Battery Charging - Shore Power

[ianhef]

Hi

Quick simple question for you experts. Just recently moved onto our boat and for the first time have the luxury of a marina berth with shore power. Usually the wind generator and the alternator kept up with any battery charging needs but now we are living onboard the fridge is on 24/7 and lights etc draw a bit. As the wind generator is fairly noisy I'd like to refrain from using that and I'm sure there are more economical ways to charge the batteries than to run up engine hours? After all we are being charged for electricity regardless of how much or if we use it!

The boat does not have a shore power plug. I was thinking of buying a cheap battery charger and plugging it into an extension lead into the dock and charging up the batteries when needed. I have two main concerns;

1) Can I keep the batteries wired up to the services when charging or would I have to disconnect everything before charging?
2) Are there any problems with using this quick fix, temporary solution?

Any thoughts, suggestions and advice as always gratefully received. We are on a steep learning curve here.

Hef

[Chief Engineer]

I don't think anyone here is going to say it is OK to run an extension cord to your boat for a semi permanent use.

Running a power tool OK but not for this.

[Bash]

Chief is right. The worst sort of neighbor in a marina is someone who buys a cheap automotive battery charger and then burns off all the neighbor's zincs in a misguided effort to save a few bucks. You save the bucks, and everyone around you pays the price.

A long while ago I was in a marina where a sea scout "ship" decided to go with the cheap charger option, and turned our whole dock into a hot dock. Not good. A few of us talked to the scout leader, but he didn't seem to care about what he was doing to our boats until he started losing his extension cords every night.

Do it right or don't do it at all.

[ianhef]

Ah yes I should make that clearer. Not an extension cord but a proper outdoor cable with a board on the end. At the moment its only used to boil the kettle. Its not connected to anything. I'm sure it will be used for power tools. I was just looking at it and wondering if I could use this source of power to charge the batteries on occasion, not a permanent set up but maybe once a week if they need a top up?

I understand the concerns about setting up something like this on a semi-permanent basis, I'm just looking for peoples thoughts on charging batteries if the boat isn't fitted with a built in u-bute one. Surely cranking the engine up twice a week isn't the only option? (Its winter in Sydney, lets not even go there with the solar panels)

[ianhef]

Originally Posted by Bash

Do it right or don't do it at all.

Bash I'm hearing you, I want nothing of the sort to happen which is why I'm asking the question. Your line above contains sage advice but how about following it up with your opinion of what you consider the do it right is?

Thats what I'm looking for, I had no idea a cheap charger could turn the dock hot, how does that work?

What options are there for charging the batteries on a boat not fitted with a build in system?

Any advice gratefully received, I'm trying to learn here.

[DeepFrz]

You are living aboard in a steel boat. Do it properly or the damage you cause could well be to you or your loved ones or your boat. You can start small but it really is a wise idea to do it right, then you don't have to do it over again after causing yourself a lot of grief.

[ianhef]

Again, great sentiments but all I'm hearing is do it right, not HOW to do it right. I want to do it right what I'm asking is HOW?

[ianhef]

Ok gents, I've been studying and trying to figure out what the problem is with using battery charger to top up the batteries but can't seem to find a straight answer. What if I used a proper dedicated marine charger like a CTEK M200 12V 15A Battery Charger shown here Whitworths Marine: CTEK M200 12V 15A Battery Charger

I'm looking for advice, any advice at all. People were fast to say don't do it but I'd really appreciate if people could explain why and maybe offer some constructive advice. Come on you had to learn all this at some stage too and I'm sure you know its not as simple as picking up a book and starting on page one.

[DeepFrz]

You could start here

Understanding Boat Wiring - MAINTENANCE

[ianhef]

Just for those new to this thread,

1) The boat does not have a 240V system.
2) The internal wiring is only for 12V.
3) There are no sockets/plugs anywhere on the boat to plug into.
4) I'm just looking for advice on the best way to keep my batteries topped up, run the engine every 2nd day or is it possible to invest in some kind of marine specific charger that will top them up? (without doing any damage to the boat or any of my neighbours)

Any advice much appreciated.

[Dockhead]

Originally Posted by ianhef

Just for those new to this thread,

1) The boat does not have a 240V system.
2) The internal wiring is only for 12V.
3) There are no sockets/plugs anywhere on the boat to plug into.
4) I'm just looking for advice on the best way to keep my batteries topped up, run the engine every 2nd day or is it possible to invest in some kind of marine specific charger that will top them up? (without doing any damage to the boat or any of my neighbours)

Any advice much appreciated.

It is all a question of grounding. You should not use AC power on board, and God forbid, on board a steel boat, without a ground in place. Period. It is a question of life and death for anyone on board.

A wacky ground -- say, the third pin in an extension cord -- might protect people, but will destroy property. More below. (And read the very good discussion in Nigel Calder's book about the tension between protecting people and protecting property, in designing on board AC system.)

