Reliable 110VAC to 12VDC converter with 3-stage smart charging. Compatible with Lithium, AGM, and Lead Acid batteries. 800W continuous output.
The PowerMax PM3-55A is a dependable AC to DC converter and battery charger that converts 110VAC shore power or grid power into clean, regulated 12VDC power for charging batteries and powering 12-volt equipment. With a robust 55-amp continuous output (800 watts), this converter provides excellent performance for small to medium-sized battery banks while simultaneously powering all your 12V devices.
Featuring advanced 3-stage smart charging technology, the PM3-55A automatically adjusts its charging profile to match your battery's needs: bulk charging at 14.6V for rapid recharge, normal charging at 13.6V for safe completion, and float charging at 13.2V for long-term maintenance. The unit also offers a fixed voltage mode with adjustable output from 13.0V to 16.5V, making it compatible with ALL battery types including LiFePO4 lithium, AGM, gel cell, and traditional lead acid batteries.
As a direct replacement for WFCO WF-9855 converters, the PM3-55A installs easily in RVs, boats, off-grid solar systems, automotive applications, and anywhere reliable 12V power is needed. Its efficient switch-mode design delivers over 85% efficiency with minimal heat generation, while built-in protection against reverse polarity, overload, and thermal issues ensures safe, reliable operation for years to come.
800W continuous power - charges 110Ah battery in 2 hours, 220Ah bank in 4 hours
Automatic charging profile: 14.6V Bulk, 13.6V Normal, 13.2V Float for optimal battery health
Fixed mode with 13.0V-16.5V adjustment - perfect for lithium batteries and custom applications
Works with Lithium LiFePO4, AGM, Gel Cell, Flooded Lead Acid - all battery types supported
Stage 1 - Bulk Charging (14.6V): When your battery is depleted (below 80% state of charge), the PM3-55A delivers maximum current at 14.6 volts to rapidly restore capacity. This "boost" mode brings batteries back to life quickly after heavy discharge. The converter stays in bulk mode as long as the battery can accept the full 55 amps. Stage 2 - Normal Charging (13.6V): Once the battery reaches approximately 80% charge and can no longer accept full current, voltage drops to 13.6V for safe, controlled charging to 100% capacity. This absorption phase ensures batteries are fully charged without overcharging damage. The PM3-55A simultaneously powers all your 12V devices during this stage. Stage 3 - Float/Storage (13.2V): After batteries reach full charge, the converter automatically switches to 13.2V float mode to maintain charge without overcharging. This trickle charge keeps batteries fresh during storage or light use, preventing sulfation and extending battery life. Perfect for RVs plugged in at home between trips. Automatic Mode Switching: The PM3-55A constantly monitors battery voltage and load conditions, automatically transitioning between charging stages as needed. When you turn on appliances that draw power, the converter instantly provides current while adjusting the charging profile. This intelligent system works 24/7 with zero user intervention required.
Small to Medium RVs & Travel Trailers: Direct replacement for WFCO WF-9855 converters. Powers all 12V lighting, water pumps, slide-outs, awnings, and electronics while rapidly charging house battery banks. Perfect for travel trailers, pop-up campers, and smaller Class C motorhomes with 100-220Ah battery capacity. Off-Grid Cabins & Solar Systems: Converts AC power from generators or grid-tied inverters into clean 12VDC for battery charging. Works alongside solar charge controllers for faster battery recovery during low-sun periods or high-demand situations. Marine Applications: Charges deep-cycle marine batteries when connected to shore power at the marina. Powers 12V electronics, navigation equipment, bilge pumps, and cabin lighting while keeping batteries topped off. Automotive & Emergency Vehicles: Powers car audio systems, emergency vehicle equipment, and mobile workshops. Fast charging between uses means less downtime and more performance. Backup Power Systems: Maintains battery banks for emergency backup power, communications equipment, and critical infrastructure. Float mode keeps batteries ready for instant use during power outages. LiFePO4 Lithium Battery Systems: Adjustable voltage mode (13.0V-16.5V) allows precise matching to lithium battery specifications. Set to 14.4V or 14.6V for optimal lithium charging without battery management system conflict. Telecommunications & Remote Monitoring: Reliable power for radio equipment, cellular sites, internet equipment, and remote monitoring systems. Converts generator power into clean DC for sensitive electronics.
