Guest ChargePro 2720A 20A 12V 2-Bank On-Board Battery Charger

The Guest ChargePro 2720A is a 20-amp, 12-volt, 2-bank on-board marine battery charger - 10 amps to each of two independent banks, designed for permanent installation in your boat's battery compartment. It's the mid-range model in Guest's ChargePro on-board lineup: enough current to recharge typical dual-bank house / starting setups overnight, with the IP67-rated waterproof construction and ignition-protected design required for below-deck mounting in fresh or saltwater applications.

What 20A / 2-bank means in practical terms. Total charger output is 20 amps split into two independent 10-amp output banks. Each bank charges one 12V battery independently of the other - the two banks have separate charging electronics, separate state-of-charge sensing, and separate output regulation. Practical implication: if one of your batteries is fully charged and the other is deeply discharged, bank 1 transitions to maintenance / float mode (keeping the topped-off battery healthy without overcharging) while bank 2 continues delivering full 10A bulk current to the depleted battery. Single-output (non-bank) chargers can't do this - they treat the whole bank as one battery, which can over- or under-charge mismatched batteries. The 2-bank design is the right architecture when you have a house battery and a starting battery (which typically have different states of charge at any given time).

How long does it take to charge? A depleted 100Ah Group 27 battery refills in roughly 10-12 hours of charging from 50 percent state of charge at 10 amps - the typical overnight scenario for marina shore power. Returning a battery from very deep discharge (20 percent SOC or below) takes longer - 14-18 hours - because the absorption stage slows the current as the battery approaches full. The 2720A is sized for overnight charging while connected to shore power, not for fast turnaround between fishing days. For boats that need full charging in 4-6 hours, step up to a 30A or 40A per bank model in the ChargePro 36A or 44A lineup.

5-stage automatic charging profile. The 2720A runs the standard 5-stage marine charging profile: (1) Analyze - the charger reads battery condition and confirms safe charging is possible. (2) Condition - low-current pulse charging on heavily sulfated batteries to recover capacity before full charging begins. (3) Bulk - the heavy-lifting stage at full 10A current until the battery reaches about 80 percent SOC. (4) Absorption - tapering current at constant voltage to top off the final 20 percent without overcharging. (5) Float / Maintain - low-current pulse maintenance to keep the battery at full charge indefinitely without water loss or plate sulfation. The charger handles all stages automatically based on battery feedback - no manual mode switching needed.

Flooded AND AGM compatible. The 2720A's charging algorithm works correctly for both standard flooded lead-acid batteries (with removable caps and water you check periodically) and sealed AGM (Absorbed Glass Mat) batteries. The voltage and current setpoints are tuned to be safe for either chemistry. Important note: the 2720A is NOT designed for lithium (LiFePO4) batteries - lithium needs different charging profiles (no equalize stage, different absorption voltage, no float). For lithium banks, use a dedicated lithium-compatible charger.

IP67 waterproof + ignition protected. The 2720A is rated IP67 (immersion-proof to 1 meter for 30 minutes) and shock-resistant. The case is sealed against bilge splash, condensation, salt spray, and the inevitable wet conditions inside a boat's battery compartment. The charger is also ignition protected per USCG / ABYC requirements - safe to install in compartments where fuel vapors may be present (the charger electronics won't spark and ignite vapors). This combination of waterproofing and ignition protection is what separates marine on-board chargers from cheaper land-vehicle chargers - don't substitute a non-marine charger for marine service.

High-frequency digital design - lighter and more efficient. The 2720A uses high-frequency switching power conversion technology (vs the old-school 60Hz transformer designs of legacy chargers). Practical benefits: about 40 percent less weight (6.6 lb vs the 10+ lb of comparable legacy units), higher charging efficiency (less AC power wasted as heat), and more precise output voltage / current control across the 5 charging stages. For boats where weight matters (tournament bass boats, small skiffs), the 40 percent weight reduction is meaningful.

Auto-Maintain energy saver mode. Once both banks reach float, the charger doesn't pull continuous AC power - it transitions to a low-duty-cycle pulse maintenance mode that keeps batteries topped off while drawing minimal shore power. For boats left plugged in at the marina for weeks or months, the energy saver mode keeps electric bills modest while preserving battery health. The pulse maintenance also avoids the boiling and water loss that constant-voltage float mode can cause on flooded batteries.

Multi-layer safety protections. The 2720A includes the full suite of marine charger safety features: reverse polarity protection (the charger won't damage itself or your batteries if you swap the + and - leads during install - it just refuses to charge until correctly wired), over-current limiting (prevents excessive draw on output cables), over-voltage shutoff (protects against runaway voltage), over-temperature thermal protection (charger shuts down before overheating), ignition protection (safe for compartments with possible fuel vapors), and in-line DC fuses on each output bank (protects the DC output wiring against shorts). Built-in wiring fault detection lights an LED if your output wiring has a problem the charger can detect - quick diagnostic feedback during install.

LED status display. The front panel shows per-bank charge status (which stage each bank is in, plus a fully charged indicator), AC power presence, and dedicated fault indicators for reverse polarity, wiring faults, and battery problems. Quick visual check at any time tells you whether the charger is doing its job. Note the display isn't a full graphical screen - it's a multi-LED indicator panel optimized for waterproof reliability rather than detail.

What's in the box and what you need. The 2720A ships pre-wired with the 6-foot 120V AC input cord and NEMA 5-15P plug attached. Output side is unterminated wire - you'll cut to length and add ring terminals appropriate for your battery posts. You'll need: 10-12 AWG marine-grade tinned cable for the output runs (length depends on charger-to-battery distance), ring terminals sized for your battery posts, heat shrink for terminal protection, mounting hardware (#10 stainless screws) for securing the charger to a bulkhead or mounting board, and an AC source on the boat (shore power inlet, generator outlet, or inverter capable of running a 20A charger).

Install location. Mount on a vertical or horizontal surface inside the battery compartment or an adjacent dry storage area, with at least 4 inches of clearance on all sides for airflow (the charger generates heat during bulk charging). Avoid direct mounting on the battery itself or directly above an unsealed battery (battery off-gassing over time can corrode the charger). Keep the AC cord routed safely away from bilge water collection points. Plan for 1-2 hours of install time for an experienced installer, longer if you need to add an AC inlet to the boat or run new output cables to the batteries.

Warranty and support. 2-year limited warranty from Guest / Marinco (part of Mercury Marine's accessories family). Save the receipt and the box. Warranty service runs through the authorized Mercury Marine service network - typically your local marina or marine dealer is the easiest path. Most failures Guest sees in field service are install-related (wrong wire gauge, corroded battery terminals, miswired AC), not charger defects - take care during install and the 2720A typically delivers 5-10+ years of trouble-free service.