Selecting a Charging System

Why Upgrade Your Charging System?
There are numerous reasons to upgrade your charging system. Here are some common complaints:

  • I can’t keep my battery charged!
  • My current alternator does not keep up with my electrical requirements/load.
  • I don’t want to run my engine just to charge the batteries.
  • I don’t want to run my generator to charge the batteries when my engine is already running.
  • I’ve added several batteries to my house bank, but I don’t think they are being charged effectively.
  • I operate predominantly at idle speed, but my battery bank doesn’t charge at idle.
  • I keep burning out alternators and/or batteries.
  • I have two engines, but my alternators don’t work together to charge the battery bank effectively.
  • My alternator charges my house bank, but I want to charge the engine start battery too without remembering to flip a battery switch.

Balmar Charging Systems can solve all these problems and more…

How to Select a Balmar Charging System
Selecting a charging system upgrade for your vessel can be a confusing task, as there are many inter-related variables to consider. The following guide steps you through a logical progression of questions and choices which must be made to select the best charging system for your needs. The selection process includes the following steps:

Step 1:  Determine Your Vessel’s Electrical Load
Step 2:  Identify Your Existing Battery Bank Technology and Capacity
Step 3:  Select Your Optimum Alternator Output
Step 4:
Identify the Alternator Mounting Style Present on Your Engine
Step 5:  Determine your Belt and Pulley Requirements
Step 6:  Select Additional Charging System Options

These 6 important steps are fully described below – Read on!

DC Loads Calculator Image2Step 1: Determine Your Vessel’s Electrical Load
(Skip this step if you are confident in your house bank’s ability to service your existing vessel loads.)

Accurate load calculations require precise measurement of your vessel’s equipment. Refer to equipment manuals for actual load ratings or consult with a qualified marine electrician to determine your actual needs. The chart at the right provides typical DC marine loads and an example of load calculations. Use this example to configure and calculate your vessel’s electrical load. Click here to upload our interactive Load Calculator and save it for your personal use.  You can manipulate the Load Calculator in either Microsoft Excel® or Google Docs®.

(Device Load x Duty Cycle) x (# of Devices) = Total Load

House battery capacity is typically derived based on the ability to meet approximately 24 hours’ worth of typical demand, but could be longer if you don’t expect to be connected to shore power for extended periods. For example, if your vessel’s typical daily electrical load is 300 Ah, then your battery bank should be sized to provide 300Ah of power storage.
Since lead acid-based batteries will be damaged if you discharge them beyond a 50% State of Charge (SoC%), then 600Ah of rated storage is required.

Add batteries to your bank if you need them!

Step 2: Identify Your Existing Battery Bank Technology and Capacity

Battery bank capacity has a dramatic impact on the size and type of alternator required to keep the batteries healthy. Identify your battery bank technology and capacity, then calculate an acceptance requirement.

(A) Standard and Deep Cycle Flooded Batteries can accept a charge load up to 25% of their capacity.
(B) Gel Cell Batteries can accept a charge load up to 35% of their capacity.
(C) AGM Batteries can accept a charge load up to 40% of their capacity.
(D) TPPL and Carbon Foam AGM Batteries can accept charge loads up to 100% of their capacity.
(E) Lithium Batteries can accept an almost unlimited charge load.

Contact your battery manufacturer to confirm their recommended charge loads and profile.

(Battery Storage Capacity) x (Battery Charge Acceptance Rate) = Maximum Alternator Output Current

For example, a bank of 3 AGM batteries, each with an individual capacity of 100Ah provide a total capacity of 300Ah. With an AGM acceptance rate of up to 40%, a 120A charging alternator could be utilized (300 Ah * 40% = 120 Ah). If you have a really large bank or a battery technology that calls for an alternator output that exceeds available alternator technology, then it will just take longer to charge your bank. Simply choose the highest alternator power which meets your budget and pulley constraints.

Mounting Styles

Step 3: Select Your Alternator Output

Now that you know the battery bank technology and charging profile, you can choose an alternator output which will optimally charge your bank. The chart at the bottom of this page shows Balmar’s most popular range of small-case, high-power alternator choices for your vessel, along with an appropriate multi-stage regulator and related temperature sensing cables. (Balmar provides a discount when you buy the package).

For 100A – 120A requirements, choose a 6-Series Alternator Package.
For 170A – 250A requirements, choose an XT-Series Alternator Package.

