Differences between AGM,
GEL and FLOODED (wet) batteries
The most common battery
for Car, Marine, RV and solar applications is the lead-acid battery,
but there are many kinds. First let's look at what makes them similar:
Lead acid batteries use an electrolyte that consists of sulphuric acid,
and plates made up of lead to chemically store electrons. These
batteries consist of cells tied together to provide an adequate amount
of electrical energy storage for the need. The lead acid battery stores
a relatively large amount of power, for a relatively long time, in a
relatively small space. This portable power makes these batteries ideal
for these applications.
So what makes these
Even though inside all AGM,
GEL and flooded batteries contain lead acid, the internal construction
of the battery divides them into their respective categories.
Absorbed Glass Matte or
"AGM" batteries are the latest and greatest in lead-acid batteries. An
AGM battery uses a separator consisting of fiberglass between the plate
and wrappers to hold the electrolyte in its place with capillary
action. Combining the lead plates, electrolyte, and fiber glass
separation fibers in a confined space, AGM batteries create a "physical
bond" by way of capillary action. Similar to how water creeps up a
towel when it is put in a bathtub. This capillary action holds the
liquid inside the glass matting, making the AGM Battery "spill proof"
if it is ever exposed. Due to the tight packing of an AGM battery, it
is also the most impact resistant, and boasts the least internal
resistance. The lower internal resistance increases the output voltage,
decreases charging time, and reduces losses to heat as power flows
through the system. AGM Batteries then bring the trump card to the
table, they are maintenance free. Premium AGM batteries recombine the
gases produced internally, back into liquid. This recombination makes
the AGM battery maintenance free. No acid leaks, no mess while
charging, no corrosion on surrounding parts. You plug in these
batteries and walk away. AGM batteries can do
anything that flooded and GEL batteries can do, just better.
Flooded or "wet cell"
batteries are the most commonly used batteries on the market today.
Flooded batteries come in the widest variety of shapes and sizes due to
their widespread usage in a multitude of industries and applications.
Flooded batteries again use lead plates, a sulphuric acid electrolyte,
and plate separators but that is where it stops. Usually flooded
batteries are not sealed, and do not recombine the gases to liquids
internally. Instead, these gases are vented externally. Internal gases
produced are released directly to the environment. Through these same
vents can flow acid, steam, and condensation, leading to maintenance.
Flooded batteries do require maintenance, in the form of water, to
routinely replenish lost electrolyte through the vents. Lead plates
start to deteriorate when they touch the atmosphere, so if you fail to
maintain your batteries, they will corrode and fail. Flooded batteries
hold very good rates of charge for the price, but require more work.
Unfortunately due to the internal construction, flooded batteries have
the weakest internal construction, and some very high internal
GEL cell batteries are
also sealed just like the AGM battery listed above. That is where the
similarities end. A GEL battery uses a silica (sand) to turn the
sulphuric acid into a jelly like substance. This jelly is then used as
the electrolyte. Great care must be taken with GEL batteries not to
expose them to high amperage situations. High amperage situations can
literally 'SCAR' the jelly inside of a GEL battery, creating a pocket.
These pockets allow the plates to begin corroding, leading to premature
failure. GEL batteries should not be used for fast
charging/discharging, or high amperage charging/discharging situations.
Use the other types listed above for these high amperage situations.
Batteries are slightly stronger in regards to internal construction
than a flooded battery, but pale in comparison to the physical strength
of an AGM battery.
The Difference between
Starting & Deep Cycle Batteries
manufacturers produce two different types of batteries. One is designed
to give all it's available power in 20 seconds (starting batteries),
the other is designed to give it's power out over time measured in
minutes or hours (deep cycle batteries). The fundamental differences
are built in during the manufacturing process, so no amount of care can
make a starting battery perform as a deep cycle battery, you just have
to buy the right one. Therefore, please select the proper type of
battery for your application, or expect it not to work so well or for
too long. Below we have taken a few paragraphs to explain the point and
proper application for each battery type.
those designed to give their power in 20 seconds or less, are designed
to start motors. The starter motor on an engine needs this amount of
power to start, and then the engine makes enough power to replace it
with either an alternator, generator, or similar device. These
batteries are not designed for prolonged electrical usage, like
lighting the baseball diamond, or running the car stereo while you work
and the truck is off. These types of activities will inevitably lead to
a shortened life on your battery.
Starting batteries are
built with thin lead plates inside the battery. These thin plates
afford maximum amount of surface area for the chemical reaction inside
the battery. The ample surface area allows the chemical reaction
necessary to generate the electricity inside the battery to happen very
rapidly. However, these thin plates are not as resilient to the acid,
and break down more quickly when they are fully discharged. This
erosion of the plates is accelerated by deep or prolonged discharging.
