A battery cycle is one complete discharge and recharge cycle (100 percent to 20 percent, and then back to 100 percent).
Battery life is directly related to how deep the battery is cycled each time. The most common cycles are 10,
20, and 50
percent.
Be cautious of ratings that list the number of cycles,
unless it also states how low the battery is
being
discharged.
For example, telephone type (float service) batteries have been advertised as having a 20-year life.
However, the
rating
only stands true
at five
percent depth of discharge (DOD), and the life span is much less
when used in an application
where the
batteries
are cycled deeper on a regular basis. Those same batteries are rated at less than five years if cycled
to 50 percent.
If a battery is discharged to 50 percent every day, it will last about twice as long as if it is cycled to 80 percent DOD.
If
cycled only 10 percent DOD, it will last about five times as long as one cycled to 50 percent.
The most practical number
to use is 50 percent DOD on a regular basis for the best use of effective storage and cost.
In addition, there is an upper limit.
A
battery that is continually cycled down
five
percent or
less will usually not last as
long as one cycled down 10 percent.
At very shallow cycles, lead dioxide tends to build up in clumps on the positive
plates rather than in an even layer.
Battery State/Voltage Chart
State of Charge
Specific Gravity
12 Volt
6 Volt
100%
1.265
12.7
6.3
75%
1.225
12.4
6.2
50%
1.190
12.2
6.1
25%
1.155
12.0
6.0
Discharged
1.120
11.9
6.0
This battery state voltage chart is used as an example. Your specific battery manufacturer's chart may vary.
Note: Both voltage and
specific gravity tests
should be performed with no load on the
batteries and without any supplied
charging. Turn off all draws and charging. Allow the batteries to stabilize, and then proceed with the test.
Battery Maintenance
Battery maintenance
is an important issue often overlooked by many RV owners and technicians.
As batteries age,
their
maintenance requirements change.
This means longer charging time and/or higher finish rate (higher amperage at
the
end of the charge).
Usually older, serviceable (unsealed) flooded
batteries need to be watered more often, as their
capacity decreases over time.
Before attempting battery maintenance, make sure all coach power sources are disabled (ignition, generator,
shore power, inverter).
Common Causes of Premature Battery Failure
Source: http://www.batterystuff.com/kb/artic...ry-basics.html
1. Deep discharges (leaving your lights on)
2. Misapplication
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Battery Cycle vs. Battery Life
