Due to the amount of traffic on this page and the number of e-mails
on boat batteries, I've decided to post some of the questions and answers
on a new page. I hope you
find this information helpful!
Marine batteries, no matter
the type, respond to charging in different ways, and using the right
battery charger in the proper way will help preserve the life of your
Insuring Your Boat
Towing, Trailering and Tires
Getting Ready for Winter
Freshwater Game Fish
by the end of October, many of the lakes have “turned
over” for the winter. Morning steam rising from the water indicates
that the heat energy stored in the lake from the long hours of summer
daylight is beginning to return once again to the atmosphere as the
water begins its annual slumber and ultimate renewal. There is
perhaps still a little time left for one final outing, but most – if
not all – of you have taken your boats out of the water and gotten them
cleaned out, “winterized” and ready for next
spring’s trek back to your favorite fishing spots. You take very
good care of your boats, motors, poles, reels and other gear inside
the boat. But have you really taken the time to look after one
of the most important pieces of equipment that you have on board – your
Most of us take our boat batteries
for granted, in much the same manner as we do our car batteries.
I used to do that. In fact, I had a car that sat in the warmth
of the garage all winter. I thought that an occasional blast from
a charger would be enough to do the trick. Boy, was I wrong.
And the result was a new battery about every other year – until, after
a lecture from my mechanic, I got a little bit smarter about batteries.
A battery can lose – depending
on how and where it is stored – up to 30% of its charge per month –
just sitting around the house or garage! And there are all kinds of
things that affect battery charge and loss thereof (like temperature,
humidity, state of discharge, age of battery, etc). Most of us never
consider any of them. Not unlike young children,
batteries require loving care: call it maintenance. Getting the
right battery for the intended task is only part of the story – keeping
that battery healthy with the proper
charging and maintenance will ultimately ensure that you will have
the necessary power when you call for it!Which type of battery you choose
is based on your needs (deep cycle vs. starting), the capacity and lifespan
you are looking for and your budget requirements. Although I have
found that the subject of batteries and battery maintenance to be a
multi-faceted subject that encompasses many different topics, I am going
to limit my discussion to a few of the most important “basics”.
I want to briefly discuss:
There are two basic
types of 12-volt batteries:
-- or starting
-- batteries: These are designed specifically to start your
main engine. They are made with thinner and more numerous
lead plates inside, allowing for more surface area and thereby providing
the quick and massive amounts of energy required for tough starting
jobs. While the motor is running, the alternator inside will
easily and quickly replenish the used energy. If your boat
is powered by a newer model outboard with sophisticated computers,
pumps and sensors, you definitely want to make certain you have
enough starting power. It's a good idea to check your owner's manual
for the recommended MCA (Marine Cranking Amps: a measurement of
the number of amps a battery can deliver at 0 ° F for 30 seconds
and not drop below 7.2 volts) rating before shopping for a battery;
always choose one with a rating equal to or greater than the recommended
batteries: These are designed to power on-board electrical accessories
such as trolling motors, fish-finders, GPS, radios and the like.
In general, these batteries use energy at a much slower rate and
often don't get re-charged until the end of the day. This
deeper and more strenuous discharge is hard on a battery and requires
a different design type; the result is a battery with fewer but
much thicker lead plates that will withstand the deep cycling.
Deep-cycle batteries can withstand the rigors of several hundred
discharge/recharge cycles, while cranking batteries cannot.
It's important to understand
that, because of their design differences, substituting one battery
type for another is not a good idea. Use a cranking battery to
power a trolling motor will cause the battery to overheat and fail.
Besides leaving you without power in a moment of need, purchasing a
new battery will definitely be in your future. Substituting a
deep-cycle battery for a cranking battery will likely not provide the
power needed to start your outboard, possibly leaving you stranded a
long way from your dock. As it turns out, the design strengths
of each battery type also are their weaknesses in opposite applications.
Having said that,
that can perform both these functions -- to some extent -- also are
available. Keep in mind however, they will not supply the same
starting power as a true cranking battery, nor will they provide the
same number of discharge/recharge cycles as a dedicated deep-cycle battery.
As if all that doesn't make things
difficult enough, batteries can be further described according to the
configuration of the electrolyte inside the battery... leading us to
four categories that all have their own advantages and disadvantages.
