IEEE 937:2019 pdf free download – IEEE Recommended Practicefor Installation and Maintenanceof Lead-Acid Batteries for Photovoltaic (PV) Systems
5.2.4 Environmental considerations
The following environmental aspects should be considered during the design or selection of the batteryenclosure:
a)The enclosure shall be ventilated, either by natural or induced means, to prevent the accumulation of an explosive hydrogen mixture, and to limit the accumulation of other hazardous gases. The hydrogenconcentration shall be limited to less than 2% by volume.The enclosure design should either avoidcreation of difficult-to-ventilate areas,including false ceilings, or make adequate provision for theirventilation. The amount of hydrogen released is typically very small under most conditions, and noextra mechanical ventilation is usually necessary if the battery enclosure is not completely “scaled.”See IEEE Std 1635TM [B5] for further information and expected hydrogen gas release.
b)To prevent battery damage, the enclosure should be designed to maintain the electrolyte temperature above its freezing point. The temperature at which the electrolyte will freeze for a given battery stateof charge and operating-specific gravity may be obtained from the battery manufacturer.Extremelyhigh electrolyte temperatures may cause excessive water usage and may damage the battery. Batterymanufacturers may recommend a maximum operating temperature for their batteries.
e)Acell electrolyte temperature of 25 °C is normally the basis for rated performance in North America.
A location where this temperature can be maintained at or below this level should contribute tooptimum battery life.Either passive or active means to reduce temperature excursions from 25 °Cshould be considered. Passive means can include partial burial of enclosures, color of exterior finish,and insulation.Active means can include forced-air ventilation.
NOTE—If the clectrolytc tcmperature varics from optimum, sizing may be affected.
d)Temperature differences between cells within the battery should be limited to 3 °C. Localized heat sources, including direct sunlight, radiators, steam pipes, and space heaters should be avoided.
e)llumination of enclosures during time of maintenance should be adequate for the safety and effectiveness of personnel.
6.5 Initial charging procedure
lt may be desirable to perform an initial charge to bring the battery to a fully charged condition, especially forVLA batteries, and to confirm all cells are equally charged. Dry-charged batteries must be activated prior toperforming this procedure (see Annex A).
NOTE 1—Field conditions may prevent strict adherence to the following procedure.NOTE2—The system load should not be connected at this time.
The preferred method is to charge the battery at a constant voltage.This should be done in accordance with themanufacturer ‘s recommendation.Unless otherwise specified, if any cell temperature exceeds 43 °C, interruptor reduce the charge until the temperature has dropped to 38°C, at which time charging may be resumed.Seethe battery manufacturer’s recommendations for more information.
The charge is complete and the battery is fully charged when the cell voltages and the charging current havenot changed in three consecutive hours. The state of charge can be estimated by taking measurements of theterminal voltages and charging current, and by using charging curves available from the manufacturer. Thespecific gravity of vented cells may be used to estimate the cell’s state of charge; however, this method dependson additional factors. If the specific gravity is out of the manufacturer ‘s recommended range after stable cellvoltages and currents have been achieved, refer to the manufacturer’s instructions for corrective actions.
lf necessary for vented cells, add water of the quality and quantity specified by the manufacturer at thecompletion of the initial charging procedure.
NOTE3—Dry-charged cell electrolyte levels should be adjusted using electrolyte of the specified specific gravity.