Wiring an Old(small) cruiser

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slig

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Anybody have any simple diagrams for wiring a 2 battery 1 altenator electrical system using an isolator.

I am using one battery for the engine and one for the domestics. From what I can see I have to take a seperate feed from the positive of both batteries to the isolator and connect the altenator directly into the isolator.

I think I have it figured but I want to be sure. If I set the boat on fire I'll never be forgiven /forums/images/graemlins/frown.gif
 
Hi,

your on the right track, just finished wiring mine and works okay hope this helps.

Capture.jpg
 
using a GOOD QUALITY 1 2 off both switch all the circuits to the common terminal and the two batteries to the other two. Select the starter battery, start the engine, when that battery is charged, switch, via "both" to the services battery.

OR

just connect the engine to the common terminal and all the other circuits to the services battery via simple isolator. Operate as above.

OR
(Better many will say) engine to one battery, domestics to the other, each with simple isolators, and a VSR to charge the second once the volts on the first have risen to the set point of the VSR plus an interconnecting switch for emergency use.

Countless variations involving split charge devices etc but remember a simple diode splitter will loose 0.7 volts.

First idea is the simplest will work quite satisfactorily but you must get a decent quality 12off both switch, or just use two simple isolator switches. Switch one on or the other or both (or neither)
Second idea is just a variation on that.

First idea is what Nairndale has drawn. BUT it must have a both position as you MUST change over via the both position if the engine is running
 
[ QUOTE ]
here is what I have so far

[/ QUOTE ] I'm being thick perhaps but what is ID and where does ? go.

I think whatever you'll need both battery negatives connected ... just an omission I guess

I think this is Ok but the individual battery switches are unnecessary or the change over switch is unnecessary.
BoatElectricsoptB.jpg


What was option 1 ? /forums/images/graemlins/grin.gif
 
[ QUOTE ]
I'm being thick perhaps but what is ID and where does ? go.

I think whatever you'll need both battery negatives connected ... just an omission I guess

I think this is Ok but the individual battery switches are unnecessary or the change over switch is unnecessary.
BoatElectricsoptB.jpg


What was option 1 ? /forums/images/graemlins/grin.gif

[/ QUOTE ]

Option 1? A fire hazard allegedly /forums/images/graemlins/tongue.gif. I used Archicad to produce the drawings, Real overkill (10K worth of architectural software) but Paint annoys the head off me

ID is Isolating Diode. To be honest the isolating Diode, although more complicated, would probably be my preferred method(if I could figure out how to wire it)

The battery switch sounds grand but I would use battery 1 for the domestics at night switching to battery 2 to start the engine in the morning and then while cruising use both. While both are selected the "juice" from the higher charged battery will flow to the lower one to make up the balance which creates 2 problems:
1. I end up with 2 half flat batteries if I get stuck instead of 1 good and one bad
2. Rapid charge & discharge of the batteries creates alot of heat.
 
You may also need to assess whether the output from your outboard is sufficient for your batteries. I've never used an outboard for charging but I am given to understand that this is not a particularly effective way to charge batteries.
 
I heard that aswell, seemingly the output from the altenator on an outboard motor isnt great. But it is all I have, its a 50HP 4 stroke motor so if I need I can probably upgrade the altenator, I only have about 3 ft of roof top space if I want to put in solar and wind is costly.
 
[ QUOTE ]
ID is Isolating Diode

[/ QUOTE ] OK.

Lets put the diagram where we can see it

BoatElectricsoptC.jpg


If it is just a simple diode then it will only have two connections. The cathode will be connected to what you label battery 1 while the anode will be connected to battery 2.

It would not be a good scheme because there would be a 0.7 volts drop across the diode so battery 1 would never be properly charged. It would not be fully isolated from battery 2.

If the device you have has three terminals it is probably a diode splitter. Two diodes with the anodes connected to one terminal and the the cathodes connected to the other two. Normally that would be connected with the alternator output connected to the common terminal and the batteries connected to the other two. BUT that would necessitate separating the charging output from starter motor supply as you would not be able to feed the starter current back through the diode. It may or may not be possible to do that.

You are also still stuck with the 0.7 volts drop. Whether or not this is important rather depends on whether your outboard has a non-regulated or a regulated rectifier. Small outboards usually have a relatively small electrical output and a non regulated rectifier, large outboards have bigger electrical output and a regulated rectifier. Yours could be either.

A VSR rather than a diode system would over come all the problems I think. It would simply require a connection to each battery and a connection to the common negative. Initially the relay would be open and so the batteries would not be connected. When the volts on the starter battery rose to a set value it would close thus linking the batteries.

The only problem left then I think is that there is no provision to use battery 1 as the starter battery in an emergency. VSR devices exist that have an override provision. A switch could be included to link the batteries. A single jump lead could be used.
(jump leads always carry a small risk of igniting hydrogen and exploding the battery, a small probability of it happening but the consequences of a face full of bits of battery and sulphuric acid would be serious. It can happen and very occassionally it does.)
 
Maybe I'm missing something, but it rather seems to me that the bit between the busbar and the switches has the polarity reversed.

I've always preferred (+) ----fuse----sw----Load----- (-), so switching off or blowing a fuse leaves everything at battery negative.

With a big lump of rusty volvo metal at battery -ve potential, it matters on my boat. It may not on yours, but I wonder if it wouldn't be better practice anyway.

A real sparks will be along in a minute to explain why I'm talking bollocks...
 
[ QUOTE ]
Maybe I'm missing something, .......... I'm talking bollocks

[/ QUOTE ]
No neither. Normally the fuses and swtiches would be on the positive side.
 
