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 > On Dec 17, 2013, at 20:45, "Rick Brass" <rickbr...@earthlink.net> wrote: > > Curtis; > > At the risk of being presumptuous, I think you have the cart before the horse. > > If your intent is extended cruising – particularly offshore cruising where > you will not be using your engine for power (and to recharge the batteries) > every day – you will first need to think about the systems you have on board > and how much power they will draw. Refrigeration is a major draw. Radar? > Autopilot? What instruments? What lights? Power for entertainment like radio > or TV? Small things like a 12 v electric coffee maker or a microwave draw a > shocking amount of power out of your batteries. > > Once you know how many amp hours you will use on average, you can figure out > how many additional batteries you need, what type, and where to put them. My > average consumption right now is under 100 amp-hours/day. But I plan to run > refrigeration (45 more AH) and to anchor out for extended periods. So my > house bank is 4 deep cycle group 27 batteries with 460 AH capacity. That > gives 230 usable AH (50% discharge) and should let me go for 2 days between > charges. In addition I have a group 29 marine starting battery as a second > bank, and a deep cycle group 24 under the v-berth to power the head and the > anchor windlass. > > The 400+ AH house bank dictates at least a 40amp, multi bank charger. I have > an older Xantrex 40+ wired to the house and starting bank. There is a solar > charger for the group 24 battery that is OK for now, but I plan to install an > ACR that will top up the charge on that battery when I’m hooked to shore > power or running the engine. > > To put 100 AH into my house bank by running the engine (with a 45 amp > alternator installed) will take at least 3 hours of run time – which is OK > when I’m traveling on the ICW but not acceptable when at anchor. SO I plan to > install a bank of solar panels over the Bimini, and maybe a wind generator as > well, to maintain the batteries at anchor. > > As you can see, the process starts with determining how much power you will > be using each day, and that will depend on what systems you have installed > for cruising. > > You said you had an “OEM” battery charger installed. Probably not really OEM, > but the question is: is it still working? If it is, spend your money on the > other systems you will be installing, and the additional batteries, and worry > about a new (probably more efficient) charger in 2017 or so. > > > Rick Brass > Washington, NC > > > > From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Curtis > Sent: Tuesday, December 17, 2013 1:16 PM > To: cnc-list@cnc-list.com > Subject: Re: Stus-List Battery charger recommendations? > > I picked up the one noted above to maintain the battery's. In my first post I > was trying to explain I needed something to keep the batt's charged while > sailing ever couple of weeks. "For Now" In 2018 We hope to shove off for > some extended cruising. > I will need to install a Good expensive on board fixed mount bank charger. > This is what I was hoping to get advice on. the Good one that will give me a > charge on all my batt's when I come in from off shore. > Sorry for the confusion. > > > > > > On Tue, Dec 17, 2013 at 12:52 PM, Josh Muckley <muckl...@gmail.com> wrote: > Evidently, we all misunderstood the question. The battery minder is > advertised to provide a "de-sufating" pulse charge to prevent loss of > capacity. This is fine and may or may not add value for your purpose. Had > any of us realized that you simply wanted to keep the batteries from self > discharging during winter storage you would have received drastically > different answers. > > For ultra cheap $20 you can find 2amp smart chargers that cycle to prevent > over charging. If conditioning or de-sufating was the goal then I would have > possibly recommended a higher power portable unit with a conditioning > feature. 10-40amps, 3 stage, and conditioning mode, $50-100. Stanley, > Schumacher, Vector all have similar units available at the big box, auto, and > boat stores. I'm not convinced that the battery minder has a more effective > de-sulfating feature than any of the others. > > Many people prefer to occasionally visit the boat to top up the batteries. > This eliminates the risks of overcharge, electical fire, and galvanic > corrosion. > > What type of charger did you already have? What was wrong with using it? > > Josh Muckley > > On Dec 17, 2013 10:29 AM, "Curtis" <cpt.b...@gmail.com> wrote: > Battery Tender Plus 12v 1.25 Amp 3 Stage Smart Charger BT-021-0128 > > Sorry I posted the wrong model. > > > Wal-mart > $66.48 > > > On Tue, Dec 17, 2013 at 9:59 AM, Bill Bina <billb...@sbcglobal.net> wrote: > Hopefully you can return it. You need a 12 volt charger, not an 8 volt > charger. You also need substantially more than 1.25 amps. This thing will > barely charge an 8 volt motorcycle battery. > > Bill Bina > > > On 12/17/2013 9:47 AM, Curtis wrote: > After much study and review I purchased a portable charger last night > > Battery Tender Plus 8v 1.25 Amp 3 Stage Smart Charger BT8v021-0152 > This is a very popular 8 volt unit for battery storage. The Battery > Tender Plus is a 1.25 amp battery charger designed to fully charge a > battery and maintain it at proper storage voltage without the damaging > effects caused by trickle chargers. The E-Z quick disconnect harness > (1 of each ring ends and alligator clips included) allows you to leave > the charger wiring attached to the battery while operating the > vehicle. Battery Tender Plus will not overcharge or boil battery when > connected long term. > > I hope it will keep them topped off when I'm not there. > > > > _______________________________________________ > 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 > > > _______________________________________________ > 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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