David, You need to calculate the amp/hours the fridge uses to know how long you can run it before drawing your battery below the appropriate SOC. Even if its on, its not running all the time.
Somewhere I have a spreadsheet that estimates all of my daily power needs. Its on a different computer, but if you ping me tomorrow I can email it to you. Joel joel.aron...@gmail.com <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> Virus-free. www.avg.com <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> On Mon, Feb 12, 2018 at 3:01 PM, David Knecht via CnC-List < cnc-list@cnc-list.com> wrote: > This discussion raises an issue I have struggled with as I have started > cruising more: deciding how much battery power I have. I have 2 AGM > batteries, one house, one starting and a panel voltmeter for monitoring. > My batteries are now separated so I no longer have to worry about being > able to start the engine if I run the house too low. The fridge is the only > major power draw, so I usually am just conservative, running it only > periodically to make sure I don’t overdraw the battery. So what is the > most efficient way to figure out how much I can safely run the fridge? If > I just watch the voltage, how do I decide if I can leave the fridge on > overnight? Dave > > Aries > 1990 C&C 34+ > New London, CT > > > On Feb 12, 2018, at 2:33 PM, Josh Muckley via CnC-List < > cnc-list@cnc-list.com> wrote: > > Much of your problem is a matter of battery capacity as much as a matter > of charging capacity. I have ~450 Ah of capacity on one bank, a 90 Amp > alternator that never reaches full load, and 200 watts of solar. Even > without the solar I was able to comfortably keep the the fridge running and > the lights on when cruising for ~2 weeks. The half hour to hour of engine > operation to anchor or moore in the evening and the same in the morning was > always enough to keep the batteries charged. > > Keep in mind that the battery capacity should be at least 4x of the charge > capacity for flooded lead acid and at least 2x for AGM. So a 400 Ah or 200 > Ah respectively for a 100 amp alternator. > > Josh Muckley > S/V Sea Hawk > 1989 C&C 37+ > Solomons, MD > > > > On Mon, Feb 12, 2018, 12:55 PM Damian Greene via CnC-List < > cnc-list@cnc-list.com> wrote: > >> A question for your collective wisdom: >> >> I am scoping out upgrading my stock 55A alternator to a 100A Balmar, and >> related upgrades to the controls. I had a very productive discussion with >> Rod Collins at Compass Marine (mainesail), and we worked out the details. >> Unfortunately he's booked out through the spring, so this job will wait >> until next winter. >> >> So thinking then about keeping the batteries charged, and the fridge >> running on our long summer cruise - where we may go for weeks without >> access to shore power, I got wondering about using a portable generator to >> charge the batteries - as an alternative to many hours of running the >> diesel. There are a couple of Hondas that might do the trick 2000 Watt, >> weighing 47#, 1000 Watt weighing 29#. >> >> Have any of you tried this? What could (would) go wrong if I plugged this >> generator into my inverter, to charge the batteries? >> >> Regards, >> >> Damian >> >> 1986 Sabre 38 Freefall >> Previously 1984 C&C 34 Ghost >> Bass Harbor, Maine >> _______________________________________________ >> >> Thanks everyone for supporting this list with your contributions. Each >> and every one is greatly appreciated. If you want to support the list - >> use PayPal to send contribution -- https://www.paypal.me/stumurray >> >> _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > > > > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > > > -- Joel 301 541 8551
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