How to convert reading of amps into amp hours

[mitiempo]

Originally Posted by Kelkara

Let's start by using the value on the manufacture's label, and see what you should expect.

1800W
120V

So if your induction top is working at full power it will draw 1800/120 = 15A ... This is the 120V draw on the inverter.

( if you're only measuring 2.47 amps ... either the cooktop is only simmering, or your measurement is faulty.)

But the inverter has to draw down the battery to supply that power ... on the 12V side, you still need to supply 1800W (plus some losses in the inverter): 1800/12 = 150A ... This is the 12V draw on the battery.

So ... if your batteries are 180Ah then, if they start out full, and you start drawing 150A...

after 10 minutes (1/6 hr) of cooking you will have used 150A * 1/6 hr = 25 Ah.
after 20 minutes (1/3 hr) of cooking you will have used 150A * 1/3 hr = 50 Ah.
after 30 minutes (1/2 hr) of cooking you will have used 150A * 1/2 hr = 75 Ah.
after 40 minutes (2/3 hr) of cooking you will have used 150A * 2/3 hr = 100 Ah.

by now your batteries are seriously depleted and you risk damaging them if you keep going

after 50 minutes (5/6 hr) of cooking you will have used 150A * 5/6 hr = 125 Ah.
after 1 hour of cooking you will have used 150A * 1 hr = 150 Ah.
after 1 hour 10 minutes (7/6 hr) of cooking you will have used 150A * 7/6 hr = 175 Ah.

And now your batteries are well and truly dead and likely damaged too ... in fact this assumes a hypothetically perfect battery, a real battery won't last that long at such a high current.

This post is almost totally accurate. The only error I see is that a battery of 180 AH is measured at a 20 hour rate. In other words a battery of 180 AH will provide that many AH if the current draw is 9 amps (9 x 20 = 180). If the draw is very large as in the above post's example the actual battery capacity will be much less than 180 AH. The opposite is also true - if the draw is say 5 amps the total AH of the battery will exceed 180.

In other words drawing 150 amps from a 180 AH battery will give much worse results than the above example describes.

[mitiempo]

Originally Posted by Dave22q

......e.g. 10 minutes at 18 amps is 10 amp-hours. Hope this helps.

Actually 10 minutes @ 18 amps is 3 AH by my math.

[hzcruiser]

Originally Posted by mitiempo

Actually 10 minutes @ 18 amps is 3 AH by my math.

You're right. He had it right all along his nice post and then stuffed up the math in the last line, what a bummer...


It's not that hard, really: 10 minutes at 18 A is just that: 10 * 18 A*minutes or: 180 A*minutes.

If you want to divide 180 by 60 you'd get the common A*h also written as Ah, or 3 Ah.

[alansmith]

[QUOTE=Wotname;2647783]You are not quite there yet (but getting closer )

2.47 amps @ 110 volts = 272 watts, not watt hr.

If you had it turned on for one hour, then you would have used 272 watt hours and so on - turned on for say 3 hours and you would have used 816 watt hours.


You are correct about that. What a concept to be able to sit down at a table and discuss a question with guys and gals that have already “wired this stuff out”

[alansmith]

[QUOTE=Jim Cate;2647802]Please note that the label on the cooker says "1800 watts". This is likely a good approximation of the power consumed at its highest setting, which is likely what you will use when boiling a kettle.

Jim, yup...I got a ways to go yet. But I am way ahead of where I was a week ago. Several people have stated that I needed to split the line before measuring the amperage. The instruction manual doesn’t state that. So, little by little. Being an older guy certainly has loss of spongy material between the ear lobes.
I am really enjoying the learning process.

This induction stove was bought for a studio apartment I rent out. Anyone have induction tops that are smaller, more effecient, or just general good feelings....or bad feelings about feel free to weigh in.

[alansmith]

Wot, thank you for the historical perspective and why we do what we do. I use metric a lot in work. I have even gotten to the point that in remodeling I prefer a metric tape versus ....5 3/4 inch “fat”.

I can’t wait to get down to the boat in San Carlos and see what space I have for the battery bank. What will be entailed in solar and seeing what PITA I will be facing to redo the electrical service box.

[alansmith]

Originally Posted by Sailmonkey

There is a HUGE error in measurement. Clamp meters don’t work unless on a single conductor. The OP is clamping both hot/neutral/ground at the same time.

Sailmonkey, see, I didn’t know that. Goes back to that well worn phrase....”all of the tools...none of the talent.” He he

The manual didn’t say anything about splitting the lines. So, thank you for edu..cate...ing..... me. If anyone needs educating ...i’m Always...alll ears and eyes and twitching fingers....smile.

I have rewired 2 houses so I understand basic electricity. Have been shocked multiple times. But this whole thing of calculating battery banks, solar arrays, generators, losses, reading wiring diagrams....it is a steep curve. But that is where you find me.