Wet-Cell or Flooded-Cell
Batteries: Generally the most popular
and the type most all of us are familiar with, they have a number
of cells inside that contain a liquid mixture of sulfuric acid and
distilled water. They have the advantages of a somewhat lesser
price, a high number of discharge/recharge cycles (if properly maintained
and taken care of), are less likely to be damaged by overcharging
and are a bit lighter in weight than comparable AGM or Gel batteries.
The disadvantages are that most have vented, interior-accessible
designs, requiring regular inspection and making certain the cells
are topped off with distilled water. Venting also releases hydrogen
gas, meaning the battery compartment must be well ventilated. Other
drawbacks include possible spilling of corrosive battery acid, a
higher rate of self-discharge (6% to 7% per month) and the fact
that wet-cell batteries are more fragile in high-vibration environments
such as boats.
AGM is short for Absorbed Glass Mat, and these batteries feature
a dense filling of very fine absorbent fiberglass matting that is
saturated with acid/electrolyte and packed tightly between the battery's
plates. The design allows oxygen to recombine with hydrogen gas,
thus replenishing the battery's water content and alleviating the
need for refilling. Advantages include being truly maintenance
free (except for external cleaning). They are sealed (which
doesn't allow for gases or acid to leak), can be installed at any
angle, are shock and vibration resistant, have a relatively low
self-discharge rate -- ~ 3% per month) and can even withstand being
immersed in water (I guess that's in the event your boat gets swamped?).
The biggest disadvantages are that AGM batteries are more expensive,
are heavier and are quite sensitive to charging currents and voltages;
they are somewhat easy to overcharge, which can ultimately ruin
Gel batteries too, are much like wet-cell batteries in that they
are filled with liquid electrolyte. The difference is that
the electrolyte is gelled with silicates before the battery is sealed.
Like AGM batteries, they use the special technology that eliminates
the need for adding water. Advantages? They are maintenance
free, sealed, low-temperature tolerant, shock/vibration resistant
and have long cycle life. Their most notable advantage is resistance
that can damage other battery types. Gels have an internal self-discharge
rate less than 1 percent per month, so they can be stored for long
periods without being recharged. And because they aren't prone to
develop life-shortening plate sulfation when left uncharged, they
are a good choice for boaters who often forget to recharge batteries
promptly after use. The bad news is that these batteries are
often almost twice as expensive as comparable flooded-cell batteries
and are also fickle about charging; they require special chargers.
Lithium-ion batteries are among the emerging “super battery” technologies.
They have a high energy density and are excellent for deep cycle
applications. Compared to flooded batteries, lithium batteries deliver
a savings of up to 70 percent in volume and weight and can offer
three times as many charging cycles. They handle incredible amounts
of current and therefore can be recharged faster than any other
type. Currently in use onboard high-performance offshore racing
sailboats and others whose owners demand extreme weight savings
and cutting-edge performance, Lithium-ion may be the future...
Be prepared and willing to pay premium prices.
will destroy a battery
There are essentially
two things that will quickly and easily destroy your battery: either
1) undercharging it or 2) overcharging it. The majority of both
deep cycle and starting batteries are simply containers for a number
of lead-plates, filled with sulfuric acid. Undercharging them
will ultimately cause lead sulfate to accumulate on the plates; this
will eventually destroy the battery because the normal chemical reaction
will be unable to continue. Overcharging the battery will accelerate
the natural corrosion of the plates due to excess electrons being literally
boiled out of the electrolyte. Ultimately, the fluid boils away
and the plates are exposed to the air, which ruins them.
Have you ever
had a battery that seems to work well but “dies” much more quickly than
expected? The problem may be a battery that is heavily
– often the result of only light use (being discharged by only 15% or
so). The sulfuric acid has become concentrated on the battery’s
bottom and sulfate crystals have begun to form. And even though
a multi-meter will indicate that all is well in terms of voltage, the
of the battery has become severely reduced. Sure, the battery
will work just fine, but it will die much sooner than normal.
There are certain chargers that have a setting that will temporarily
boost the charging voltage for a brief period of time, causing a mixing
of the electrolyte, and dissolving the crystals. The process is
called equalization and can be done – depending on the manufacturer
– about once a year. But beware: this should only be done on wet
cell batteries; this same process can ruin other types.