A proper, as opposed to a wacky ground requires a proper shore power connection with the ground bonded to your hull, engine, and other major metal lumps on board, not just brought on board through the third conductor of an extension cord. Without a proper shore power connection (and proper wiring inside your boat), which leads away stray currents safely, those stray currents can leak through the water and eat up other boats appendages, zincs first we hope, but soon propellors and so forth.

It happened to my expensive Brunton prop, and a dozen other props in our marina (due to some f*ckwad using an extension cord-powered automotive battery charger over the winter in the marina), so that is why I am not quite indifferent to the question of shoddy AC installations in marinas. One killed propellor costs more than the whole AC system on most boats; and boats can sink when the electrolytic corrosion in a hot marina finishes with the props and starts in on bronze through-hulls.

A wacky AC installation in a marina, and for God's sake on a steel boat, is an utter menace. You will lucky if the result would be only missing extension cords. I've heard about sea cocks failing at night without explanation . . .

So you have two alternatives to running your engine to keep batteries up, and really only two:

1. Put in a proper shore power installation with proper grounding and bonding, properly tested by a good electrician; or

2. Use solar to trickle charge your batteries.

Option 1 will not be cheap, especially on a steel boat, but you do get the benefit of AC power for other uses.


P.S. Not using AC on board without a proper ground includes using a kettle from a socket mounted on a board. If you prefer being alive to being dead, do not do it. Do not bring AC power near your steel boat -- and that includes double-insulated power tools (sorry to disagree with one of the other posters here), without a proper shore power installation.

[nigel1]

Originally Posted by Bash

Chief is right. The worst sort of neighbor in a marina is someone who buys a cheap automotive battery charger and then burns off all the neighbor's zincs in a misguided effort to save a few bucks. You save the bucks, and everyone around you pays the price.

A long while ago I was in a marina where a sea scout "ship" decided to go with the cheap charger option, and turned our whole dock into a hot dock. Not good. A few of us talked to the scout leader, but he didn't seem to care about what he was doing to our boats until he started losing his extension cords every night.

Do it right or don't do it at all.

Is there a quick and easy way to discover if the dock is hot??, or own boat is suffering from harmful stray currents.

[Dockhead]

Originally Posted by ianhef

Ok gents, I've been studying and trying to figure out what the problem is with using battery charger to top up the batteries but can't seem to find a straight answer. What if I used a proper dedicated marine charger like a CTEK M200 12V 15A Battery Charger shown here Whitworths Marine: CTEK M200 12V 15A Battery Charger

I'm looking for advice, any advice at all. People were fast to say don't do it but I'd really appreciate if people could explain why and maybe offer some constructive advice. Come on you had to learn all this at some stage too and I'm sure you know its not as simple as picking up a book and starting on page one.

OK, the short answer, as several have said, is don't do it. The long answer I gave above. Now I'll tell you why not in this particular case.

That battery charger, no doubt made in China, has a transformer inside, among other electrical components. The chassis of the charger is grounded to the third pin on the AC side of it.

If this charger were plugged into a proper shore power system, you would have no problem. That is because the AC-side ground is bonded to the boat, which is also bonded to the DC-side negative. So if there is some fault inside the transformer -- and such faults are extremely common -- the stray current is led harmlessly away to the ground on shore and there cannot be a potential between your DC negative and your AC ground, and the current doesn't leak into the water.

If, however, you choose to just hook it up to an extension cord, there is no bond between the chassis of the charger and your boat. A stray current should be led away through the extension cord ground, but since that ground is not bonded to your boat, there can be a potential between the charger's chassis and your boat's hull, and thus the negative side of the DC system, even if the charger is grounded to shore. So you could end up with all kinds of wacky things -- electrical potential from the boat trying to get to shore through the extension cord ground, or on the contrary, trying to get to shore through the water, which is what eats props. So if there is a fault which lets high voltage potential into the chassis, it can get loose into your boat through anything touching the chassis, or throught the DC side of the charger.

Unfortunately battery chargers like that one are mass produced in sweat shops in China and faults are extremely common.

[LiFeTech Energy]

Speaking in my capacity as an electrical engineer and licensed electrical contractor/electrical supervisor there is no problem using an extension cord from the dock to power a battery charger for topping up your batteries so long as a few simple rules are followed.
1) Always use a power board with an ELCB (earth leakage circuit breaker). If there is any current leakage to earth the breaker will trip so you have protection.
2) All mains powered electrical appliances which are safe to use in Australia (as deemed safe by the state electrical authorities) will have a C-tick and electrical safety approval number marked on them. Only use appliances which have these marks.
3) Very few battery chargers made these days use the old traditional heavy transformers. They are all switch mode devices and if there is any leakage the ELCB will trip out.

[DeepFrz]

On a metal boat you should also use an isolation transformer. You may get away with a sub-standard setup, good luck.