shore power and 12 volt electronics

Apr 11, 2013
9
Catalina 350 Sackets Harbor
I have purchased a 2004 catalina 350 and the prior owner has been a great help. I want to confirm something because it does not make sense to me. Supposedly, when plugged into shore power, there is no transformer that converts 120v to 12 v. Instead, you must use shore power to charge batteries which in turn powers the 12 volt. In short, dead batteries even when plugged into shore power means no 12v electronics. Does this mean that when plugged into shore power and going home until the following weekend, you leave the battery charger on all week? Thanks for any advice.
 
Jul 14, 2015
840
Catalina 30 Stillhouse Hollow Marina
Your charger should have a trickle mode that comes on and off to maintain the batteries
 
Feb 26, 2004
22,760
Catalina 34 224 Maple Bay, BC, Canada
Your charger should have a trickle mode that comes on and off to maintain the batteries
I would think that it would depend on what charger he has on his boat.

A basic boat electrical book, like Charlie Wing's excellent Boat Electrics Illustrated, will answer this and many other questions you may have about your system.

If your battery bank is fully charged before you leave the boat, YOU have the choice of leaving it plugged or unplugged.

Many of us believe unplugged is safer.

Many believe keeping it plugged in, to charge the bank, or keep the fridge running, is better.

I, personally and professionally, choose to NEVER leave my boat plugged in when I'm not there. The addition of solar to recharge your batteries when you're gone has improved in quantum leaps in the past few years. Look into it.

Your boat, your choice.

But really, first read up a little bit more. You have NICE big boat. None of us was born an electrician, but those who wanted to learned what needed to know.

A good start is here:

http://c34.org/bbs/index.php/topic,5977.msg40656.html#msg40656

Good luck, happy reading. :)
 
Jul 27, 2011
4,989
Bavaria 38E Alamitos Bay
I have purchased a 2004 catalina 350 and the prior owner has been a great help. I want to confirm something because it does not make sense to me. Supposedly, when plugged into shore power, there is no transformer that converts 120v to 12 v. Instead, you must use shore power to charge batteries which in turn powers the 12 volt. In short, dead batteries even when plugged into shore power means no 12v electronics. Does this mean that when plugged into shore power and going home until the following weekend, you leave the battery charger on all week? Thanks for any advice.
Some do, some don't. If the batteries are fully charged when you leave the boat, turning off the charger, or AC breaker, or unplugging the shore power cord altogether should not harm them and might cut down on electrolysis if you're unplugged. Some like to unplug and leave a low-watt solar panel (trickle charge) to maintain the charge. Usually when I leave the boat the batteries are fully charged, the power cord is unplugged, and nothing is getting DC power aboard except the bilge pump and the high water (bilge) alarm. No hay problema.
 
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May 24, 2004
7,129
CC 30 South Florida
Yup. The use of transformers is for RVs which rely more on land based power distribution than boats that have to store and carry their own power around. A boat requires a larger battery bank and also a more sophisticated battery charger. We run a 20A 3 stage smart battery charger 24/7 while the boat is docked. In our experience the batteries have not been noticeably damaged nor keeping and active 120V circuit has resulted in a fire or a short. We do not shut the power off in our home when we go out and neither do we feel the need to do so in the boat. As a matter of fact we also keep the refrigerator running. Recharging batteries may require 5 to 6 hours so when we get to the dock we are not going to sit around and wait for them to recharge so we can get home. Of course if there are any doubts about the condition of the 120V wiring, panel and breakers an electrician should survey it. I did cook a battery once in an RV by keeping it plugged into the transformer/charger for too long. Immediately after that I installed a marine charger into that RV. Of course there are exceptions like named storms for which we will shut down all power and disconnect the power cord.
 
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Apr 11, 2013
9
Catalina 350 Sackets Harbor
Thanks for all the advice, there is more to the story. I have two large solar panels above the bimini. My batteries this season have never even been half drained even after 6-8 hour sails with all electronics, fridge, et cetera running. when I get back to the dock, batteries are still fully charged. I guess I worry about the one scenario that I am gone for a week, a leak develops, the bilge pump is continuously running, and it is cloudy. A perfect storm as they say. I don't see any other reason to be plugged in especially since I do not run the fridge if I am gone for a few days. I assumed the charge was a trickle charger and would shut off when not needed but I am not sure of this.
 

danvon

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Dec 18, 2014
14
Catalina 27 Seattle
If you don't have a manual for your charger download one. Most likely it has a trickle charge mode that will automatically keep your battery topped up. Lots of us do exactly what you are talking about (leave the boat on charge 24/7). I do it partly for the reason you cite (the idea of a leak running the bilge pump and killing the battery).
 
Mar 20, 2012
3,983
Cal 34-III, MacGregor 25 Salem, Oregon
if you have solar panels, what would one need a trickle charge mode for?.... if the panels and controller is not functioning to its potential for the conditions, then it should be repaired before the shore "trickle" charger... good solar panels do charge on cloudy days, because even though the sun isnt shining brightly on them, they are getting daylight, and as the panels will be at a cooler operating temperature, they will be charging more efficiently....not to potential, but still charging.

how many watts are the panels rated at, and is the controller an MPPT or a PWM controller?
 
Apr 11, 2013
9
Catalina 350 Sackets Harbor
Centerline, I'll have to look that up next time I am at the boat and have the manuals in front of me. I don't know much about solar panels yet but I do know I love them. The batteries are always full no matter what I have run thus far.

Again though, I am just trying to think of the worst case scenario. Ie there is a leak, the bilge pump is running continuously, cloudy weak, not plugged into shore power or plugged in with battery charger off, and I won't be back for 7 days. This scenario is very unlikely of course.

The answer may be to figure the watts/hr the pump would consume, the watts my batteries store when fully charged, watts produced by panels on an average day, and how many hours it would take for batteries to be fully drained to account for night time when panels are not charging.
 
Nov 7, 2012
678
1978 Catalina 30 Wilbur-by-the-Sea
My marina chargers $45 a month for 30 amp shore power. My solar setup paid for itself in the first few months of the 3 years we have not been using shore power.
 
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