12V Boat Wiring Diagram

[Mavis]

Hi.
During last season I posted a thread asking for advice as my batteriies seemed to be discharging too quickly http://www.ybw.com/forums/showthread.php?t=284081

Now the boat is ashore and winterised I am still trying to get to the bottom of the problem and doing my own wiring checks. I have already found a couple of faults which I have now rectified, but nothing conclusive that is the definitive cause of the apparent disharge.

I want to make sure that the main wiring layout is correct so that I can discountand it from my research. I would be most grateful if someone with knowledge could either draw a simple sketch, or describe in words, or point me to a diagram on the web showing the correct, most efficient wiring layout for connecting:

One dedicated Starter battery with it's own Main switch
Two Leisure batteries, controlled by one main switch running the domestics, and instruments.
Engine alternator and (Smartbank) relay.

The wiring diagram on the Smartbank site is a help, but does not show everything I need, and everything else I have seen is slightly different from my setup.
Thanks

.

 

[VicS]

The diagram posted by SJF for the benefit of Demonboy might be a good starting point but modified for the Smartbank rather than the Sterling Alternator to Battery charger.

 

[VicS]

You may also find the "Boat electrical notes" on Tony Brooks' website useful

see http://www.tb-training.co.uk/

 

[SJF]

The diagram posted by SJF for the benefit of Demonboy might be a good starting point

Pleased to see its still of use to others...

 

[Mavis]

Thanks for your help, unfortunately I am still no better off as it appears every thing is wired correctly as expected.

I have had the batterys tested by a mechanic where he used a device with thick copper bars (drop tested?) and he said they are fine. Is there any other way of testing these batterys to allow me to eliminate them??.
Thanks.

 

[TrueBlue]

Perhaps a bottom up approach is needed:-

Get a cheap digital volt meter with a current (amp) range.
Get a cheap inspection light with a 12v bulb (20 watt or brake lamp size would be nice)

Switch all the switches off including the isolators
Disconnect both sets of batteries.

Gently touch the disconnected cable to its battery in turn. If there's a spark or "ziss" then something you've missed is in circuit.

If not does the inspection lamp turn on,
If not select volts on the meter. If a reading then there's something in circuit.
Try the current range at its greatest range (as otherwise you'll blow the meter). If there's a reading then something is in circuit.

Repeat the whole procedure in turn including both batteries connected in circuit as if one is dodgy it may be dragging down the other.

You've already done the obvious now you need to do some legwork aided by some equipment.
Not rocket science,
No point in pondering wiring diagrams,
get down there and trace the fault

Here's an inexpensive meter to do the job If you search the site you'll fine inspection leads and some LED torches for not much money to make the carriage charge more practicable.

 

[Plevier]

That sort of test is based on engine starting requirements. It's not a valid test of what Ah capacity your domestic batteries can provide with a sustained moderate load. The only way of verifying that is with a carefully monitored discharge test at a current appropriate to the rating of the battery.

By the end of your previous thread it was looking as though possibly your batteries were never getting fully charged. Have you thoroughly investigated that?

 

[VicS]

The "drop test " does little more than confirm that the batteries are capable of delivering the high current required for operating the starter motor.

Your problem seems to be that your batteries are losing their charge..... forgive me if I dont go back and read the whole of the previous thread.

this may because something is discharging them, that they are genuinely not holding a charge, or if you are relying on a Smartgauge reading it is giving a false indication.

If something is discharging them you will be able to detect that with a the aid of multimeter on its current ranges. If a significant discharge current is detected it can be tracked down by disconnecting/ reconnecting various circuits until the cause is found.

To check the batteries themselves I would get them home and on the workshop bench. Charge them independently until each gives a reading of 12.7ish volts, preferably more, 24 hours after being taken off charge and allowed to stand. Any one that cannot be charged to this level would be suspect.

I would then monitor their voltages for as long as possible. I'd expect the volts to fall fairly quickly at first but then more slowly. I'd expect a good battery to take a good few weeks to fall below 12.6 volts.

The Smartguage ?? it works purely by monitoring voltage. Maybe a small discharge ( a radio memory circuit for example) would confuse it into showing a much lower state of charge than actual.



Maplin BTW are offering their least expensive meter at under £5 at the moment . Get two. You are bound to wreck one doing current checks cos you'll forget its on a current range then connect up to measure volts. Dont ask how I know this!

 

[Plevier]

The Smartguage ?? it works purely by monitoring voltage. Maybe a small discharge ( a radio memory circuit for example) would confuse it into showing a much lower state of charge than actual.

