This product uses a micro processor to monitor the multiple battery bank outputs which are to be charged by an alternator; it ensures the batteries are all charged in conjunction with each other and prevents any back feed through the device in the event of high loads on one battery bank. The system also has the ability to disconnect the alternator and individual battery bank outputs in the case of problems caused by the alternator or other power items in the system. It does all this and still offers only a max voltage drop of less that 0.01V, much less than any so called 0V drop mosfet / diode system. Many so called 0V drop systems simply do not come close, the Mastervolt battery mate is as high as 0.6V at full power (where it counts) while the Sterling is at 0.09V, a 500% performance improvement over the Mastervolt battery mate unit and about 1100% over a standard diode.
Faster battery charging Apart from the obvious charging benefits of the 0V drop across the unit which dramatically helps battery charging from the standard alternator, the Pro Split R has another unique feature to boost this ability even more. The main problem with split charge systems is that they are trying to charge 2 battery banks (or more). Usually one is already almost full (the engine battery) while one is empty (the domestic battery bank). The problem is that when you try to charge the 2 batteries with conventional splitting systems the higher voltage from the full engine battery fools the regulator on the alternator into thinking that the combined battery states are in fact better than they actually are. The trick is to isolate the engine battery (when it is safe to do so) so, the only voltage presented to the standard regulator is the empty domestic battery. This ensures a one on one charging experience between the empty battery and the alternator regulator which dramatically improves the regulator’s charging performance into this battery bank. Then, when it’s prudent to do so, we re-engage the engine starter battery at a level where it does not affect the maximum charge ability of the regulator.
How does the unit work? This unit on the surface looks like a simple device, however, this is a very complex software control device. Under normal operation the unit has a simple operating mode. Being engineers we are not only concerned about normal operation conditions, we also like to build into our products as much safety and control as possible to both protect your electrical system and to ensure the available power is directed to where it is required most.
What is the problem? Voltage drop across splitting systems (such as diodes) will cause poor performance when trying to charge batteries. This can be easily compensated for by using things like advanced alternator regulators or battery sensed alternators, however this, in itself, can cause problems (particularly with prolonged use and sealed batteries such as AGM and gel) with other batteries in the circuit, i.e. an over charge can take place, as explained in the diagrams below.
All boats have at least two battery bank outputs, some have three. These tend to be the engine start battery, the domestic battery bank (please note that if you join three or four batteries together in your domestic battery bank it is still one battery), and the bow thruster battery. Having introduced 2-3 battery bank outputs onto your boat, the problem then is how do you charge them from one alternator source (or two alternators which I will discus later).
Example 1 shows a typical split charge diode installation with a standard alternator with no advanced regulator nor battery sensing regulator. The test assumes a 60A alternator, the diode is 70A rated and there is an average cable between the alternator and the battery bank. The alternator voltage is assumed to be about 14.2V, however, in real life this could vary from 13.9-14.8 volts depending on the manufacturer and the internal regulator fitted to the unit. Important to note on example 1 is the fact that the alternator produces 14.2V at the alt but, by the time it gets to the domestic battery, there is only 12.8V left, this is an appalling voltage and would result in you having extremely bad charge performance at your battery bank. However, note that the engine battery is at 13.6V (this higher voltage is not an issue in this case but the phenomenon will cause a problem in later examples) this is because at 60A the voltage drop across the diode to the domestic battery is 1V, however, because the starter battery is almost full it is only drawing a few amps from the alternator and so its voltage drop is only going to be about 0.4A (remember the voltage drop across a diode is not linear but is proportional to the current flow, i.e. the more current flow through a diode the greater the voltage drop).