Complete power fail while docking

[Scatman_f]

Hi Tugs! We have a 2017 sc25. We recently purchased and this was our second time out on the casco bay.
After about 4 hours on the water today, we were returning to our slip and the power completely went out. All Garmins, lights, radio...everything went dead and the engine turned off. We had the inverter on and I did use the bow thrusters a few times but only for a second or 2 each time. We never got the power back on.
Plugging in shore power did not help.
Anyone else ever had this happen?
Thanks for reading!

Peter
"Half Step"

 

[Scatman_f]

We ended up figuring it out...I checked all grounds, wiring at helm and finally started shaking cables on the battery post. Turns out the positive post on D was lose. Tightened it up and Half-step roared to life! The rest of the weekend was saved!
It did surprise me that we lost the engine with a battery issue. Hopefully that is the only single point of failure on the sc25.

 

[Seakr25]

Glad you saved the weekend. It’s a good lesson on modern diesels also. Common rail engines rely entirely on computers for operation. Kill the power kill the engine. It’s a shame really as the good old IDI diesels were entirely mechanical and only needed electrical to turn over the starter …. Even then some had hand crank options. Emissions have almost killed that era off.

 

[OdyseaII]

I had a similar problem following a haul out where my batteries died and even when plugged in to shorepower I was not getting any charge or power.

I am not 100% sure but it seems the inverter/charger would not turn on as the battery voltage was too low and it could not see the battery. The solution was to connect an external batter booster/charger and after 10 minutes there was sufficient charge and voltage that the inverter would turn on.

After a few hours things seemed to be fine. Only concern is long term impact on draining house AGMs to this low a voltage.

 

[SJI Sailor]

Glad you saved the weekend. It’s a good lesson on modern diesels also. Common rail engines rely entirely on computers for operation. Kill the power kill the engine. It’s a shame really as the good old IDI diesels were entirely mechanical and only needed electrical to turn over the starter …. Even then some had hand crank options. Emissions have almost killed that era off.

Just wanted to check on this, as it surprises me. I had imagined (TBH without looking at any schematic) that the alternator would provide power to the diesel system even without 12v input after starting. Maybe I am too accustomed to the older tech as Seakr25 notes!

 

[Seakr25]

You are correct that the Alternator does supply power when the engine is running. After its been excited by the battery it will keel on trucking usually ... but there can be issues and I have seen it first hand over the years in marine and land based engines. Alternators also need a DC batt connected to help smooth out to voltage spikes .... Computers act funny when voltages they receive as signals from sensors vary too much ... they can be unpredictable. When you loose the connection entirely to a battery you can run into all sorts of problems, one of them being a total engine stall. just my 2 cents for what its worth.

 

[SJI Sailor]

Thank you and that makes complete sense. More computers = less reliable even when there is a backup. Reminds me of how I reboot my phone and laptop every few days "just because" 🙂