The simplest and best system IMHO is firstly the engine is wired in the usual way to the start battery with an isolation switch. (simple on off.)
The domestic battery is wired again in the normal way with +ve going via na isolation switch and fuse/cb to distribution of loads.
Now connect the negatives of the 2 systems together with a high current cable. Run a wire via a switch from the positive of one battery to the pos of the other battery. This switch (simple on off) should be capable of high current. ie 200Amp. It becomes the charge switch for the domestic battery and the emergency jump start for the engine battery.

Once engine is started operate the charge switch and when the engine is topped open the charge switch to provide isolation.

When you get the urge (or funds) replace or bypass the charge switch with a VSR Voltage sensing relay which automatically connects the domestic battery for charging when the engine is running by sensing the higher engine battery voltage.
While isolation diodes will do this job the voltage drop will mean neither battery will be fully charged unless you can get at the regulator on the engine to sense voltage at the battery or increase the regulated voltage to make up for diode loss.
In your diagram the 3rd terminal of the ID would go to the alternator output which would have to be disconnected at the motor from the battery wire (at the stater solenoid)

Yes the 50HP outboard probably has a regulated charging system that will suffice for your needs. An ampmeter would best to confirm your actual charging current which you will be able to relate to the current used on domestics.
If you find the batteries not being charged enough because engine is not used enough then a solar panel will help. More solar the better but even 10W will help a lot. good luck olewill
 
[ QUOTE ]
I heard that aswell, seemingly the output from the altenator on an outboard motor isnt great. But it is all I have, its a 50HP 4 stroke motor so if I need I can probably upgrade the altenator, I only have about 3 ft of roof top space if I want to put in solar and wind is costly.

[/ QUOTE ]

I can't give you definite figures but we had a 50HP outboard connected to one 110AH battery for both engine start and domestic on our last boat. Easily kept up but we only had a few simple instruments and domestic lights (no Fridge etc which is the killer)

As a routine we never plugged into mains to charge the battery. Of course the 50 HP doesn't take much to start for a battery like this and if ever I killed the battery *technically* I could start by hand! This never happend though.

Do you have a fridge or other power sucking device (I can't read the diagram from my current connection) if not do you really need to have a more complicated set up than my old one ?

Just a thought.
 
Thanks everybody for your replies. I'm learning alot here, just a few additional questions though.

VSR. what does it stand for, any links to where I could get one. I fully intend to keep the batteries seperate if possible and in an emergency I can still manulally pull start the engine.
I like the sound of this system. I also assume that there is now no need to take a seperate lead from the altenator.

We have no essentials on the domestics, the cabin lights can be replaced with a flash light and the bilge pump can be upgraded by using a bucket.

From my interpretation the second battery is always kept charged up by the engine and the domestics battery becomes an overflow essentially. This would suit me perfectly as on long trips the domestics would still get fully charged while on short journeys the main battery would still be maintained.

RE: the switch panel, as I said the wiring is pretty bad, there are 2 blue leads coming from the battery to the panel at the minute and I must have confused them when they reached the switch panel. I'll ammend my diagram to suit that
 
VSR is voltage sensitive relay. they are set to close at someting like 13.5 volts IIRC which means that its normally open but when the volts rises to that value it closes and connects the other battery.
There are elecronic (solid state if you prefer) ones as well mecahnical ones.

Generally available from all the places that sell all the other electrical stuff.

I assume by
"From my interpretation the second battery is always kept charged up by the engine and the domestics battery becomes an overflow essentially"
you mean that the domestics battery is cahged via a diode. trouble with athat is that there will be a 0.7 volts drop across the diode so the domestics battery will never be properly charged. A VSR has no volts drop hence its advantages.

Not properly charging a battery is not good for it.
 
I have just look up your profile and realise you are a motorboater.

So whilst travelling along you needs are going to be catered for by the charging circuit on your 50HP battery. Every minute whilst motoring you will be "putting more in" then you are taking out from depth/log/running lights. Mine always was when I had a sailing boat which motored a lot. Assuming the alternator on your 50HP is working OK.

So UNLESS you a running a Fridge (Are you?) or some other high drain device air con/heater/tv/microware do you really need to have more than one decent battery ?

Unless I am missing something I can't understand why you have the need to move away from one (big 110AH) simple battery. It will easily start the OB and you will have plenty for a couple of hours of domestic light for the odd evening.

Simpler, cheaper and easy.

If you were a sailer there might be a different answer (no power whilst travelling for a lot of the time), if you run a fridge the battery won't keep up.
 
No I have no fridge, all the electrics I have are fairly basic, couple of lights, radio, fishfinder etc. I very rarely spend nights on the boat but every year we would spend 3-4days on a cruise down the Shannon.

I could probaly get away with a single battery but as I already have 2 leisure batteries I like the sense of security of not having to worry about the engine one getting drained.
 
[ QUOTE ]
VSR is voltage sensitive relay. they are set to close at someting like 13.5 volts IIRC which means that its normally open but when the volts rises to that value it closes and connects the other battery.
There are elecronic (solid state if you prefer) ones as well mecahnical ones.

Generally available from all the places that sell all the other electrical stuff.

I assume by
"From my interpretation the second battery is always kept charged up by the engine and the domestics battery becomes an overflow essentially"
you mean that the domestics battery is cahged via a diode. trouble with athat is that there will be a 0.7 volts drop across the diode so the domestics battery will never be properly charged. A VSR has no volts drop hence its advantages.

Not properly charging a battery is not good for it.

[/ QUOTE ]

Sorry I worded that wrong. What I meant is the main battery(engine starting) is always topped up by the engine first and once thats full the additional power goes to the second battery(domestics)

Like this?
http://s666.photobucket.com/albums/vv29/adrianaplus/?action=view&current=BoatElectrics4optD.jpg
 
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