To always connect shore power when leaving the boat or to power off?

[Seahope]

My natural inclination is to disconnect shore power and turn off the battery switches when I leave the boat. SWMBO thinks this is unnecessary effort and that we should leave on shore power and let the battery charger keep the batteries topped-up.

As I have just installed new batteries (2 x 110 amp hour) I was wondering which approach will keep the batteries in best condition?

I should add that I often forget to actually turn off the main battery switches when we leave the boat and that there is something called a mercathode system installed and a galvanic isolator installed on the boat. With the original batteries within a week they ran down to the point the engines would not crank.

Apologies if this is a regular thread, but I didn't see anything obvious when I searched the forum.

 

[sarabande]

It sounds as if the power consumption when the boat is not in use is rather high. Approx 50 amp hours in a week ?


Do you have any figures from an ammeter when the boat is at rest ?

At that rate leaving the power connected is the only sensible choice.

 

[Seahope]

It sounds as if the power consumption when the boat is not in use is rather high. Approx 50 amp hours in a week ?


Do you have any figures from an ammeter when the boat is at rest ?

At that rate leaving the power connected is the only sensible choice.

No, unfortunately I don't have any instruments that could tell me that information.

 

[RIN]

I asked a similar question a few weeks ago. It depends on whether you have a modern 4 phase charger (IUoUo) I haven't so I will be fitting a timer to give me a couple of hours per week. Thread here http://www.ybw.com/forums/showthread.php?t=232658 I always leave the batteries switched on.

I think you may have an electrical problem as you should not be running 2 x 110AH leisure batteries down in a week.

 

[PaulGooch]

My natural inclination is to disconnect shore power and turn off the battery switches when I leave the boat. SWMBO thinks this is unnecessary effort and that we should leave on shore power and let the battery charger keep the batteries topped-up.

As I have just installed new batteries (2 x 110 amp hour) I was wondering which approach will keep the batteries in best condition?

I should add that I often forget to actually turn off the main battery switches when we leave the boat and that there is something called a mercathode system installed and a galvanic isolator installed on the boat. With the original batteries within a week they ran down to the point the engines would not crank.

Apologies if this is a regular thread, but I didn't see anything obvious when I searched the forum.

You say the original batteries went down in a week, is that when they were in good condition, or of late ? Good batteries didn't ought to go flat in a week.

Personally, i always turn the isolator switch off, that way nothing can run the batteries down and there is no chance of anything nasty happening, such as a wiring fault setting light to the boat (unlikely, i know).

With good batteries and the isolator turned off, it won't make a tremendous difference to the life of the batteries if you are visiting regularly and they are not getting too discharged. Leaving the shore power on would depend a lot on the type of charger you have fitted.

 

[KevB]

A possible draw back for leaving plugged in if you don't have a Galvanic Isolator is you might find your anodes 'go' quicker.

 

[Angele]

Also, turning off the charger when away lessens the possibility of the charger overcooking the batteries. This may not be a problem on all systems and, assuming they are the wet type, not a problem if you regularly check the elctrolyte levels. But, if you don't, there is a risk that you could "boil" them dry.

 

[Philiz]

We leave the shore power lead on but only to run a dehumidifier and heater. The main isolator switches are left off. I dont like leaving a battery charger on because batteries that are a bit iffy, but have only just been disconnected from the charger might easily start the engine, but after a couple of days away, say at anchor, they they may let you down. I also think it's safer to turn as much off as possible.

 

[RIN]

At the back of my mind I have the view that if you have any sort of water ingress into the boat when you are not there, the 12V bilge pumps are going to work fine for an hour or two then you are in trouble. If the battery charger is connected, The pumps will run until they wear out, effectively taking the power from the 240v system. But you do need a charger capable of not boiling the batteries.

Incidentally. if our boat is anything to go by, there are a number of devices hardwired into the batteries, that you cannot switch off with the battery switches. VHF Radio, Bilge Pumps etc. But not the cockpit lighting which makes things difficult if arriving on the boat in the dark.

 

[Scubadoo]

I turn off my batteries every time I leave the boat and leave the shorepower connected only during the winter months for the heaters etc. However I do have a solar panel to trickle charge one of my batteries (domestic) which seems to do the job nicely. The only other things that is always connected is the bilge pump.

