electrics question

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atlowers

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Help, re-wiring battery banks. with starter battery on, domestic bank off (2 breakers not 1 switch) I am getting 12v to all domestics. surepower isolator with A 1 & 2 connections. If I just connect alternator connection to A should I get 12 v at 1 or 2 with nothing else connected. I also get 12v at A if I just connect starter battery 12v from the crcuit breaker switch to 1. New Isolator?
 
<<<If I just connect alternator connection to A should I get 12 v at 1 or 2 with nothing else connected.>>>

The live output from the alternator should be connected to stud on the 1-2-off switch so that the selected bank can be charged.
 
No offence but I think you need to express your questions more clearly or provide a diagram. It's not at all clear whether you are describing 'circuit breakers' in the technical sense or isolator swithes (plural) or indeed a rotary selector/isolator switch, or some combination of the above.
 
I agree with Ken. I cannot make much sense of your description.

A diagram of what your have done should explain it all. A picture is worth 1000 words.

I deduce that you are using separate battery isolator switches , not a 1, 2, both, off switch but you dont say if you are using any form of split charging system. You refer to shore power but you dont say how that relates to the 12 volt system, a double outlet charger or what.

Tell us exactly what equipment you are using for splitting the alternator output between the two banks (if indeed you are) and shorepower charger you are using. If necessary we can then download the manufacturer's data sheet.

Scan in a hand drawn diagram if you have a scanner , or even photograph one. Otherwise do a diagram in MS Paint
 
Hi,
From what I can understand the Sure Power unit is a simple split diode and you have two separate single pole switches. If this is correct:
Connect a wire from the alternator to the terminal marked A in the Sure Power unit.
Connect a wire from the terminal marked 1 on the Sure Power unit to the starter battery positive terminal.
Connect a wire from the terminal marked 2 on the Sure Power unit to the positive terminal of the domestic battery bank.
Make sure all the negative wires are connected together and to the negative terminal on the alternator.
If the alternator has a sense wire or connection, connect the alternator sense terminal to the positive terminal on the domestic battery bank.
This will allow the alternator to charge both battery banks, the sense wire should compensate for the ~0.7volt drop across the diode and optimise the charge on the domestic battery bank.
Fit one switch between the positive terminal of the starter battery and the starter motor ..... can’t be more exact because you’ve not provided enough info’.
Fit the second switch between the positive terminal of the domestic battery bank and the domestic load, usually in the cable to the main fuse/switch panel. Again need more info’ to be more exact.
This will allow you to “switch off” either or both batteries when you leave the boat, but won’t allow you to switch in the domestic battery to help start the engine in an emergency, but you can always do this with jump lead.
Hope this helps.
 
I read surepower as shorepower earlier (well it was early for a Sunday and it was not capitalised)

With that cleared up I agree with all you say.

Just the following comments.

The alternator output must go directly to terminal A of the Sure power unit with no connection to anything else.

The connection from the starter battery isolator should supply all the engine circuits. Probably taken off from the starter solenoid connection anyway.

Personally I would fit a third switch to interconnect the battery banks in an emergency rather than use a jump lead. The spark produced when connecting or disconnecting a jump lead can, and very occassionally does, ignite the hydrogen given off by a battery with disastrous results!
 
Thank you chaps, sorry about the lack of clarity, it was a bit of a rushed post. Ian has managed to clear the fog and his description is accurate. I have fitted a seperate link switch to the two battery on?off switches. I have tried to get a diagram but cannot scan it onto here. Ok all that said, I am confident my wiring is as per Ians post.
Starter battery to sw1. other side of sw1 to starter and to terminal 1 on the surepower isolator.
domestic battery to sw2.-other side to domestics and to terminal 2 on isolatore.
aternator to terminal A on isolator.
Link sw across sw1 and 2.

My problem is that with the starter battery switch on I am not isolating the domestic side and therefore my starter only battery is crossing somehow to the domestic side. All switches are ok.
with domestic side sbattery on and starter battery switch off I do not get power to starter
with engine battery on and domestic off iget power to everything.
I did a diode check on the disconected isolater and appars ok but applying 12 v to terminal a gives me 12 v at terminal 2. which is the domestic side so does this mean the isolator is faulty.
My concern is that somewhere I have a crossed feed onto the domestic side from the engine which will be a nightmare to find. (New engine with 20 year old loom)
hope this is a bit clearer.
Thanks
andy
 
My first thoughts are that if there is a connection somewhere between the domestic supply and the engine supply then both would be energised which ever isolating switch is closed.

Therefore I think I would be suspecting the diode assembly. If the diode supplying the starter battery has failed to a short circuit then that would explain what you observe.

Disconnect it completely and test it with a multimeter with a "diode test" range. You should get no reading between 1 & 2 in either direction. You should get a reading between A & 1 in one direction but not the other. Similarly between A & 2.

Alternatively simply swap the connections to 1 & 2 over. If the fault is what I suspect you will now have the domestic battery energising everything rather than the starter battery doing so.


BTW to get a scanned image onto here upload it to a Photobucket or other suitable photo hosting site account and then use in the same way as any other picture.
(Tinypic.com is a no frills Photobucket site.)
 
Thankyou vics, I will give that a try and also sort out the upload capability. I think the diode pack is the problem and sods law Ian has just sold the very item on this forum. Hows my luck?
 
just back from boat, no short between terminal A and terminal 2 and yet when i apply 12v to terminal A I get 12 v at terminal 2 with nothing connected to it. Any advice most welcome as I am bemused. I assume diode is breaking down when 12v applied.
 
In your post above, you say: " Link sw across sw1 and 2."
What does this mean? Do you have a link across SW1 and SW2?

Also, result of your last test seems normal to me: if you put +12v on the "A" terminal of the diode splitter, then you should see +12v at both the outputs 1 and 2.
 
I have put a 3rd isolator switch in so that I can link both battery`s if reuired.
If with engine battery switch made but engine not started should I get 12v straight though to the terminal 2 from the alternator and if this is the case is it normal to be able to run domestics off of the starter battery. ie domestic feeds are linked to termnal 2 so with 12v on terminal 1 and thus to terminal A I will always be getting draw off of starter bank even with domestic bank battery switch off. This is driving me mad!
 
Thanks for clarification.

(1.) The third isolator switch should be on the "output" side (i.e. load side) of the isolator switches.

(2.) With +12v on terminal 1, you should not see +12v on the 'A' terminal and thus neither on the terminal '1'. If you see +12v on the "A" terminal (engine/alternator off) then the diode for the domestics is "duff" ............... or there is another path from the engine battery to the "A" terminal.

I would suggest removing the diode pack from the boat and test it as a "stand alone item" to see if one (or more) of the diodes is passing current when reverse biased as described by VicS above.

Alan.
 
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