And you will need to make sure that you disconnect
the batteries from the electrical system to prevent the higher voltage
from damaging other equipment.
come a long way since the 60’s. Back then, most – if not all –
wet cell batteries were dry to start with. In the storeroom of
the gas station at which I worked, there was a large box with a plastic
bag filled with electrolyte – sulfuric acid. I found out it was
acid the hard way; in filling a battery, I once managed to splash the
electrolyte all over my pants. I didn’t realize the power of the
stuff until my work pants got washed. They looked as if I had
been shot by a machine gun: one leg was nothing but holes! Now
there is an incredible variety of batteries that are available for every
imaginable use: marine starting & trolling, auto, agricultural,
industrial). They all have at least one thing in common: they
need to be maintained to some degree – even the “maintenance free” types.
They will lose their electrolyte during normal use and need to be checked;
all need to be recharged. Most of us still use the wet cell types
for marine applications, although there are essentially three distinct
types of lead acid batteries (see "Categories"
above) manufactured for marine applications, and any one type can be
designed and built for either starting or deep cycle applications. As
I mentioned, the gelled acid and AGM types are essentially maintenance
free since they are sealed. But because of this, be very careful
when recharging them; "smart charger" technology is required
or damage can easily result. They are also more expensive but
do have their advantages. The most important thing for the flooded
acid variety is to keep them full. Top them off with distilled
water only whenever possible, as minerals in tap water can contaminate
the electrolyte. Keep the terminal clamps clean and free of corrosion;
coat them with anti-corrosion spray or even petroleum jelly. Check
connections and keep them tight; watch for frayed wires and replace
them. And for a few bucks spent at your local auto parts store,
a Battery Hydrometer – used to check the specific gravity (concentration
of acid) is a good investment. It is a great way to determine
if one of the cells is bad. If the difference in specific gravity
is 30 points or more… it’s time to replace your battery!
Checkup and Storage
Whether or not
your boat is stored for the season in a warm garage or out in the cold,
your best bet is to remove all batteries and bring them inside.
A fully charged battery with a perfect electrolyte level can probably
withstand temperatures down to zero degrees without freezing.
But the colder it gets, the more easily a battery can discharge, and
therefore the more easily it can then freeze at higher temps.
If even one of the cells freezes, the battery is shot! Fully charge
them about once a month over the winter and they will be ready when
you are in the spring. Try to keep them off of concrete floors
if possible and cover the terminals to help prevent discharge.
The last thing you want is a dead battery on the launch ramp on opening
day, or a dead trolling motor battery.
No matter what kind of battery
chemistry you choose, follow these recommendations to get the best performance
and longest life from your batteries:
Stay with one battery chemistry
(flooded, gel or AGM). Each battery type requires specific charging
voltages and currents. Mixing battery types can result in under-
or over-charging, which may mean replacing all batteries on board
at the same time.
Never mix old batteries with
new ones in the same bank. Old batteries tend to pull down the new
ones to their deteriorated level.
Regulate charge voltages
based on battery temperature and acceptance (either manually or
with smart-sensing devices) to maximize battery life and reduce
charge time. Ensure that your charging system is capable of delivering
sufficient amperage to charge the battery banks efficiently.
Keep batteries clean, cool
Check terminal connectors
regularly to avoid loss of conductivity.
Check fluid levels and add
distilled water to flooded lead acid batteries when needed. Keep
batteries charged; leaving them in a discharged state for any length
of time will damage them and lower their capacity; it also reduces
Clean corrosion with a paste
of baking soda and water.
With summer now officially
here, I hope that most of you have either fished the opener somewhere
or are, like me, chomping at the bit to head to the lakes once again.
Make sure to check your batteries before
you head out. And when next October rolls around, you will perhaps
remember a few things from this article and make sure to take proper
care of those very important pieces of equipment: your batteries.
For information on charging and chargers, see my article on
Boat Batteries.See you
On the Lake! I
and use the
Dual Pro 15 Amp/Bank Professional Series 2 Bank Charger
in my 16' Lund - Mr. Pike Anniversary Edition!