Altronix SMP5PMP4 Dual-Output 24VDC Power Supply & Battery Charger
The Altronix SMP5PMP4 is a compact 24VDC power supply and battery charger purpose-built for access control, door locks, and distributed security infrastructure requiring continuous output with battery backup during mains failure. The unit accepts a wide input range of 16–28VAC, delivering two independent 24VDC outputs with a combined maximum capacity of 4A — enough to power multiple door strikes, electronic locks, or control modules in small-to-medium installations. What separates this from a basic power supply is the integrated battery charging circuit: when AC input drops, the SMP5PMP4 automatically switches to battery power and triggers AC Fail supervision so you know the system is running on reserves.
Key Features
- 4 independently fused outputs: Each output is circuit-protected, so a short on one door lock or reader won't cascade to the rest of the installation. Isolation also means you can segment power delivery — one pair of outputs for door strikes, another for readers or access control panels — without cross-contamination of noise or load spikes.
- Dual 24VDC outputs: Two separate output connectors let you distribute power to different zones or panel inputs without daisy-chaining, reducing voltage drop across long runs. Maximum 4A combined capacity is realistic for 2–4 access points or a small multi-door system; don't expect to power a large distributed network from a single unit.
- Integrated battery charger with automatic switchover: The SMP5PMP4 monitors mains voltage and charges a backup battery (not included) automatically. When AC fails, it switches to battery supply without dropping the 24VDC output — critical for fail-safe or fail-secure locks that must maintain power during outages. No operator intervention required.
- Wide-range 16–28VAC input: Accepts secondary transformer outputs from legacy HVAC systems or non-standard power distribution, so you're not forced to install a dedicated transformer if one already exists in the cabinet. Reduces installation cost in retrofit scenarios.
- AC Fail, Low Battery, and Battery Presence supervision: Three discrete status signals notify your access control panel or central station if mains power is lost, battery charge drops below usable threshold, or the backup battery is missing or disconnected. Supervision integrates with standard alarm panels supporting supervised auxiliary outputs.
- Compact form factor (7" × 4" × 1"): Fits inside standard access control cabinets or DIN rail enclosures without consuming significant real estate. Lightweight enough for wall-mounted installations where cabinet space is premium.
- CE mark compliance: Meets European electrical safety and EMC standards, required for installations in EU territories or projects with European equipment certification requirements.
- Lifetime Limited Warranty: Manufacturer stands behind the unit for the lifetime of the original owner, reducing long-term replacement costs and underscoring confidence in the design.
Integration & Compatibility
The SMP5PMP4 is panel-agnostic — it works with any access control system that expects 24VDC input (Salto, HID, Bosch, Honeywell, Kaba, or proprietary controllers). The three supervision outputs (AC Fail, Low Battery, Battery Presence) are dry contact signals compatible with any alarm panel or controller that monitors supervised auxiliary inputs. Battery selection is your responsibility: the unit is designed for standard sealed lead-acid batteries (12V or 24V configurations, depending on your circuit design); consult the product datasheet for recommended amp-hour ratings and charge current limits. Avoid oversizing the battery — excessive amp-hours will extend charge time and heat dissipation in the supply.
When to Choose a Different Model
If you need higher current capacity (more than 4A) or more outputs, explore higher-capacity Altronix power supply models in the same family. If your installation does not require battery backup or supervision, a basic non-regulated 24VDC supply costs less. If you're powering high-current loads like electromagnetic locks rated for 6–12A, the SMP5PMP4 will undersupply and may not meet the duty cycle; step up to a purpose-designed power amplifier or larger charger supply.
Frequently Asked Questions
Q: Does the SMP5PMP4 require an external battery?
A: Yes. The unit includes the charger circuit, but you must provision a separate 12VDC or 24VDC sealed lead-acid battery. Consult the product datasheet for recommended amp-hour ratings and charging current limits specific to your backup duration requirement.
Q: What happens to the 24VDC output if AC mains fails?
A: The SMP5PMP4 automatically switches to battery power. The 24VDC outputs remain active as long as battery charge is sufficient; Low Battery supervision will alert you when charge drops below usable threshold.
Q: Can I use the SMP5PMP4 with a standard 120VAC transformer, or do I need a special secondary?
A: The unit accepts 16–28VAC input, so a standard 24VAC secondary transformer works fine. Verify your transformer rating falls within that window before wiring.
Q: What is the maximum battery capacity I can charge with this supply?
A: Charging current and amp-hour limits are specified in the product datasheet. Oversizing the battery will extend charge time and cause excessive heat; follow manufacturer guidance for your backup duration target.
Q: Does the SMP5PMP4 work with PoE-powered devices?
A: No. This is a 24VDC supply for access control and low-voltage security systems. It is not suitable for PoE cameras or network devices, which require 48VDC PoE injectors or PoE switches.
Q: Is the SMP5PMP4 NDAA or TAA compliant?
A: No compliance certifications beyond CE are listed in available documentation. If NDAA or other government procurement compliance is required, contact Altronix directly for statement of compliance.
Ted PerryPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
The Altronix SMP5PMP4 is a workhorse for access control backup power in small-to-medium deployments — exactly the kind of unglamorous but essential piece you don't think about until mains power drops and your fail-safe locks go limp. The dual 24VDC outputs with integrated battery charger and three supervision signals (AC Fail, Low Battery, Battery Presence) mean you have real-time visibility into power status without hunting through cabinet lights.
Technical Highlights:
- 4A @ 24VDC capacity with 4 independent fused outputs: Enough headroom for 2–4 door strikes or a small multi-zone access panel. The independent fusing is the win here — a shorted lock on one circuit won't collapse power to the others, and you isolate noise coupling between circuits.
- 16–28VAC input tolerance: Real installations have transformer voltage variation; this window is wide enough to accommodate aging transformers or non-standard secondary outputs. Fewer compatibility calls to the site.
- Automatic switchover to battery with three supervision signals: The SMP5PMP4 doesn't require your central station to monitor a relay; supervision outputs are dry contacts the panel understands. When AC fails, you know it immediately, not 10 minutes later when someone can't unlock the front door.
- Compact 7" × 4" × 1" footprint: Fits inside a standard 3-gang or 4-gang access control cabinet. No retrofit enclosure needed on most retrofits.
Deployment Considerations:
- Battery capacity and amp-hour rating are your responsibility — the datasheet will specify maximum charging current and recommended battery type. Undersizing the battery defeats the backup; oversizing extends charge cycles and generates heat. Size for your actual fail-safe duration target (typically 24–72 hours for small installations).
- The 4A cap is a hard ceiling. If you're powering multiple 1.5A door strikes plus a control panel, you're already at 75% of available current. Don't stack loads on the assumption there's margin — there isn't much.
- Wide input range is a feature, but verify your transformer output sits in the 16–28VAC window before installation. An over-voltage transformer will damage the supply.
Deploy the SMP5PMP4 where you have 2–4 access points, battery backup is a contractual requirement, and cabinet space is tight. It's not a panel power supply for large distributed systems — that's where you move to a larger Altronix charger or a distributed power controller. For a small office, warehouse receiving area, or server room needing fail-safe door control with supervision, this unit pays for itself the first time mains power hiccups and your locks stay powered.
