Altronix SMP5CTX220 4A 12/24VDC Selectable Power Supply with Battery Backup
Overview
The Altronix SMP5CTX220 is a filtered, regulated DC power supply designed for professional security installations where both voltage flexibility and supervised backup power are non-negotiable. Supporting 12VDC or 24VDC output at up to 4A, and accepting either 115VAC or 230VAC input, this unit is purpose-built for integrators working across mixed-voltage infrastructure or deploying in regions with different mains standards. Housed in a large lockable cabinet measuring 13.5" x 13" x 3.25", the SMP5CTX220 gives you room for two sealed lead acid or gel batteries up to 7AH each — enough runtime to keep access control panels, door strikes, or camera infrastructure alive through a typical power interruption.
If you're sizing power supplies for an IP security camera deployment or an access control head-end, the SMP5CTX220 fits the profile of a rack-adjacent or wall-mounted central power node that serves multiple low-voltage devices off a single supervised output. Browse the full Altronix power and accessory line for companion products in this family.
Key Features
- Selectable 12VDC or 24VDC Output: A single SKU covers both common security device voltages. Lock in 12V for most IP cameras and door contacts, or switch to 24V for electric strikes and specific access control readers — no separate supply needed for mixed loads on a single project.
- 4A Continuous Output Current: At 4A, you have enough headroom to power multiple devices simultaneously — for context, a typical access control panel with two to four door readers pulls well under this ceiling. Budget your load at 80% of rated capacity to maintain headroom under inrush conditions.
- Dual Voltage AC Input (115VAC or 230VAC, 50/60Hz): The SMP5CTX220 accepts either North American or international mains voltage, making it usable in global deployments and on job sites where the mains supply is uncertain. Input draw tops out at 115VA on 230VAC input — a light load for any 15A branch circuit.
- Dual Battery Capacity — Up to Two 7AH Sealed Lead Acid Batteries: Two 12VDC/7AH batteries fit inside the enclosure. That's up to 14AH of backup capacity, which at a 2A load (roughly half the rated output) translates to approximately 5–6 hours of runtime depending on load — meaningful for access control or alarm scenarios where overnight outages can occur.
- AC Fail Supervision via Form C Contacts: Form C (SPDT) relay contacts for AC fail supervision let you wire a direct supervisory signal into your alarm panel or monitoring system. When mains power drops, the panel gets a hard-wired notification — not just a status LED on the box. That's the difference between catching a power fault during a break-in and discovering it the next morning.
- Low Battery Supervision via Form C Contacts: A separate Form C relay monitors battery state. If backup capacity degrades below threshold, your panel sees it immediately. On large sites where dozens of power supplies are distributed across floors or buildings, this supervisory output is what makes the difference between proactive maintenance and reactive failures.
- 0°C to 49°C Operating Range: Rated for operation in environments from freezing to well above room temperature — appropriate for most indoor IT closets, mechanical rooms, and security head-end spaces. Not rated for outdoor or uncontrolled environments; plan enclosure placement accordingly.
- Large Lockable Cabinet Enclosure (13.5" x 13" x 3.25"): The cabinet is sized for battery integration without external battery boxes cluttering the installation. Lockable construction satisfies most AHJ and UL installation requirements for supervised power supplies in commercial applications.
Integration and Compatibility
The SMP5CTX220 is compatible with a broad range of 12VDC and 24VDC security devices — access control panels, door strikes, magnetic locks, motion detectors, and low-voltage cameras. The selectable output voltage and Form C supervisory outputs make it straightforward to integrate with virtually any alarm panel or building management system that accepts dry contact inputs. Pair it with a compatible power supply distribution module from the Altronix line if you need to distribute output across multiple individually fused zones. For installations requiring PoE for IP cameras, this supply feeds PoE injectors or midspans on the 12V or 24V rail — verify your injector's input voltage requirements before wiring.
Frequently Asked Questions
Q: Can the SMP5CTX220 be used on 230VAC mains without modification?
A: Yes. The SMP5CTX220 accepts both 115VAC and 230VAC input at 50Hz or 60Hz. No internal jumper changes or external transformers are required — the unit is designed for both North American and international mains voltages.
Q: What batteries does the SMP5CTX220 support?
A: The enclosure accommodates up to two 12VDC sealed lead acid or gel-type batteries, each up to 7AH capacity. Flooded (wet cell) batteries are not compatible. Total onboard backup capacity is up to 14AH.
Q: What do the Form C supervision contacts connect to?
A: The AC Fail and Low Battery Form C (SPDT) relay outputs wire directly to a compatible alarm panel, FACP, or building management system dry contact input. These provide hardwired supervisory signals for both mains failure and battery degradation — they are not digital bus connections.
Q: What is the output current of the SMP5CTX220, and how should I calculate my load?
A: The SMP5CTX220 delivers up to 4A continuous at either 12VDC or 24VDC. As a general practice, size your connected load at 80% of rated output (3.2A) to maintain headroom under startup inrush from locks, motors, or relays.
Q: Is the SMP5CTX220 suitable for outdoor installation?
A: No. The operating temperature range is 0°C to 49°C and the enclosure is designed for indoor use. For outdoor or environmentally exposed locations, a separate weatherproof enclosure or rated outdoor housing would be required.
Q: Can the SMP5CTX220 power both 12V and 24V devices simultaneously?
A: No. The output voltage is selectable — either 12VDC or 24VDC — but not both simultaneously from a single unit. If your installation requires both voltages, plan for a second supply or a distribution board that accepts one voltage and provides regulated outputs at both levels.
The SMP5CTX220 is one of those workhorses I keep specifying for mid-size access control head-ends because of a specific combination that's hard to find in one box: dual AC input voltage, a genuinely useful 14AH battery capacity (two 7AH cells), and dual Form C supervisory contacts — all in a lockable cabinet that doesn't require a separate battery enclosure bolted alongside it. If you're deploying in a building where the electrician hasn't confirmed whether the IDF closet is wired for 115V or 230V before your team arrives, the SMP5CTX220 takes that variable off the table entirely.
Technical Highlights:
- Selectable 12/24VDC Output at 4A: One supply covers both common low-voltage security rails. At 4A rated output, budget to 3.2A (80%) for reliable long-term operation under inrush from mag-locks or relay coils.
- Dual Form C Supervision: Separate AC Fail and Low Battery SPDT relay contacts wire directly to your alarm panel — no polling, no software dependency. The panel sees power faults in real time, which matters on sites where the power supply is in a remote IDF room and not visible to on-site staff.
- 14AH Onboard Battery Capacity: Two 7AH sealed lead acid or gel cells fit inside the enclosure without expansion hardware. At a 2A load, expect roughly 5–6 hours of backup runtime — enough to cover most overnight outages on a small access control zone.
Deployment Considerations:
- The 0°C to 49°C operating range is fine for conditioned indoor spaces, but mechanical rooms that exceed 49°C in summer — common near HVAC equipment or in poorly ventilated equipment closets — will stress this unit. Verify ambient temperature before mounting.
- The output is selectable to one voltage at a time. If a project requires simultaneous 12V and 24V distribution (mixed mag-locks and strikes on the same head-end), either specify two SMP5CTX220 units or add a downstream distribution module that can handle both rails from a single input.
This supply is the right call for a 2–4 door access control installation where a supervised, battery-backed, voltage-flexible power node belongs in one tidy lockable cabinet — particularly in healthcare, education, or light industrial facilities where the AHJ expects documented supervisory outputs on every power source in the system.
