Current draw with batteries off.

[Interlude]

I have a 1998 Beneteau 461. There are 3 isolation switches for the batteries; positive for engine, positive for house and common negative.

There is a shunt on the battery side of the negative switch with battery monitor connected. If I switch off the negative before the positive there is a 0.2 Amp ongoing load. If I switch off the positive before negative there is zero amp draw.

One other observation is that when I switch off the negative before positive, the auto bilge indicator light is not illuminated, when I go positive before negative the light is on. Interesting that when the light is on there is no current and when it is off there is current. The indictor light is a small LED panel lights and obviously draws nothing.

The auto bilge has power with both the light on and off - seems that this must be the problem circuit.

Any ideas? or suggest tests?

Regards
Stuart

Interlude
Sydney Australia

 

[Stu Jackson]

Sounds like the bilge is wired directly to the house bank. Turning off the Beneteau negative wiring to ground (the engine) stops any flow through the shunt. What you're seeing with the 0.2A is the parasitic drain of the battery monitor (since you have a shunt you must have a monitor, right? Just like you said...). So what else is on when you shut off the positive?

Just to add my favorite: It all depends on how it's wired.

 

[Interlude]

Thanks Stu. The bilge is wired directly to the house bank. The only other thing that is directly wired is the engine room alarm.

The confusing thing for me is that there is no drain when I turn the positive off before negative, but there is a drain when I turn negative off before positive. The boat is a 1998 Beneteau 461.

Regards
Stuart

 

[Stu Jackson]

That's truly bizarre.

Again: Just to add my favorite: It all depends on how it's wired.

Really - I understand the Beneteau wiring design basics, but unless you have a complete (repeat) complete wiring diagram, there's really no way we can help.

Ron? Are you there, C'mon, help us out here.

 

[Brian D]

Well an LED is a diode. If you are getting an ON condition when it if off, then it might be wired in reverse. As far as current flow when the NEG is switched off, you might have another ground somewhere. There could be a ground loop in your boat.

 

[Don12364]

A Thought and a Suggestion

Just a thought but it seems possible that the additional 200mA could be drawn by something which is bypassing one of your master switches - e.g. the bilge alarm.
One would want to know if the power to the pump and float switch went off so I presume the LED could be associated, either to indicate the power was on, or again, to show it was not on.
Either way the bilge alarm box could have a relay which comes in to sound an external alarm bell or buzzer should the power to to the pump and float switch be interrupted. Though you may not have a buzzer fitted the relay could still be present and drawing current.
Turning off the positive supply would cause this relay to be energised and the current drawn would show on your meter, but by removing the negative first the relay would not be able to come in so there would be no current.

I suggest the only way to get to the bottom of this will be to disconnect each wire in turn from the battery terminals or master switches and insert a milliammeter in series with each and then to go through the two different switching routines. You are really looking for the small wires rather than the main cables.

The concept of having an 'always on' supply is quite common and on my boat it powers the following:-
1) Link 1000 - Battery voltage monitor lead to each of house and starter batt positives. Quiescent 41mA Display On 56mA.
2) Adverc External Alternator Regulator - Battery voltage monitor 5mA from starter battery only.
3) NASA Navtex 45mA - always on to ensure a weather forecast immediately available on our arrival.
4) Bilge pump and float switch via a 10 amp breaker next the engine master switch - no draw current except when pump is running, then 3 Amps.
5) Battery voltage monitor for the mains charger - 5mA.
6) Battery voltage monitor for the solar charger - 2mA.
7) Eberspacher Heater - via 30 amp fuse - 18 A on start up and switch off and 1-3 amps when running. By passes master switches to prevent inadvertent switching off before it has completed its own shut down routine.
My shunt is in the common negative of both batteries so it reads all of the above.

Thus I have a constant drain of 100mA on my batteries - or 72 Amp Hours per month - i.e. a whole battery full!
My boat sits on a mid-stream mooring with no shore power so I rely on my solar panels to keep the batts topped up.

IMPORTANT All these small wires are permanently energised and each is connected directly to a battery terminal and not via one of the master switches or circuit breakers; so the positive connections to each item MUST BE FUSED. I use 1 amp fuses. For info the makers of the Adverc the need for deny this.

Is your switch in the negative intended to remove all power including the battery voltage measurement circuits of the Batt Mon and the alternator charger?
You might find it more useful to use it to connect both house and starter batteries should one be low (Assumes none of your 3 switches is an Off/1/2/All type).

 

[larryw]

Gotta love that French wiring! On my boat, I never turn the house bank off. I keep my fridge running, the stereo presets need a bit, and the monitor itself will draw a bit. Turn off the engine start circuit and leave it at that.

 

[Interlude]

Thanks to all for the excellent thoughts, comments and suggestions. I have started the process of updating the wiring diagram as I have added a number of items to the boat over the past few years as we get close to joining the extended cruising world. Items include generator,wind, solar, new 12v fridge, inverter, electric winch, electric head and electronics such as HF and AIS - lots of new wires, and as Stu says.."it all depends on the wiring" very good advise and as I have had different people wiring in these components (including me), there could easily be some issue.

I will certainly follow up the auto bilge circuit. There is a bilge alarm that activates when the bilge is running, but I am not sure if there is a relay in the circuit that might also activate the alarm when power is interrupted. Donalex's clear explanation of the possible role of a relay is much appreciated and I will certainly take this on.

I also like the idea of wiring all the permanent circuits (bilge pump etc) directly to the battery terminals (with fuses) rather than than the hot side of the switches - this would make them clearly accessible and reduce the pile of connectors currently on my terminals.

In response to Donalex's questions:

1. The power to the float switch and pump remains on with the LED on and off.

2. the negative shunt is on the battery side of the switch and the alternator, generator and shore power charger negatives are also on the battery side. The boat is on a swing mooring and not connected to shore power.

Thanks again for all the advice. I will report back after following up your these suggestions.

Stuart

 

[Mike B]

Check to see how the battery monitor is wired. I suspect the ground is not switched but wired directly to your ground via the shunt. If that's the case then you always have ground to the monitor which would explain why you still see some current flow even with the ground switch turned off. The hot side is likely switched which is why you see zero with the house bank turned off. BTW that current draw is probably the monitor.
As for the bilge pump, it should be wired so it has power regardless of the switch position. This way it will always run if need be, no matter if the switches are on or off.