The Smartgauge does only monitor voltage, not current directly, but it's not fair to imply that it is just a voltmeter - which I think your words could suggest. It's a lot more than that.

 

[VicS]

The Smartgauge does only monitor voltage, not current directly, but it's not fair to imply that it is just a voltmeter - which I think your words could suggest. It's a lot more than that.

I know it only actually monitors the volts, unlike say the BM1 which measures current via shunt

So how does it work ? I have never seen an explanation.

Some say it's a better battery monitor than the BM1

 

[Mavis]

Thanks for all your advice.

I am afraid that I all ready have the multimeter, lamp tester, etc and have done all as advised. I have had a (domestic) sparky on board with his various more techinical meters and there is no stray current. The batteries maintain their voltage when the main switch is off. I have had a lot of good help from Merlin the Smartguage people and we did find a wiring fault that would mean the lesuire side was not getting the full charge but that does not explain the loss when charged by a mains battery charger.

Somehow I think it just has be the batteries at fault. You are probaly right in that I need to get them home on the bench and test them perhaps with a set load on them.
Thanks.

Incidently I must say that apart from my own problems the Smartguage system seems to me to be excellent, just about fit and forget.

 

[VicS]

If the batteries hold their charge when switched off but don't when switched on you have a fault or something switched on that is discharging them!

 

[Plevier]

I know it only actually monitors the volts, unlike say the BM1 which measures current via shunt

So how does it work ? I have never seen an explanation.

Some say it's a better battery monitor than the BM1

I would love to know properly too! Can't blame Chris Gibson for being cagey though. http://www.smartgauge.co.uk/sgadesc.html is not very explicit. I think it does something like reconstruct the battery discharge curves from voltage gradient measurements. If you know both the voltage and the gradient you have uniquely defined the point you are at. I don't know whether it does it by analytical relationships or look up tables. I have no idea how it copes with different battery types or ageing.

As a long time traditional battery industry person I used to say it couldn't possibly work, but the evidence seems to be stacking up. Military approval doesn't come easily. I notice that Enersys (which has absorbed many battery companies including the one I was in) is now marketing the military version and Cosworth is collaborating with Merlin on military vehicle power and battery management.

I don't have one only because my sort of sailing doesn't justify it.

 

[demonboy]

Pleased to see its still of use to others...

I'm still refering to it myself, SJF! I have it printed in triplicate

 

[fisherman]

I expect you're up to speed with this, sparky to help and all that, but just in case...from my limited knowledge but years of make do get-you-home boat leccying:
take off the battery live cable, set multimeter to amps, connect the battery live to meter live and the cable to meter neg, this will show any discharge in amps. Then isolate circuits one by one until the discharge stops. Not sure what would happen to the meter if there was a huge discharge, like trying the starter.....

 

[fisherman]

Thanks for your help, unfortunately I am still no better off as it appears every thing is wired correctly as expected.

Is there any other way of testing these batterys to allow me to eliminate them??.
Thanks.

I was told to test with a hydrometer, whether charged or not , if any cell is more than minimally different gravity it's knacked.

 

[kenhick]

You need someone with a amp clamp bang it on the battery lead check for draw keep switching thing off until there no draw, should not be to difficult to work out what is going on if no draw sorry you need batteries.

 

[VicS]

You need someone with a amp clamp bang it on the battery lead check for draw keep switching thing off until there no draw, should not be to difficult to work out what is going on if no draw sorry you need batteries.

Clamp type meters usually have a high current measuring capability. The sensitivity might only be 0.1 amps. That may not be sufficiently sensitive to detect the small current the OP could be looking for.

 

[Mavis]

Thanks all.
I have planned a day on the boat at the weekend, and armed with various testers I intend to slowly go through the whole system as advised. Thanks.

Once everything is sorted I thought I ought to install a mains battery charger and have just posted this question on our own Sadler forum - 'With two 80 amp leisure and one dedicated starter battery I thought it about time I installed a mains powered charger for the odd time during the season that we are alongside with shore power available to be able to boost the batteries. I have been advised that a 20 amp smart charger will do the job. Simple I thought, just Google one and order it - Not!.

With so many to choose from I am blinded by science but have now narrowed my choice down to the Merlin M Power adaptive, the Sterling Pro Charge Ultra, or the CTEK (15amp). All costly and probaly over the top for my needs but perhaps sensible in the long term.

Can anyone recommend any of these ??'

If anyone would like to add anything??

 

[Plevier]

In your previous thread you said you had tested your batteries by going onto shore power until they were fully charged.
If you haven't got a proper charger - how?
What did you use and for how long?