Battery charging and isolator switches

Murv

Murv

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Another quick question...

I have 3 separate battery isolator switches (all unmarked)
I assume that give me the option of using either battery, both, or all off.
if I'm running on one battery, does the second one still get charged when the engine is running or is that purely down to the configuration of the charging circuit?

Also, it's a real nuisance to get to the islators as they're under the engine hatch. All the boats we looked at on the non-tidal side of the river had a rotary isolator switch in the cockpit, is there any reason I can't, or shouldn't, fit one to mine?
 
It's difficult to answer this without knowing how your boat is wired.
Why do you have three? Normally one would be for the house bank and one for the starter battery. Why the third? Inverter, bow thruster?

The isolators should be easily accessible in the event of emergency. There is no reason why it shouldn't be up in the cockpit except that it shouldn't be susceptible to water ingress or corrosion..
 
Started to compile an answer but it really is necessary to know how these are wired, if there is any form of split charging and if engine and domestic circuits are completely separate or if switching one isolator on powers up both.

Draw a wiring diagram and post it.

Fitting a rotary switch may be considered a retrograde step ... esp if the existing has been done to completely sparate engine and domestic circuits.

They went out of fashion, in favour of separate switches at one time. If you fit one be sure its a good quality one
 
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VicS said:
Started to compile an answer but it really is necessary to know how these are wired, if there is any form of split charging and if engine and domestic circuits are completely separate or if switching one isolator on powers up both.

Draw a wiring diagram and post it.
Click to expand...

Boat detail would also be useful, make, model, engine layout.

Brian
 
MartynG said:
Murv

Perhaps you have two isolator switches and a link switch ??
Click to expand...

If the engine electrics and domestic electrics are fed separately that would be likely. If however they are fed together from which ever battery is chosen to be in service then there is no need for a link switch ... you just switch both batteries on.

As already said full details in the form of a wiring diagram are needed before any meaningful advice can be given.
 
VicMallows said:
OP's profile is odd....

About Murv

Interests
Fishing, cycling. Not boating though, never really seen the appeal in that.


:confused::confused:
Click to expand...

Sorry, that was in response to an old thread because it was pointed out that I hadn't listed boating as in interest, it seemed a bit obvious to me if active on a boating forum!
It was just a light-hearted comment.

Apologies all, my question was too vague really, spent another whole day struggling with the boat today so only had time to get a couple of quick snaps of the isolators.

IMAG0112.jpg


IMAG0113.jpg


IMAG0114.jpg


I think I have totally underestimated the magnitude of work involved in trying to learn how everything works.
For instance, there are more switches revealed in the above images that I have absolutely no idea what they do.
Think I need to get on with the priority jobs, get the boat back in the water and try and enjoy it before sorting everything out turns it from a hobby into a chore.

The boat is a '79 Fairline Holiday, Volvo 270 leg but the engine was replaced with a Lancing Marine 2.5 FSTDI diesel in 2003.
Seems the guy who did all the work on it originally built it up to a fairly high spec but it's not had the benefits of such loving care since...
Consequently, very little now works and there are more than a few bodge jobs in place and no wiring diagram.
There are some images (but no details) on some of the works carried out in the past here: EDIT: There were a load of images on the Fairline holiday club website, but that sadly seems to have shut down :(
Anyway, it showed the shiny new engine being installed as well as photos of a full hull strip and recoat etc.
 
sorry cannot tell whats what from the photos.

If the two heavy red wires leading away from the LH and RH switches go to the batteries and the orange coloured one goes to the engine

PERhaps the LH switch is the isolator for the domestic circuits and the other two select which battery is to be used for starting ( and also be charged from the engine)


two black things lower down with buttons on the tops ... overload trips (MCBs ) protecting a couple of circuits ????????/
 
Thanks for that, I appreciate it's a bit of an impossible task.
I will investigate further.

One quick way I could do it (when it's back in the water) is to simply take voltage readings across the batteries with the engine running and the switches in their different positions.
At least that way I'd know what is being charged and when.
 
Murv said:
Thanks for that, I appreciate it's a bit of an impossible task.
I will investigate further.

One quick way I could do it (when it's back in the water) is to simply take voltage readings across the batteries with the engine running and the switches in their different positions.
At least that way I'd know what is being charged and when.
Click to expand...

You probably know already but be sure never to switch off both batteries while the engine is running. With no where for all the electrons the alternator is pushing out to go there will be a voltage surge that could blow the diodes in the alternator. A bit like the front BMW on the m'way slamming on the anchors ... all the rest pile up at 120mph.
 
