I talked to a Nova-Cool rep at one time who said that typically a 100w solar panel could keep one of their 12v refrigerator system operating indefinitely. There are too many variables to say this absolutely but lets assume the rep was right. The Nova-Cool system is based on a Danfoss compressor which is pretty ubiquitous, has plenty of parts and service knowledge. I have and Alder-Barbor system which is based on the Danfoss compressor. I'm quite satisfied and would recommend that you consider a Danfoss unit.
Lets consider some hypothetical numbers based on the rep's info. If a 100w panel were %100 effective and operated for 8 hours, you would get 800w-hrs of power per day. 800w divided by 12v = 67amp-hrs. 67 divided by 24hrs = 2.8amps current draw on average. That kinda gives you a ball park for what type of loads you'll be facing. Round up to 5amps/hr if you like for margin. 5 *24=120AHr per day. A typical automotive size lead-acid battery has ~100AHrs capacity and you don't want to discharge below 50% so a minimum of 2 batteries in parallel (200AHr) would be required as your house battery bank to run only your refrigerator 24 hours a day with only a 100w solar panel. If you are not on the boat you probably don't need the fridge on so the solar would keep the batteries topped up and if you are on board then you are probably starting the engine to at least get in and out of port (or on and off the hook). Lets assume that you run the engine a cumulative total of 1 hour per day and you have a minimum size alternator of 35 amps. Lets also assume that it is putting out the full 35amps during the entire hour (it doesn't because output current is based on engine rpm). Lets also assume that the charging efficiency of the batteries is 100%. You can see pretty quickly that 35amps per day is not going to keep up with the 120amp (or even the 67amp) per day load of your refrigerator. So now you have options, run the engine longer or get a larger alternator. You have to be careful that the alternator charge current is not going to exceed the charge rate for the type of battery which you have. Lead acid = 25% of capacity. Gel = 30%, and AGM = 40%. So if you have 2 auto style AGM batteries at ~100 amps each then your bank is 200AHrs and you should limit your max charging current to 80amps. At 80 amps and 1 hour of run time per day you're getting closer to being able to keep up with the needs of your refrigerator. AGM does not NEED to be charged at a higher rate but it CAN be. AGM does need to be charged at a slightly different voltage profile otherwise gassing can occur and since it is AGM once the gas is gone it can't be put back in. Even with a higher capacity alternator you will still need an external voltage regulator which would allow you to select the AGM profile. Almost all battery chargers, alternators and solar controlers will charge a lead-acid (as a base model or by default) and if gassing occurs you can and should replace it by watering. If you have room I suggest increasing your bank to the largest available lead-acid configuration and sizing the charging equipment as applicable. IMO You'll get more bang for your buck and save yourself a bunch of other complications. Obviously there are a lot of variables but you should be able to apply your own needs and expected usage. As a point of reference I have ~450Ahr on bank 1 and ~200AHr on bank 2. I have 200w solar and a 90amp alternator. I've been able to go on multi week trips and have never pulled into port because of a need for shore power or ice. In my case water is the first limiting necessity (I have ~70 gallons) followed in the far distance by a need to pump my holding tank (~150 flushes). Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Oct 14, 2017 11:50 AM, "DON JONSSON via CnC-List" <cnc-list@cnc-list.com> wrote: > Hi > > I previously lamented engine problems on my 1982 C&C 34. I had the > original Yanmar 3GMD. The problem was leaking oil from the intake manifold > caused by serious blow back. There is also a transmission problem, where > it doesn't always go into gear. > > So the decision has been made to put a new engine in, and as someone > mentioned over capitalize the boat. But we sail to the outside of > Vancouver Island and up north to where engine problems would be a super > pain. (Soon I will post information about the engine and extra parts in > case anyone is interested. It has an almost brand new exhaust riser on it > built by Gartside.) > > The old engine is out and we are now sound insulating the engine > compartment. > > The boat currently has an ice box but putting in refrigeration is high on > the list. Getting ice rapidly becomes a challenge as you head off. This > would imply more battery power and an alternator to keep it going. We are > looking at a Beta 25 for which you can get a 75 or 120 amp alternator. > Because of limited battery space I'm thinking of using AGM batteries which > you can suck more amps out of. > > Has anyone got some words of wisdom and/or experience with this? > Including what is the minimum amount of available amp hours you need? The > water is cold up here and it usually doesn't get too hot. It seems with > AGM batteries you need a fair bit more charging capability. > > Although the refrigeration project is a little further off I don't want to > but too small of an alternator now. > > Thanks > Don Jonsson > Victoria, B.C. > > > _______________________________________________ > > The bills have started coming in for the year 2018 and have gone up > again. October will be our fund raising month. Please consider sending a > small contribution to help keep this list running. Use PayPal to send > contribution -- https://www.paypal.me/stumurray > > All contributions are greatly appreciated! >
_______________________________________________ The bills have started coming in for the year 2018 and have gone up again. October will be our fund raising month. Please consider sending a small contribution to help keep this list running. Use PayPal to send contribution -- https://www.paypal.me/stumurray All contributions are greatly appreciated!
