Technical Article: #011

Title: Hustler Rewire Part 3 – Installing a Sterling Pro Split-R
Date Added: 28th October 2012
Article Author: Andy
Hustler 30 – Hariette B
Rewiring a boat is no task to undertake lightly. It can be a very complex task and many different things need to be taken into account. This article is intended to share my experience. Hopefully it’ll help other Hustler owners when considering rewiring or even just adding a new electrical component to their boats. To cover this in one article isn’t practical so I’ll be splitting my experience over a number of articles namely:

Rewire Part 1 – Considerations and Planning

Rewire Part 2 – The Tools, Rewire and Battery installation

Rewire Part 3 – Installing a Sterling Pro Split-R

Rewire Part 4 – Installing a Solar Charger

Rewire Part 5 – Installing a new Stereo

Rewire Part 3 – Installing a Sterling Pro Split-R
Whilst looking at my power needs one thing that always bothered me was the manual battery switch. I wasn’t sure when to switch over to charge the appropriate battery. How would I know it’s charging properly and most pertinent of all surely there’s a better way of doing things now?
I looked at a variety of solutions battery to battery chargers, alternator to battery chargers, mains to battery chargers, advanced regulators and so on. The problem is there are so many choices, options and a whole world of possibilities. I had to remind myself that I have a Hustler 30 and I have simple needs. I do not have TV’s, Washing machines, Bow thrusters and massive 20-inch screen all consuming cameras/radar/chart plotter/fish finder combos. Therefore, I need a straightforward simple solution. I then discovered the Sterling Pro Split R.

What is a Pro Split R?
So what is it? I hadn’t heard of one of these before nor had I seen them reviewed. Here’s the official blurb from Sterling…

This product uses a micro processor to monitor the multiple battery banks 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 banks in the case of alternator problems or other power items in the system. It does all this and still offers only a max voltage drop of less than 0.01 volt!

So what does all that mean? Well in plain English the Sterling Pro Split R is a Battery Isolator/Intelligent Digital Alternator Distribution System.

It means I can eliminate the need for the manual battery isolator switch as the Pro Split R acts as an automated isolator battery switch. The Pro Split R also monitors the charge state of the batteries to ensure they are charged evenly (The intelligent distribution bit).

This appeared to be the perfect solution for me. The Pro Split R appeared to fulfil my requirement to have something manage the batteries charge state without having to worry about switching over manually. The key benefits of the Pro Split R are as follows:

  • Distributes the most power to the battery bank that demands it.
  • Prioritises the starter battery first so I can always start my engine
  • Isolates a battery bank when full and restricts any attempt to back feed the power from the full battery bank to a lower battery bank.
  • Isolates all full battery banks except the main load battery in the event of a massive load on any battery bank.
  • L.E.D. display on the unit shows what it’s doing.
  • Overload design, for example our unit, which is rated for a 150 amps, is actually continually rated for 240 amps with an overload of in excess of 1000 amps.
  • Fail-safe: in the event of unit failure the engine start battery and alternator remain connected, ensuring the safe running of the boat/vehicle.

Wait! Surely there’s a catch…

The downside to this intelligent approach is that should for whatever reason the starter battery fails and the house batteries are good I cannot manually switch to start from the House batteries.

I catered for this scenario by ensuring House battery one is next to the starter battery. This way I disconnect the terminals from the starter, split the house pair and connect House battery one to the starter battery terminals. So, with the choice assessed, understood and contingency planned for my mind was made up to get the Pro Split R

Installation of the Sterling Pro Split R
I opted to buy the Pro Split R 120A 12v 2 out version (as seen below). It was around 110GBP and is available from most Chandlers. Here is a link to the US Sterling site for more information. Bizarrely, even though Sterling is a UK company the US web site has more information.
Sterling Pro Split R
Included with the Pro Split R are a number of end caps for the cables and nuts to attach your battery cables. This is another reason why I opted to make my own battery cables, as I wanted the right lengths to connect to and from this device.

The installation of the device was very straightforward find a suitable spot and bolt it down. Connect the relevant cables as per the instructions and that’s it! It really is that simple to install no configuration tweaking, programming simply bolt, connect and go.

The manual advises not to install it somewhere hot, yet it should also be close to the batteries. Ideally the Pro Split R should be no more than a metre away from the batteries as this reduces the possibility of voltage drop and ensures peak performance from the alternator to the Pro Split R to the batteries.

This caused a me problem for my installation. Next to the batteries wasn’t possible as there wasn’t enough room! If I placed the Pro Split R where the manual switch had been then this would have been above the fuel filter so I didn’t want that. I had no choice but to put it towards the back of the engine bay above the Alternator. It’s in a great place for all the battery connections. However, it get’s hot in the engine bay… I took the chance and thought I’ll mount it in the bay and I’ll see what happens.

My engine bay can get pretty hot. However, there’s a lot of space at the back of the engine (extending to under the cockpit) so I figured the air will circulate towards the back of the engine and cool the further back it gets.
It turns out that the Pro Split R has been perfectly happy in the chosen spot (as per the picture) it didn’t get hot at all. This is the wiring diagram for a typical installation two-battery bank installation. As you can see it’s quite straightforward.
The installation took me around an hour. I think it was easier as I had already mapped out where everything was going in Part 1 the Planning. In addition, as I’d stripped a lot of the old stuff out I knew where the wiring was routed so I’m pretty sure this helped.

How do you know it’s charging?
Apart from the LED’s on the front of the unit lighting up to tell you what’s going on I wanted to know what the state of charge the house batteries were in. I installed the NASA BM-1 battery monitor for this purpose. I’ve used one of these before and they are an essential piece of kit for any boat. They show at a glance how much battery capacity is left, the voltage of the batteries, whether the batteries are being charged and most important of all amps used.

In Summary
The installation was very easy and the product has proven to be totally reliable over the summer season. I genuinely cannot fault it and I think this device should be standard on every boat. I have no need to manage the battery banks or worry about the charge as the Pro Split R just happily sits there and handles it all for me.
As a side benefit by using the NASA BM1 and Pro Split R I can also monitor the health of my Alternator as I can see the voltage being pumped out of the Alternator into the batteries. When the batteries are charged the Pro Split R dissipates the excess load. However, I normally have the fridge on, radio, iPods charging, Plotter and so on when the engine is running. So there’s always something for the Split R to top up.

Brilliant bit of kit and I think one my best buys of the 2012 season.

UPDATE: Dec 2013
Still doing a fantastic job. I do not worry about battery charge at all. The Pro Split R should be standard in all boats they are that good!

Next is part 4 – Installing a Solar Charger

The article above is related to works that the author has carried out to their own boat at their own risk. This article is intended to share the authors experience with other readers only. It is not intended to be a comprehensive step by step instruction guide. Anyone choosing to do any work as a result of reading this article do so at their own risk. If there is any doubt about whether to conduct work on your own boat call a professional to assist.