Xantrex Technology SW Series Page 67, Battery Type, Bulk Volts, Float Volts, Operation

OPERATION

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

Sealed Gel

Lead Acid battery

A.G.M.

Lead Acid battery

Maintenance-Free RV/Marine Lead Calcium Battery

Deep-Cycle, Liquid Electrolyte Lead Antimony Battery

NiCad or NiFe Alkaline Battery* (using 10 cells in series)

Bulk Volts

14.1VDC BULK

14.4VDC BULK

14.4VDC BULK

14.6VDC BULK

16.0VDC BULK

Float Volts

13.6VDC FLOAT

13.4VDC FLOAT

13.4VDC FLOAT

13.4VDC FLOAT

14.5VDC FLOAT

Equalizing Charge Process

Not Recommended - Consult manufacturer

Charge to 15.5 VDC or as per manufacturer

Not Recommended - Consult manufacturer

Charge to 15.5 VDC or as per manufacturer

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).

 2001 Xantrex Technology, Inc.	Telephone: 360/435-8826	SW Series Inverter/Charger
5916 - 195th Street N. E.	Fax: 360/435-2229	Part No. 2031-5
Arlington, WA 98223	www.traceengineering.com	Rev. C: February 2001

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