How to find unkown load on start battery with switches off?

[danstanford]

2007 Beneteau 323 with the 3YM20 engine. This year as I out the cable on the start battery I could see enough arcing to know that I had a small load. I looked around the corner and all 3 battery switches were off and I did not have shore power connected. All breaker switches were off and I do not have a float switched bilge pump wired outside the panel (always live).
When I installed the house batteries I did not have the same arcing in the same condition of main battery switches off. Looking at the basic wiring diagram in the manual, there appears to be nothing connected between the battery and the battery switches but I am going to traced the leads to verify this.
How would I go about tracing this load? I haven't yet put my meter on it to determine amperage but it is enough to mostly kill the battery if left off the charger.
Thanks, Dan

 

[pateco]

It is most likely a direct lead to your bilge pump.

 

[dlochner]

bilge pump, stereo (for the memory functions), a short.

Start at the battery switch, see what is connected.

 

[JimInPB]

I would start with a clamp on ammeter.

 

[MisterR6]

Do a draw test using test light or meter with audible tone. Systematically remove possible loads( fuses, relays ). Shouldn't take long.

 

[Ron20324]

Look at your battery switch's lugs. Most likely you will find a small-ish wire on the same lug as the cable that goes to one of your batteries via a glass fuse close to the switch.. For now, take the fuse out and/or lift off ANY wire other than the batt cables. Next time, lift the cables off the batteries themselves. Don't you have the 323 manual? It lists all the wires and ID number thereon. And if you find the fuse, get some spares.

When I rewired to add a third battery, I moved ALL the little wires to the other/off side of the switch (which becomes the 12 volt buss). This way, when I turn off ALL switches, ALL voltage is off.

 

[kloudie1]

Don't forget the charger itself; could have some bad ju-ju in some diode that is letting current out of the batt..

 

[Head Sail]

Unless your the original owner, you can't rely on the owners manual. Many owners make changes to the OEM wiring. Answers by others are good starting points. If you have and ACR, it may have been in the combined state when you removed the wire and saw the arch.

 

[LloydB]

How would I go about tracing this load?

Remove positive DC connection(s) at battery. Verify that there is no voltage on each circuit to be tested (both DC&ac) before measuring amount of resistance of each. Smaller ohms bigger draw bigger ohms less load. Flash testing is generally not recommended as it usually leads next testing level (SMOKE TEST). Also reverse leads -\+ at each circuit when testing as an unknown diode may appear to be an open circuit.

 

[jeepbluetj]

Don't forget the charger itself; could have some bad ju-ju in some diode that is letting current out of the batt..

Or, as would be quite common, a large filter capacitor on the output of the charger. The spark may be charging up that cap (i.e. a pretty high initial current, then pretty much nil)

Stereo memory is always a good suspect, but only a blitherin fool would connect that upstream of the switches.

Electronic bilge pump would also be a suspect. A float type should be zero current draw unless it's on.

Use the current setting on your meter. If it's a very small current you're gonna need a $$$$ DC clamp on to find it. But wire in a freebie harbor freight on the 10A setting will be fine.

See how much current it's pulling. Then start pulling fuses, etc..

 

[Ron20324]

Here is a pic of Chuck's B323 boat, not mine. I think it is all OEM, but can say for sure.

 

[Benny17441]

Check the back of the battery switches as you obviously have something connected or wires shorted that bypass the cutoff switches. A visual inspection of the wiring and switch contacts should reveal a hard wired circuit or a short circuit.

 

[Ken Cross]

My refrigerator installation says to wire the DC directly to the battery. I discovered that by killing the house batteries while on the hard. New to me boat, t thought shutting the battery switch off would be enough. I must turn the fridge switch all the way to off. That was expensive.

Ken

 

[danstanford]

Thanks Everybody, I will go first check the wiring at the switch and then start tracing stuff using an ammeter. Will let you know what I find.
Dan

 

[Hello Below]

Along with the bilge pump and stereo radio, there may also be hardwired smoke, fire or CO detector(s) that are powered all the time. These devices will normally bypass battery switches.