How to convert reading of amps into amp hours

[john61ct]

Originally Posted by alansmith

at 110 voltage my meter shows me 1.7 amps. If I used that induction stove top for one hour it would be 1.7 amp hours. If I used it for 30 minutes it would be 0.85 amp hrs. Do I have that correct?

Say 200W at that power setting, which I agree sounds low, but as an example for units discussion, rough numbers follow.

With inverter losses call it 25A @12V

20 min would use say 9AH.

5 hours would be 25% of your 600AH usable capacity.

> Can the inverter handle that intense of a draw?

Yes, just a question of money.

Quality of the maker and watts rating taking startup surge into account are the main factors.

[aluijten]

Originally Posted by alansmith

Oh yah...back to the multimeter...sorry...So, I took one of our induction modules in the kitchen and placed a steel pan with water on it. Turned that sucker up to high power. Put the jaws of the multimeter on it and got an amperage reading. 1.7 amps.

Like the previous poster said. Simply clamping the full powercable is not correct. You are measuring both the feed and the return-line together. Theroretically you should measure zero in that case but cable-orientation plays a role as well. Make sure you use only one conductor (either one). The next problem you may have is that your meter only supports DC Amps and not AC Amps. Make sure you select AC for this measurement.

Now for the power consumption you can muliply the number of amps with the current AC voltage that is supplied to the stove.
One thing I’m not sure about for induction-stoves is if there is a powerfactor involved. For normal electric stoves the current-draw and the voltage are in sync (AC voltage goes up and down at a rate of 50 or 60 Hz). For induction there may be a Cos-phi factor to incorporate (i.e. 0,9 or 0,95). This tells you how much the current draw is out of sync with the voltage. This influences the actual power consumption.

Cheers,

Arno

[john61ct]

Most accurate will be a shunt-based DC AH counter on a battery, actually cook a breakfast, note AH consumed, make a pot of soup or red sauce, note AH consumed.

Including the URL inverter overhead and all the other variable inefficiencies involved.

[Pete7]

Originally Posted by john61ct

Easy peasy with the right tools.

A reasonably accurate AH-counting meter can be bought for under $60

If you will want to ongoing estimate SoC of your bank, a quality BM can also be used for the same purpose, more accurate, but costs a lot more.

They also show instantaneous Amps real-time like a clamp meter.

I have a BM but it cost a tad more than that. It does indeed estimate (rather than measure) the SOC of the bank. It doesn't and cannot isolate the fridge from the other electrical loads and no I am not rewiring the boat just to work this out.

Originally Posted by john61ct

Say 200W at that power setting, which I agree sounds low, but as an example for units discussion, rough numbers follow.

With inverter losses call it 25A @12V

20 min would use say 9AH.

5 hours would be 25% of your 600AH usable capacity.

> Can the inverter handle that intense of a draw?

Yes, just a question of money.

Quality of the maker and watts rating taking startup surge into account are the main factors.

That is a pretty in-efficient inverter, I am sure they were in the 85-90% range last time I looked which would bring the loads right down.

[john61ct]

The specs given by a mfg are best case rare circumstances.

Put a Killawatt on a device running from mains.

Then a DC AH counter when it's running off 12V, Watt's Up is a trivial example.

Compare the two in actual watt-hours, and you'll see the Real number.

It is highly variable depending on the quality of the mfg - AIMS vs Magnum, true sine vs msw, and the percentage of total amps capacity for a given appliance.

[john61ct]

And I did say rough numbers, just illustrating proper use of units for the OP, just one step up the learning curve, way station down the rabbit hole.

[john61ct]

Originally Posted by Pete7

I have a BM but it cost a tad more than that. It does indeed estimate (rather than measure) the SOC of the bank. It doesn't and cannot isolate the fridge from the other electrical loads and no I am not rewiring the boat just to work this out.

I did say they cost a lot more, did you miss that?

And I wasn't telling you to do anything.

Just saying if the OP was planning on buying a 712-BMV anyway, no point in throwing money away on a cheap AH counter as well.

I have my AH-counting meters (including full-fledged BMs with separate shunts) wired in place with Anderson plugs so they can be easily moved as needed.

They can measure a charge source's contribution or a load device's consumption in isolation at any time when needed.

And then be returned to their usual location once I'm done with the temporary diagnostic or benchmarking project.

[john61ct]

Originally Posted by john61ct

Including the URL inverter overhead and all the other variable inefficiencies involved.

That should have been IRL

in real life

as opposed to theoretical ballpark calculations.

Always best to work from real data

[Privilege]

John,

I don't think that your initial observations have been done correctly. You have measured your water heater at 1.7amps AC which, as others have explained equates to a draw of just over 200 watts. (The reason that appliances use watts is because that stays the same no matter what voltage is being supplied).

If you consider that an ordinary electric kettle will consume 3000 watts and an electric water heater can be anywhere upwards of 2500 watts, I don't think that any power source of 200 watts will ever heat your water.

[john61ct]

A small quantity, slowly

[Bleemus]

Are you sure you are putting the ammeter on only a single leg of the power cord? Seems very low for induction cooktop.

[Bill Seal]

Before we get too confused, remember:

Amps = miles per hour
Amp hours = miles driven

If you are driving at 35 miles, (amp hours) what the hell does that mean ???

[KS84047]

Originally Posted by Zil

amp hour is a measurement of charge in the battery. 1 amp hour equals the capacity of 1 amp draw for 1 hour. Those AH's are different depending on the rate of discharge. AH is not a measurement of power. We need to work with watts to get a closer approximation of power used during any work by appliances. Converting 120 volt x amps = watts to 12 volt x amps = watts is the only way to determine battery need. Remembering the loss during any conversion.

Finally, I was wondering if someone would give him the correct answer.

[Brewgyver]

Originally Posted by aluijten

(snippage) The next problem you may have is that your meter only supports DC Amps and not AC Amps. Make sure you select AC for this measurement.

Most inexpensive clamp-type multimeters will ONLY measure AC current (amps).

[guyrj33]

Originally Posted by deblen

Correct. Amps x hrs = amp hrs
Also Watts x hrs = watt hrs


Attachment 171271

and
power watts = VxI which is an instantaneous reading, you need power for a length of time to do any work. That's why our electric bills use KWH Killo Watt Hours as the unit of billing.

12 volts x 1 amp = 12 watts
120 volts x 1 amps = 120 watts

with at 12v battery
1 amp x 1 hour = 1 amp hour or 12 watts (the 12 volts are implied)

with a 120v circuit
1 amp x 1 hour = 1 amp hour or 120 watts (the 120 volts are implied)

From the above it's easy to see how amp hour is an imprecise term and that's it's better to use watts and watt hours when converting between systems.