Step 4: Identify the Alternator Mounting Style Present on Your Engine

It is critically important to determine how your existing alternator is mounted to match with the alternator you have chosen. Marine alternator mountings generally fall into one of four possibilities:

(A) 1″ Single Foot “Spindle” (Motorola-style – Westerbeke, Lehman, Hino, Pathfinder)
(B) 2″ Single Foot “Spindle” (Delco-style – Volvo, Deere, Perkins, Mercruiser, GM-based)
(C) 3.15″ Dual Foot “Saddle” (Hitachi-style – Yanmar, Westerbeke, Lehman, Perkins)
(D) 4″ Dual Foot “Saddle” (J180-style – John Deere, Cummins, Caterpillar)

Examples of these mounting styles are shown on the right. Review your existing alternator mounting to determine the appropriate mounting for your upgrade. Each Balmar alternator mounting style is identified by a unique part number.

Step 5: Determine Your Belt and Pulley Requirements

Engine drive belt style and width is also a critical factor when selecting a Balmar replacement charging system. Higher output alternators require more drive power to be taken off the engine. All belts have specific limitations regarding the amount of power take-off (“PTO”) loads they can support. Failure to specify an adequate belt/pulley system could result in premature belt wear, belt slippage and potential damage to the alternator and engine. Balmar alternators are shipped with pulleys which are appropriate for the alternator’s output.

6-Series 100A Alternators can ship with either a Standard ½” Single Deep Vee, Dual Deep Vee or K6 Serpentine Pulley.*
6-Series 120A Alternators can ship with either a Standard ½” Dual Deep Vee or K6 Serpentine Pulley.*
XT-Series Alternators can ship with either a Standard ½” Dual Deep Vee or K6 Serpentine Pulley.*
Pulley Kit* Note: Balmar’s ½” Deep Vee Pulleys (Single or Dual) can accept a 3/8” and 7/16” belt.

Identify the pulley style and size present on your engine and water pump before upgrading the charging system. If the alternator output you have chosen exceeds the capability of your existing belt/pulley system, you can upgrade the pulley system using one of Balmar’s patented AltMount® Pulley Conversion Kits. Click here to find the applicable AltMount® Conversion Kit for your engine and alternator choice. Here are some additional rules-of-thumb to guide your choices:

  • Balmar 6-Series 100A Alternators can perform with a ½” Single Vee pulley. If you need to charge above 100A, then you will need a Dual Vee or K6 Serpentine pulley system to be present on your engine to avoid a pulley upgrade. If a Dual Vee or Serpentine is not present, then an AltMount® Conversion Kit is required.
  • Many boaters choose to limit their charging system upgrade to a 100A 6-Series Alternator Package to avoid the additional purchase of a pulley conversion.
  • Unless you own a recently produced engine which already contains a Dual Vee or Serpentine pulley system, the superior power afforded by the XT-Series Alternator Packages will in most cases require an AltMount® Conversion Kit upgrade.
  • Choose wisely! Need more help? – call Balmar Technical Support to review your existing configuration and needs.

With the completion of these 5 Steps, you have reviewed all the critical variables required to choose the correct charging system upgrade for your vessel. The chart below identifies common small case configurations of 6-Series and XT-Series charging systems. Use our interactive Charging System Configurator to determine your exact needs.

Small Case Alternator Kit Selection Chart – Common Configurations

Balmar Product FamilyOutputMountingPower Take OffAlternator Part NumberBalmar External RegulatorTemp SensorsAlternator Kit NumberAltMount®
Pulley Kit
6-Series100 A1-2″ Spindle4.0 HP621-100-SVMC-618-HMC-TS-A
3.15" Saddle60-100-SV60-YP-MC-100-SV
120 A1-2″ Spindle4.8 HP621-120-DV621-VUP-MC-120-DVYes,
If Dual Vee or
Pulley is Not
Already Present
AltMount® Conversion Chart
3.15″ Saddle60-120-DV60-YP-MC-120-DV
70A, 24V1-2″ Spindle4.3 HP621-24-70-DVMC-624-H621-VUP-24-70-DV
3.15″ Saddle60-24-70-DV60-YP-24-70-DV
XT-Series170 A1-2″ Spindle5.2 HPXT-SF-170-DVMC-618-HXT-SF-170-DV-KIT
3.15″ SaddleXT-DF-170-DV
250 A1-2″ Spindle6.6 HPXT-SF-250-DVXT-SF-250-DV-KIT
3.15″ SaddleXT-DF-250-DVXT-DF-250-DV-KIT
90A, 24V1-2" Spindle4.8 HPXT-SF-24-90-DVMC-624-HXT-SF-24-90-DV-KIT
3.15" SaddleXT-DF-24-90-DVXT-DF-24-90-DV-KIT

UBB (Rotate)
Step 6: Select Additional Charging System Options

Now that you have selected an appropriate Balmar Alternator Kit, complete your purchase by adding a SG200 Battery Monitor and a Belt Buddy Tensioning Kit!