Pro Split R 0.0V Drop Alternator Splitter

£172.80£367.20 (ex. VAT)


Pro Split R 0.0V Drop Alternator Splitter

DC Voltage Max Alt Amps Battery Banks Size L x W x D mm Weight Kg Part Number
12 120 2 150 x 80 x 120 0.6 PSR122
12 180 2 150 x 80 x 140 0.7 PSR182
12 250 2 150 x 80 x 155 0.9 PSR252
12 120 3 150 x 80 x 130 0.9 PSR123
12 180 3 150 X 80 X 150 1.0 PSR183
12 250 3 150 x 80 x 180 1.3 PSR253
Twin 12 2 x 130 4 150 x 80 x 295 1.8 PSRT134
24 60 2 150 X 80 X 120 1.8 PSR62
24 100 2 150 X 80 X 140 0.6 PSR102
24 150 2 150 X 80 X 165 0.7 PSR152
24 240 2 150 X 80 X 250 1.2 PSR242
24 60 3 150 X 80 X 150 0.7 PSR63
24 100 3 150 X 80 X 175 1.0 PSR103
24 150 3 150 X 80 X 220 1.3 PSR153
Twin 24 2 X 80 4 150 X 80 X 295 1.8 PSRT84


Product Information

Instruction Manual

Pro Split R Alternator Splitting System

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. It also 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. This is 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). 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

This 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. This 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 with as much safety and control as possible. This is to protect both 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

This 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).

Conclusion: in example 1

There is no danger to anything. But there is an appalling low charge voltage presented to the batteries making the charging system grossly ineffective.

Example 2

This is replacing the standard regulator with a battery sensed regulator. This in effect, says to the alternator, give me 14.2V at the domestic battery bank (or at the end of the battery sensed cable) regardless of what voltage the alternator has to produce to achieve this goal. This will improve charge at the domestic battery a great deal. I.E. you can see that the voltage will rise on the battery from 12.8V in example 1, to 14.2V  in example 2.

However, when the voltage is checked through the system (and taking into account the voltage drops across the diodes) the engine battery voltage is now 15.2V. This would rise even more if the cables were longer i.e. if you had 4 or 5 meters of cables. Then the voltage drop in the cables could be up to 1V. This would drive up the starter battery by another 1V etc.


The starter battery should be open lead acid type as it is going to gas a little. In the short term the batteries would simply gas a little, and a regularly maintained battery would be ok. However, with a sealed, gel or AGM  type any gassing could damage this type of battery.

Example 3

This is pretty much the same as example 2. Except a modern advanced regulator will push the batteries up to 14.8V. In some cases the new calcium batteries could go as high as 15.1V. This simply adds another 0.6V onto example 2 with the same conclusions, only worse.

The solution: Example 4

If the voltage drop across the splitting device could be eliminated then there would be no excessive rise in voltage on the starter battery. This way the gassing / high charge rate of the secondary would be the same as the domestic battery bank and under control. This would prevent excessive gassing taking place and causing excessive water loss in the starter battery. It also has many added features associated with this new technique.

Other advantages of the Zero Volt Drop Intelligent Alternator Distribution System

1)   Distributes the most power to the battery bank which demands it.
2)   Isolates a battery bank when there is any attempt to back feed the power from the full battery bank to a more demanding battery system.
3)   Isolates full batteries to ensure empty batteries can charge faster from a standard regulator maintaining the engine start battery requirements as paramount.
4)   Isolates the main alternator from all the batteries in the event of a failure of the alternator’s own regulator. This prevents the batteries from boiling.
5)   Isolates any battery bank which tries to back feed a high voltage from a different source. i.e. if there was a defective battery charger on one battery bank trying to back feed into another battery bank then the unit would disconnect that battery bank to save the others.
6)   L.E.D. display shows which channels are in use and which are not.
7)   Overload design, for example, our model rated for a 180A is actually continually rated for 240A with overload in excess of 2000A
8)   Fail-safe, in event of unit failure the engine start battery and alternator remain connected, ensuring the safe running of the boat/vehicle. It prioritizes the engine start battery charging over all other battery bank outputs.


Additional information

Weight N/A
Power Variant

PSR122 12V 120A 2 battery banks, PSR182 12V 180A 2 battery banks, PSR252 12V 250A 2 battery banks, PSR123 12V 120A 3 battery banks, PSR183 12V 180A 3 battery banks, PSR253 12V 250A 3 battery banks, PSRT134 12V 2x130A 4 battery banks, PSR62 24V 60A 2 battery banks, PSR102 24V 100A 2 battery banks, PSR152 24V 150A 2 battery banks, PSR242 24V 240A 2 battery banks, PSR63 24V 60A 3 battery banks, PSR103 24V 100A 3 battery banks, PSR153 24V 150A 3 battery banks, PSRT84 24V 2x80A 4 battery banks