I was estimating 3000A-hr too. That's 30 group 27 batteries! Not sure you want to do that.
Most people opt for generators to power the air conditioning overnight. You only need a small 2kw unit. The little red Hondas are popular for this purpose. You can set them on the foredeck and run a shore power cord aft to your normal shore power plug. Not sure how long they are rated to run on one tank of gas. Of course this means keeping gasoline on board too. A little diesel genset is the best option if you can make room to mount it. Then it can be fuelled from the ship's tank. Oct 18, 2023 15:13:56 Marek Dziedzic via CnC-List <cnc-list@cnc-list.com>: > The simple math shows that if you need 12.5 A at 120 V, you will need 125 A > at 12 V. This is assuming 100% efficiency of the inverter. I bet that they > are around 80%, so add 20% to that number (1.2 x 125 A = 150 A). Run this for > 12 h and you will use 150 A x 12 h = 1800 Ah. In order to accomplish that, > you need a 3600 Ah battery bank (lead-acid), or around 2250 Ah if lithium. > > In short, you will need a small power station to power it (a 2000 W generator > will recharge that battery bank in more than 12 h). > > These calculations did not include the Paukert effect or potential issues > related to heat generated when discharging or charging the batteries. > > The only good news I could think of is that you won't need 12.5 A all the > time (a good chance is that after the initial run, the AC will be cycling on > and off, and will run about half of the time). Which means that a smaller > battery bank will be needed (2000 Ah (L-A)/1250 Ah (Li)). > > > There might be other considerations that might help reducing that size (e.g., > AC that draws less current). > > Hope it helps > > Marek > Ottawa, ON > > Sent from my Android-based can on a string > > > > > -------- Original message -------- > From: CHARLES SCHEAFFER via CnC-List <cnc-list@cnc-list.com> > Date: 2023-10-18 20:18 (GMT+01:00) > To: Stus-List <cnc-list@cnc-list.com> > Cc: "Della Barba, Joe" <joe.della.ba...@ssa.gov>, CHARLES SCHEAFFER > <cscheaf...@comcast.net> > Subject: Stus-List Re: [EXTERNAL] Re: Sizing an inverter > > -------- Original message -------- > From: CHARLES SCHEAFFER via CnC-List <cnc-list@cnc-list.com> > Date: 2023-10-18 20:18 (GMT+01:00) > To: Stus-List <cnc-list@cnc-list.com> > Cc: "Della Barba, Joe" <joe.della.ba...@ssa.gov>, CHARLES SCHEAFFER > <cscheaf...@comcast.net> > Subject: Stus-List Re: [EXTERNAL] Re: Sizing an inverter > > Very helpful. > > What is the proper math to determine battery bank size needed to run our AC > unit for twelve hours? I know a softstart would make it possible, and the > rated amp draw is 12.5 amps at 120vac. I'm considering getting a lithium > 200 ah and keeping a 100 ah AGM as a start battery. Solar panels are being > considered also. > > > > Thanks, > Chuck > > >> On 10/18/2023 12:50 PM EDT Della Barba, Joe via CnC-List >> <cnc-list@cnc-list.com> wrote: >> >> >> >> If it helps, think of the inverter as a special kind of extension cord. It >> passes power from Point A to Point B. It does not create or store power. It >> needs to be bigger than the expected load put on it. >> >> The batteries need to be up to the task, but they do not create any power, >> they store it. If you want to use a lot of power, you have to generate a lot >> of power somehow. >> >> A huge battery bank, say big enough to run an air conditioner overnight, on >> a C&C with a stock charging system would work one night and then you would >> need to motor about 8-10 hours if you wanted to do it again. >> >> Joe >> >> Coquina >> >> >> >> *From:* Dreuge via CnC-List <cnc-list@cnc-list.com> >> *Sent:* Wednesday, October 18, 2023 12:06 PM >> *To:* Richard Bush <bushma...@aol.com> >> *Cc:* cnc-list@cnc-list.com; Dreuge <dre...