Altronix SMP3PM 12VDC 4A Board-Mount Power Supply with Battery Backup
The Altronix SMP3PM is a board-mount regulated power supply engineered for security and access control applications that cannot tolerate AC loss. It accepts a wide input range of 16–28VAC—making it compatible with most standard transformer outputs—and delivers up to 4A continuous at 12VDC. The built-in battery backup capability ensures that critical loads remain powered during AC outages, while integrated supervision circuitry continuously monitors AC status, battery presence, and low battery conditions. This is not a generic power supply; it's designed specifically for always-on security deployments where downtime is unacceptable.
Key Features
- 4A continuous output at 12VDC: Sufficient for mid-range loads such as multiple door locks, smaller camera arrays, or intercom systems without requiring a larger supply. Verify your peak inrush current during commissioning to avoid nuisance resets.
- 16–28VAC input acceptance: Works with a range of transformer sizes, reducing the need to stock multiple input variants. Simplifies integration across distributed security installations with varying power infrastructure.
- Integrated battery backup with AC fail detection: Automatically switches to battery-backed operation upon AC loss with no manual intervention. Supports your site's ability to maintain door access, alarm signaling, and critical communication during brief utility failures or planned shutdowns.
- Low battery supervision output: Provides a dry contact or logic-level signal when battery voltage drops below a usable threshold. Wire this to your alarm panel or building management system to trigger alerts before the battery is completely exhausted—critical for remote or unmanned locations.
- Battery presence detection: Monitors whether a backup battery is physically installed and in serviceable condition. Prevents false confidence in backup capability if a technician forgets to reinstall the battery after maintenance.
- Compact board-mount form factor (7" × 4" × 1"): Fits into enclosures, cabinet rails, or DIN-mount assemblies without consuming excessive real estate. Its thin profile makes it suitable for installations where space is limited, such as in the back of door controllers or within equipment racks.
- Lifetime Limited Warranty: Reflects manufacturer confidence in the design. Covers manufacturing defects, though not damage from misapplication or external faults (confirm specific terms with the product datasheet).
Integration & Compatibility
The SMP3PM is most commonly deployed as an auxiliary power module within larger access control systems, supplying regulated power to card readers, electronic locks, and request-to-exit (REX) buttons. It also supports distributed NVR and camera power infrastructure in multi-zone installations where centralized UPS protection is not practical. The supervision outputs integrate with any alarm panel or building automation system that accepts dry contacts or logic-level signals. Pair it with an appropriate 16–28VAC transformer and a sealed lead-acid or lithium backup battery (not included) matched to your load and desired runtime.
When to Choose a Different Model
If your application requires higher continuous output (above 4A), look to larger Altronix models in the same family that support 8A or 12A output. If you need integrated battery charging management for larger battery banks, consider Altronix supplies with more sophisticated charge-control circuits. If your input is 12VDC rather than 16–28VAC, the SMP3PM is not a fit—verify your transformer voltage before ordering.
Deployment Considerations
Confirm that your backup battery (sold separately) meets the SMP3PM's voltage and capacity requirements—undersizing the battery will result in short runtime, while oversizing increases cost and footprint unnecessarily. Test the AC fail and low battery supervision outputs during commissioning to ensure they integrate correctly with your alarm or monitoring system. In outdoor or humid environments, house the board-mount SMP3PM inside a sealed enclosure or cabinet to protect against corrosion and condensation. Allow adequate clearance around the unit for heat dissipation during continuous 4A operation.
Frequently Asked Questions
Q: Can I use the SMP3PM with a 12VAC transformer?
A: No. The input range is 16–28VAC. A 12VAC transformer will not provide sufficient voltage. Use a 20VAC or 24VAC transformer to stay safely within the specified range.
Q: Does the SMP3PM include a battery?
A: No. The battery is sold separately. You must source and install an appropriate sealed lead-acid or lithium battery matched to your runtime and load requirements before deploying the unit.
Q: What does the low battery supervision output do?
A: It provides a signal (typically a dry contact closure or logic-level transition) when battery voltage falls below a safe operating threshold. Wire this to your alarm panel or building management system so you receive an alert before the battery is completely depleted.
Q: Can I mount the SMP3PM vertically or at an angle?
A: The board-mount form factor is designed for horizontal mounting. Vertical or angled mounting may affect cooling and component reliability. Consult the datasheet for approved mounting orientations before installation.
Q: What's the maximum output I can draw continuously?
A: Up to 4A at 12VDC. Do not exceed this rating without external load distribution or a higher-capacity supply model.
Q: Does the SMP3PM work with my access control panel?
A: If your panel accepts 12VDC auxiliary power input and can work with the supervision signal outputs (AC fail, low battery, battery presence), then yes. Verify voltage and signal compatibility with your specific panel before ordering.
Ted PerryPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
I've specified the Altronix SMP3PM in dozens of access control retrofits, and it consistently delivers what's promised: reliable 12VDC regulation with battery backup that doesn't require a separate charge controller. The 4A output and 16–28VAC input window make it one of the more flexible mid-range supplies for distributed security—you don't have to buy different models for different transformer configurations across a multi-site deployment.
Technical Highlights:
- 4A continuous output with 16–28VAC input: Covers the majority of door lock arrays, multiple card readers, and auxiliary intercom loads without oversizing. The wide AC input range eliminates the need for custom transformers.
- AC fail detection with automatic battery switchover: No relay clicking or manual intervention—the SMP3PM seamlessly transitions to battery power within milliseconds. Your locks stay accessible during a utility blip or a planned shutdown.
- Low battery supervision and battery presence monitoring: These aren't just nice-to-haves. Low battery supervision tells your alarm panel to alert you before the battery dies in an unmanned location, and battery presence detection catches a technician who forgot to reinstall the backup after maintenance.
- Compact 7" × 4" × 1" board-mount footprint: Fits easily into DIN rail assemblies, enclosure interiors, and cabinet backs. Space efficiency matters when you're integrating power infrastructure into legacy control rooms.
Deployment Considerations:
- Battery sizing is on you. The SMP3PM does not include a battery—you must select and install one based on your load and desired runtime. Undersized batteries give you minutes of backup; oversized ones waste money and space. Validate the calculation during design.
- Confirm your AC input voltage. A 12VAC transformer will not work; the minimum is 16VAC. I've seen installations delayed because someone pulled a 12VAC supply off the shelf without checking the SMP3PM's datasheet first.
- Heat management: At full 4A output, the SMP3PM does generate heat. Do not bury it in a sealed enclosure without ventilation. Ensure airflow around the board during continuous operation.
Deploy the SMP3PM when you need reliable, unattended backup power for access control or small camera arrays, and when a full UPS installation is either overkill or budget-constrained. It's not flashy, but it works.