Certified Electrician Installation Required • Professional Installation Mandatory: All PowerMax converters must be installed by a certified electrician per NEC code requirements. • Ventilation Critical: Minimum 1" free air space required at each end for proper cooling. Do NOT install in zero-clearance compartments. • AC Circuit Requirements: Connect to dedicated 15-amp 120VAC circuit within 36" of converter. Do NOT share circuit with high-draw appliances. • Wire Sizing: Use minimum 8 AWG copper wire for DC output connections. Larger wire recommended for long runs to minimize voltage drop. • Battery Disconnect: ALWAYS disconnect battery positive (+) terminal BEFORE connecting converter to prevent sparks and reversed polarity damage. • Never in Flammable Storage: DO NOT install in compartments containing batteries, gasoline, propane, or other flammable materials. • Proper Grounding: Connect 8 AWG ground wire from chassis to converter bonding lug for safety and code compliance. • Terminal Torque: Tighten all DC connections securely - loose connections cause overheating and fire risk.
In The Box: • PM3-55A Converter/Charger Unit • Built-in 36" AC Power Cord • Chassis Bonding Lug (Pre-installed) • Mounting Flanges with Holes • Reversed-Battery Fuses (Internal) • Owner's Manual with Wiring Diagrams • Warranty Documentation NOT Included (Required for Installation): • 8 AWG or larger DC wiring • Wire terminals/lugs for DC connections • Mounting screws/bolts • 8 AWG chassis ground wire • Professional electrician installation service
Compare the PM3-55A with other models in the PM3 Series to find the right converter for your power requirements.
Estimated time to charge from 50% to 100% state of charge (bulk + absorption phases). Actual times vary based on battery type, temperature, and condition.
Note: Charging times assume battery can accept full 55A charge rate. Absorption phase may take additional 30-60 minutes to reach 100% capacity. Lithium batteries typically charge faster than lead acid due to higher charge acceptance rates.
Why the PM3-55A is Perfect for Lithium: The PowerMax PM3-55A offers adjustable voltage output (13.0V-16.5V) that allows precise matching to your lithium battery manufacturer's specifications. Most LiFePO4 batteries charge optimally at 14.4V to 14.6V, and the PM3-55A can deliver exactly that voltage continuously. The 55-amp output is ideal for lithium banks from 100Ah to 200Ah, providing safe charge rates without overwhelming the battery management system. Setting Fixed Voltage Mode for Lithium: 1. With the converter unplugged, locate the two switches on the side of the unit 2. Move Switch A (right) to "Fixed Voltage" position 3. Plug the converter into 120VAC power 4. Using a voltmeter on the DC output terminals, adjust Switch B (up/down dial) until you reach your desired voltage 5. Common lithium settings: 14.4V (most conservative), 14.6V (faster charging), or per your battery manufacturer's specs 6. Once set, the converter will maintain this exact voltage every time it's powered on Important Lithium Considerations: • Consult your battery manufacturer's charging specifications before setting voltage • Battle Born recommends 14.4V | RELiON recommends 14.6V | Lithionics recommends 14.4V • Ensure your lithium battery has a proper Battery Management System (BMS) that will disconnect charging if cells become imbalanced • The PM3-55A's 55-amp output is safe for most lithium banks 110Ah and larger (0.5C charge rate or less) • Lithium batteries charge much faster than lead acid - expect 50% faster charging times • Monitor first few charge cycles to ensure battery BMS and converter work together properly Returning to 3-Stage Mode: To switch back to standard 3-stage lead acid charging, power down the unit, move Switch A back to "Three Stage" position, power up, and use Switch B to adjust voltage to 14.6V with a voltmeter.