@gmail.com> >> *Subject:* [EXTERNAL] Stus-List Re: Sizing an inverter >> >> >> >> Richard, >> >> >> >> My point is that one should not size an inverter relative a battery, but >> size it to ones expected needs. Folks often mix up or misuse terminology. >> If the maximum power consumed from an electric coffee pot is 1000 Watts. >> Then one would need at least a 1kW inverter, but should get something larger >> to avoid maxing the operating limits. Now the question is what battery can >> provide a constant 1000W for the 5 minutes to brew coffee. Of course >> battery needs are greater than brewing coffee and an energy audit would give >> a better estimate, but for the sake of simplicity, let’s only consider >> coffee needs. >> >> >> >> For a 12V battery system (12.5V lead acid), the 1000W of power (P = >> voltage* current) is provided by a battery current of 1000W/12.5V = 80A. >> So one would need a battery that can provide 80A of current for 5 minutes. >> A single 100A*hr lead acid type battery would be a poor choice as it would >> end up nearly depleted. Relative to a 100 A*hr LiFePO4 battery, the >> LiFePO4 battery would brew about 10 times more coffee! >> >> >> >> >> >> >> >> >> >> - >> Paul E. >> >> 1981 C&C Landfall 38 >> S/V Johanna Rose >> Fort Walton Beach, FL >> >> >> >> http://svjohannarose.blogspot.com/ >> >> >> >> On Oct 18, 2023, at 8:55 AM, Richard Bush <bushma...@aol.com> wrote: >> >> >> >> Paul, If I understand your point, it is that we shouldn't be relying on >> battery power for any appliances or coffee pots...etc.; is there any >> alternative that doesn't involve solar? thanks! >> >> >> >> Richard >> >> 1985 C&C 37 CB; Ohio River, Mile 584: >> >> Richard N. Bush Law Offices >> >> 2950 Breckenridge Lane, Suite Nine >> >> Louisville, Kentucky 40220 >> >> (502) 584-7255 >> >> >> >> >> >> On Wednesday, October 18, 2023 at 07:12:19 AM EDT, Dreuge via CnC-List >> <cnc-list@cnc-list.com> wrote: >> >> >> >> >> >> Hi Chuck, >> >> >> >> First off, 12V * 100 A*hr = 1200 W*hr. But keep in mind that A*hr battery >> ratings for a 100 A*hr battery is tested typical at 5 amps(or 0.05C). That >> is your 100 A*hr is 5A * 20hr. At this rate the battery is only providing >> 12.5V * 5A = 63 Watts. At higher current loads, your effective battery >> capacity will be much much less due to Peuket Effect losses. In fact, a >> 100 A*hr rated lead-acid battery at 100 amp load would only provide about 20 >> A*hr of energy(and lots of heat). To add to the insult, lead acid based >> batteries like AGM should not be depleted below 50% capacity to limit >> damage, so reserving 1 battery for start leaves only 50 A*hr for your house >> bank at loads of about 5 amps. At a 20A load, the 100 A*hr (50 A*hr >> effective) only provides 60 A*hr (30 A*hr effective). That’s about 30 A*hr >> / 20A = 1.5 hrs of use. >> >> >> >> A 1000 W inverter could draw a max of 1000W / 12.5V = 80 Amps (but likely >> higher due to a voltage drop). This would drain your battery in 6 - 10 >> minutes. >> >> >> >> I gave a talk to some local Hams about Solar Off-Grid Systems. I posted the >> slides on my blog (see link below). On slides 5 & 6, I discuss battery >> discharge capacity and bank sizes. >> >> >> >> >> >> >> >> >> https://svjohannarose.blogspot.com/2021/10/solar-off-grid-system.html >> >> >> >> >> >> On Johanna Rose, I have a 2000W inverter charger. When I run my microwave, >> it draws about 100A from a 560 A*hr LiFePO4 battery. Like Dennis, I have >> my inverter connected to my panel powering all AC loads except for my A/C >> unit and water heater. The inverter has a built in transfer switch which >> automatically (and smoothly) transfers to shore power when available. >> >> >> >> - >> Paul E. >> >> 1981 C&C Landfall 38 >> S/V Johanna Rose >> Fort Walton Beach, FL >> >> >> >> http://svjohannarose.blogspot.com/ >> >> >> >> >> On Oct 17, 2023, at 7:27 PM, via CnC-List <cnc-list@cnc-list.com> wrote: >> >> >> >> OK, an DC/AC Pure Sine Wave inverter looks attractive >> >> >> >> I've heard some boats have 1000 watt, some 2000watt and some 3000 or more. >> >> What size inverter is right for a boat equipped with two 100Ah AGM >> batteries? >> >> One battery provides 12v x 100ah: 1200watts. My system can provide 2400 >> watts but I usually reserve one battery to restart the engine and run on the >> other battery. Does the inverter get fed from a bus common to both >> batteries, or to the selector switch marked, "Off, 1, both, 2"? >> >> >> >> Thanks, >> >> Chuck S >> >> >> >> >> >> Please show your appreciation for this list and the Photo Album site and >> help me pay the associated bills. Make a contribution at: >> https://www.paypal.me/stumurray >> Thanks for your help. >> Stu >> >> >> >> Please show your appreciation for this list and the Photo Album site and >> help me pay the associated bills. Make a contribution at: >> https://www.paypal.me/stumurray >> Thanks for your help. >> Stu
Please show your appreciation for this list and the Photo Album site and help me pay the associated bills. Make a contribution at: https://www.paypal.me/stumurray Thanks for your help. Stu
