There is crossover/intersection between the marine battery charger type and the multibank battery charger type (a.k.a. multi-output battery charger), so there will be mention of boats in this tutorial as well. The multiple output of the multibank chargers are designed in different ways. The first type are units that have a separate positive and negative connection for each output, and a separate microprocessor as well. The other multiple bank charger type has multiple positive terminals and a single negative terminal. These usually have a single microprocessor.
The independent output chargers (separate positive and negative, separate microprocessor) allow batteries of differing type, size, and state of charge to be connected to the same battery charger. For instance, a three bank charger can be used for a three battery boat with a single 12 volt starting battery, and two other 12 volt batteries in series for a 24 volt trolling motor. How the batteries are wired (i.e. series in this 24 volt situation) is not a concern for the charger, after each battery gets its own positive and negative from the charger. This attribute can be used to solve a battery charging problem involving higher voltages like 24 or 36 volts, where one of the 12 volt batteries in the string is tapped at 12 volts for lights, radio, PLC, etc., resulting in an imbalance. Using a straight 24 volt or 36 volt output charger in this case would result in improper battery charging, and shortened battery life. So, there are some charging applications that are only correctly served by a multi-bank, independent output charger. There are low (4 to 6 amps), medium (10 amps), and high (15 amps) output multi-bank chargers, with one to four banks, available in the Dual Pro line that we carry. These also are marine chargers, meaning in this case, waterproof, vibration proof and mountable. Once again, 'marine' applies to the application or environment the charger is used in and its attributes, not the batteries it is hooked to. This makes the Dual Pro charger suitable for outdoor, moist, or hazardous situations, including industrial use. A low output unit may be applicable for maintenance use, such as maintaining generator or pump starting batteries, or a low battery use or low amp hour battery situation. A medium output charger would be applicable for medium use, such as a trolling motor used only on weekends, etc., or an industrial application with medium amp hour capacity. A high output unit would be used in high amp hour battery applications (200 ah for example), or a tournament fishing application, where fairly rapid recharge is continually called for.
The second multibank charger type has multiple positive terminals and a single negative terminal. These usually have a single microprocessor. Some (most) of these units are designed for multiple banks where the banks are charged and discharged together, i.e. a group of batteries on one side of an RV, and a matching set on the other side, where both sets are parallel connected for use. The chargers don't deal well with battery banks used for entirely different functions, where one bank may be significantly discharged, and the other not. Their owner's manuals usually state that caveat somewhere. The Samlex chargers we carry are of this type, with 2 or 3 positive and one negative terminal. This type is called for in some applications, like power supply situations, bench testing applications, etc. We use this type in R&D, robotics, uninterruptible power supply, etc., and frequently only use one positive and one negative (all charger output is available at all positive terminals).
Back to the multibank, independent output type, there are the alligator clip type designed for battery shops, motorcycle shops, industrial shops, etc, where batteries are rotated through for recharge or top off, or simply floated until they are sold or installed. There are 2, 4, 5, 6, and 10 bank units that we are aware of. Unfortunately, we don't offer any on the website. Two excellent units of this type are the Autometer 6 station, 5 amp per bank charger, and the Interacter 5 station units. The Interacter is available in 5 and 10 amp per bank versions.