Battery switch wiring

[Stig]

On my First 40.7 I have 3 x 90 degree turn switches for my batteries. One black for the common negatives and two reds, positives, one each for the engine and domestic batteries.

The wiring is such that with either or both batteries on I can start the engine and run the domestic equipment.

My understanding is that the domestic deep cycle batteries should not be used for engine starting as it can damage them. And obviously the preference is not to use the engine battery for domestic use as you want to keep it charged for starting the engine.

My routine <u>should</u> therefore be:
go below - engine battery on
on deck - start engine
go below - domestic battery on
back on deck - start sailing, engine off
go below, engine battery off
back on deck
to start engine, go below etc etc in reverse order......
All very cumbersome.

In fact I just turn on both, start the engine on both and go sailing with both left on. If planning to sail for a long time - turn off engine battery. Then when I want to start the engine - go below - turn on engine battery.......
Often this does not happen and I restart the engine on the domestic battery (tut tut). This would also be the case if the engine is required in an emergency.

On my friend's Oceanis 411 (also Beneteau, same vintage) the switches are the same but wired differently - there is no link between the two batteries. He cannot start his engine on the domestic battery and vice versa. This seems much simpler - switch on both batteries - use domestic toys until batteries need to be charged safe in the knowledge that the engine battery is fully charged.

The only disadvantage I can see in this system is that in the unlikely event that the engine battery is discharged you cannot start the engine from the domestic batteries - but a set of jump leads would solve that.

Questions

Are my assumptions to this point correct?

How easy would it be to change the wiring on my boat or is it worthwhile? It seems simple enough from the supply side but i don't fully understand the charging circuit

How much damage is being done to the domestic batteries by starting the engine on them?

Over to the panel..............

 

[maxi]

£50 and 20 minutes to fit a voltage sensing relay, and you have a fit and forget system that does all that your switch will do, without the hassle or the potential for expensive misuse.
Have a look at Merlin's site. Oh yes, it's easy to do, even for us amateurs.

 

[pvb]

It\'s wrongly wired...

[ QUOTE ]
The wiring is such that with either or both batteries on I can start the engine and run the domestic equipment.

[/ QUOTE ]
If this is the case, it's wrongly wired. You should get it checked if you don't fully understand it, because you run the risk of discharging your batteries and not being able to start your engine. A professional would be able to sort it very quickly, and you'd have some peace of mind that it's working properly. Sounds like your friend's Oceanis is working properly.

 

[Stig]

Re: It\'s wrongly wired...

Thanks Maxi and pvb for your replies

Maxi - I will try the Maplins site

pvb - is this not exactly the same wiring as would be on the four way "off, 1, 2, both" type switch? This is what I had on a previous boat and the effect was the same. Is it "wrong" or just an alternative?

 

[pvb]

Re: It\'s wrongly wired...

If, as you said, you can start the engine with the engine battery switched off and the domestic battery switched on, there's something wrong. Similarly, if you can run the domestics with the engine battery switched on and the domestic battery switched off, there's something wrong. The idea of separate circuits is so that you can preserve the charge in the engine battery for engine starting.

PS The site Maxi recommended to you was the Merlin site, not Maplin.

 

[Stig]

Re: It\'s wrongly wired...

Absolutely agree. I much prefer the other system - hence the original post. I will have it investigated.

Merlin - thanks - slip of the fingers /forums/images/graemlins/blush.gif

 

[Malcb]

Re: It\'s wrongly wired...

That's the standard wiring for an off, bat1, bat 2, batt &2 switch.
Both batteries negatives go to a common negative bus bar and the batteries' positives go to the battery switch which feeds to a positive bus bar.
This means that you can use either battery for starting or domestic. When cruising I usually alternate the batteries so that on even days batt 2 is the start battery with batt1 domestic and vica versa on odd days.

 

[pvb]

Re: It\'s wrongly wired...

Think you need to read stig's original post again.

 

[Malcb]

Re: It\'s wrongly wired...

[ QUOTE ]
Think you need to read stig's original post again

[/ QUOTE ]
I was responding to pvb's post as it is not abnormal to be able to start off either battery as he was saying.

 

[pvb]

One last time...

OK, I'll try to explain. If you read stig's original post, you'll see that he hasn't got a 1-2-Both switch like you have. He's got 2 separate simple on/off switches. These are supposed to isolate the 2 battery circuits. However, they don't do this. That's why there's something wrong.

 

[Malcb]

Re: One last time...

I know he hasn't got a 1-2-both switch. But in effect his system is operating in exactly the same way as a 1-2-both switch. He is able to isolate the batteries independently, but he is able to start off either battery exactly like a 1-2-both switch does. And as a lot of boats' battery systems work using both or either batteris for starting there is nothing inherently wrong with his system. IMHO

 

[pvb]

Fine...

