Xantrex Technology SW Series - Manual (Page 75)

OPERATION
 2001 Xantrex Technology, Inc.
5916 - 195th Street N. E.
Arlington, WA 98223
Telephone: 360/435-8826
Fax: 360/435-2229
www.traceengineering.com
SW Series Inverter/Charger
Part No. 2031-5
Rev. C: February 2001
Page
67
Once the battery voltage nears the BULK VOLTS DC setting, the voltage will be held at this level while the
current into the battery tapers off. The time allowed for this tapering period is called the ABSORPTION
TIME period. This setting is very important for systems which use generators since it determines how long
a generator will run and when the generator shuts off. Using a generator to “trickle” charge a battery is not
efficient and should be avoided. Some users may want to decrease the ABSORPTION TIME to keep
generator-running time to a minimum. This may result in the batteries not being fully charged. The higher
the BULK VOLTS DC setting and the longer the ABSORPTION TIME period, the more fully charged the
battery would be when the charger is shut off. Often, the generator is used only to “BULK CHARGE” the
battery and the solar array is allowed to trickle charge the battery to a full charge condition.
The following chart provides a guideline in setting the battery charger settings for several different types of
batteries. The battery manufacturer is the best source of information and should be consulted if your
battery type is not shown. Since the settings also depend on the system design, other factors may apply.
Table 4, Charging Setpoints For Common Battery Types
TYPICAL BULK AND FLOAT SETPOINTS FOR COMMON BATTERY TYPES
Battery Type Bulk Volts Float Volts Equalizing Charge Process
Sealed Gel
Lead Acid battery
14.1 VDC BULK 13.6 VDC FLOAT Not Recommended - Consult manufacturer
A.G.M.
Lead Acid battery
14.4 VDC BULK 13.4 VDC FLOAT Charge to 15.5 VDC or as per manufacturer
Maintenance-Free RV/Marine
Lead Calcium Battery
14.4 VDC BULK 13.4 VDC FLOAT Not Recommended - Consult manufacturer
Deep-Cycle, Liquid Electrolyte
Lead Antimony Battery
14.6 VDC BULK 13.4 VDC FLOAT Charge to 15.5 VDC or as per manufacturer
NiCad or NiFe Alkaline Battery*
(using 10 cells in series)
16.0 VDC BULK 14.5 VDC FLOAT Consult manufacturer
Note: Values shown are for 12 volt systems. For 24 volt systems multiply the settings shown by 2.
For 48 volt systems multiply the settings shown by 4. These settings are guidelines, refer to your
battery manufacturer for specific settings.
EQUALIZING BATTERIES (UNSEALED OR VENTED BATTERIES ONLY)
In many of the inverter/charger applications, batteries are subjected to less than ideal operating
conditions. This can result in significant differences in the state-of-charge level between the individual
battery cells. Furthermore, the low charge rates and extended periods at partial charge levels can result in
both stratified battery electrolyte and inactive areas of battery plate material. If the condition is allowed to
remain for extended periods of time, the battery can “sulfate” and become unusable.
To correct this condition, many manufacturers recommend a periodic “equalization” charge to mix up the
electrolyte, re-activate unused battery plate material, and bring up all of the individual cells to a full state of
charge. This requires that the battery be given a controlled “overcharge” by increasing the charge voltage
for a limited period of time. The voltage and time required are both dependent upon the amount of
correction required. The more frequently the batteries are equalized, the lower the equalize voltage and
shorter the time period.
Equalizing a battery is only recommended on unsealed or vented batteries. The process will cause the
electrolyte to gas and will release hydrogen and oxygen in the process. The chance of explosion due to
the accumulation of these gasses is therefore a realistic hazard. The batteries must be provided with good
ventilation with no ignition sources present. Some users have found that the battery cell caps are subject
to clogging during an equalization charge and therefore remove them during this process. Since the
batteries may rapidly bubble while being charged, it is advised that the battery be refilled only after the
equalization process is finished (if the battery electrolyte level is low, add enough to cover the plates
before charging).