Product Documentation: Download PM3 Series Owner's Manual (PDF) Download PM3 Series Specification Sheet (PDF) Lithium Battery Resources: Using PowerMax with Battle Born Batteries (External Link) Warranty Information: 2-Year Limited Manufacturer's Warranty Covers defects in materials and workmanship under normal use No forms required - call tech support for rapid replacement Replacement unit shipped promptly upon defect confirmation Return shipping arranged for defective unit Company Website: www.powermaxconverters.com PowerMax Converters 5107 Lena Road, Suite 108 Bradenton, FL 34211
A: Yes, the PM3-55A is an excellent choice for most travel trailers and represents the most popular converter size for this application. Here's why it works so well: Typical Travel Trailer Power Requirements: A standard travel trailer (20-30 feet) typically has 100-200Ah of battery capacity and runs the following 12V loads: LED lighting (10-15 amps total), water pump (8-10 amps when running), furnace fan (5-8 amps), USB chargers and electronics (5-8 amps), awning motor (15 amps for 30 seconds), slide-out motors (15-20 amps for 30 seconds). Total continuous loads are typically 25-35 amps, with brief spikes to 50 amps when pumps or motors activate. PM3-55A Performance: The converter delivers 55 amps continuously, which easily handles these loads while charging batteries at 20-30 amps simultaneously. After a day of boondocking that drains batteries to 50%, the PM3-55A can fully recharge a 200Ah battery bank in 3-4 hours while powering all your lights and appliances. When to Consider Upgrading: You might need the PM3-65A or PM3-75A if: (1) You have 300Ah+ of batteries and want faster charging, (2) You frequently run high-draw equipment like power inverters, (3) You have residential appliances that draw significant 12V power. Real-world feedback: Most RV owners with the PM3-55A report excellent performance and rarely come close to maxing out the converter's capacity. It's the "Goldilocks" size - powerful enough for typical RV use, but not overkill that wastes money or requires heavier AC wiring. If your RV currently has a WFCO WF-9855 (55 amp), the PowerMax PM3-55A is a perfect direct replacement with improved features and reliability.
A: The PM3-55A is a direct drop-in replacement for the WFCO WF-9855 with several important improvements that justify the upgrade. Both are 55-amp converters with the same physical footprint, but the PowerMax offers: (1) Adjustable voltage output for lithium batteries - The PM3-55A has a fixed voltage mode (13.0V-16.5V adjustable) that allows proper charging of LiFePO4 lithium batteries. The WFCO WF-9855 is designed only for lead acid batteries and lacks voltage adjustment. If you upgrade to lithium batteries (or plan to), the PM3-55A is essential. (2) True 3-stage smart charging - More sophisticated charging algorithm (Bulk/Normal/Float at 14.6V/13.6V/13.2V) compared to WFCO's simpler charging profile. This extends battery life and ensures complete charging. (3) Quieter operation - Temperature-controlled proportional fan adjusts speed based on load and heat. Runs quietly during light use, full speed only when needed. WFCO fans often run at constant speed regardless of load. (4) Better reliability - PowerMax converters have an excellent reputation for long-term reliability with lower failure rates than comparable WFCO models. (5) Same efficiency and AC requirements - Both achieve >85% efficiency and use standard 15-amp AC circuits, so electrical requirements are identical. Installation: The PM3-55A uses the same mounting holes and wire connections as the WF-9855. Installation takes 30-60 minutes for an RV technician. Many RV owners perform upgrades themselves following the included instructions. Bottom line: If your WFCO WF-9855 is still working, the upgrade is optional but recommended if you want lithium compatibility or quieter operation. If it's failed, the PM3-55A is the superior replacement choice.
A: Yes, absolutely - the PM3-55A works excellently with a single 100Ah lithium battery, and this is actually a very popular configuration. Here's why it's ideal: Charge Rate Considerations: A 55-amp converter charging a 100Ah battery provides a 0.55C charge rate (55A ÷ 100Ah = 0.55C). Most quality lithium batteries can safely accept 0.5C to 1.0C charge rates, so 0.55C is right in the sweet spot - fast charging without stressing the battery. Your 100Ah lithium battery can easily handle the full 55-amp output from the PM3-55A. For comparison, a 100Ah Battle Born battery can accept up to 100 amps (1.0C) continuously. Real-world performance: Starting from 50% state of charge, a 100Ah lithium battery charges to 100% in approximately 1 hour with the PM3-55A. This is dramatically faster than lead acid batteries of similar capacity. You can run errands, take a shower, or have lunch at a rest area, and your battery is fully recharged. BMS Protection: Your lithium battery's Battery Management System (BMS) will regulate charging automatically. If the battery is cold, near full charge, or experiencing any issues, the BMS reduces charge acceptance and the PM3-55A automatically adjusts current output. This protection is built into quality lithium batteries, so you never risk overcharging. Voltage Setting: Set the PM3-55A's fixed voltage mode to 14.4V or 14.6V per your battery manufacturer's specifications. Battle Born recommends 14.4V, RELiON recommends 14.6V. This constant voltage charging is exactly what lithium batteries prefer. Future expansion: If you later add a second 100Ah battery (200Ah total), the PM3-55A is still perfect, providing a 0.275C charge rate which is conservative and safe for long battery lifespan.