Fine, if there's nothing inherently wrong with his system I'm sure he'll take your advice and leave it alone.

 

[Stig]

Re: One last time...

....except that the two battery banks are different - deep cycle and cranking. That's why I would prefer to use each exclusively for its own purpose but without having all the switching.

 

[johna]

<< Often this does not happen and I restart the engine on the domestic battery (tut tut). >>

The only possible problem with this is that the reduced voltage during starting can cause the GPS and other electronics to crash.

On the KIS basis I would prefer separate batteries for the two duties with a VSR for split charging.

 

[andy_wilson]

However

I doubt you will do any damage to the domestic bank by cranking the engine off them, unless it turns out you have a particularly hard starter. The opposite would be true if you used the cranking battery for long deep discharges.

Put another way, if the cranking battery failed, would you use the domestic bank to get going?

Course you would, you have done many a time unintentionally!

 

[Guest]

Re: It\'s wrongly wired... is it ????

There are thousands of boats out there with this arrangement where any or both will run domestics & Starter .....

OK it may be that this particular boat from manufacturer may normally have a factory system as you or he describes .... I just find it strange that you say clearly its wrong - which disagrees with so many boats ....

My boat has 1 - Both - 2 - Off .......... giving me whichever battery I decide for domestics and / or start duty .... So my boat is wrong ??

Not trying to be rude ... just putting the record straight about so many boats out there !!

/forums/images/graemlins/tongue.gif

 

[pvb]

Re: It\'s wrongly wired... is it ????

The original post explained how stig's Beneteau has separate switches for the engine start battery and for the deep cycle domestic batteries. He explained that his friend's Beneteau has similar switches which work differently from his. When manufacturers fit 2 separate on/off switches in this way, rather than a 1-2-Both switch, it's almost always done to ensure that the engine start battery is properly isolated. On stig's boat, this seems not to be the case, so he's right to query it and it's fair for me to say it's not now wired the way Beneteau intended. Incidentally, my boat also has separate switches for the engine and domestic batteries, so I do understand the concept.

You're right to say that many thousands of boats have 1-2-Both switches. My belief is that these switches are no longer appropriate and have considerable potential for confusion leading to discharged batteries. Today's boats (and equipment) place greater demands on their domestic batteries, and many owners now have 2, 3 or even more batteries in their domestic bank to cope with power needs. To get better endurance, so-called "deep cycle" or "leisure" batteries have been developed and are rightly popular. But these batteries aren't really intended to be used for engine starting (and indeed, as ShipsWoofy has said in another thread, it can even void the battery warranty). So keeping the engine and domestic batteries separate is highly desirable. In times gone by, the 1-2-Both switch fulfilled a basic need in terms of controlling charging, but there are much better solutions available to us today - and, best of all, they don't require anyone to fiddle about with the switch.

So, yes, I reckon stig's boat isn't correctly wired. And, yes, I know thousands of people have 1-2-Both switches (and I've had a few myself in the past) but there are much better solutions available which will become increasingly popular. If you were to look into callouts to boats with engine failure, I bet you'd find that many of them were the result of flat batteries brought about by incorrect setting of a 1-2-Both switch.

 

[Guest]

I have no problem with the concept and use of ...

I wasn't rattling the cage ....

I just interpreted your post as "implying" that all boats should be as you suggest.

I agree that it is best to have an isolated start battery - but many boats don't and survive for years and years with this ....

I am actually considering fitting a 3rd battery - leaving existing on the "old" switch - but introducing a separate start battery .... where that will be controlled by another switch that will connect it while disconnecting original start battery. This will give me the "get-u-home" capability that I lack at present..... without the big changes that fitting another system would entail.

 

[kingfisher]

But what if you don't want an automatic system? As far as I know, an automatic system cannot fullfill my requirements:

I want the engine battery topped up at all times, (so need to give priority to one of the batteries). I cannot top up both batteries by just running the engine, as I have a SAILboat, and only run the engine occasionally. The household battery gets charged at assorted marinas

AND

I want to be able to emergency start the engine on 1, 2 or both.

An automated system will charge both batteries equally, rather than prioritising the engine battery, and cannot join both batteries for emergency start?

Or am I wrong. Because getting rid of the switch would be a plus.

My current procedure:
Come on board, switch batteries from OFF to 1 (engine)
When pottering (canals, locks, no wind), switch from 1 to 2 regularly to top them up.

En of day: switch off, to physically disconnect batteries. The only live wired items at that point is the memory of the radio and the volt meter on the panel.

 

[halcyon]

You can get a automatic system that has the engine battery always connected to the alternator, you can set the voltage, thus the engine battery recharge level, that the service battery is linked in for charging.
It will allow the engine battery to be charged from the service battery if you fit solar panels or wind generater, when the charge voltage is up.
It will allow you to link the engine battery to service battery for starting if required at the push of a remote button.

What else do you want to do ?

Brian