acid that gets into the bilge will not be harmful.
Battery Chargers
Cheap chargers will ultimately do more harm then good and here's the thing to remember. A brand new, good quality 12 volt battery,
depending on size, will generate between 13.0 and 14.5 volts. That is because each cell will generate slightly more than 2 volts per
cell when they are new. But as the battery ages, they will progressively generate less voltage and power per cell. Cheap battery
chargers cannot adjust for these changes in total voltage over time.
ALWAYS use a battery charger designed for charging AGM Deep Cycle Batteries.
Ensure that your installation has a charging system with a program for AGMs or ask us about our 10amp and 20amp automatic
chargers specifically designed for AGM Batteries, which can be found on our website at
AGM Battery Chargers.
Cable Connectors
It is very common for builders of smaller boats to attach battery cables to the terminals with substandard connectors.
Foremost among these are ring terminal ends attached with wing nuts to threaded studs. There are a number of things wrong with this
arrangement, not the least of which is the tendency of the connections to come loose. Secondly, it's likely to be creating a high
resistance connection.
The bottom line is that the cables should never be connected in this way. Nor should cable ends use steel end clamps that
will rust and create resistance. Cables should be swaged to heavy lead lugs with the standard clamping arrangement to the battery post.
If your system does not have swaged lead terminals, get them changed soon because they can be causing damage in more ways than one by
creating a high resistance connection.
Summary
Even if you own a boat with a substandard DC electrical system that has a continual problem with battery discharge,
it is neither difficult nor particularly costly to upgrade your system and keep it functioning at maximum performance.
Correcting one or more of the above defects, if you have them, will save hundreds, even thousands of dollars in damage and replacement costs.
A good quality DC system should have no problem lasting three years or longer. Compare that with the cost of breakdowns and replacing
batteries every 18 months or so.
First StartAGM Battery Special:FS-12V 90A/H
First StartAGM Battery Special:FS-12V 100A/H
