Estimated Autopilot current draw

[ICENI]

Whilst in lockdown 2 I am doing some planning.

In order to come to a conclusion of power management I am trying to assess several things.

As my previous boat had a tiller autopilot, I would be very grateful of some help.

I am going down the solar route to increase battery capacity on my Bavaria 32.

My question is has anyone checked their battery monitor (Current drawn) on a Wheel steered autopilot with a reasonably well balanced boat when just on autopilot as a check please? 

During the Summer months on a swinging mooring, I am off grid so rely on engine and solar to keep the batteries in a good state of charge.

I know the approximate current drain and time my fridge is on and have checked my instrumentation current drain, but can only do a rough estimate of what current my autopilot takes.   Up to now I have not used the autopilot whilst sailing to save running the new batteries down too far.   

Any information on this which, I know, will only be approximate, but would be grateful of some input on this.

Whilst writing, on my previous boat I had a good service battery bank and 4 x 40watt Sunshine solar panels on a custom made solar arch which, in the Med worked very well in a liveaboard situation with the fridge and freezer on a lot of the time. 

I also would be extremely grateful on solar panel comparison input.   I feel the Victron panels may be a good choice but as I said, the Med performance of Sunshine Solar panels was very good.   Now back cruising in the UK I am aware things may well be very different.

At this present time I am using 2 small 6watt panels just to keep my batteries 'up' whilst the boat is laid up.   Tested last Winter they kept the old batteries charged and in a recent test in quite low light showed that their output was quite good.

Thanking anyone in advance for their input.

[symphony2]

Suggest you read the thread just below on battery upgrade.

To summarise, the main current draws are fridge and navigation gear - the former is typically 25-30AH (running about 25-30% of time at 3-4amps) and navigation including autopilot around 30-35AH at a typical 10-12 hour sailing day. Add around 10AH for lights, radio and pumps you are looking at 70-80AH. Night sailing with nav lights obviously adds more. So if you ignore any charge you need a nominal battery capacity of 200AH+ to keep within 50% discharge. The typical Bavaria OE was a single 140AH lead acid and an optional of the same size, so 280AH. This is more than adequate for "normal" UK cruising. As to charging, 2 hours motoring a day will put in 20-30AH (as well as be good for your engine).

In practice most people motor for more than 2 hours a day - not unusual to spend 40%+ passage time motoring, but even if you only do 2 hours a day your deficit is around 40AH out of your nominal 280. I would suggest a 100w solar panel would more than replace this if you are on a swinging mooring. It really is not the same as the Med - your energy consumption is far less in the UK, primarily because of the lower fridge requirements, and generally speaking people spend far less nights at anchor. Have a look around at other similar boats and you will find that very few have significant solar or wind as they manage their energy consumption well within the sort of battery capacity that is suggested above.

Suggest you run with what you have for a year and monitor your actual energy use. Even if you do find your service bank runs down, you can still start your engine independently. If you feel the need to improve your system then the priorities for expenditure are first reducing consumption (LEDS, insulating the fridge or simply keeping frozen liquid in it all the time) then improving the performance of your batteries. AGMs have greater usable capacity, higher charge acceptance and lower self discharge than flooded lead acid.

[ICENI]

Thankyou Symphony 2,

In my seventy years of sailing My last two boats have been overloaded with energy greedy electrics.

From the early days when I used just a compass, leadline and careful plotting, things have drastically changed!

I still totally enjoy the sailing experience but being on a peaceful swinging mooring has its disadvantages.

I have to adopt care in the use of the many electrical creature comforts.

From all the reading on this very helpful forum, my next house batteries will be AGM's

[Salty]

Whilst in lockdown 2 I am doing some planning.

In order to come to a conclusion of power management I am trying to assess several things.
.
I am going down the solar route to increase battery capacity on my Bavaria 32.

.
During the Summer months on a swinging mooring, I am off grid so rely on engine and solar to keep the batteries in a good state of charge.


I also would be extremely grateful on solar panel comparison input.   I feel the Victron panels may be a good choice but as I said, the Med performance of Sunshine Solar panels was very good.   Now back cruising in the UK I am aware things may well be very different.

At this present time I am using 2 small 6watt panels just to keep my batteries 'up' whilst the boat is laid up.   Tested last Winter they kept the old batteries charged and in a recent test in quite low light showed that their output was quite good.

Thanking anyone in advance for their input.

In response to your original queries, I purchased two 100 watt panels from an ebay supplier same as the one in the photo attachment. As stated these were each rated at 100 watts, but on more than one occasion on a nice sunny day I noticed that the input to my Marlec charge controller was recording at 217 watts for the combined input from the two 100 watt panels. These are basically house roof type solar panels rather than “Marine” versions, but they have worked remarkably well, and have far exceeded my expectations.