I have a Hayabusa motorcycle. I had a army helicopter engineer build me a harness and bixenon lights. Couldn’t buy this $hit back in 2008. I rode country roads late at night coming home from the hospital. Anyway...after 10 years they crapped out. It took me a full two weeks to figure it out. I had 2 wiring harness, 2 bulbs, 2 fuses, 2 bulb exciters, and 2 voltage amplifiers....oh and 2 relays. It was a nightmare. But it ended up being the voltage amplifier and one fuse. Even Suzuki couldn’t figure out what was wrong without spending 500 dollars plus. So, I dug in and went at it. Put it all back together ...and it worked before puttin skins back on the bike....then found out there was a clearance
Issue behind the lamp exciter and the instrumention panel. Ai Ya!!! (Chinese form of expressing exasperation)

I will get there. I also know that I can get solid advice by approaching the forum with hat in hand mentality. Thanks guys for your mentoring...

[transmitterdan]

Alan,

You can buy a simple device that splits the line safely. They are also available for most standard plugs in the world.

Search: Extech-480172-AC-Line-Splitter

[Pete7]

This induction stove was bought for a studio apartment I rent out. Anyone have induction tops that are smaller, more efficient, or just general good feelings....or bad feelings about feel free to weigh in

There is a reason so many cruisers use butane or propane to cook with as do millions of people around the world. The amount of energy stored in a small container is huge and its cheap to buy. Same for cooking with Kerosene (parafin) or using petrol and diesel for propulsion, it is hard to replace that stored energy with wiggly amps.

Hate to say this but I am struggling to see how an induction hob is going to work for you on a 28ft yacht. Running a Honda 20i to generate electricity to either use directly or store in Lithium batteries doesn't really make sense and tricky when sailing. Storing a large amount of energy in batteries is going to be costly up front and I suspect you don't have the space. Same for a huge bank of solar to run the induction cooker either via batteries or directly. Might be better to cook directly with solar using one of those mirrored reflective cookers with food inside a glass tube.

You have a 28ft Freedom Cat rig yacht which is an interesting alternative, but I am willing to bet you need to watch the weight or she will sail like a dog and go sideways more than forward.

We have a similar sized yacht and 4.5kg of Butane gas will last us all summer and cost $20 to refill. Bang for buck that is hard to beat.

Pete

[alansmith]

Pete, My current set up is propane. She is 30 foot Condor tri. So, yes, you are on the button about space. But with Lithium you can sure get a lot of bang for your buck also. The boat is down in San Carlos, Mx. I am dying to get down there and start measuring things up for what can and can not be done.

I am in full agreement that using an induction stove top is sexy and easy if you have the juice to do it. I have plenty of real estate to solar farm it. The deciding factor will be if I have enough room to lay out and maintain the battery farm.

But now I have a much better idea of how much energy an induction top consumes. It really is amazing how much amperage is taken. Yes, propane is much cheaper and more practical. Safe if done correctly. Appreciate your advice

[Pete7]

You didn't say you have a tennis court of deck space for solar :-)

Always a worth while exercise to go through even if it proves something isn't feasible.

However, since weight is a really big issue to you trimaran guys even down to cutting the handles off tooth brushes, lithium might a really good solution for running the boats 12v domestics. Then keep the induction hob loose for placing on the stove when in harbour with mains electric.

[guyrj33]

Originally Posted by Kelkara

Your example would have been excellent ... except you missed out the word "hours" ... you said "watts" instead of "watt-hours". Hopefully just an honest mistake that was well corrected.



There are people on this forum who happily use such erroneous units when discussing electricity, but when trying to teach a newbie what's what (pun intended) I feel this is a great disservice. Especially on this thread when the OP effectively asked in the title what is the difference between "amps" and "amp-hours" ... that "hours" is important.

Kelkara;
Thanks for the explanation, you're absolutely correct I used the wrong units.
Guy

[TeddyDiver]

Originally Posted by alansmith

This induction stove was bought for a studio apartment I rent out. Anyone have induction tops that are smaller, more effecient, or just general good feelings....or bad feelings about feel free to weigh in.

Counting the max output is kind ridiculous as you were to warm up a pro moonshine still..
Boiling a kettle of water takes a few minutes and that's what your energy comsumption estimates should be based on. Cooking food for longer times the cooktop might be 3sec on and 20sec off ones it has reached the desired temperature. The effiency of induction is unbeatable to whatever you compare with and so is yours.

Teddy

[guyrj33]

Efficiency.
There are no Energy Star® certifications for ranges, but research by the U.S. Department of Energy indicates an induction cooker is 84% efficient at energy transfer, versus 74% for a smooth-top electric unit, giving it a heating performance comparable to a gas element.
Jul 25, 2014
How Energy Efficient is Induction Cooking? - Insteading
https://insteading.com/blog/energy-e...ction-cooking/

[john61ct]

Which is fine for those whose solar capacity is sufficient, or burning dino juice regularly anyway, ideally assisted by LFP.

But for people "camping" on small boats with limited solar, intentionally trying hard to keep consumption down within that limited capacity, any heat production is a wastefully high-current consumer of scarce electricity.