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Storage Batteries
Installation.
General. Storage batteries in solar photovoltaic system shall be installed in accordance with the provisions of Article 480. The interconnected battery cells shall be considered grounded where the photovoltaic power source is installed in accordance with 690.41.
Dwellings.
Operating Voltage Storage batteries for dwellings shall have the cells connected so as to operate at less than 50 volts nominal. Lead-acid storage batteries for dwellings shall have no more than twenty-four-2-volt cells connected in series (48-volts nominal).
Exception: Where live parts are not accessible du4ring routine battery maintenance, a battery system voltage in accordance with 690.7 shall be permitted.
Guarding of Live Parts. Live parts of battery systems for dwellings shall be guarded to prevent accidental contact by persons or objects, regardless of voltage or battery type.
Current Limiting. A listed, current-limiting, overcurrent device shall be installed in each circuit adjacent to the batteries where the available short-circuit current from a battery or battery bank exceeds the interrupting or withstand ratings of other equipment in that circuit. The installation of current-limiting fuses shall comply with 690.16.
Battery Nonconductive Cases and Conductive Racks. Flooded, vented, lead-acid batteries, with more than twenty-four 2-volt cells connected in series (48 volts, nominal) shall not use conductive cases or shall not be installed in conductive cases. Conductive racks used to support the nonconducticve cases shall be permitted where no rack material is located within 150 mm (6 in.) of the tops of the nonconductive cases.
This requirement5 shall not apply to any type of valve-regulated lead-acid (VRLA) battery or any other types of sealed batteries that may require steel cvases for proper operation.
Disconnection of Series Battery Circuits. Battery circuits subject to field servicing, where more than twenty-four 2-volt cells are connected in series (48 volts, nominal), strings into segments of 24 cells or less for maintenance by qualified persons. Non-load-break bolted or plug-in disconnects shall be permitted.
Battery Maintenance Disconnecting Means. Battery installations, where there are more than twenty-four 2-volts cells contnected in series (48 volts, nominal), shall have a disconnecting means, accessible only to qualified persons, that disconnects the grounded circuit conductor(s) in the battery electrical system for maintenance. This disconnecting means shall not disconnect the grounded circuit conductor(s) for the remainder of the photovoltaic electrical system. A non-load-break-rated switch shall be permitted to be used as the disconnecting means.
Battery Systems of More Than 48 Volts. On photovoltaic systems where the battery system consists of more than twenty-four 2-volt cells connected in series (more than 48 volts, nominal), the battery system shall be permitted to operate with ungrounded conductors, provided the following conditions are met:
- The photovoltaic array source and output circuits shall comply with 690.41.
- The dc and ac load circuits shall be solidly grounded.
- All main ungrounded battery input/output circuit conductors shall be provided with switched disconnects and overcurrent protection.
- A ground-fault detector and indicator shall be installed to monitor for ground faults in the battery bank.
Charge Control.
General. Equipment shall be provided to control the charging process of the battery. Charge control shall not be required where the design of the photovoltaic source circuit is matched to the voltage rating and charge current requirements of the interconnected battery cells and the maximum charging current multiplied by 1 hour is less than 3 percent of the rated battery capacity expressed in ampere-hours or as recommended by the battery manufacturer.
All adjusting means for control of the charging process hall be accessible only to qualified persons.
Diversion Charge Controller.
Sole Means of Regulating Charging. A photovoltaic power system employing a diversion charge controller as the sole means of the regulating the charging of a battery shall be equipped with a second independent means to prevent overcharging of the battery.
Circuits with Direct-Current Diversion Charge Controller and Diversion Load. Circuits containing a dc diversion charge controller and a dc diversion load shall comply with the following:
- The current rating of the diversion load shall be less than or equal to the current rating of the diversion load charge controller. The voltage rating of the diversion load shall be greater than the maximum battery voltage. The power rating of the diversion load shall be at least 150 percent of the power rating of the photovoltaic array.
- The conductor ampacity and the rating of the overcurrent device for this circuit shall be at least 150 percent of the maximum current rating of the diversion charge controller.
PV Systems Using Utility-Interactive Inverters. Photovoltaic power systems using utility-interactive inverters to control battery state-of-charge by diverting excess power into the utility system shall comply (1) and (2).
- These systems shall not be required to comply with Circuits with Direct-Current Diversion Charge Controller and Diversion Load reqireme3nts above. The charge regulation circuits used shall comply with the requirements for Systems Over 600 Volts.
- These systems shall have a second, independent means of controlling the battery charging process for use when the utility is not present or when the primary charge controller fails or is disabled.
Battery Interconnections. Flexible cables, as identified in Article 400, in sizes 2/0 AWG and larger shall be permitted within the battery enclosure from battery terminals to a nearby junction box where they shall be connected to an approved wiring method. Flexible battery cables shall also be permitted between batteries and cells within the battery enclosure. Such cables shall be listed for hard service use and identified as moisture resistant.
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