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<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
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