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Author Topic: leaving boat on shore power when gone  (Read 2548 times)

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Bobg

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leaving boat on shore power when gone
« on: August 29, 2016, 09:00:02 AM »

I don't leave my boat plugged in when not there, what is the danger of leaving my boat plugged in.  I am the only one in the marina that unplugs my boat when I leave for a week or so.  other boaters have questioned why I do this, I do it on the advice I have read on this forum, but, I would like to be able to explain why.  I did  lose my onboard charger because the boat 3 slips over got hit by lightning, that is pretty rare.  I know Stu and Ron leave theirs unplugged.  so I do too.  Thanks everyone
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Bob Gatz, 1988 catalina 34, Hull#818, "Ghostrider" sail lake superior Apostle Islands

Noah

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Re: leaving boat on shore power when gone
« Reply #1 on: August 29, 2016, 10:40:35 AM »

I leave mine on all the time and have no worries. However, my boat is newly re-wired (I trust my equipment/systems) and I am berthed at a marina I know is well maintained and monitored. Your circumstances may differ so, no set rule that I know of.
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1990 hull #1014, San Diego, CA,  Fin Keel,
Standard Rig

britinusa

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Re: leaving boat on shore power when gone
« Reply #2 on: August 29, 2016, 01:46:25 PM »

And... Have you upgraded your Shore Power connection at the Boat to a Smart  Plug?

Recently, at a Marina, I saw the plastic decking adjacent to the power pylon, the residues of a melted Power Plug, it must have been so hot that when disconnected it was dropped and subsequently melted the surface of the decking.

Paul
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Paul & Peggy
1987 C34 Tall Rig Fin Keel - Hull # 463

See you out on the water

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Lance Jones

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Re: leaving boat on shore power when gone
« Reply #3 on: August 29, 2016, 02:11:30 PM »

We've had our boat for 7 years and except for sailing or transport, it has always been plugged in. If you don't keep your fridge or AC on, it shouldn't be an issue to unplug.
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Lance Jones
1988  C-34 Kitty's Cat
S/N 622

lazybone

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Re: leaving boat on shore power when gone
« Reply #4 on: August 29, 2016, 02:12:15 PM »

Let's say I get a small leak, somewhere, somehow, who knows where?  Its not too bad but it keeps the bilge pump busy... 

That's my nightmare if I unplug my boat.
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S/V LAZYBONES  #677

Ron Hill

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Re: leaving boat on shore power when gone
« Reply #5 on: August 29, 2016, 02:14:30 PM »

Bob : Let's turn the question around - Why do you want to stay plugged in?

You are wearing out items like the battery charger if nothing else is ON.  Why leave the fridge ON when you're not there?   Easy to stop by 7/11 and pick up a cold 6 pack on the way to the boat. 
To keep the condiments & stuff cold you say?  The girls look at the expiration date and throw most of the stuff out after a couple of weeks anyway!!

If for what ever reason, the shore power breaker should trip (on the boat or on the dock power tower) you'll have flat batteries is short order!!

When I leave the boat the batteries are always at 90% to 100% charge and I leave nothing ON with the battery switch OFF.  My AGMs do not sufficiently self discharge is a week to even measure.

A few thoughts

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Ron, Apache #788

Jim Hardesty

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Re: leaving boat on shore power when gone
« Reply #6 on: August 29, 2016, 02:40:53 PM »

I leave mine plugged in.  That's after the fridge is started.  That's necessary to keep the beer cold.  But then I live 4 miles from my boat and it's a rare summer day that I don't at least stop by, may be just for a cold beer.  So I guess the only reason I keep my boat plugged in is to keep the beer cold.  Reason enough.
FWIW  If I didn't go to the boat so often I'd leave it unplugged.
Jim
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Jim Hardesty
2001 MKII hull #1570 M35BC  "Shamrock"
sailing Lake Erie
from Commodore Perry Yacht Club
Erie, PA

lazybone

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Re: leaving boat on shore power when gone
« Reply #7 on: August 29, 2016, 02:45:39 PM »

I'm thinking I should throw the main breaker on my house when I go down to the boat.
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S/V LAZYBONES  #677

kwaltersmi

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Re: leaving boat on shore power when gone
« Reply #8 on: August 30, 2016, 04:36:17 AM »

Let's say I get a small leak, somewhere, somehow, who knows where?  Its not too bad but it keeps the bilge pump busy... 

That's my nightmare if I unplug my boat.

That's the primary reason I keep mine plugged in. I have a smart charger, so no worries that I'll cook my batteries but I know they'll always be charged when I arrive. I leave the fridge on too, to keep condiments fresh and not have to wait for it to cool down on a warm summer day when we get onboard.
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'87 C34 TR/WK M25XPB
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jstrane

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Re: leaving boat on shore power when gone
« Reply #9 on: August 30, 2016, 05:26:35 AM »

I always leave ours plugged in.  Owned boats sail (and power) for 30+ and never had any problems.  Old trickle chargers even worked well if you kept the batteries filled and now with smart chargers no worries what so ever in my mind. 
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Brenda J
Hull #1759
Lake Lanier, Georgia

mainesail

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Re: leaving boat on shore power when gone
« Reply #10 on: August 30, 2016, 08:26:21 AM »

I like to use current examples...

Got this text on Saturday evening at 5:10 PM from one of my full time cruising customers...