Like you, my boat was kept on a swinging mooring essentially from April 1st through to October 31st, with no opportunity to be able to plug into a 240 volt shore supply at any stage through that period. I did run the engine on a couple of occasions, but only for a few minutes just to check the engine prior to going off sailing for a day or two. The charge controller was set up to charge only the domestic batteries, and a separate bank of batteries used for an electronic antifouling system. The engine start battery did not have a charging feed from the Marlec charge controller, though it was first on the line whenever the engine itself was running.

[symphony2]

If one wants to benefit from all the electrical goodies now available then you have to accept that "pure" sailing has to be compromised. Some people post on forums how proud they are that they barely use their engines, sailing on and off their moorings and only run the engine for a few minutes at a time. Then they complain about their engines getting coked up exhaust elbows and salt deposits in the heat exchanger, and how difficult it is to keep the battery charged, then festoon their boats with unsightly solar panels.

Treat the boat as a system and accept that if you want to consume electrical energy you have to store it and then replace it as it is used. This means increasing storage capacity and then choosing the best way to replace your usage. Far and away for the type of sailing most do around our coasts the best strategy is using the engine - under load, so also moving the boat rather than just charging the battery. Solar has its place if you do not have access to shorepower to put a bit back in when the boat is unattended, but it is of more use to replace some of your daily usage than to fully charge a big bank in the same way that a mains charger does.

Interestingly with my last boat we only had a single 140AH lead acid as originally fitted. The boat was used for charter in Corfu  and would normally run up 4-5 hours a day under engine and moor at a quay overnight. Electrics were basic - highest consumption was the fridge, but that was usually stocked full of cold beer and wine, so actual energy usage was relatively low. Never had a problem with flat house battery, but it only lasted 4 years because of the high number of discharge cycles. The engine though did 3500 hours in 7 years with no problems and no coking of the exhaust. When I took the boat out of charter, I increased the bank to 230AH to cope with the change in usage pattern.

[Goboatingnow]

Personally , I wouldn’t touch AGMS. They have no better discharge characteristics then FLA and their superior charge acceptance and low standby discharge are characteristics you can’t make much use of on a boat. To top that up they are more sensitive to overcharging and cost more.

I would say to people, batteries merely store electricity. You need to balance consumption demands with generation ability , not battery bank size.

In my case I have 280Ah domestics and just upgraded from 200 W of solar ( 2x100W) to 360 W ( 2x 180 w) if I can find space I’ll redeploy the existing 200W

My next task is to build the VSR , which is an open source alternator regulator to try and eek out more from the 60A alternator.

I run the standard fridge and this year would like to add the little standalone dometic freezer

[symphony2]

What you say perfectly supports my argument - you build your your energy system to reflect your usage. As I explained when I had my boat in Greece I used FLA - but in the UK, where the OP and myself use our boats, AGMs are superior to FLA as we rely on the engine to provide most of our charge and AGM's fast recharge is clearly an advantage. Equally our boats are left unused for most of the time, so the low self discharge is a benefit. As to discharge characteristics, the discharge cycles are greater than FLA in general, although there are FLAs with high cycles they are typically far more expensive than the sort of AGMs that are now available derived from automotive use. Look at the figures I quoted earlier.

Not sure why you would want to "build" a VSR. They are simple items available off the shelf for less than £100. If you continue to use FLAs then consider using a Sterling charge booster as this will up the charging voltage from your alternator and so increase the speed of charge into your batteries.

Agree about balancing your usage and generation capacities - and yours is different from mine (and many in the UK) so the solutions are different. Very few UK boats have significant solar for 2 reasons. First we don't have the sun to make the best out of them and second our usage rate is best served by greater capacity and using the engine.

[ICENI]

I agree with Symphony 2 regarding improving the alternator output.

Having used one very successfully on my old boat, soon after buying my Bavaria I fitted a Sterling Advanced alternator regulator.

Although installing these units do require slight alternator dismantling and soldering wires to the alternator brushes, together with the use of a BEP DVSR instead of the diode splitter which can reduce the feed to the batteries by as much as 0.7 volt,   This not only improves the output from the standard 60ampere alternator but also causes it to function like a modern three stage mains charger and starts from the over 14 volt Absorbtion state through to the lower float voltage state thereby monitoring what the battery bank needs which is much better than just running the engine and hoping.

My main problem is I love sailing and hate motoring which is why I have been asking helpful posters like Symphony 2 and others  lots of questions.