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 > > mailto: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 mailto: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 > > > mailto: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
