Altronix AL400ULXPD4 4A Dual-Voltage Power Supply with Battery Backup
The Altronix AL400ULXPD4 is a UL-listed dual-voltage power supply engineered for security infrastructure that demands uninterrupted DC power and fault detection. Rated for 4A output at 12VDC or 3A at 24VDC, this unit integrates battery backup and comprehensive supervision functions — AC Fail, Low Battery, and Battery Presence monitoring — so you get both continuous operation and real-time visibility into power system health. It arrives pre-mounted in a BC400 enclosure, reducing on-site assembly time and simplifying commissioning. This approach is standard for access control, surveillance, and alarm system deployments where power loss to locks, sensors, or auxiliary devices cannot be tolerated.
Key Features
- Dual-voltage output (12VDC or 24VDC, field-selectable): Match the voltage requirement of your end devices — locks, readers, sensors, or gate operators — without swapping units. The ability to configure on-site reduces inventory overhead and deployment flexibility in mixed-technology sites.
- 4A @ 12VDC / 3A @ 24VDC current delivery: Sufficient headroom for multi-load access control circuits, alarm panels, and auxiliary surveillance equipment. At 12VDC, you can power four typical electronic door locks (0.8–1.0A each) with margin; at 24VDC, the current limit serves lighter loads or a redundant pair of devices. Check your load schedule before deployment — exceeding these limits will trigger shutdown or fuse protection.
- Integrated battery backup: When AC input fails, the onboard battery maintains DC output without interruption. Holding power to access control locks, card readers, and exit devices for the duration of an outage preserves security posture and prevents unauthorized entry during extended power loss. Battery capacity depends on total load and is field-tested during commissioning.
- AC Fail supervision: Detects primary power loss and signals a contact closure or relay output to your control panel. This allows the system to log the event, trigger alerts, or initiate failover procedures — critical for compliance audits and incident response.
- Low Battery supervision: Monitors reserve capacity in the backup battery and signals when reserve drops below threshold. Prevents complete battery discharge and gives maintenance staff advance warning to schedule replacement before the next outage.
- Battery Presence detection: Confirms that a backup battery is physically present and connected. Catches installation errors or accidental disconnection before a power failure exposes the gap.
- UL Listed certification: Meets Underwriters Laboratories safety and performance standards. Insurance carriers and building authorities recognize UL listing, simplifying compliance verification and reducing project friction during inspection.
- BC400 enclosure (included): Steel, DIN-rail-mountable housing designed for utility closets, electrical panels, or equipment racks. Protects the power supply and battery from physical damage, dust, and accidental contact. Dimensions and terminal configuration optimized for standard cabinet integration.
Integration & Compatibility
The AL400ULXPD4 integrates into access control systems as the primary power source for distributed lock circuits, reader modules, and control relays. Supervision contacts wire directly to alarm panels or security control panels for event logging and alerting. Standard 12VDC or 24VDC output is compatible with any security device rated for those voltages — door locks, magnetic switches, solenoids, and relay coils. For CCTV systems, use the AL400ULXPD4 to power auxiliary equipment (pan/tilt motors, heaters, IR illuminators) rather than relying on camera-embedded supplies, which improves reliability and allows independent power supervision.
Before specifying, confirm that your total connected load (sum of all devices drawing power simultaneously) does not exceed 4A @ 12VDC or 3A @ 24VDC. If peak demand approaches these limits, consider a higher-capacity power supply in the Altronix family or a redundant pair of AL400ULXPD4 units on separate circuits. Consult the power supply sizing guide for load calculation methodology.
When to Choose a Different Model
If your application requires higher current output — for example, powering eight door locks at 1.2A each (9.6A total) — move to the Altronix AL624 or AL844 series, which offer 6A or 8A capacity respectively. If you need multiple independently supervised circuits (e.g., separate power feeds to two access control zones), evaluate dual-output or modular power supply configurations. If the environment is harsh (outdoor cabinet, high moisture), pair the AL400ULXPD4 with environmental monitoring or heater/fan modules available as accessories.
Warranty & Support
The AL400ULXPD4 includes a Lifetime Limited Warranty covering manufacturing defects in materials and workmanship. Refer to the full warranty terms for coverage scope and exclusions. Technical support and replacement parts are available through authorized Altronix distributors and integrators.