A: PowerMax makes two different PM3 series lines that serve different applications, and it's important to choose the right one: PM3-55A (LK Series - This Product): This is the standard PM3 converter with mounting flanges, designed to mount on any flat surface (wall, floor, shelf). It has a standard rectangular case with pre-drilled mounting holes. This is the correct choice for: (1) New installations where you're adding a converter to an RV or boat, (2) Replacing WFCO 9800-series converters (WF-9855, WF-9865, WF-9875, etc), (3) Installing in a custom location or equipment cabinet, (4) Retrofitting any application where you have mounting flexibility. PM3-55A MBA Series: This is a special lower-tray design that fits directly into RV power distribution panels that use WFCO 8900-series MBA converters. The MBA has a different form factor - it's designed to slide into the bottom tray of a power distribution center. This is the correct choice ONLY if: (1) Your RV has a WFCO 8900-series distribution panel (not 9800-series), (2) You want to replace just the converter portion while keeping the existing breaker panel, (3) Your converter literally slides in/out of a bottom tray. How to tell which you need: Look at your existing converter. If it has separate mounting flanges and mounts to a wall/surface → you need the PM3-55A LK series (this product). If it slides into a bottom tray under a breaker panel → you need the PM3-55A MBA series. When in doubt, the LK series (this product) is more versatile since it can be mounted anywhere. The MBA series is specifically for power distribution panel integration. Note: Both series have identical electrical specifications (55A output, 3-stage charging, same features). The only difference is the physical form factor for mounting.
A: Yes, the PM3-55A works perfectly alongside solar charge controllers, and this combination is extremely common in RVs and off-grid systems. Both devices can charge the same battery bank simultaneously without any conflict. Here's how they work together: Complementary Charging: Solar charge controllers and the PM3-55A both sense battery voltage and adjust their output accordingly. During sunny days when solar provides most/all charging power, the PM3-55A reduces output or enters float mode automatically. When you plug into shore power or run a generator (especially at night or during cloudy weather), the PM3-55A takes over primary charging duties while solar contributes what it can. Neither device "fights" the other - they cooperate automatically based on battery voltage. Additive Current: When both are charging simultaneously, their currents add together. If your solar controller is delivering 30 amps and the PM3-55A is delivering 55 amps, batteries receive 85 amps total. This additive charging is completely safe and actually beneficial for rapid battery recovery after heavy use. Common Setup: Many RV owners have 400-800 watts of solar with a 30-50 amp MPPT controller, plus the PM3-55A for shore power charging. This gives them: (1) Solar charging during boondocking (no generator needed for typical daily use), (2) Fast AC charging when plugged in between trips (batteries fully recharged in 2-3 hours), (3) Both systems working together during partial sun conditions for maximum charging speed. Voltage Coordination: Both devices typically charge at similar voltages (14.4V-14.6V bulk, 13.2V-13.6V float), so they naturally stay coordinated. For lithium systems, set both to the same voltage (usually 14.4V or 14.6V) for optimal performance. No special wiring needed: Simply wire each device to the battery bank independently. Both positive wires go to battery positive, both negative wires to battery negative. No special combiners or controllers required.
A: The PM3-55A represents the best value for most RV owners with small to medium battery banks, and upgrading to higher amperage models only makes sense in specific situations. Here's the decision framework: Choose PM3-55A (best for most people) if: (1) Your battery bank is 100-220Ah - the 55A provides ideal charging rates (25-55% capacity), (2) Your typical 12V loads are under 40 amps - you'll have 15+ amps left for charging even during peak use, (3) You want excellent performance at the best price point - the PM3-55A costs $30-50 less than the PM3-65A and $60-80 less than the PM3-75A, (4) Your RV has standard 30-amp AC service - the PM3-55A only needs 11A AC input, leaving plenty of AC capacity for other appliances. Upgrade to PM3-65A if: Your battery bank is 200-260Ah and you want faster charging, or you frequently run 40-50 amps of 12V loads. The extra $30-50 buys you 10 more amps of capacity. Upgrade to PM3-75A if: Your battery bank is 300Ah+ or you have unusually high 12V loads (50+ amps continuous). The PM3-75A uses 13A AC input which leaves less headroom on a 30-amp RV service. Diminishing returns: The charging time difference between 55A and 75A on a 200Ah battery is only 30-45 minutes. Unless you're in a rush, this doesn't matter much. Most RVers are plugged in overnight or for several hours, so even the PM3-55A has plenty of time to fully charge batteries. Real-world perspective: The PM3-55A is PowerMax's most popular model because it hits the sweet spot of performance, price, and versatility. Unless you have specific needs for more power (large battery banks, high continuous loads), the 55A is the smart choice that saves money without compromising performance.