Marine-Battery Charging and RegulatorsMARINE-BATTERY CHARGING The following article on battery charging is extracted from The Marine Electrical and Electronics Bible and The Motorboat Electrical and Electronics Manual by John Payne, both available from Amazon.com and West Marine.
ABOUT ALTERNATOR REGULATORS The regulator, and not the alternator output size is the key to all alternator charging systems. The function of the regulator is to control the output of the alternator, and prevent the output from rising above a nominal set level, typically 14 volts, which would otherwise damage the battery, alternator and electrical equipment. Essentially the regulator is a closed loop controller, monitoring the output voltage and varying the field current in response to voltage output variations. In practice a regulator does not control the charging process significantly until the battery charge level increases to approximately 50% of capacity. Prior to that level a battery will absorb a fairly large charge current. When the voltage of the battery rises to this threshold, the regulator starts limiting the voltage level. The charge current levels off as the voltage level rises. The traditional automotive alternator is fitted with a regulator designed for automotive service. This requires the replacement of a relatively small amount of discharged power, which it does in a short time period. The alternator then supplies the vehicle electrical loads during running periods. This is totally inadequate in vessel in yacht applications. To recharge a marine-battery properly the charging system must overcome battery counter voltage, which increases as charging levels increase. The typical scenario as we all know is one of a high charge at initial start-up and then a rapidly decreasing current reading on the ammeter. As a result few boat batteries are ever charged much above 70% of capacity. One of the many undesirable effects of standard regulators is that when a load is operating on the electrical system, charging current also decreases. As an example, based on tests I have made with an alternator with a total output of 30 amps at 14 volts and a vessel electrical load of 24 amps, I found that only 6 amps was flowing into the battery with a terminal voltage of only 13.2 volts.
ABOUT SMART FAST CHARGE REGULATORS A regulator is a fully automatic device which ensures a stable output from the alternator. The primary function of a regulator is to prevent overcharging of the marine-battery and damage to the alternator and this point should be considered when selecting a controller. Standard Regulators are factory fitted to alternators. Cycle Regulators use a cyclic regulator control. Stepped Cycle Regulators use a timed cycle of voltage steps. Manual Controllers have no regulator function and control alternator output manually by operator control. Fast charge regulators are designed to provide the correct charge voltage at the marine-battery terminals, which means that which compensates for voltage drops within cables and connections. In addition the charge voltage also compensates for ambient temperature. What did you put on your boat? A common question! After much assessment I opted for the British made Adverc Regulator. Having installed several hundred of the now defunct TWC regulators and had one perform flawlessly for years the Adverc was a logical choice. The system uses a series of cycles that raise the charge voltage to a nominal 14.4 volts. The cycles are timed at 5 mins at 14 volts and 14.4 volts for 15 minutes. I do not have a large bank, as physical space does not permit, so efficiency is everything. I do suffer from a small alternator which I am trying to upgrade (but the diesel I inherited with the boat is difficult to upgrade). The Adverc in my case is indispensable, it gets the batteries fully charged in a relatively short time to near 100% so I get maximum capacity availability, I would recommend it over most systems, not only because it works, but it is sensibly over engineered, it doesn't require adjustment. It is what we all want in boating gear, it is simple! In addition this unit is paralleled to the original regulator and therefore if the unit fails the standard is still working giving some redundancy.
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