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Old 07-11-2016, 00:55   #226
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Re: What is your Real Amp Hour per Day Usage

Not sure if the OP is satisfied with the info in here yet. Electrical usage on boats varies WIDELY, so you pretty much have to do your own calculations. For instance, we typically go through ~130Ah/day, but we only have a single fridge/freezer & it's well insulated (but still uses half that energy budget). Our son did an energy budget for us when he was 15 (we made it a school project) & he published his findings, as well as his methods. It takes some time, but it's not difficult, & having an amp-hour meter will help. Also, his analysis was done before we switched over to LEDs, which can make a huge difference when living aboard.
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Old 07-11-2016, 02:03   #227
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Re: What is your Real Amp Hour per Day Usage

We use 30-40 AH o/n at anchor, 70-80 AH couple o/n. fridge/freezer and at this point still see no reason to increase my 360 W/480 AH gel setup. Batteries full, normally before midday.

We use series of cheap 20 AH chinese lithium batteries that get charged during day to have considerable extra power if needed for gadgets powering.
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Old 07-11-2016, 10:12   #228
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Re: What is your Real Amp Hour per Day Usage

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Neither quoted power.
"15 A / day sailing" indicate power. "15 Ah / day sailing" indicate energy.
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You don't "use" power, you use energy. As you correctly state, Power is a RATE of doing work (a.k.a. amount of energy consumed per unit time).
Yes you can. For example: The average city property uses 24 kW of power per day.
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You can't "use" Amps or Watts over a time period. So talking of usage in terms of Amps/day or Amps/hr demonstrates a failure to comprehend the difference between power and energy.
Yes you can, if / represent per or for. For example:
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While underway the autopilot and nav system uses about between 9-12 amps per hour additional.
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The problem is that when it is done incorrectly like this you have to try to interpret what Barnakiel meant by "15 A / day sailing"
Do not have to try, he mean exactly "15 A / day sailing"
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Is he a very heavy energy user or a very light user?
Very light user and it is why he can do with a

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House bat 100 Ah.
By the way a 100 Ah bat can also be expressed as 5A for 20 hours, which is more informative. "15 A / day sailing" will give more than 6 days of use.
I guess that Stevens 47 carry more than one 100 Ah battery.
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Old 07-11-2016, 10:21   #229
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Re: What is your Real Amp Hour per Day Usage

Question, on an average day in the "Caribbean" during the Winter months how much Solar is needed to replace 100 AH?

I know there are huge variables, and I do know my average consumption, just trying to get a feel as to how much Solar is needed.
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Old 07-11-2016, 10:24   #230
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Re: What is your Real Amp Hour per Day Usage

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Either confused or just unaware of the correct terminology.
But if we are really interested, from his figures we can tell his power demand. (Although his energy usage, as per the Thread Title in this case is far more important)

Living at anchor: 200-250AH/day = an average power demand of 8.3-10.4 Amps

While Underway 300-400AH/day = an average power demand of 12.5 - 16.7 Amps.
Well, nobody's perfect.
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Old 07-11-2016, 10:34   #231
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Re: What is your Real Amp Hour per Day Usage

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Question, on an average day in the "Caribbean" during the Winter months how much Solar is needed to replace 100 AH?

I know there are huge variables, and I do know my average consumption, just trying to get a feel as to how much Solar is needed.
100 x 15v = 1500(watt hours)
1500wh / 5 hours of overhead sun = 300wh
300w @ 80% efficiency = 375w for 5 hours
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Old 07-11-2016, 10:41   #232
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Re: What is your Real Amp Hour per Day Usage

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But be aware that the people who wrote some of those references are also very confused about the difference between Amps and Amp hours and use them incorrectly in many places. (FWIW, I wouldn't put too much faith in advice from sources which can't even get the basic units right)
Also there are some very good and very poor electrical installations on this forum.
It is why,
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Old 07-11-2016, 10:42   #233
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Re: What is your Real Amp Hour per Day Usage

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100 x 15v = 1500(watt hours)
1500wh / 5 hours of overhead sun = 300wh
300w @ 80% efficiency = 375w for 5 hours
I get confused by your numbers, but I won't pick.



No matter, I guess what is important is that on average there are 5 hours of usable sun, and that a panel will on average return 80% of rated capacity.
Is that correct?
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Old 07-11-2016, 12:55   #234
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Re: What is your Real Amp Hour per Day Usage

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I get confused by your numbers, but I won't pick.



No matter, I guess what is important is that on average there are 5 hours of usable sun, and that a panel will on average return 80% of rated capacity.
Is that correct?
Like you first said, large variables. A semi-swag is 375w worth of solar would be the least amount to restore 100ah.
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Old 07-11-2016, 13:04   #235
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What is your Real Amp Hour per Day Usage

Got it, roughly three to one if you ignore units.
I have to wonder how some seem to get by on a couple of small panels, I assume they are chronically undercharged and run the motor often?
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Old 07-11-2016, 13:06   #236
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Re: What is your Real Amp Hour per Day Usage

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Question, on an average day in the "Caribbean" during the Winter months how much Solar is needed to replace 100 AH?

I know there are huge variables, and I do know my average consumption, just trying to get a feel as to how much Solar is needed.
You already have enough solar and a generator. Stop throwing money away

BTW - while I don't know how the caribbean might work out location wise, 4 years of my boat being on a mooring with the frig running says that you can count on 300W providing about 60AH/day with it doing 100AH/day if sunny and the panels some how manage to track with the sun all day.
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Old 07-11-2016, 13:14   #237
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Re: What is your Real Amp Hour per Day Usage

I think this thread has reinforced my desire to replace all my incandescent automotive backup lamps that someone installed in my boat (possibly Hunter, the time period seems right) with LED lighting. The price per fixture is not horrible if I am careful, the life of the lamp is far higher, and the energy consumption of the LED is so far below the incandescent that if I make this change alone, I will save a tremendous drain on the batteries over the course of a day. I normally don't use these lights unless I absolutely MUST because of the drain they represent, but the Admiral likes to sit up at night and read paper books, and as a diabetic she is deathly concerned about stubbed toes.
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Old 07-11-2016, 13:16   #238
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Re: What is your Real Amp Hour per Day Usage

90 litre freezer, 100 litre fridge both 240 volt run through inverter, Village marine tech watermaker, roughly 40 litres per day, lights, TV, computer etc, we usually seem to use around 2 kWh per day.


800 W of solars runs it easily.
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Old 07-11-2016, 13:23   #239
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Re: What is your Real Amp Hour per Day Usage

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You already have enough solar and a generator. Stop throwing money away



BTW - while I don't know how the caribbean might work out location wise, 4 years of my boat being on a mooring with the frig running says that you can count on 300W providing about 60AH/day with it doing 100AH/day if sunny and the panels some how manage to track with the sun all day.

OK, so more like four to one, five to one to be conservative.
So if your consumption is 200 AH a day, you will need a Kilowatt of panels.
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Old 07-11-2016, 13:24   #240
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Re: What is your Real Amp Hour per Day Usage

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I get confused by your numbers, but I won't pick.

No matter, I guess what is important is that on average there are 5 hours of usable sun,
Not exactly. There are more like 10-12 hours of "usable sun" (depending on latitude and time of year).

But over that time, the angle of the sun and consequently the power available varies from very little in the early morning and late afternoon to quite a lot at midday.

In total, the panels should generate about 5 hours worth of rated power over that 10-12 hour period.
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