Advice on an 12v electrical problem

[Scubadoo]

Looking for some advice/direction on resolving a 12volt electrical problem on my Sealine S24…..last weekend I discovered that the engine battery is leaking voltage to the domestic battery/circuit. The “leakage” seems to be no more than about 0.5amps (the boat domestic volt meter fluctuates 8 to 12v when switching on an led light), the problem occurs when I switch the engine battery key on and I leave the domestic battery key switched off.

I have already checked the “Battery link” solenoid by disconnecting, also removed the battery key panel and all looks okay and disconnected the bilge pump fuse. Looking at the Sealine wiring diagrams (which is not that helpful) I can’t see any other connections where the two batteries circuits could connect.

Anyone got any suggestions where I should look next or have experienced anything similar, any advice gratefully received. Failing that, anyone know of a good marine electrical engineer?

 

[Converging]

I had faulty battery isolators that had become old and corroded. Gave the impression of switching off but didnt,

 

[volvopaul]

Alternator blocking diode, or if its still got sealines **** quality solenoid that usually melts when you use it to switch both start and domestic batteries together.

Other than that, look at retrofitted appliances that can bo wrongly wired.

 

[halcyon]

Looking for some advice/direction on resolving a 12volt electrical problem on my Sealine S24…..last weekend I discovered that the engine battery is leaking voltage to the domestic battery/circuit.

I can only think of three points were the engine and service batteries meet, as standard.

The bilge pump is supplied via fuse / float switch from engine battery, and circuit breaker and switch from service battery. So common with float switch closed and helm panel switch set to on.

The link relay coil is supplied via diodes from both engine and service battery.

You may have the radar diode pack fitted, this supplies radar, chart plotter from both engine and service battery. Avoids low voltage and spikes when starting from service battery on twin engine boats.


If it's a diode you will see around 0.7 volt fixed drop between voltage on engine battery and voltage on service cable.

If the service voltage drops dramatically for a small load, you have a leakage via a piece of equipment, or between terminals. Try increasing load, switch on cabin lights, does the voltage fall to zero ? if so it's probably tracking some where, due to salt / moisture.

Brian

 

[Scubadoo]

I can only think of three points were the engine and service batteries meet, as standard.

The bilge pump is supplied via fuse / float switch from engine battery, and circuit breaker and switch from service battery. So common with float switch closed and helm panel switch set to on.

The link relay coil is supplied via diodes from both engine and service battery.

You may have the radar diode pack fitted, this supplies radar, chart plotter from both engine and service battery. Avoids low voltage and spikes when starting from service battery on twin engine boats.


If it's a diode you will see around 0.7 volt fixed drop between voltage on engine battery and voltage on service cable.

If the service voltage drops dramatically for a small load, you have a leakage via a piece of equipment, or between terminals. Try increasing load, switch on cabin lights, does the voltage fall to zero ? if so it's probably tracking some where, due to salt / moisture.

Brian

Thanks Brian, very helpful comments.

The bilge pump is on the service battery including circuit breaker and switch, there are no connections to the engine battery, so I can rule out the bilge pump.

You make an interesting point about the diodes from the engine and service battery, I had not consider that, so I will have a look at that. I have no radar system to worry about.

You comment on 0.7volt drop, I did see a 0.8volt drop, but need to double check that. But I also noted the dramatic voltage drop when I switch on two cabin lights as you suggested and the voltage did drop to zero. But I have no equipment connected to the engine battery apart from the the usual trim tabs, stern drive electrics etc, everything else seems to run off the service battery.

Hopefully this weekend I will have another look and keep in mind your suggestions, thanks!

 

[Scubadoo]

Alternator blocking diode, or if its still got sealines **** quality solenoid that usually melts when you use it to switch both start and domestic batteries together.

Other than that, look at retrofitted appliances that can bo wrongly wired.

Thanks Volvopaul, yes it does have the sealine "quality" solenoid, but I have already ruled that out by disconnecting it completely and the fault persists.

I will have a look at the alternator blocking diode, good point, where about is it on the alternator (Volvo AD31 engine), is it obvious.

Apart from that, I don't have any retrofitted appliances, well I did have 11years ago, so probably not that.

Thanks for your suggestions.

 

[mario]

You could try calling ADAM on 07921764251
He's just finished contract work on "hugo boss" quite a young chap but really bright helpful and knows his stuff,might also mention he's grerat value at £15 ph ?
He's based in the the portsmouth/chichester area,just mention mario...
good luck

 

[halcyon]

Thanks Brian, very helpful comments.

The bilge pump is on the service battery including circuit breaker and switch, there are no connections to the engine battery, so I can rule out the bilge pump.

The one thing is to take a length of 1 sq mm cable with you about the length of the boat.

Attach one end to one of the negatinve battery terminal posts, remove battery clamp, but the wire between the post and clamp. you now have a common zero point.

Strip the other end and twist it rount the negative probe of your multimeter, and tape. Your meter now measures voltage relative to the common zero point.

You can now measure both positive and negative voltages relative to the common point, at any point on the boat. Thus avoiding changes in earth voltage as you move away from the battery, it also shows earth faults as you always work from this common negative zero point.


Best of luck

Brian

If y

 

[aquatom]

Engine bay fan relay causes this on a Fairline (not sure how sealine do it) the fans are switched from the ignition (start batts) but are fed from the service batts.

 

[Scubadoo]

Engine bay fan relay causes this on a Fairline (not sure how sealine do it) the fans are switched from the ignition (start batts) but are fed from the service batts.

Thanks, but I am pretty sure the engine bay fan is all on the service battery. I only need to switch on the service battery switch and the fan will work without the engine battery.

 

[gazz]

batt charger?

 

[hamster]

you need a multimeter to see if you have engine battery voltage on the domestic circuit when the domestic switch is off ?

or is everything powered up even when the domestic switch is off but engine switch is on?

How do you know it is 0.5 Amps ?

Battery charger will probably be hard wired to all batteries and not through the battery switches so if there is a problem with shorting out the batteries then it will be there all the time and one battery will always drain into the other.

 

[Scubadoo]

you need a multimeter to see if you have engine battery voltage on the domestic circuit when the domestic switch is off ?

or is everything powered up even when the domestic switch is off but engine switch is on?

Correct, I have the domestic switched off and the engine battery switched on and it shows 12v on the domestic voltmeter (just under 12v).

How do you know it is 0.5 Amps ?

Kind of estimated, when I switch on the cabin lights, the more I switch on the more dimmer they get, so basically each one is rated around 0.163ma and hence switch on 3 lights and that is it, and the voltmeter reads zero (this is still with the domestic battery switched off).

Battery charger will probably be hard wired to all batteries and not through the battery switches so if there is a problem with shorting out the batteries then it will be there all the time and one battery will always drain into the other.

No battery charger on the boat, that at least is one thing I can rule out.

Thanks Hamster for your advice.