I think it likely that, when attached to shore power, your permanently installed battery charger is maintaining the batteries as the shore power is providing power to any AC outlets you have. That's one of the reasons that you need a battery charger with a "float" charge rate. Charging the batteries with 14+ volts full time (as the old fero-resonant chargers did) or until the internal resistance was high enough to shut off the charger (as a semi-old charger might do) will boil away the water in the batteries and kill a set of batteries very quickly.
The 1.5 amp "trickle charger" you bought is probably delivering a tenth of an amp or so at around 13v to maintain your batteries when in "Float" mode. That sort of charger is good when you are day sailing and leave the boat plugged in to shore power for long periods, but it will literally take days to recharge a significantly discharged batter at just 1/5 amps max current. You can verify that the shore power is powering your DC systems pretty easily. Plug into shore power and turn off your DC systems.. Measure the voltage across the terminals of your house bank with a voltmeter. If you see 13v or more, the battery charger is powering your DC system (up to the maximum current that the 1.5 amp or the "OEM" charger can supply). If it is 12.5v or less, then it is not. Rick Brass From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Curtis Sent: Wednesday, December 18, 2013 10:33 AM To: cnc-list@cnc-list.com Subject: Re: Stus-List Battery charger recommendations? comment about alternators 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
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