Frequently Asked Questions
Q: What capacity battery should I install in the AL400ULXPD4?
A: The AL400ULXPD4 ships ready for a 12VDC sealed lead-acid (SLA) battery, typically 7–18 Ah depending on required hold-up duration. For example, a 7 Ah battery powering two 1A locks at 12VDC provides approximately 3.5 hours of backup operation. Consult the datasheet or an Altronix applications engineer to select battery capacity based on your load profile and desired hold-up time.
Q: Can I set the output voltage to 24VDC and still draw 4A?
A: No. The AL400ULXPD4 is rated for 4A at 12VDC or 3A at 24VDC. At 24VDC, maximum output current drops to 3A due to internal power dissipation limits. If you need 4A at 24VDC, you will need a higher-capacity model.
Q: Does the AL400ULXPD4 include a battery, or do I need to purchase one separately?
A: The unit includes the charger and battery terminals but does not ship with a battery installed. You must procure and install a compatible sealed lead-acid battery separately — a common practice that allows integrators to right-size capacity for each deployment.
Q: How do I wire the AC Fail and Low Battery supervision outputs?
A: The AL400ULXPD4 provides normally open relay contacts for AC Fail and Low Battery events. These contacts close when a fault is detected, allowing you to wire them in series or parallel to alarm panel inputs, status LEDs, or remote alert systems. Consult the included wiring diagram for terminal assignments and contact ratings.
Q: Is the AL400ULXPD4 suitable for outdoor installations?
A: The BC400 enclosure provides basic protection from dust and mechanical damage but is not rated for direct outdoor exposure (rain, submersion). Install the unit indoors — in an electrical closet, utility room, or protected cabinet — and run power and supervision wiring to outdoor devices. For outdoor equipment, add a weatherproof sub-enclosure or cabinet with environmental monitoring.
Ted PerryPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
The Altronix AL400ULXPD4 is a straightforward, reliable choice for distributed access control power and surveillance auxiliary circuits where uninterrupted operation and fault visibility are non-negotiable. The 4A @ 12VDC and 3A @ 24VDC rating handles typical multi-lock and panel circuits, and the integrated AC Fail and Low Battery supervision functions eliminate the need for external monitoring relays — that simplification cuts wiring complexity and reduces failure points.
Technical Highlights:
- Dual-voltage selection (12VDC or 24VDC, field-configurable): Eliminates SKU proliferation. Order one model, set voltage on-site to match your device ecosystem. Especially useful in mixed-technology sites where some locks run 12V and panels run 24V.
- Battery backup with integrated charger: The onboard charging circuit maintains the battery in ready state and automatically supplies DC output during AC loss. No external charger or UPS module needed — reduces cabinet clutter and simplifies troubleshooting.
- Three supervision functions (AC Fail, Low Battery, Battery Presence): Relay contacts signal faults to your control panel. Low Battery warning gives maintenance advance notice to swap or charge the backup battery before capacity expires. Battery Presence detection prevents silent failures caused by loose or disconnected battery terminals.
Deployment Considerations:
- Battery not included: You must specify and install a compatible 12VDC sealed lead-acid battery. Get capacity wrong, and your hold-up time suffers. For a typical two-lock circuit (2A draw), a 7 Ah battery yields roughly 3.5 hours of backup. Size battery during design, not in the field.
- Current limits are firm: The AL400ULXPD4 cannot exceed 4A @ 12VDC or 3A @ 24VDC. If you're powering four locks at 1.2A each (4.8A total), this unit will not work — you need an AL624 or higher. Calculate total simultaneous load before ordering.
- BC400 enclosure is DIN-rail mount in indoor panels only: It's not weatherproof. If outdoor cable runs or remote cabinet installation is required, either keep the supply indoors and run supervised power out, or add an environmental cabinet with heater/fan.
The AL400ULXPD4 fits mid-sized access control nodes and alarm panel auxiliary supplies where continuous operation during AC loss is mandated but total current demand stays below 4A. It's particularly useful in retrofits where you're adding door locks to an existing panel without replacing the panel itself — the AL400ULXPD4 becomes the dedicated supply for the new locks, leaving the panel's original supply for sensors and logic. If you're designing a new system with higher current or more sophisticated power distribution, evaluate modular or redundant power architecture instead.
