If your boat is wired correctly, the battery charger feeds the battery and all your DC loads will function exactly as normal.
I suggest you, and anyone else who doesn't have one, purchase a copy of Nigel Calder's Boat Owners Mechanical and Electrical Manual. An excellent all round resource. http://www.amazon.com/gp/aw/d/B006QA720O Rich > On Dec 18, 2013, at 11:33, Curtis <cpt.b...@gmail.com> wrote: > > So here's a dumb question? > If I'm on shore power is just my battery charger and the DC outlets using > shore power or can I run the cabin lights and radio on the DC system? and if > so how? > > > >> On Wed, Dec 18, 2013 at 10:23 AM, Rick Brass <rickbr...@earthlink.net> wrote: >> Dwight; >> >> >> >> Rich and I were addressing the power systems for a boat used for long term >> live aboard cruising. IIRC you are on a dock and use your boat for daysails >> and the occasional weekend or vacation cruise. For than situation, the OEM >> alternator is just fine. >> >> >> >> Starting your engine draws somewhere around 200 amps for something around 30 >> seconds. That is less than 2 AH reduction in capacity. Add a 2 to 3% >> reduction for self discharge over a month at the dock. Call it another 4 AH >> on a typical group 24 battery. So you need to put around 6 AH back into >> your start battery while the engine runs, and the battery is probably at >> around 95% charge when you start out, so there is high resistance to >> charging and reduced acceptance rate. You probably need to run the engine >> for 20 or 30 minutes to recharge the start battery. >> >> >> >> All your boat systems except the bilge pump are turned off when at the dock, >> except when you are on vacation. So you only have to replace the loss from >> self discharge in your house bank. Two golf cart batteries is probably >> around 275 AH capacity, times 3% per month, is around 8-9 AH. Your OEM >> alternator is probably able to accomplish that while you motor out and raise >> the sails. >> >> >> >> I’m sort of surprised that the house bank was able to run your refrigeration >> for 5 days. Most refrigeration systems seem to use 45 or more AH in a 24 >> hour period. But then, you are in the great white north so maybe the lower >> average temperature differential reduces the cooling load and thus the >> current draw. >> >> >> >> Rick >> >> >> >> From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of dwight >> Sent: Wednesday, December 18, 2013 9:39 AM >> To: cnc-list@cnc-list.com >> Subject: Re: Stus-List Battery charger recommendations? >> >> >> >> Hi Rich >> >> >> >> I am not sure what my alternator output rating is but my ammeter never shows >> more than 60 and even that is not for long as it settles out to between 15 >> and 30 fairly quickly, like after a a minute of steaming. If I switch from >> one battery bank to the other during steaming I can sometimes notice a >> slight drag on the engine (it seems to slow down a bit) but even that is >> momentary (a second or 2). My house bank is two, 6 volt deep cycle >> batteries connected in series and my start bank is one Group 24 deep >> cycle…they have been on the boat for 7 years continuous and have never let >> me down. I run an old 1720 Furuno radar when I need it (fog or dark) and I >> run an Adler Barber in icebox refrigerator freezer. I try to remember to >> manually cycle the fridge on and off since I disconnected the thermostat and >> now can’t remember which wires go where to reconnect it…Last season I left >> the boat unattended on the mooring for about 5 days but I forgot to turn off >> the fridge. Much to my surprise after those 5 days there was still power >> left in the battery and the fridge was still cold and I have no added >> insulation around the ice box yet!! I was able to start the engine from my >> start battery and recharge my house bank from the engine. Probably some >> sailors use more power on a regular basis than I do but 100 amps seems like >> a pretty high charge rate. Would a 100 amp charge rate not be hard on the >> cells? >> >> >> >> >> >> From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Rich >> Knowles >> Sent: December 18, 2013 8:38 AM >> To: cnc-list@cnc-list.com >> Subject: Re: Stus-List Battery charger recommendations? >> >> >> >> And to increase the presumptuous factor: >> >> >> >> The alternators that were supplied as original equipment with most small >> boat engines until recently were from 35 - 55 A with internal, single >> voltage output regulators. A good percentage of the engines were destined >> for use in small motor vessels and these alternators were adequate for that >> application. For our use, which sees greatly increased loads from, as Rick >> notes, radar and refrigeration, and lengthy battery discharge periods >> between charges, those alternators are bordering on inadequate, and >> certainly not as efficient and appropriate as higher power units with multi >> stage regulators. >> >> >> >> For sailing vessels, a central component of optimizing the electrical system >> should be upgrading the generating capacity of the charging system. This >> will involve replacing the alternator with the largest unit that can be >> fitted, taking physical restrictions, drive belt capacity and depth of >> pocket book into account. For most 20-35 HP engines, around 100A works well. >> There are a number of external regulators available that should be >> considered for installation as part of the new system. A new alternator with >> a multi-step regulator will considerably reduce the engine run time needed >> to replenish the batteries. Other devices such as wind generators and solar >> panels are important for long range travels as well to further reduce the >> dependency on the engine. >> >> >> >> For calculation purposes, I generally consider the usable capacity of >> batteries to be 30% rather than 50% of rated capacity. This stems from the >> fact that a 50% discharged battery will charge to around 80% at a fairly >> linear rate which will drop significantly as the state of charge nears 100%. >> Trying to achieve the last 20% can take a long time compared to the first >> 30%. This will vary depending on battery type and condition, so my 30% >> figure is somewhat arbitrary, but fairly realistic. >> >> >> >> A shore power fed battery charger from 20-40A will generally suffice to >> sustain loads from refrigeration, lighting and entertainment devices >> operating while the boat is alongside, and also provide enough power to >> replenish the batteries. Again, a multi-step unit designed for marine use >> should be chosen. There are lots of good marine chargers on the market. >> >> >> >> I note that non-marine AC chargers may not completely isolate the input from >> the output, a potentially dangerous situation on the water, and should be >> avoided. >> >> >> >> As Rick notes, designing an efficient, reliable electrical system is >> complex. >> >> >> >> It's snowing again. Grrrr! >> >> >> >> Rich Knowles >> >> INDIGO - LF38 >> >> Halifax, NS >> >> >> >> >> >> >> _______________________________________________ >> This List is provided by the C&C Photo Album >> http://www.cncphotoalbum.com >> CnC-List@cnc-list.com >> > > > > -- > “Sailors, with their built in sense of order, service and discipline, should > really be running the world.” - Nicholas Monsarrat > > _______________________________________________ > This List is provided by the C&C Photo Album > http://www.cncphotoalbum.com > CnC-List@cnc-list.com
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