7.3 Volts

Battery service 7.3V

I woke up and (like I often do) opened my app to check that Charlotte (the boat) was where she was supposed to be. Hmm. No data? Weird.

I tried contacting the Raspberry (the small computer aboard collecting the data) over the internet, but that wasn’t answering either.

“Maybe some mastermind boat thieves have up and away with the boat,” I thought to myself. “And then skilfully turned off all the devices broadcasting position data, including my small Raspberry.”

After a quick breakfast, I walked down to the harbor to check whether my theory was true.

It wasn’t! The boat was still there.

I climbed aboard, opened the companionway, and stepped down the few stairs into the boat.

“Wait, what on earth is that?”

The DC Panel Did It

The switchboard above the navigation table had come alive in a way that I had never seen before. It looked like it was doing some kind of Christmas light show, with all the lights going on and off in a slow and steady rhythm.

I bent forward to check the LCD screen for any indication of what had happened.

“SW 1.27,” it said, shortly, and with little emotion.

“SN 253,” it continued, just a second later.

Then, suddenly, all the lights lit up, and – just a breath later – everything went dark. (“Dr. Chandra, will I dream?”)

But just as I opened my mouth to answer, it woke up again.

“SW 1.27,” it repeated, a bit robotically this time. “SN 253”. Lights!

And then dark again.

I had just a few minutes before I had to get back home to my first video meeting of the day, so I turned off the main service power and left the boat.

As I was walking back home, I started writing a short mail to my Hanse dealer (“Can you explain this?”), hoping there would be an obvious and easy fix to the problem.

The Voltage Did It

“I’ve never heard of anything like that,” answered my dealer. “But I will forward it to Hanse. Let’s see what they say.”

Nothing obvious then, sighs.

After my day of work, I headed back to do some real “debugging” to find the problem. (I know it’s not very maritime to “debug“, but I’ll call it that anyway, if you’ll excuse me!)

STEP 1: Check the voltage of the batteries with a multimeter.

I put the sensor sticks on the poles and looked at the multimeter’s LCD screen.

7.3V …Wait, what?! 7.3V!!

Oh crap. The batteries were dead.

Suddenly the DC panel behaviour made a lot of sense. It started, showed its software version and serial number. Then, when it wanted to activate the switches, the power demand got too high and the voltage too low, and it died. (Ken Mattingly from Apollo 13 would know all about this!)

But why were the batteries dead? I looked at the shore power panel, and the “AC mains” light was bright and green. There seemed to be shore power in the boat, but for some reason, the charger hadn’t been charging. Weird.

First things first, though.

AGM batteries don’t fare well when the voltage drops this catastrophically low, so I needed to get some charge into them, quickly. I went outside and started the Yanmar engine, and then I put some idle throttle to get the alternator some more charging power.

I went back in and looked at the DC panel. The gremlins were gone, for now, luckily. The panel went through its normal startup up and everything looked ok.

“What is the voltage on the main bus?” I asked it, politely, but with a sense of urgency.

“Battery service, seven point three volts,” it replied, monotonically.

Next, if Hanse really had supplied our 388 with a talking central computer, I would have said “All systems, damage report!”, but since they don’t, I had to continue my debugging manually.

The Charger Did It

So, my first assumption about master thieves having sailed away with her, that was clearly incorrect. My second assumption, that the DC panel itself was somehow at fault, this was incorrect as well. Two strikes, one left.

STEP 2: Check the shore power charger.

On the AC panel, the “AC mains” light was on, but the “shore power” light wasn’t. It was a bit weird

The Mastervolt Charger/Inverter seemed completely dead, so if there was power, it wasn’t getting that far.

Getting back to basics, the shore power light was really off, so maybe the problem wasn’t in the boat, but with the actual power supply from the harbor?

STEP 3: Check the shore power supply.

I took a multimeter and measured the AC voltage from the end of my shore power cable. 236 volts, just as it was supposed to be.

Then I plugged a hairdryer into the shore cable to see whether putting a load on it would make any difference. No difference. The hairdryer worked perfectly.

I plugged the shore cable back into the boat and – to my surprise! – heard the charger starting inside!

STEP 4: Recheck the charger/inverter.

The charger was running for maybe ten seconds. Then the voltage meter started to shudder a bit, dropping to 200 volts. And then, suddenly, everything went off. Then flicked on and off again a couple of times. There was obviously something really wrong somewhere. Either the charger wasn’t getting good AC, or the gremlins were located in the charger itself.

STEP 5: Check if there is good AC reaching the charger/inverter.

I turned off the charger and opened its cover. Then, with the shore power connected, I carefully measured the voltage of the “AC input”.

No AC! 0.0V.

The problem wasn’t in the charger. The problem was that the charger didn’t receive any energy, or when it did, very sporadically.

Most likely, then, the problem was somewhere in the AC panel. And since only licensed electricians are allowed to mess with those, this was the third strike for me, and I was out.

The only way to solve this would be to get a boat electrician to come over and look at my problem.


The Mastervolt charger/inverter opened up. The wires on the left are AC input, the middle connectors (without wires) are AC “passthrough” output and the third ones (with wires) are for the inverter AC output.

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