Deep Cycle Batteries
Deep cycle batteries are
designed to give power out over time measured in minutes, hours, or
days. These batteries are designed to run electronics, or systems over
time. The telecom industry uses them to keep the cell phone towers
running. Your boat needs this power for radar, communications, and
navigation. You like having the power to run the kitchen as well,
stove, refrigerator, and microwave. There is not an electrical circuit
that can not be powered by deep cycle batteries when you have inverter
too. When you want power, you pull it from a deep cycle battery, push
it directly to the load or through an inverter to make AC power.
Install the proper plugs, and you can run the appliances from home.
Deep Cycle batteries are
built with very thick lead plates inside the battery. These thick
plates are able to sustain the acid without breaking down for a longer
period of time. The thicker plates are designed to be in the chemical
reaction that produces the electricity for a longer period before the
plates erode into the acid. This longer period allows you the customer
to run electronics for long periods of time, recharge the battery, and
see very little capacity lost.
Battery Charging 101
Charging a battery is
like filling a water tank, how long depends greatly on the size of the
hose. Fill the tank with the garden hose, your going to be there a
while, and may not have the right stuff for the job. Fill the tank with
the fire department's equipment, and you'll be done in a few minutes,
they always have the right tools. Same thing goes for battery chargers,
there is a right tool for the job, and size matters.
The right tool for the
job is important, no matter what you do. With a battery the same
applies. There are predominantly 3 types of battery chargers:
1. One stage battery
chargers - aka no brains, hook battery directly to generator
2. Two stage battery chargers - electrical computer brains to monitor
3. Three stage battery chargers - higher tech computer brains to
Long story short, if you
aren't as attentive for 24 hours as the computer will be, buy the
better charger. A two or three stage charger is mandatory if you don't
want to harm those batteries. Remember that your batteries weren't
cheap, and you are now protecting that investment. A computer chip is
basically your insurance.
Long story short, both 2
and 3 stage chargers flip through a series of stage, cycles, or modes
as they charge the battery. Each mode has pros and cons, and so by
using a symphony of these modes, you get the best results. Bulk mode
fills the battery as fast as the sticker on the side of the charger
allows, until it gets about 80% full. The bigger the charger, the
faster float mode runs up to 80% full. Next a charger flips to float or
absorption. Absorption finishes the battery quickly at higher voltages.
Float finishes the battery slowly (24-96 hours), and compensates for
sulfation in a prolonged storage scenario. For a complete explanation
of battery charging modes click here.
Batteries and the stuff
inside of them are not inherently stable. The electrons they contain
are desperately trying to move. As those electrons are held in check by
the chemicals in the battery, a bit of power is lost, perpetually. We
call this loss self discharge, or the self discharge rate for a
battery. Trickle chargers compensate for this phenomenon.
Trickle Chargers, Float
Chargers, Self Discharge Rates and How it Works Together
Batteries are not
inherently stable, they are holding onto power, electrons, that
desperately want to move. As they are held in check, a bit of power is
lost, perpetually. We call this loss self discharge, or the self
discharge rate for a battery. Generally a battery starts to self
discharge in the first seconds it is removed from the charger.
In the first 24 hours
the battery will lose between 2% (Premium AGM batteries) and 10% of
it's original charge. Again this process will repeat itself over the
next 30 days to leave an AGM battery at 90% (100% - 5% day 1 - 5% over
30 days = 90%) full. For a flooded battery one should expect to return
to an 70% charged battery in 30 days due to self discharge, (100% - 15%
day 1 - 15% over 30 days = 70%). The moral of
the story, if you want to leave a battery unattended, you need to
replace that lost current, or your well will run dry all by itself.
Some like the water tank
analogy; your battery is a power tank, like a water tank, but it has a
leak. If you don't charge it with a small trickle, the hole in the
bottom will drain your tank.
Trickle chargers are
designed to compensate for the self discharge loss involved with the
sustained storage of lead acid batteries.
When using large banks
of batteries and installed chargers, the trickle function is usually
inherent, but referred to as the float cycle.
A float cycle is a
charge at the same voltage as the full battery. If the battery is full
at 13.1 volts, 13.2 or 13.1 volts would be the proper trickle charge
for the longest life.
Should you want to keep
the batteries a little fresher (more charged), but not as long (months
between replacements), you tune that trickle or float voltage up a bit
to say 13.5 volts.
Battery Charger Warnings
Always read and follow
the manufacturer's battery charging instructions prior to connecting
your battery, or trying to charge a battery bank. Do not attempt to
charge batteries in a confined environment. Explosive and hazardous
gases are an inherent byproduct of battery charging, do think ahead.
Batteries contain sulphuric acid, and lead, both of which are hazardous
material if removed from the battery, or disposed of improperly, do
take care to be environmentally responsible. Batteries are useful, just