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Gel/Lead-Acid Selector Function
According to battery manufacturers, the ideal charge regimen for
gel-cell and wet or flooded lead acid batteries differs somewhat.
The gelled electrolyte in a sealed battery may be lost or damaged
by high voltage and, once lost, cannot be replaced as it can
with a wet lead acid battery. Manufacturers of gel-cells usually
recommend an ideal charge voltage which is slightly lower for a
gel-cell than a lead acid battery.
However, when the charger is in the float voltage mode over
lengthier periods of time, gelled electrolyte in a sealed battery
is not susceptible to evaporation, as is the non-immobilized
electrolyte of a wet lead acid battery. This evaporation can be
accelerated by the applied voltage. Consequently, the ideal float
voltage is slightly higher for a gel-cell than a lead acid battery.
Some batteries are available which do not conform to
conventional descriptions as "gel-cell" or "lead-acid". If you are
unsure about your battery type, consult the manufacturer and use
the battery type selector setting which most closely conforms to the
recommended voltages. See the SPECIFICATIONS section for the
actual preset charge and float voltages for each battery type and
charger model.
H) Temperature Compensation Option
Installing the Probe
The optional Temperature Compensation Probe (available from
NEWMAR, model TP is provided with 25' of cable, with the probe
at one end and a keyed five-pin plug at the other. Installation of
the probe proceeds as follows:
1) Ensure A.C. power to the charger is shut off. The charger will go
into a shutdown mode if the temperature sensor is installed when
power is on.
2) If the drip shield is installed, remove it.
3) Refer to Figure 5. Locate the access plate on top of the PT-24-
45W and loosen the two Phillips head screws (DO NOT REMOVE
SCREWS.) Remove the access plate.
4) Locate the five-pin keyed receptacle which is recessed in the
black internal module. (Note: There may be a self-adhesive black
plastic cover approx. 1 1/2" x 1 1/2" square, over this receptacle,
remove cover.)
Battery
Temp° C
Lead Acid/AGM
Float
10
28.0
20
27.4
25
27.1
30*
26.8
40
26.2
50
25.6
* Output voltages with no Temperature Probe installed
10
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24 Volt
GEL
Absorption
Float
Absorption
29.6
28.4
29.0
27.8
28.7
27.5
28.4
27.2
27.8
26.6
27.2
26.0
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5) Route the temp. sensor end of the TP through the black bushing
on the access plate. Insert the 5 pin connector end of the TP firmly
into the receptacle. Replace the access plate and tighten the two
Phillips head screws.
6) It is recommended that the cable running to the battery be
secured with the provided cable clamps to prevent the plug from
accidentally being dislodged. One cable clamp tie point (10-32
Phillips head screw with washers) has been provided to secure the
cable as it exits the top of the charger.
7) The probe itself should be mounted on the inside of the battery
box, or more ideally, mounted directly onto one of the batteries
using a clamp or a small amount of silicon-type adhesive.
Important note: When wiring multiple units in parallel and using
the temperature compensation option, you must use a separate
probe for each charger, and the probes must be mounted close
together in the same battery box or on the same battery for proper
operation.
Temperature Compensation Probe Function
Because low battery temperature increases resistance to charging
and high battery temperature reduces impedance, requiring
a lower charge voltage, the ideal charging voltage will vary
depending on the temperature of the battery's environment when
it is being charged.
If a charger has a fixed output voltage which is ideal at, say 77° F,
that same output may cause a battery charged in a consistently
high temperature environment to be overcharged, resulting in
excessive loss of electrolyte. Conversely, if the batteries are located
in a consistently cool environment, they may be chronically
undercharged, resulting in sulfation of the battery plates. Either of
these two conditions will shorten battery life.
Therefore, the Phase Three charger is designed to utilize
an optional probe which provides automatic temperature
compensation. The function of the probe is to signal the charger to
fine tune its output voltage so that it is properly optimized for the
temperature of the battery or battery environment. The adjustment
rate is approximately -5 mV per cell per °C.
To give some idea of the effect of the temperature compensation
probe, the chart below lists the charge/float output voltages of the
charger when no sensor is installed (or when batteries are at 25°
C) and some sample charger output voltages at colder or hotter
battery temperatures with the probe installed:
Lead Acid/AGM
Float
Absorption
29.2
37.3
28.6
36.5
28.3
36.1
28.0
35.7
27.4
34.9
26.8
34.1
32 Volt
GEL
Float
Absorption
39.5
37.9
38.7
37.1
38.3
36.7
37.9
36.3
37.1
35.5
36.3
34.7
38.9
38.1
37.7
37.3
36.5
35.7
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