Choosing the ideal alternator and regulator for your vessel can be a daunting task. Output ratings, mounting styles and a variety of other factors can make selection a bit overwhelming. To simplify the process, the best way to get started is to look at the engine and existing alternator. Some simple questions will get you on your way to an informed decision.
What is the alternator's mounting style?
When inspecting the existing alternator, the mounting is specifically in regard to the point where the alternator pivots off of the engine block. In the vast majority of marine diesel engines, one of the four mounts included above will be consistent with the existing alternator. Please note that some additional spacers may be required to ensure a proper fit, as well as proper pulley alignment. Balmar offers an assortment of heavy duty spacers. See our current catalog for details.
What is the size and type of drive belt?
In larger engines, dual vee belts are more commonplace. More recently, some engine manufacturers are offering the option of a serpentine type belt. Each of these belt types have a limited horsepower draw they are capable of supporting. The following chart provides a basic sizing guideline based on belt type and size.
What are the size(s) and type(s) of the batteries being charged?
That being said, it's still important to understand the relationship between your batteries and the charging system that supports them – particularly as newer battery technologies emerge in the marine market.
Traditionally, boaters relied on thick-plate lead acid batteries to support house electrical demands. These deep-cycle flooded batteries tended to be fairly manageable due to their slower charging and discharging characteristics. In most cases, golf cart and similar deep-cycle batteries were limited to an acceptance rate equal to roughly 25 percent of their available capacity. As such, a 400 amp-hour deep cycle flooded battery bank would be well suited to a 100-amp rated alternator to support its charging needs. This proved to be an excellent match for any system with a single 1/2" single vee belt (typical on most marine diesel engines over about 25 horsepower).
The introduction of newer battery technologies, including AGM and gel batteries has made it increasingly difficult for the boater to design a system that balances battery capacity with alternator output. Where the deep cycle flooded battery was limited to an acceptance rate of approximately 25 percent of available capacity, these other technologies would accept 40 or 50 percent (or more) of their available capacity. As a result, a 400 amp-hour AGM battery bank has the potential to demand 125 or more amps from the alternator. Unfortunately, the limits of the engine and drive belt on the majority of smaller marine diesel engines make it difficult to support the greater demands of these newer battery technologies.
In the past, the only options were to reduce battery capacity, accept slower charging, or push your system to its breaking point. The growing availability of serpentine pulley kits for a multitude of marine diesel engines provides the ability to replace the standard vee belt with a more powerful serpentine poly-vee type belt which greatly increases horsepower transfer while at the same time reduces noise and engine vibration.
Balmar has entered the serpentine pulley market with the aquisition of industry pioneer AltMount, enabling us to provide a growing number of popular marine diesel engines with high quality conversion kits. When combined with our high output AT-Series alternators, these kits offer the boater a substantially improved option for dealing with bigger battery banks and newer, high-acceptance battery technologies.
Is a multi-stage regulator worth the extra cost?
This can be a real problem for the standard, manufacturer-installed alternator. Like the alternator you can find under the hood of your car, the typical OEM alternator is controlled by a very simple built-in voltage regulator. In nearly all cases, this built-in regulator is designed to charge at a non-adjustable, unchanging voltage. While that's a reasonable charging solution for a small battery that's normally being charged whenever it's being used, that just doesn't cut it when you've got big deep cycle batteries.
In comparison, alternators with external, multi-stage voltage regulators are able to charge large, deep-cycle battery banks more in league with smart shorepower chargers – by modifying charging voltage to meet the changing needs of the battery bank as the batteries become more fully charged. In addition, a smart regulator can be programmed to match the voltage requirements of a variety of battery technologies, as each battery type has a range of target voltages that ensures a safe and efficient charge profile.
The current generation of Balmar's multi-stage Max Charge and ARS-5 regulators have an additional feature that's critical to the health of gel, AGM and other sealed battery technologies. By adding an optional battery temperature sensor, the installer enables the Balmar regulator to monitor for changes in ambient battery temperature and modify charging voltage to compensate for warmer or colder temperatures than default (24ºC). This allows the charging system to maintain optimal charging without damaging over- or under-charging.
So ... is the multi-stage worth the extra cost? If your batteries are important to your boating experience, the answer is absolutely "yes".
Belt dusting and early belt failure – Is there any way to avoid it?
There are a number of ways that belt dusting can be addressed. The easiest way, when using our Max Charge or ARS-5 voltage regulators, is by adjusting the regulator's Belt Load Manager (or Amp Manager in our MC-612 regulator's advanced programming mode). This regulator adjustment mode enables the user to modify the regulator's field pulse bandwidth to reduce the horsepower load the alternator applies to the belt. The wider the pulse bandwidth, the less stress on the belt.
While the Belt Load Manager is exceedingly effective at reducing belt stress, it's always important to ensure that the problem is not a result of wear caused by poor pulley alignment. Pulley alignment can often be measured by placing a straightedge across the front of the alternator and crankshaft pulleys and identifying any misalignments. In addition, pulleys should be inspected for rust, nicks or other irregularities that could cause premature wear.
Quite often, the source of excessive belt wear can be attributed to the geometry of the crank, alternator and water pump pulleys. If the amount of contact area between the belt and the alternator pulley is limited due to a less-than-ideal drive angle, the issue can be remedied by replacing the alternator pulley with a larger diameter pulley. Balmar offers a large number of replacement pulleys, which can be seen on our website.
Another effective belt dusting solution may be replacing the standard belt with a higher capacity aftermarket belt. Notched vee belts, like those sold under the Dayco Top Cog brand, may provide better "grab" than traditional smooth profile vee belts, resulting in better power transfer and less premature wear. Newer belt technologies that integrate stronger, more stretch-resistant fibers may also provide a marked improvement over standard vee belts.
Even under the best conditions, belts do have a tendency to stretch. The best way to avoid dusting and premature belt failure is to closely monitor and correct belt tension. We recommend that you inspect your belts on a frequent and regular basis to ensure that your belt never has an opportunity to loosen and slip.
Copyright 2013. All Rights Reserved. Revised 04/23/2013