So do you really want to walk away from your batteries and ignore the possible outcome? Many do. As a marine electrician, I see it all, you could not pay me to leave a boat charging without a thermal protection system and the smallest possible charger to maintain charge.  These guys live on the boat 24/7/365 so were there to stop the potential thermal runaway and eventual explosion.. 186F !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Remember 55% of all boat fires are electrical in nature...!!
« Last Edit: August 30, 2016, 08:35:20 AM by mainesail »
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-Maine Sail
Casco Bay, ME
Boat - CS-36T

https://marinehowto.com/

lazybone

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Re: leaving boat on shore power when gone
« Reply #11 on: August 31, 2016, 05:31:08 AM »

The battery charger should have had a temp. Sensor.  Standard fare on a quality charger.
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S/V LAZYBONES  #677

mainesail

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Re: leaving boat on shore power when gone
« Reply #12 on: August 31, 2016, 09:52:32 AM »

The battery charger should have had a temp. Sensor.  Standard fare on a quality charger.

It did and it was on the wrong battery!! This gets to the meat of an industry wide major problem... 1 temp sensor for vessels with multiple banks is simply inexcusable... Sadly I can't get any traction on the Electrical PTC at ABYC to jump on this.

In a perfect world all marine battery charge sources would have the ability to wire in as many temp sensors as you have batteries and any one of the sensors could then shut the charger down.

Sadly we don't live in a perfect world and the marine charge equipment market has failed us on the safety front. One could easily argue that the ABYC has let us down on this front too. Seriously why is one sensor standard practice and "acceptable" on a boat with ten batteries..?? The simple answer is that it should not be acceptable.

The technology to do this is easy, industry gold standards such as the LM335 temp sensors are 96 each. Add a bit of wire and a terminal with some epoxy and charge $40.00 each and they are actually making money in a big way. It would at least be nice, even if it was an add on option, but as of yet not one single charger company I know of offers multiple battery temp sensors. The Balmar MC-614 can monitor two batteries, a step in the right direction, but that is still not enough on boats with multiple battery battery banks and multiple banks.

As for what the average owner can do?

#1 Conduct yearly Ah capacity tests. This is as easy as applying a load of;

Ah Capacity 20 = Applied Discharge Load

A 100Ah battery would get a 5A load until the battery voltage hits 10.5V. Try to rig a system that lets you adjust the load as the voltage decays to keep it steady. A bank of light bulbs or resistor works or even a PWM 12V dimmer can work to keep the load as close to C20 as possible. Recharge immediately after hitting 10.5V.

Start a count down timer (there are free apps on your phone for this) when you turn the load on and note the time the battery ran for and remained above 10.5V. For example a 100Ah battery that ran for 16 hours at 5A is delivering 80% of its 20 hour Ah capacity rating.

Conduct the test with the battery temp between about 74F and 80F or the capacity will be off a bit. Any battery falling below 80% of its stated capacity is getting into the "time to think about new batteries" zone.. For coastal cruising as low as 70% with AGM or GEL can be fairly safe but if going off shore you really don't want them to drop much below 80% of rated capacity. Below 80% is where I start to see trouble occurring.

Impedance testers (Midtronics, SPX, Argus etc.) really don't tell us much about state of health as a house bank and really nothing at all about Ah capacity, but if you start with a baseline, when new, they can tell you a little bit of a story/history.

#2 When leaving a vessel unattended it's best to use the absolute smallest charger necessary to maintain the bank. In my opinion one of the poorest practices I see at docks is using 100A - 150A + inverter chargers as your maintenance charger. Having a 150A potential in order to supply mA of charge current, when your not there, not my bag of tea. I would go so far as to call this a dangerous practice.

Why is this a poor practice?

With a 5A charger if you have a shorted battery, that may now be a 10V battery, that battery will begin sucking charge from the 12V batteries but the differential voltage is still around 2V or less. When you stack a small 5A charger on top if this, it does not create a real huge difference. Add a 150A charger on top of four other 12V batteries feeding the shorted one and you've got real issues. That 1 temp sensor is almost never going to be on the shorted battery. This is the failing of the charger industry I talk about.

#3 Internal shorts most often start out small and present themselves in faster than usual voltage decay when not charging. When charging they present themselves in a manner that the charge current never drops as low as it once did. For example with no loads on, with a typical float voltage, your bank may have normally been accepting 0.5A of charge current and now it never drops below 9A.. This is a red flag.. If you pay close attention to your ammeter and battery voltage, using an accurate voltmeter that reads to the hundredths (12.72V) not just tenths (12.7V) then you can learn to spot any irregularities in the bank voltage and full charge amperage performance.

Large chargers left unattended are simply going to remain a dangerous practice until charger makers begin to provide us with the ability to sense the temp of every battery on board...

You as a human are still the best defense against battery failures. I rarely see them fail rapidly and more often than not see them fail starting out as a small leak/short that slowly gets worse...

Course if you are on-board your Model 1 Schnoz should alert you to a shorted battery as it did for this guy...

Shorted Trojan 154F
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-Maine Sail
Casco Bay, ME
Boat - CS-36T

https://marinehowto.com/

lazybone

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Re: leaving boat on shore power when gone
« Reply #13 on: August 31, 2016, 10:48:58 AM »

Thanks for that Mainsail.  I'm just a little bit less ignorant now.
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S/V LAZYBONES  #677

Breakin Away

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Re: leaving boat on shore power when gone
« Reply #14 on: August 31, 2016, 10:54:20 AM »

Thanks, Mainesail. Very eye-opening. My new (to me) boat has a 50 amp charger/1000w inverter.

Are you suggesting that we install a separate dedicated float charger that we should leave on, and turn the bigger charger off while away from the boat?
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2001 MkII Breakin' Away, #1535, TR/WK, M35BC, Mantus 35# (at Rock Hall Landing Marina)
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