Bav 30 battery charging

[Bavnav]

Hi.
We have just bought our Bav. 30 (2006). I was told by a marine engineer to turn the 240v. shore supply off at the switch board when I leave the boat for the week and return the following weekend (safer). However, if I do that, will the batteries charge. If they are on charge will they stop charging when fully charged?
What do most people do?

[Symphony]

If it is a proper marine charger it will switch off when the batteries are fully charged. Discharge if you are not using the boat is very low, but it should switch on again to keep full charge. However, unless you are a heavy user of power without running the engine when out cruising your batteries should be near fully charged, so no need to run the mains charger when you are not there. Better to use a small solar panel to keep the house battery bank topped up. The charger's main use is when you are on the boat, using power and not running the engine, for example in an overnight stop in a marina.

[Trapeze Artist]

+1.

I very rarely use my shore power except in winter when I need it to power the dehumidifier. So generally, that is one less thing to do when going out or getting home, and less risk of galvanic corrosion eating my anodes.

Some of the next few weekends may be exceptions as I will probably appreciate being able to run a fan heater while on board.

[Ripster]

Like others, we use shorepower when there on the boat and a hook up is available.  When we leave the boat, except in the warmer months, no SP is left connected - no need as we are not running anything and if you have decent batts, they will be fine for 2-3 weeks say or longer without a boost.  In winter of course Nov to Feb (south UK) SP is connected thus charging the batts by default (via a smart charger) and to run the frost heaters.

[MIA]

Marinas have an RCD fitted at each shore power point and your boat should have an RCD installed as well, if you have a splitter diode then the batteries should charge evenly, my boat has a battery monitoring system and all RCD protection, I go away for at least 4 weeks at a time (work overseas) and have had the shore power on and off and have no problems with any equipment, even the batteries have had enough charge never been less that 11.8V on any of them. I turn off the battery main isolator normally when I leave to avoid draining if theres any earth leaks on the 12VDC side. Even if you do go to the boat and the battery is below normal voltage you can charge it by the shore power.

Stevie

[Bavnav]

Many thanks folks.
Bavnav.

[Ricd]

For the past 7 year I have always left the boat (up to 5 weeks at a time) with the 12VDC switched off, shore power connected and smart battery charger (Sterling) operating.  Never any issues and Batteries are now 8 years old and in prime condition.  In winter I leave as above but with a 120W bar heater and a dehumidifier permanently on..again no issues.

Why would you not leave the battery charger running and doing its job?

[landes_h]

Why would you not leave the battery charger running and doing its job?

.... because the most common failure in electric (electronic) equipment (like your charger) is fire, due to over-current or bursting electrolytic capacitor. Also an attraction for lightning. Unless your boat is self-extinguishing it is not smart to leave land power plugged in while the boat is not manned, in many marinas it's actually prohibited. Insurance may refuse to cover such risk.
One day Murphy will strike 

[Ricd]

 

I take your point landes_h, but this seems a very negative and not consistent with other rsiks we take in life.  My multi-stage battery charger specifically states it is safe to leave continuously on and actually recommends this mode of operation to maximise the life of the batteries.  If it were not how would I ever charge my batteries as I run the engine ideally only to leave the marina. Likewise, if I cannot trust the shore power connection to be left unattended, I would certainly not trust it while on board in the marina at night with my family on-board.  In addition, during the winter months, I and thousands like me, leave shore power connected in order to run a heater and or dehumidifier.  I accept that these need to be in good nick or they are a potential fire risk but that is no different to the electrical equipment we run in our own homes every day of our lifes.