Technical Article: #012

Title: Hustler Rewire Part 3 – Installing a Sterling Pro Split-R
Date Added: 4th November 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 4 – Installing a Solar Charger
I’ve always had a solar panel onboard every boat I’ve owned as a way of keeping the batteries topped up. I don’t have a mains connection that can be used to charge the batteries, as my mooring is a pile mooring. In addition, I’ve never viewed a solar panel as a primary means of charging the batteries as the UK rarely has enough Sun to make this a reliable proposition.
Small Panel Install
However, as general maintenance of the batteries and enough to charge the batteries should the bilge pump switch on my needs are small then a small panel is fit for purpose for me.

Deciding what’s suitable
As we all know every boat is different and their requirements for power are different. I’ve tried to break this down into a number of scenarios. I’m not saying this is the definitive view but it’ll give you an idea of what solar panel is used in what scenario. I’ll list a few example scenarios.

Scenario: The Weekender
Visits the boat every weekend sometimes if tide, weather or time is against them this sailor leaves sailing till the following weekend. Not much in the way of electronics just small plotter/log/depth/radio. Occasionally uses a tiller pilot but only when it’s calm and motoring.

Sometimes it’s just nice to sit on the boat to watch the world go by on the mooring. Charging of phone/iPad/Hand held Games batteries and lights are the primary use. Sailing consists of primarily day sailing from mooring to anchorage or marina. The longest passage time underway would be 20 hours before reaching their destination.

The primary battery charge period being when the engine comes on when motoring in and out of harbours to a mooring. Battery configuration is typically a single 80-100ah house battery and 60ah starter battery.

For this scenario a 5–10 watt panel could fit the bill to keep the batteries topped up.

Scenario: The cruiser
Keeps a boat on a swinging mooring, sails regularly and only uses the engine when motoring in and out of harbour.
There is a more expansive array of electronics fitted and other items demanding 12v power. These items are typically large screen plotter, Radar, Depth/Log/Radio, fridge and even possibly a TV screen.

This sailor does regular 20-40 hours passages sometimes more under sail wherever possible. Sometimes the autopilot is switched on the fridge is running intermittently and the heater is on if the temperature drops whilst underway. The cruisers battery banks consist of the 70ah starter battery, 2 or 3 100+ah house batteries.

For this scenario a couple of 30watt panels will help charge the batteries. However whilst this sailor is aboard it won’t be enough to keep the batteries fully charged for the amount of energy that is being used.

The other scenario is the long term live aboard that’s either in the med or Blue Water long distance cruising. Which whilst there are Hustlers that have done this for the majority of us we fall into the weekender, the cruiser or somewhere in between brackets. Therefore, I won’t cover this scenario.

I fall into the bracket of the weekender with a little bit of cruiser. I have the odd two week cruise but it’s mainly coast hopping as I need to replenish water after a few days of being away from any marinas with my full crew of 4. So how did I determine my Solar Panel needs?

Calculating the panel size
The wattage of the solar panel you need is perhaps the most important thing to get right when assessing your requirements.

If you underestimate the amount of panel power you need you could be very disappointed with the results, as the batteries won’t be charged to your expectations. Overestimate and you might end up spending more than you need to. There are three to consider when thinking about a solar charging system.

  • Power use
  • Power generation (the solar panel)
  • Power storage (the battery)

To work out the wattage correctly, the panel needs to be sized according to how much power you are going to use. If you’ve followed the advice in the first part of the rewiring project then you will have this information to hand as you will have conducted an electrical audit of the boat. To work out the watts used by your boat here’s the formula…

Watt = amp × volt

Yep, it’s that easy! Simply multiply the number of amps used by your volts and this gives you an idea of how many watts are used per hour. This will give an idea of how much power the panel will generate. The higher the wattage of the panel the more energy will be put back into your battery bank.

Divide the daily total Watt-hours you require by the hours of usable light you expect in an average day. This will give you your minimum panel wattage. In the UK, allow 1 hour of light in winter, rising to 4 hours by mid-summer. I found the table below quite helpful when calculating what the sun output is for the UK. It’s based on a 10 Watt panel for the four seasons of the year (It assumes 6 hours of daylight per day).

Seasonal Output

LocationLat (degrees N)Dec - FebMar - MayJun - AugSep - Nov
S England501Ah3.5Ah3.5Ah2Ah

A worked example
So in my case consider the following scenario…

I’ve had a full days sailing. All instruments have been on for 8 hours. I’ve not used any engine at all. The fridge has been on for 4 hours to chill the wine. I’ve dropped anchor and we’ve still got the chart plotter on as the Anchor drag alarm. Evening starts to draw in around 8pm the interior lights and Anchor light goes on, it gets a bit chilly and the heater is switched on (I’ve not got a heater yet but plan to!). We have music playing too as we while away the night.

I’ve used a total of 68 amps battery capacity for the days activity.

In my case I have a 7.5 watt Solar Panel. This is not enough to charge the batteries after this much use as it would take approximately 18 days to charge the batteries back to full capacity assuming 6 hours of sunlight per day. Alternatively, if I had a 30 Watt panel it would only take 4 days to fully charge the batteries.