Murv said:
Thanks for that, I appreciate it's a bit of an impossible task.
I will investigate further.

One quick way I could do it (when it's back in the water) is to simply take voltage readings across the batteries with the engine running and the switches in their different positions.
At least that way I'd know what is being charged and when.
Click to expand...

Just turn on the port isolator, then try cabin lights do they work ? turn on ignition key, do the engine instruments power up ? turn off isolator.

Turn on starboard isolator, try same test.

One is probably engine, the other domestic power, cabin lights etc.

Turn on the centre isolator, try same test. may have no effect, if so turn on port isolator as well, do all circuits power up.

Try same test centre and starboard isolator, you could have the same result, the centre one could be a link to start engine from the other battery bank.

Boating is logic, do not guess, it leads to large bills.

Brian
 
Isolation switches

I think you will soon find that the switches need to be accessible if only for checking "off" when leaving the boat and turning on when you arrive.
As said I think the 3 switches are an ideal arrangement if wired as we might hope.
Firstly are both batteries identical? If they are it might indicate a symetrical battery arrangement where either battery can be used for start and for domestic loads.
If this is the case it might be that both engine start and power and domestic (lights etc) go through the same switch from one battery or the other or both. Charging of both will be via the 3rd switch.

If one battery is smaller so presumably for engine start the bigger one might be deep cycle for domestic use.
Then it is more likely that small battery has a switch to feed just engine panel and start. The large battery then will have its own switch which goes to domestic load.
(so question is can the engine be powered but not the domestics or can the domestics be powered without the engine)
You may then find that one of the switches combines both batteries and loads for emergency starting and possibly for charging.
Lastly it may have a Voltage sensing relay (or even diodes) to provide auto charging to both batteries when engine is running. If not then you will have use the combining switch for charging and I would suggest fit a VSR to automate this function. good luck olewill
 
the central switch looks as if it is a master switch to break all the circuits, with the L and R ones being designed to join batts for e.g. starting. You do need to investigate what does what - precisely.

Ok, Murv, you indicate that you might put this back a bit when you have time, but it is pretty crucial to the boat safety and (expense) management to prevent messing up alternators, diodes and other electrical bits.

Drawing up a diagram before doing any switching as suggested by previous posters will take a bit of time, but it gives you the chance to apply some logic to finding about how someone put the switches together.

Testing circuits (e.g. engine lights, cabin lights, etc) with a meter and noting voltage readings and absence of power when a switch is turned will help establish what does what. DONT do this with the engine running , as has been pointed out.

When you have the rough circuit diagrams, post it on here and we may be able to give you more certain ideas. (The final diagram goes in your maintenance book BTW ) :)
 
I suspect the smaller items in that picture are circuit breakers, probably for bilge pumps or something else that needs to have power when the batteries are isolated.
 
Many thanks all, greatly appreciated :)
Will do some more investigative work at the weekend, and ascertain exactly what does what.
The only thing that I'm not going to know is what battery is charging and when, but that can be tested when the engines running (can't start it whilst it's on the hardstanding)
I won't switch any batteries off when the engine is running.


One battery is a starting battery, the other is a larger leisure type.
They're both at home being charged at the moment and so that I can get them checked (one is showing a Red warning on the built-in indicator)
Seems to make sense to start with known good batteries.

Will report back once I know more info.

Thanks again,

Chris
 
OK, finally got to the bottom of it!

Port switch = Domestic supply from leisure battery
S'board switch = Engine start from start battery
Middle switch - on: Either switch (port or s'board) supply power to both engine start and domestic supply from their respective batteries.

So, I guess in normal use, middle switch off, port and starboard on to supply power to engine and domestic supply. Then, if the start battery dies for some reason, engage the middle switch and start it from the leisure battery.
Sound reasonable?


I still don't know how the charging system is configured, but when we're back in the water it will be a quick test with the voltmeter to see which battery is charging (or hopefully both) when the port and s'board switches are on.

Of course, true to form with this boat, one of the isolators has now developed a dodgy connection so I've had to order another one...
 
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Murv said:
OK, finally got to the bottom of it!

Port switch = Domestic supply from leisure battery
S'board switch = Engine start from start battery
Middle switch - on: Either switch (port or s'board) supply power to both engine start and domestic supply from their respective batteries.

So, I guess in normal use, middle switch off, port and starboard on to supply power to engine and domestic supply. Then, if the start battery dies for some reason, engage the middle switch and start it from the leisure battery.
Sound reasonable?

...
Click to expand...

But turn off the dead battery or you may kill the good one too.
 
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