Getting a handle on kW usage

[-TX-]

So, after thinking there would be no chance of AC in my rig when onsite, now I'm gleefully curious. I cranked my EE AC up for the 1st time, noticed no more then a second of 12amps, then it settled at 3.7 amps with condenser on. That was very surprising because it's rated at 6.2amps. Is this service in play? Strictly, it should be when I'll need it - at night. Over 8 hours, that's 3500w being fed by a 16,560wh battery bank. But than again, this board refers to higher draw equating to lower battery life. Is 3.7a a high draw?

[Sunking]

Its all relative. 3.7 amps on a 37 AH battery is C/10 and that equates to around 4 hours until you are 50% DOD. 3.7 amps on a 370 AH battery is C/100 and 2 full days until 50% DOD.

[-TX-]

I like what I hear! So, 3.7 amps on my 690ah battery is C/186, good for way longer than I'd ever be onsite?

[-TX-]

Boom!

use.png

[Sunking]

I like what I hear! So, 3.7 amps on my 690ah battery is C/186, good for way longer than I'd ever be onsite?

Huh? The 3.7 amps you are referring to is at 120 VAC right? At 24 VDC is 444 watts / 24 volts / .88 Inverter efficiency = 21 amps. Try C/32

You have a 24 volt 690 AH battery gives you a reserve capacity of 16.5 Kwh. If you use 8 Kwh per day you are discharging your battery 50% each day. One Cloudy day will require you to shut down or run the generator.

[-TX-]

Its all relative. 3.7 amps on a 37 AH battery is C/10 and that equates to around 4 hours until you are 50% DOD. 3.7 amps on a 370 AH battery is C/100 and 2 full days until 50% DOD.

K, I see this:
3.7 amps on 37ah battery = C/10
3.7 amps on 370ah battery = C/100
3.7 amps on a 690ah battery = C/32??????????

Huh? The 3.7 amps you are referring to is at 120 VAC right? At 24 VDC is 444 watts / 24 volts / .88 Inverter efficiency = 21 amps. Try C/32

OK, now I'm absolutely convinced you just make **** up along the way to bully. I'm trying to get something accomplished here and you're not helping. NOT. ONE. BIT. I am however glad that after all your groundless criticism you finally understand my setup, at least the battery part.

[SunEagle]

K, I see this:
3.7 amps on 37ah battery = C/10
3.7 amps on 370ah battery = C/100
3.7 amps on a 690ah battery = C/32??????????




OK, now I'm absolutely convinced you just make **** up along the way to bully. I'm trying to get something accomplished here and you're not helping. NOT. ONE. BIT. I am however glad that after all your groundless criticism you finally understand my setup, at least the battery part.

What SK is trying to tell you is that 3.7amps draw at 120volts for your A/C system converts to 21amps draw on your 24volt battery system due to the voltage change and DC to AC conversion loss of 12%. What that calculates to for your 690Ah battery is a discharge rate of 690/ 21 = 32.8 or approximately C/32.

[Sunking]

K, I see this:
3.7 amps on 37ah battery = C/10
3.7 amps on 370ah battery = C/100
3.7 amps on a 690ah battery = C/32??????????




OK, now I'm absolutely convinced you just make **** up along the way to bully.

No I am not. Like Suneagle, Mike, and many others are trying to tell you is the 3.7 amps you are quoting is what you seeing on the 120 VAC side, not 24 VDC from the battery. I have given you the math many times but it is not getting through. .

Watts = Voltage x Amps

120 volts x 3.7 amps = 444 watts that your air conditioner uses and that sounds right for a small window shaker air conditioner of 1/2 ton size. You further stated your Inverter is 88% efficient. So that means it requires 444 watts / .88 = 504 watts on the input from your 24 volt battery.

Amps = Watts / Volts

504 watts / 24 volts = 21 amps from your battery

So 690 AH / 21 A = 32.8 Hours. So I was wrong, it is C/33 if you round up to make it sound better. It is not BS it is fact. Common sense should tell you that. I am trying to help you. Stop and think about it. since 120 volts x 3.7 amps = 444 watts, try to apply that to the battery 24 volts x 3.7 amps = 88.8 watts does not equal 444 watts. Once you take the Inverterter efficiency into account draws 504 watts from the battery. The DC current has to be higher than the AC current because the DC voltage is lower than the AC voltage.

[-TX-]

I ask:

Is 3.7a a high draw?

You answer:

Its all relative. 3.7 amps on a 37 AH battery is C/10 ...... 3.7 amps on a 370 AH battery is C/100......

I continue the math:

So, 3.7 amps on my 690ah battery is C/186

You respond: Of course that's not right

Huh? The 3.7 amps you are referring to is at 120 VAC right? At 24 VDC is 444 watts / 24 volts / .88 Inverter efficiency = 21 amps. Try C/32

Either your first or last statement is accurate. They both can't be unless the first was specifically made to complicate the matter.

You've posted before how larger draws on a battery lead to lower total output. I asked, "Is 3.7amps a large draw"?
The answer is yes, no, depends on this, that or the other, but generally no (or yes).

[Sunking]

I give up on you.

How much power is 3.7 amps?

Answer, there is no answer because no voltage or capacity was specified. It is an incomplete question which forced me to make assumptions. I had to make an assumption and was not aware of your battery capacity. It was only later when we all learned it was your Air Conditioner AC current. That is when I knew it had to be AC, not DC. You are confusing yourself and me by asking incomplete questions with important missing data.

So let me ask you a question. Is 5 fast or slow?

[-TX-]

No voltage was specified on an air conditioner that I have specifically said was AC powered? Also, there's no such thing as an DC powered room air conditioner. Or if there is, it certainly shouldn't assumed anyone posting here has one.

[Sunking]

Also, there's no such thing as an DC powered room air conditioner. Or if there is, it certainly shouldn't assumed anyone posting here has one.

Sure there is, lots of them because they are extremely efficient and used by some off grid folks They make 24 and 48 volt units. I use them in telecom to cool outdoor cabinets on 24 and 48 volt battery. They are real popular with cross country truck drivers to keep their sleeper cabs cool at night while they sleep. I believe there is now a law requiring them in all new rigs for truckers so they do not have to idle their engines.

Most truckers use Artic Breeze. Twice as efficient than your unit. You have a 1/2 ton Window shaker using 440 watts. The Arctic Breeze is 1 ton and uses 400 watts.

[-TX-]

Cute product

But at 2000 BTU it would take 5 of them to equal a standard room AC, like mine. And at 220w per 1000 BTU it is hardly efficient.

[Sunking]

Cute product

But at 2000 BTU it would take 5 of them to equal a standard room AC, like mine. And at 220w per 1000 BTU it is hardly efficient.

Huh! WTF are you talking about?

It is 12,000 BTU aka 1-ton. Your Window shaker is 6000 BTU aka 1/2 ton. Both use roughly the same amount of power, 400 watts. It would take two of your window shakers to equal 1 Arctic Breeze because it is twice as efficient.

[-TX-]

Yeah, the unit I followed was 2000 btu. The 12,000 btu looks pretty impressive.

Jesus, I just tried to get a price on one from a half dozen 'dealers' across the states. They had no idea.

edit: Should have just called Arctic Breeze. About $5500 not including installation. Some of the top end RV manufacturers should consider the option because the roof mounts are all terrible. Inefficient, loud, ugly.