Upgrading Your Boat's Charging System

Modern technology is a major presence on boats these days. From computerized navigation, sophisticated fish finders and mapping devices, high-powered amplifiers and sound systems and more, the demands on your boat's electrical and charging system have never been greater. Most boats are not built with the battery charging system needed to sustain all of these advanced technologies. Upgrading a boat's charging system has become a very common need for the modern boater.

Why upgrade?

Some common reasons for upgrading a boat's charging system include:

  • Can't keep the battery charged
  • Alternator doesn't keep up with the electrical requirements
  • Don't want to run the engine or generator just to charge the batteries
  • Batteries have been added, but they may not be charging effectively
  • Battery bank doesn't charge at idle
  • Alternators keep burning out
  • With twin engines, the alternators don't work together to charge the batteries effectively
  • Don't want to have to flip a switch to charge the engine start battery instead of house batteries

Don't Fix the Problem Before You Know the Problem

Many people assume (incorrectly) that upgrading the charging system means replacing the battery charger.  Or, they may add more batteries to the house battery bank.  Neither of these addresses the most common weak point in the charging system, which is an undersized alternator. Most alternators that are installed on marine engines just don't have the capacity to keep up with the modern technological requirements.  If your charging system is struggling to keep up with your electrical load, you may want to consider an alternator upgrade.  But, before you replace anything, you should learn more about what your actual needs are.

Know the Electrical Load First

The first step in correctly upgrading your charging system is to identify your vessel's electrical load. This requires precise measurement; refer to equipment manuals or consult with a qualified marine electrician for help.  Once you have a list of all your devices and their required electrical loads, use Balmar's interactive load calculator to get an accurate total of the electrical load for the entire vessel.

Now You Can Add Batteries (If Needed)

Now that you know your electrical load demands, you can assess how well your battery bank measures up.  First, you need to know what type of batteries you have.  Standard and deep cycle flooded batteries can accept a charge load up to 25% of their capacity.  Gel cell batteries can accept a charge load up to 35% of their capacity. Standard AGM batteries can accept up to 40% of their capacity.  TPPL and carbon foam AGM batteries can accept 100% of their capacity.  Lithium batteries can accept an almost-unlimited charge load (and their price will reflect that).  We typically recommend you use at least standard AGM batteries for your house battery bank.  Spending a few extra dollars on an AGM battery pays off huge in the long run.  You'll want to find out from the battery manufacturer what the specific charge loads and profiles of your batteries are.

Get the Right Alternator for the Job

The next step in upgrading your charging system is to make sure the output of your alternator matches your load requirements.  We highly recommend that you consider the Balmar high output alternator kits, which include a multi-stage voltage regulator and temperature-sensing cables.  They offer a variety of alternators with different output ranges and mounting styles to suit most applications.

If you end up upgrading your alternator, you'll want to also choose a model that has the same mounting style that is currently present on your engine.  There are four common marine alternator mounting styles:

  • 1 inch single foot - the Motorola style
  • 2 inch single foot - the Delco style
  • 3.15 inch dual foot - the Hitachi style
  • 4 inch dual foot - the J-180 style

The Belts & Pulleys Need an Upgrade, Too

When you upgrade an alternator, chances are you will need to upgrade the belt & pulley system as well.  Higher output alternators require more drive power from the engine.  All belts have power limitations that they can support.  Without a belt strong enough to handle the increased power take-off, belts can slip and potentially damage the engine and the alternator.  Don't skip this step!  You've invested in a powerful new alternator, so make sure it can perform to the best of its abilities with the right belt & pulley system.  Here's some more information, including some handy application charts for different engine models.

Don't Forget a Monitor

If you don't already have one, an accurate and reliable battery monitor will help you keep tabs on the health of your battery bank.  Invest in one that provides all the critical battery parameters, like state of charge, state of health, current flow, time remaining and more.  Make sure the monitor can support your type of battery, as well.  Modern battery monitors are often bluetooth capable, so that you can track the status of your batteries even when you are not at the helm.  We recommend the Balmar SG200 - a smart, next generation monitor that is not only powerful and full of capabilities, but also very stylish and easy to read.

Be Precise, Be Thorough and Ask for Help

Calculating the correct electrical needs for your vessel is not a quick task, but it doesn't have to be difficult.  Take the time to collect all the correct information.  Read more about upgrading a marine charging system from the experts at Balmar.  Don't cut corners when it comes to battery or alternator requirements.  Consult with a qualified marine electrician if needed.  You can also give us a call - we've got experienced marine mechanics available who can offer some assistance to you.