High-performance 110VAC to 12VDC converter with 3-stage smart charging. Compatible with Lithium, AGM, and Lead Acid batteries. 1095W continuous output.
The PowerMax PM3-75A is a robust 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 powerful 75-amp continuous output (1095 watts), this converter can rapidly charge medium to large battery banks while simultaneously powering all your 12V devices.
Featuring advanced 3-stage smart charging technology, the PM3-75A 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-9875 converters, the PM3-75A 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.
1095W continuous power - charges 150Ah battery in 2 hours, 300Ah 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 PM3-75A 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 75 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 PM3-75A 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 PM3-75A 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.
RVs & Travel Trailers: Direct replacement for WFCO WF-9875 converters. Powers all 12V lighting, water pumps, slide-outs, awnings, and electronics while rapidly charging house battery banks. Perfect for Class C motorhomes and travel trailers with 200-400Ah battery capacity. Off-Grid 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 & Performance: Powers car audio systems, bowfishing lights, emergency vehicle equipment, and mobile workshops. Fast charging between uses means less downtime and more performance. Emergency Backup Power: Maintains battery banks for backup power systems, 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. Communications & Off-Grid Cabins: Reliable power for ham radio stations, cellular boosters, internet equipment, and small cabin electrical systems. Converts noisy 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: • PM3-75A 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 PM3-75A 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 75A 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 PM3-75A is Perfect for Lithium: The PowerMax PM3-75A 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 PM3-75A can deliver exactly that voltage continuously. 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 PM3-75A's 75-amp output is safe for most lithium banks 150Ah 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: The decision between the PM3-75A and PM3-100A depends on your battery bank size and typical power consumption. Here's how to choose: Choose the PM3-75A if: (1) Your battery bank is 200-300Ah - the 75A output provides a safe 25-37% charge rate for lead acid batteries. (2) You have moderate 12V loads (30-50 amps total including lights, water pump, fans, basic electronics). (3) You want to save $50-100 over the 100A model. (4) Your RV has a 15-amp AC circuit that might be shared with other loads. Choose the PM3-100A if: (1) Your battery bank is 300Ah or larger - the extra power charges large banks significantly faster. (2) You frequently run high 12V loads (50+ amps) - inverters, multiple slide-outs, large water pumps, etc. (3) You have lithium batteries that can accept higher charge rates without damage. (4) You want the fastest possible recharge times after boondocking. Real-world example: A typical 30-foot travel trailer with 200Ah of batteries and standard loads (lights, water pump, furnace fan) works great with the PM3-75A. A 40-foot motorhome with 400Ah lithium batteries and heavy loads (residential refrigerator, multiple slide-outs, washer/dryer) benefits from the PM3-100A's extra power. Both converters have the same physical size, so installation space is not a factor in the decision.
A: The PM3-75A is a direct drop-in replacement for the WFCO WF-9875 with significant improvements. Both are 75-amp converters with similar physical dimensions, but the PowerMax offers: (1) Adjustable voltage output - The PM3-75A has a fixed voltage mode with adjustable output from 13.0V to 16.5V, making it compatible with lithium batteries. The WFCO is limited to lead acid charging voltages only. (2) 3-stage smart charging - More sophisticated charging algorithm (Bulk/Normal/Float) that extends battery life compared to WFCO's simpler 2-stage charging. (3) Quieter operation - Temperature-controlled proportional fan runs quietly during light loads, while WFCO fans typically run at constant speed. (4) Better build quality - PowerMax converters are known for reliability and longevity, with fewer warranty claims than WFCO units. (5) Equal efficiency - Both achieve >85% efficiency, so power consumption and heat generation are comparable. The PM3-75A uses the same mounting holes and wire connections as the WF-9875, making upgrades straightforward. Many RV owners report improved battery charging performance, reduced fan noise, and better compatibility with modern lithium battery systems after upgrading from WFCO to PowerMax. Installation typically takes 30-60 minutes for an experienced RV technician.
A: The PM3-75A is designed to work with 110VAC shore power or generator input - it cannot charge batteries when boondocking unless you're running a generator. However, it works excellently alongside solar charge controllers in a complete power system. Here's how they work together: While Boondocking (No AC Power): Your solar charge controller charges the batteries from solar panels. The PM3-75A sits idle with no AC input. Your 12V loads draw power from batteries, which are replenished by solar during daylight hours. When Plugged In (Shore Power or Generator): The PM3-75A takes over charging duties, delivering up to 75 amps to rapidly recharge batteries that may have been partially depleted during boondocking. Solar charge controllers and the PM3-75A can charge simultaneously without conflict - they both sense battery voltage and adjust output accordingly. Total charge current is additive: if solar is delivering 30 amps and the PM3-75A is delivering 75 amps, batteries receive 105 amps total. Best Practice Setup: Install the PM3-75A for shore power/generator charging, and install a separate MPPT solar charge controller (30-60 amps) for solar charging. This gives you the best of both worlds: fast AC-powered charging when available, and solar maintenance charging when boondocking. Many RVers rely primarily on solar for daily power needs but use the PM3-75A's high-current charging to quickly "catch up" after several days of heavy battery use or cloudy weather.