One of the reasons I don't like the shorepower always connected is if there a fault develops such as causing anodes to dissolve quicker etc. I also simply don't like the idea of batteries always on when unattended and the added security that you can't start the boat without the battery keys etc.

 

[VicS]

My natural inclination is to disconnect shore power and turn off the battery switches when I leave the boat.

"Mercathode" system.

Does that not mean that you have to leave the shorepower on? Or is its power consumption so small that it can be supported by the battery for prolonged periods.
Also does it need the battery to be switched on to operate or is it fed directly from the battery.

Your galvanic isolator should protect you from the galvanic corrosion/excessive anode wastage that might result from leaving the shorepower connected.

 

[Seahope]

"Mercathode" system.

Does that not mean that you have to leave the shorepower on? Or is its power consumption so small that it can be supported by the battery for prolonged periods.
Also does it need the battery to be switched on to operate or is it fed directly from the battery.

Your galvanic isolator should protect you from the galvanic corrosion/excessive anode wastage that might result from leaving the shorepower connected.

I wish I knew. The number of wires in the engine room baffles me and it is located at the back of the engines where I certainly can't reach it. All I know is that it is working as my surveyor suggested I get it checked as operating.

 

[VicS]

I wish I knew.

I think this is something you should find out.

The installation instructions show a direct connection to the battery, so it's on all the time. They also show an 8amp fuse in the supply ... that implies a fairly substantial current drain from the battery. I have also found a statement that with a Mercathode you need a battery charger because it will drain the battery.

On the other hand the sales blurb talks of an "insignificant" current !

I have not succeeded in finding out just what the typical current drain is .. I guess it can vary depending upon the amount of additional impressed current cathodic protection is required though

My gut feeling is that with a Mercathode system you will need to keep a battery charger on all the while.

It may well be what has drained your battery.

Are your two batteries permanently in parallel or can you isolate them individually.

 

[Seahope]

I think this is something you should find out.

The installation instructions show a direct connection to the battery, so it's on all the time. They also show an 8amp fuse in the supply ... that implies a fairly substantial current drain from the battery. I have also found a statement that with a Mercathode you need a battery charger because it will drain the battery.

On the other hand the sales blurb talks of an "insignificant" current !

I have not succeeded in finding out just what the typical current drain is .. I guess it can vary depending upon the amount of additional impressed current cathodic protection is required though

My gut feeling is that with a Mercathode system you will need to keep a battery charger on all the while.

It may well be what has drained your battery.

Are your two batteries permanently in parallel or can you isolate them individually.

There are separate battery isolator switches up-top with a parallel switch so I think that they can be individually isolated. Why?

 

[BGW]

There are separate battery isolator switches up-top with a parallel switch so I think that they can be individually isolated. Why?

If you are asking why they can be isolated independently, it's to let you save one battery for engine cranking.

You should maintain one battery in isolation so you will always be able to start your engine.

 

[VicS]

I think that they can be individually isolated. Why?

As BGW says basically. If your Mercathode system is permanently connected to one battery but the battery isolators and the linking switch are open then even if it runs that battery flat you should still be able to start the engine on the other.

Bad for your battery to be run flat though so sort out the Mercathode and the charging to ensure that does not happen.

Now tell me. You have two engines each with its own Mercathode system. connected to its own battery.

 

[hlb]

Mines been on shore power for the last ten years, I switch off what I dont need, but leave the charger on. As said above, if it decides to sink, I want the pumps and claxton to work. Never been a problem.

 

[carlton]

The Mercathode will drain your boats batteries. The harder it has to work the faster the drain. If you are keeping your boat in the water you NEED to keep a battery charger on the battery or the battery will go dead and you could sink the boat. Make sure you use a marine rated fully regulated and fully rectified battery charger.
/QUOTE]

...from Here.

The Mercathode system, (I believe - but may be wrong) puts out 20 to 40 mA in fresh water, and up to 200 mA in salt water.

 

[Bloater]

Have you got a fridge that you have left on? You say that you sometimes forget to switch off the batteries, could this mean that you also have forgotten to switch off the fridge?