Stus-List Re: Sizing an inverter
Paul; Thanks for sending this out. I had composed a draft with similar information, but not sent it out until I had confirmed my pre-retirement recollection that the A*h calculation was based on the 5 amp current draw. (Decades ago I was the marketing guy for batteries for a construction equipment manufacturer and later the aftermarket guy for a fork lift manufacturer, but that seem like an astonishingly long time ago now that I think about it.) I suspect a lot of us don’t really realize where the A*h capacity ratings come from. On a somewhat related note, I noticed that one of the postings in this topic mentioned the reserve capacity of his batteries. Reserve capacity is how long it takes for the battery to discharge 100% at a current draw of 20 (or maybe it is 25) amps. Which, BTW, is what your average car consumes if the alternator or voltage regulator give up the ghost. So it is meant to give you an idea of how long you have to get to a repair shop after the little red light on the dash comes on in your car. It is basically a measurement that is not relevant for boat batteries. Rick Brass Washington, NC From: Dreuge via CnC-List [mailto:cnc-list@cnc-list.com] Sent: Wednesday, October 18, 2023 7:12 AM To: cnc-list@cnc-list.com Cc: Dreuge Subject: Stus-List Re: Sizing an inverter 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 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 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
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 Landfall 38 S/V Johanna Rose Fort Walton Beach, FL http://svjohannarose.blogspot.com/ > On Oct 18, 2023, at 8:55 AM, Richard Bush 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 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 > 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 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 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
Stus-List Re: Sizing an inverter
I recommend you size your inverter at 2x anticipated load. Also, if you use a lithium battery the internal BMS output may limit draw. My 200 ah lithium has a 100 ah limiter, do max output of inverter 100x 12 = 1,200 watts. Get Outlook for Android<https://aka.ms/AAb9ysg> From: Joe Della Barba via CnC-List Sent: Tuesday, October 17, 2023 3:31:05 PM To: 'Stus-List' Cc: 'CHARLES SCHEAFFER' ; j...@dellabarba.com Subject: Stus-List Re: Sizing an inverter Inverters are sized to the expected loads. Batteries are sized to how long you want to run those loads. Example: My wife’s hair dryer on 500 watts is drawing about 50 amps. If she ran it for an hour that would be 50 amp/hours, which would be all you can use out of a 100AH battery. Thanks to Peukert’s equation, with lead acid batteries it is a little worse than that. (heavy loads draw them down faster than the formula, light loads a little less than the formula) As for the switches, I don’t know how your boat is wired. My inverter runs off the house bank with its own switch. BTW – your math is a bit off. A 100 amp hour battery can probably supply around 500 amps or more, which is 6,000 watts. It can’t do it for very long though, but long enough to start an engine. Amps, amp-hours, watt-hours, and so on can get confusing. I’ll post how to figure this out when I get a chance. Joe From: CHARLES SCHEAFFER via CnC-List Sent: Tuesday, October 17, 2023 4:03 PM To: CNC boat owners, cnc-list Cc: CHARLES SCHEAFFER Subject: Stus-List Sizing an inverter 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
Stus-List Re: Sizing an inverter
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 37 CB; Ohio River, Mile 584: Richard N. Bush Law Offices2950 Breckenridge Lane, Suite NineLouisville, Kentucky 40220(502) 584-7255 On Wednesday, October 18, 2023 at 07:12:19 AM EDT, Dreuge via CnC-List 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 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 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
Stus-List Re: Sizing an inverter
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 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 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
Stus-List Re: Sizing an inverter
Touche' has a 1000 watt inverter. I don't run any sensitive electronics from it, just the coffee maker and the Admiral's low wattage travel hair dryer. The unique thing about Touche's inverter system is that it can power all the 120 AC receptacles throughout the boat. I have a rotary isolator switch which switches the receptacles from shore power to inverter power while still routing the power through the boat's AC panel. That is, all the breakers on the AC panel except the AC receptacles' breaker are shore power only and the receptacles' breaker is switchable between shore power and the inverter. Took some creative configuration behind the panel to do that. Inverters can require a tremendous DC current. Be sure to properly size the cables from the batteries. Be sure to install an appropriately sized breaker. Typically, a 1000 watt inverter needs a 175 amp breaker and perhaps a 2/0 cable depending on TOTAL cable run (there AND back). Touche's house bank is two Delco Voyager Series 29's. Reserve capacity: 210 each -- Dennis C. Touche' 35-1 #83 Mandeville, LA On Tue, Oct 17, 2023 at 3:03 PM CHARLES SCHEAFFER 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
Stus-List Re: Sizing an inverter
Inverters are sized to the expected loads. Batteries are sized to how long you want to run those loads. Example: My wife’s hair dryer on 500 watts is drawing about 50 amps. If she ran it for an hour that would be 50 amp/hours, which would be all you can use out of a 100AH battery. Thanks to Peukert’s equation, with lead acid batteries it is a little worse than that. (heavy loads draw them down faster than the formula, light loads a little less than the formula) As for the switches, I don’t know how your boat is wired. My inverter runs off the house bank with its own switch. BTW – your math is a bit off. A 100 amp hour battery can probably supply around 500 amps or more, which is 6,000 watts. It can’t do it for very long though, but long enough to start an engine. Amps, amp-hours, watt-hours, and so on can get confusing. I’ll post how to figure this out when I get a chance. Joe From: CHARLES SCHEAFFER via CnC-List Sent: Tuesday, October 17, 2023 4:03 PM To: CNC boat owners, cnc-list Cc: CHARLES SCHEAFFER Subject: Stus-List Sizing an inverter 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
