Random Electrical Vampires

[Hydraulicjump]

Perhaps stochastic is the better word, but posting this to the chat to see if there are good ideas on finding a solution.

Three evenings ago in Reid Harbor we went to bed with just the fridge and masthead light on. On the usual check of the anchor around three in the morning the batteries had gone flat (four house AGMs three years old and otherwise normal in performance). I turned off the house batteries at the main switch and voltage rebounded to about 12.4. Still not good. IN the morning I experimented with pulling fuses. Sure the fridge was a draw, as expected, but disconnecting the DC Dash 1 fuse block had the most measurable reduction in draw. Included the switch panels on the dash and the head and transducer (wired differently than the factory manual). My guess was that I was having a problem with the masthead light, although I was surprised that the transducer creates draw when it is supposedly off.

Next night, anchored out in Hardy Bay off Malaspina Straight I left the fridge on low and did not turn on the masthead light. Bingo. Perfect evening with the batteries only down slightly in the morning (12.7) with the fridge on low all night.

Feeling I had solved the problem, we set up the same ritual last night in a very crowded Heriot Bay. substituted an LED flashlight for the masthead light, then set the fridge to low and went to bed. You guessed it, same result as night one. Batteries down to 12v around 3:00 in the morning. Turned them off at the main switch and they recovered to 12.5. I am currently annoying my neighbors by running the engine to charge things up.

For the life of me I cannot think of a vampire that works one night versus another. The only difference was we ran the inverter continuously while the engine was running trying to charge our Torqueedo. But the inverter was turned off shortly after arriving at our anchorage, so it should not be drawing on the batteries.

Suggestions welcome! Can't blame the batteries I think....

Jeff

ps: nice to see folks coming back from the Broughton rendezvous. Headed that way (hopefully).

 

[Connerkip]

Just a couple of thoughts.

When you went to bed the night your batteries went dead, were they fully charged?

The third morning your batteries were at 12v. If these are AGM, they are considered almost dead at 12v. Should try to not let them go below 12.3v (50% SOC).

I would not give much credence to the “rebound” voltages you see, as a measure of good batteries. With low loads, there really shouldn’t be much of a rebound unless the battery is failing or weak.

Is your anchor light LED?

I anchored a lot. With full charged batteries at bed time, fridge and anchor light did not pull the batteries down even close to 12.3v, except when they were bad.

Keeping the chartplotter on is a fair draw.

Good luck with your analysis.

 

[Hydraulicjump]

Thanks for the quick reply. Some clarifications. Batteries were not fully charged at bedtime because we had been on the hook for a while before that.

I am very aware about not discharging below 50%, which is why this causes so much anxiety, believe me. And the reason I reported the rebound voltage is that you cannot tell the soc when the batteries are under load. Turning everything off allowed me to assess what the actual soc was.

Plotters (command bridge and cabin) are most certainly off.

I am going to eventually find the source of this and will--with tail between my legs--report to all.

Jeff

 

[Red Raven]

Perhaps the difference between the nights is whether the refrigerator compressor was actually running when you checked the battery voltage. When our batteries failed we would see a full volt drop each time the refrigerator compressor turned on. Listen for your refrigerator to cycle on and watch the battery voltage. If you see a large swing it is likely your batteries are toast.

Curt

 

[Cessna172]

I don't believe you should ever rule rule out failing batteries. My House batteries failed at 2 years 8 months. Symptoms were very similar to yours.

The House bank would die overnight with next to nothing turned on (one interior LED light and the mast light). With everything shut off, my C28 displays a .55 amp draw. I believe this is from the Garmin autopilot CPU because the needle fluctuates when the A/P light blinks.

Even using a 1000 Amp load tester, the batteries tested good. Came to find out a standard load test isn't adequate for deep-cycle AGM's.

 

[oneeyedjackass]

On our R23 the dash switches are lit up and cannot be turned off (expect w/ main house switch). It’s on my list to add a switch. You also have the carbon monoxide detector, but that shouldn’t draw that much. Good luck
Mark

 

[scross]

Just some thoughts on power conservation at anchor....
Our batteries are getting old. Will be replacing all six batteries at the end of the season. We have wet group 27 batteries going on 5 years old. They are regularly checked and topped off with distilled water when needed.
For anchoring we turn off everything at night except the refrigerator and LED anchor light. All interior and exterior lights on the boat are now LED except the red chart lights and the light in the head. Carbon monoxide detector replaced with two 10 year battery units. Solar LED dock lights are installed in the cockpit. In the evening we use mason jar lamps at the dining table that are powered with a coin battery so as to minimize the cabin lights drain on the house set of four batteries. We haven’t used the inverter once in five seasons.
On shore power we are not at all frugal with the lights or other equipment.

 

[Hydraulicjump]

Thanks for the input everyone. We are about to hoist anchor and head to catch Dent Rapid at slack. While I have a cell connection, I thought I would remind the key observation: batteries were fine two night ago, working to spec. Not fine last night or the night before. Something is draining them and I can’t find it yet.

Off to the Broughtons having to run the engine to top up batteries before bed. Just like the rest of the stinkpots out here,

Jeff

 

[Pilotnavigator]

When looking for which device is using current the simple tool is a DC clamp meter. Everyone should have one! Turn things off and on and check each line from the battery toward the devices.

 

[Hydraulicjump]

Yep. Have one. But difficult when it is gangs of wire.

This morning at Shoal Bay with just the fridge going all night had 12.67v showing. Victory, right? Nope. At 7:00 the colts crashed and I turned on the engine. I am starting to think short. Now how to find it.

Into the Broughtons today.

 

[macnmm]

I had a similar problem with older original equipment AGMs where the house would draw down rapidly and so would the engine battery overnight on anchor. My theory is that with bad batteries, even the propane solenoid left on draws 1-2 amps and can do it if the relays are also combining the banks due to solar charging and then everything drawing down together overnight so the relays stay on. Fridge is over 5 amps with compressor on and bad ventilation behind the fridge (in theory would draw less if cool air was back there). Anchor light is .4 amps so not a factor for me anyway. Displays and sonar are about 8 amps so they stay off.
Put your clamp meter on the house negative and show dc amps. Then you can see what is drawing it down as you turn things on and off. If even a small draw kills the house bank, time to get better batteries.


Sent from my iPhone using Tapatalk