A: This is normal behavior and happens due to the relationship between the converter's output capacity, your loads, and battery charging. Here's what's happening: The PM3-75A can deliver a maximum of 75 amps total. This current is split between (1) powering your 12V loads and (2) charging your batteries. Example scenario: Your batteries are partially discharged and the PM3-75A is charging them at 60 amps while also powering 15 amps of lights and electronics (75 amps total). You turn on a large 12V load like an electric water pump (25 amps). Now the total demand is 100 amps (60A charging + 15A lights + 25A pump), but the converter can only deliver 75 amps. The converter prioritizes powering loads over charging, so it delivers all 75 amps to your loads (15A + 25A = 40A to devices, plus 35A to batteries). With reduced charge current, battery voltage drops slightly. Why this happens: The converter cannot instantly provide more than 75 amps. When demand exceeds 75A, batteries must supply the deficit. As batteries discharge (even slightly), voltage drops from 13.6V to 13.2V or lower depending on load and battery state of charge. This is completely normal and will not damage batteries. Solutions if voltage drops are problematic: (1) Upgrade to the PM3-100A for 100 amps total output capacity. (2) Reduce simultaneous high-draw loads - don't run everything at once. (3) Increase battery bank size so voltage remains stable during high-load periods. (4) Install larger wire from converter to batteries to minimize voltage drop from resistance.
A: Yes, it's completely normal for the PM3-75A to generate significant heat during operation - in fact, heat generation is unavoidable in power conversion. The converter is converting 120VAC to 12VDC at up to 1095 watts output, and even with >85% efficiency, that means roughly 150-190 watts of heat is generated during full-load operation. Normal operating temperatures: The converter case can reach 120-140°F (49-60°C) during heavy charging or high loads. This is warm to the touch but not dangerously hot. Internal components operate at even higher temperatures (up to 185°F / 85°C) which is within design specifications. The temperature-controlled fan activates when internal temperature rises, pulling air through the unit to dissipate heat. You'll hear the fan speed up during heavy charging and slow down or turn off during light loads. When to be concerned: If the case is too hot to touch (160°F+ / 71°C+), this indicates inadequate ventilation or potential internal problems. If the converter shuts down unexpectedly, thermal overload protection may have activated due to excessive heat. Ensuring proper cooling: (1) Maintain minimum 1" free air space on both ends of converter for airflow. (2) Don't mount in sealed cabinets without ventilation holes. (3) Keep vents clear of dust, debris, and obstructions. (4) In extremely hot climates (100°F+ ambient), consider adding a small auxiliary fan to improve airflow. (5) Mount converter away from other heat-generating equipment (like inverters or additional converters). If thermal shutdown occurs repeatedly even with proper ventilation, contact PowerMax technical support - the unit may have a defect covered under warranty.
A: The PM3-75A works excellently with AGM (Absorbed Glass Mat) batteries - in fact, AGM batteries are one of the most common battery types used with PowerMax converters in RV and marine applications. The factory default 3-stage charging profile (14.6V bulk, 13.6V normal, 13.2V float) is ideal for AGM batteries and will provide long battery life without any adjustments needed. Why PM3-75A is perfect for AGM: (1) The 14.6V bulk charge voltage is within the recommended charging range for most AGM batteries (14.4V-14.7V). (2) The 13.6V absorption voltage safely completes the charge without overcharging. (3) The 13.2V float voltage prevents sulfation during storage without causing gassing or water loss (AGMs are sealed and cannot have water added). (4) AGM batteries accept high charge rates without damage - the 75-amp output is safe for AGM banks from 150Ah to 400Ah. Using fixed voltage mode with AGM: Some AGM manufacturers recommend slightly lower charging voltages (14.4V instead of 14.6V) for maximum longevity. If your AGM battery documentation specifies a particular charging voltage, you can use the PM3-75A's adjustable fixed voltage mode to set the exact voltage recommended. Simply follow the voltage adjustment procedure in the manual to set your desired voltage (typically 14.4V for AGM). Common AGM brands that work perfectly with PM3-75A: Lifeline, Odyssey, Optima, Northstar, Full River, Universal Battery, Interstate, and many others. The PM3-75A has been used successfully with AGM batteries in thousands of RV, marine, and off-grid installations with excellent results and long battery lifespan.