Catalina 34

General Activities => Main Message Board => Topic started by: Bobg on August 29, 2016, 09:00:02 AM

Title: leaving boat on shore power when gone
Post by: Bobg 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
Title: Re: leaving boat on shore power when gone
Post by: Noah 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.
Title: Re: leaving boat on shore power when gone
Post by: britinusa 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
Title: Re: leaving boat on shore power when gone
Post by: Lance Jones 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.
Title: Re: leaving boat on shore power when gone
Post by: lazybone 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.
Title: Re: leaving boat on shore power when gone
Post by: Ron Hill 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

Title: Re: leaving boat on shore power when gone
Post by: Jim Hardesty 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
Title: Re: leaving boat on shore power when gone
Post by: lazybone 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.
Title: Re: leaving boat on shore power when gone
Post by: kwaltersmi 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.
Title: Re: leaving boat on shore power when gone
Post by: jstrane 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. 
Title: Re: leaving boat on shore power when gone
Post by: mainesail 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...

(http://www.pbase.com/mainecruising/image/163987400.jpg)

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...!!
Title: Re: leaving boat on shore power when gone
Post by: lazybone on August 31, 2016, 05:31:08 AM
The battery charger should have had a temp. Sensor.  Standard fare on a quality charger.
Title: Re: leaving boat on shore power when gone
Post by: mainesail 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
(http://www.pbase.com/mainecruising/image/162906329.jpg)
Title: Re: leaving boat on shore power when gone
Post by: lazybone on August 31, 2016, 10:48:58 AM
Thanks for that Mainsail.  I'm just a little bit less ignorant now.
Title: Re: leaving boat on shore power when gone
Post by: Breakin Away 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?
Title: Re: leaving boat on shore power when gone
Post by: Stu Jackson on September 06, 2016, 09:52:21 AM

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?

This "keep your boat plugged in and/or the fridge on all the time" has been a recurring topic since this forum started and since Mainsheet started publishing tech notes. 

I don't want my boat to be destroyed because I was too lazy to pick up a cold six pack at 7-11 on the way to the boat.

Forget about smaller chargers, get a solar panel.  I did, and for a month before I left and for the month that I was away from the boat, it maintained the batteries just fine, fridge off.

Maine Sail has been recommending solar for boats on moorings for many years.  Just apply the same logic if you're in a slip.

Your boat, your choice.  :D   I know what mine is.
Title: Re: leaving boat on shore power when gone
Post by: Fred Koehlmann on September 08, 2016, 08:33:10 AM
Solar is a good way to keep your battery(s) topped up.

In our case howeer, when we were planning to do it, and because we wanted them not to be mounted to the dodger or bimini (looking at the separate arch over the bimini), the cost came in too expensive for our taste, and the work too intensive (would have robbed us of some sailing weekends at the start of the season). So we opted for a fuel cell, eFOY. It takes in methol alcohol, and outputs distilled water and CO2. The water a CO2 is warm coming out, so we vent it out of the locker. It's not a generator replacement, because its more of a trickler charger, but it runs silently and runs whether its cloudy or at night. It has run without issue for the last three seasons so far.

We also disconnect the boat from shore power when we are not there. Only the bilge pump fuse/switch is left on when we leave.
Title: Re: leaving boat on shore power when gone
Post by: Clay Greene on September 08, 2016, 09:51:03 AM
I've read too many stories about electrical damage from remote lightning strikes in which the owner reports that the pathway into their boat was a plugged-in shore power cord.  Why take the risk of that when there is no benefit to me by leaving it plugged in?