How to Choose the Right Onboard Boat Battery Charger
- by Joe Weber - updated on 6/27/2025
Looking for the best way to keep your boat batteries charged and ready? This guide breaks down everything you need to know about onboard marine battery chargers—including how they work, what size charger you need, how often to charge your boat batteries, and which charger is best for your setup. We'll also share top product recommendations and expert installation tips to keep your boat powered up and on the water.
- Learn how to choose the right onboard charger
- Discover how often to charge marine batteries
- Get expert product picks from Batteries Plus
- Find out how to install and use your charger safely
Whether you're running a trolling motor, starting engine, or full electronics suite, Batteries Plus is your go-to marine power destination.
What is an Onboard Boat Battery Charger?
An onboard boat battery charger is a permanently mounted charging system that connects directly to your marine battery or battery bank. Unlike portable chargers, onboard chargers remain wired to the boat and simply need to be plugged into a power outlet when the batteries need charging.
These systems are designed to withstand the harsh marine environment, making them more durable and water-resistant than standard battery chargers.
Why You Need a Marine-Grade Battery Charger
Marine batteries face tough conditions like moisture, vibrations, and temperature swings. Using a charger that's not designed for marine use can result in corrosion, failure, or even damage to your boat's electrical system.
Marine battery chargers offer:
- Corrosion-resistant construction
- Waterproof or water-resistant housings
- Vibration protection
- Multi-bank support for charging more than one battery at once
- Smart charging profiles to prevent overcharging and extend battery life
Recommended Onboard Marine Battery Chargers
At Batteries Plus, we carry a variety of high-quality onboard marine battery chargers designed to keep your boat's batteries charged, maintained, and ready for the water. Here are a few of our most popular options:
- NOCO GENPRO 10x2 2-Bank, 20-Amp On-Board Battery Charger & Maintainer
Ideal for dual-battery setups, this 2-bank charger delivers 10 amps per bank and features advanced safety protections, waterproof housing, and smart charging profiles for AGM, flooded, and lithium batteries. - NOCO GENPRO 15x3 3-Bank, 15-Amp Onboard Battery Charger
Perfect for boats with multiple battery types, this 3-bank charger provides 5 amps per bank and includes built-in thermal sensors to prevent overcharging in hot climates. - NOCO GENPRO 10x4 4-Bank, 40-Amp Onboard Battery Charger
Designed for larger boats or battery-intensive systems, this powerful 4-bank charger delivers 10 amps per bank, ensuring fast and efficient charging for up to four batteries at once.
All of these models are fully sealed and built for the marine environment, making them perfect for long-term installation on fishing boats, pontoons, and more.
However, finding the right marine charger is important. If you have any questions, stop by or call your local Batteries Plus for more guidance.
How to Charge a Boat Battery the Right Way
When charging your boat battery, it's crucial to match your charger to the type of battery you're using:
- Flooded Lead Acid Batteries – Require regular maintenance and venting. Compatible with most smart chargers.
- AGM Batteries (Absorbed Glass Mat) – Sealed, maintenance-free, and require a charger with an AGM setting.
- Lithium Marine Batteries – Require a charger programmed for lithium chemistry to avoid damage to the battery.
If you're not sure what type of marine battery you have, visit your local Batteries Plus. We'll help you identify the battery and select the proper charger.
How Often Should You Charge Your Boat's Batteries?
To keep your marine batteries in peak condition, it's best to charge them after every use, even if you only spent a short time on the water. Leaving batteries partially discharged can shorten their lifespan and reduce performance over time.
If your boat is in storage or hasn't been used recently, check the battery charge every 4-6 weeks and top it off as needed. Using an onboard marine battery charger with a maintenance mode or float setting is the easiest way to ensure your batteries stay healthy year-round without overcharging.
What Size Charger Do You Need?
Choosing the right size charger depends on the amp-hour (Ah) rating of your battery. As a general rule, your charger's output should be 10-20% of your battery's total capacity. For example, a 100Ah battery would pair well with a 10-20 amp charger.
If you're charging multiple batteries, consider a multi-bank charger. These let you charge several batteries at once, keeping your house battery, trolling motor battery, and starting battery powered up and ready to go.
Tips for Installing an Onboard Marine Charger
- Mount in a Dry, Ventilated Area – Choose a location away from direct water spray and ensure good airflow.
- Secure the Unit – Use corrosion-resistant mounting hardware and ensure the unit won't shift during rough waters.
- Wire Carefully – Follow the manufacturer's instructions and use marine-grade wire and terminals.
- Fuse the System – Protect your boat's electrical system by adding inline fuses near the battery terminals.
- Test the Setup – After installation, check the connections, plug in the charger, and confirm proper function.
Need help with installation? Stop by your nearest Batteries Plus location. We're happy to help guide you through the process.
Batteries Plus is Your Marine Power Destination
Whether you need a new onboard boat battery charger, a replacement marine battery, or both, we've got you covered. Batteries Plus offers:
- A wide selection of onboard marine chargers for single and multi-bank setups
- Marine batteries from top brands like X2Power, Duracell Ultra, and Odyssey
- Expert guidance to match the right charger to your boat and battery type
- In-store battery testing and recycling services
FAQs About Onboard Boat Battery Chargers
What's the difference between a marine battery charger and a regular charger?
Marine chargers are built to resist water, salt, and vibration. They also include smart charging profiles for marine battery types.
Can I leave my onboard charger plugged in all the time?
Yes, if it's a smart charger with float or maintenance mode. It will automatically regulate the charge to avoid overcharging.
Do I need a separate charger for each battery?
Not necessarily. Multi-bank chargers can charge multiple batteries at once while keeping them electrically isolated.
Can I use an onboard charger with lithium batteries?
Only if it supports lithium charging profiles, using an incompatible charger can damage lithium batteries.
How long does it take to charge a boat battery?
It depends on the battery size and charger output. A 10-amp charger will take about 10 hours to charge a 100Ah battery from 0% to full.
Shop Marine Battery Chargers at Batteries Plus
Ready to upgrade your boat's charging system? Browse our selection of onboard marine battery chargers online or stop by your local Batteries Plus. If you need new batteries for your boat, we've got an impressive selection of marine batteries to fit whatever power demand your boat has. As the experts in charge, we will help you choose the best battery for your boat and the perfect charger and make sure you're ready for the water.