Altronix AL300ULB Dual-Voltage Power Supply/Charger 2.5A
The AL300ULB is a compact dual-voltage power supply and battery charger engineered for access control, alarm, and surveillance installations that require uninterrupted operation during AC mains loss. This unit accepts 28VAC/100VA input and delivers selectable 12VDC or 24VDC output at 2.5A maximum continuous current — enough to sustain a typical credential reader, magnetic lock solenoid, or small alarm signaler during a power failure. The AL300ULB integrates supervision contacts for both AC failure and battery low conditions, allowing integration with a control panel or monitoring system to alert staff of power events before they impact field operations.
Key Features
- Selectable 12VDC or 24VDC output: Switch jumper-selectable voltage to match your access control or alarm panel requirement — no need to stock two separate units for mixed-voltage deployments.
- 2.5A continuous current capacity: Delivers sufficient power for a single-door reader and electronic lock, or two concurrent alarm signaling devices. Verify your load total before installation to avoid nuisance shutdowns.
- 28VAC/100VA input specification: Designed to work with standard hardwired transformer taps found in most commercial HVAC or electrical panels. Confirm your site's available transformer capacity before commissioning.
- AC Failure supervision contact (Form C): Dry relay contact closes when mains AC is lost, enabling remote notification to a central station or building management system. Useful for unattended sites or overnight-monitored facilities.
- Battery Low supervision contact (Form C): Closes when the backup battery voltage drops below usable threshold, signaling that the battery has depleted and the system will lose power if AC is not restored soon.
- Sealed lead acid and gel-type battery compatibility: Supports standard 12V or 24V SLA or gel batteries (sold separately). Size your battery capacity based on load current and required runtime — a 5Ah battery provides roughly 2 hours of runtime at 2.5A draw, depending on temperature and battery age.
- Operating temperature range 0°C to 49°C (32°F to 120°F): Suitable for indoor electrical closets and equipment rooms. Do not install in unheated outdoor enclosures or environments subject to freezing, as this will degrade battery charging performance and may trigger false low-battery alarms.
- Board dimensions 7.0" × 4.0" × 1.75": Compact form factor fits most standard DIN-rail or shelf-mounted enclosures. Shipping enclosure is 10" × 8" × 4" — verify your receiving dock and installation cabinet space before ordering in bulk.
Integration & Compatibility
The AL300ULB pairs well with standalone access control panels, hardwired alarm systems, and small surveillance recording devices that require 12V or 24V DC backup power. The dual supervision contacts integrate directly with most control panels' alarm input circuits, enabling automatic event logging when AC fails or the battery is depleted. When specifying this unit, confirm the exact DC voltage requirement of your end device — switching output voltage requires opening the enclosure and adjusting a jumper, so select the correct voltage during initial installation to minimize callback visits.
When to Choose a Different Model
If your load exceeds 2.5A continuously, or if you require a higher-capacity battery charger with integrated UPS functionality, consider a larger Altronix model in the same product family. If you need AC output backup or three-state supervision (AC, battery, low-battery), evaluate alternative charger configurations. Always verify the total DC load (in amperes) of your connected devices against the AL300ULB's 2.5A maximum before final purchase.
Frequently Asked Questions
Q: Can I install the AL300ULB in an outdoor electrical enclosure?
A: The AL300ULB's operating temperature range is 0°C to 49°C (32°F to 120°F). Outdoor enclosures subject to temperatures below freezing or above 49°C will exceed the device's rated operating envelope and may damage the charger or prevent proper battery charging. Install only in climate-controlled electrical closets or conditioned equipment rooms.
Q: What size battery should I pair with the AL300ULB?
A: Battery capacity depends on your load current and required runtime. At 2.5A continuous draw, a 5Ah 12V or 24V SLA battery provides approximately 2 hours of runtime. For 4+ hours, use a 10Ah or 12Ah battery. Verify the battery's amp-hour rating and expected discharge curve with your battery supplier to confirm runtime meets your site's AC downtime requirements.
Q: Are the AC Failure and Battery Low contacts Form C (changeover)?
A: Yes. Both supervision contacts are Form C (single-pole double-throw), which means each contact has a common (COM) pin, a normally open (NO) pin, and a normally closed (NC) pin. This allows you to wire the alarm input as either an open-circuit detector or a closed-circuit alarm loop, depending on your panel's supervision mode.
Q: Can I use a gel-type battery instead of sealed lead acid?
A: Yes. The AL300ULB supports both sealed lead acid (SLA) and gel-type batteries. Gel batteries may offer slightly longer cycle life in some applications, but both types must be 12V or 24V DC rated and sized to your runtime requirements. Consult the battery manufacturer's datasheet to confirm the charger's voltage regulation is compatible with your specific gel-cell chemistry.
Q: Is the AL300ULB's output voltage field-selectable without opening the enclosure?
A: No. The output voltage (12VDC or 24VDC) is selected via an internal jumper on the main board. You must open the enclosure to access the jumper and reconfigure it. Set the voltage correctly during initial installation to avoid repeat site visits.
Q: What is the warranty on the AL300ULB?
A: The AL300ULB includes a Lifetime Limited Warranty from the manufacturer, covering defects in materials and workmanship under normal operating conditions within the specified temperature and electrical ratings.
Ted PerryPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
The AL300ULB is a no-frills companion for any single-door or dual-reader access control deployment that cannot tolerate a brief power outage. At 2.5A continuous current, it's sized right for a credential reader and an electronic strike or magnetic lock — not for powering a whole cabinet of gear. That constraint is actually its strength: it forces you to think clearly about load budgeting and battery runtime before you commission the site.
Technical Highlights:
- Jumper-selectable 12VDC or 24VDC output: Both voltages from one unit eliminates dual SKU management, but requires a trip back to the enclosure if you need to change voltage after installation. Plan your voltage during project planning, not in the field.
- Form C AC and battery supervision contacts: Dual-state reporting (closed on AC loss, closed on low battery) integrates cleanly with any control panel supporting dry relay input. Enables true remote notification of power events — crucial if your site doesn't have onsite staffing during off-hours.
- 2.5A @ 28VAC input: Standard transformer sizing for commercial buildings means you're unlikely to need a dedicated transformer run. Most electrical closets already have 28VAC available; confirm your building's transformer capacity to avoid nuisance trips during high-load periods (e.g., HVAC startup).
Deployment Considerations:
- Budget your battery size upfront — runtime scales linearly with amp-hour capacity, but oversizing a battery adds cost and requires extra enclosure volume. A 5Ah SLA covers 2 hours at full 2.5A load; larger facilities or critical access points may justify 10Ah+ batteries.
- Operating temperature limit of 49°C excludes hot electrical closets in sun-exposed buildings or data centers without climate control. If your site runs above 49°C, this unit will not charge the battery reliably, and you'll see false low-battery alarms.
- The AL300ULB does not supervise the battery itself — it only tells you when voltage drops below a threshold. If a battery internally fails or sulfates, the charger will not flag it until the next power loss occurs. Pair with periodic manual battery testing or consider a charger with built-in battery health monitoring for mission-critical doors.
Deploy the AL300ULB in small-footprint access control projects — single-door entrances, emergency egress verification, or gatehouse credential readers — where load is predictable and runtime expectations are measured in 2–4 hours, not overnight. It's not a universal backup power solution, but for its intended scope it's straightforward to install and troubleshoot.