However, the reality is that in my case as a weekender I would have the engine on to leave harbour. I would sail for the day. The engine goes back on when approaching the anchorage to circle for a suitable spot and pull on the anchor to ensure it sets. Then I’d motor off the next day.

My current panel would only be trickle charging the batteries during the day sail (4-5 amps per day in the summer). Again, for my needs to keep the batteries at peak charge when away as a weekender and topping up during a day sail it suits me fine.

I hope this gives an idea as to the considerations that’s needed when thinking about the size of panel. As I’ve already mentioned, for me I only wanted to trickle charge. If I wanted to travel further and not rely on the engine I’d definitely look at upgraded to a couple of high wattage panels.

Location, Location, Location
A key point around Solar Panels, think about where they are located. It’s important to remember that shadows, cloudy skies, dust and dirt can all reduce the effectiveness of your panel. So it’s really important to factor this in when it comes to placement of the panel on the boat and the number of panels. For example if the panel is mounted on the coachroof. Depending on the time of day the boom may block the panels access to the soon by casting its shadow.
In my case I found the perfect place on the rear rail on the Pushpit.

My Installation
So having covered the basics of Solar panels. Here’s my solution and installation. As has already been mentioned I opted for a small trickle charge panel for the following reasons:

  • I only wanted to maintain the batteries all year round
  • I didn’t want to use the Solar panel as my primary charging source. However, if I wanted to later on I had the option to switch panel size
  • It was cheaper and fit my needs

Choosing The Right Panel
There are many, many Solar Panels for all shapes and sizes of boat/needs. I’m not going to cover the options and types available, as there’s plenty of great resources out there that cover the topic. I’m only going to cover what I did.

In my case I wanted something I could mount on the rail. I’ve had coach roof mounted panels before. Yes it worked quite nicely but I just didn’t want to drill holes into the coach roof. I also wanted something that I could detach and put away if I wanted. The panel also needed to be compact enough not to get in the way when we are working around the Pushpit area.

This severely limited what I could get wattage and price wise. It was either high wattage and high price or low wattage and low price. Seeing as though I wanted the trickle charge it didn’t matter if it took a few days to charge the batteries, as I’m a weekender.
This is what I opted for:

The Sunsei 7.75W Solar trickle charger
Sunsei Solar Grip Mounting Kit For SE-400 and SE-500 Solar Panels 10555

Note: This also has the name DZ energy and A+ life – I think this is one of those Chinese franchises hence the name changes! Despite the name change they are all the same product.
The Sunsei/DZ Energy Panel

The Sunsei/DZ Energy/A+ Solar Panel – Note the blue charging light

The Solar panel is an extremely rugged panel, it came with all the cables necessary and it also allows me to daisy chain two or three together to create a 22.5 watt array if I needed to. Which if using my scenario above my charge time for the sample days usage would drop to 5 to 6 days! Another big factor was the mounting kit. This kit has a clamp that attaches to the panel and this clamps to the rail, no drilling, and no fuss. The kit allows me to detach the panel as the connector plugs are waterproof and have sealing end caps. Perfect!
The Sunsei waterproof sealed plug

Sealed Plug allowing me to disconnect the panel and keep connections dry

The Sunsei Panel Mount on the rail

The rail mount – There’s plenty of room for another two panels here and the back rail seems to be always in the sun

Installation was very straightforward simply mount the clamp, mount the panel and run the wiring back to the batteries (see my wiring diagram in Part one of this series).
Obviously, keep in mind the length of wire used. The longer the cable the more voltage drop. However, in my case it was so small I could barely register any drop.

Please remember to keep the panel covered when installing as it will be generating electricity even if just lying on the side. You don’t want to create sparks when wiring it all together.

The Regulator
There was one change I made to the standard install. This was to include a charge regulator. As this was a 7.5-watt panel there was little chance of the panel overcharging the batteries. However, there was a chance, especially if I couldn’t get to the boat for months on end (No chance! But you never know what could happen). I didn’t want the batteries over charging and gassing. In addition I also wanted to charge the starter battery and the house batteries.
I used this solar regulator from Maplins by a brand called Kemo. Here’s the specification:

  • Separately charges 2 batteries
  • Maximum charging capability: 2 x 8A or 1 x 16A
  • The battery with the lowest charging voltage will receive more charging current
  • LED status lights
  • Power consumption of less than 2mA is taken from the battery
  • Reverse current protected (no additional diode required)
  • Easy to install
  • Would cater for any expansion needs

Not only would it fill my needs but it also has a little charge light on it (This is in addition to my NASA BM-1 showing the battery charging too).
Kemo Regulator installed

The regulator installed in my Battery Bay, note the charge lights.

I’ve used the panel all season and it’s been perfect. I’ve never run out of battery power. The batteries have always been topped up and there’s never been any problem with charge. I thought I’d need to take the panel off in rough weather but the clamp has proven itself to be extremely sturdy. I just do the odd twist to tighten every month and it’s fine.
The finished install

The finished panel installed on the rail

All in all the panel, the mount and the regulator cost me just over 100GBP. It’s been brilliant and given me peace of mind all season.

Update: Dec 2013

This has been superb. I do not worry about the batteries charging at all now as they are always topped up. I leave this plugged in over winter too and again no issues at all. An excellent bit of kit.

Next is part 5 – Installing a new Stereo

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.