How many Amps Hours do you use a day?

[OceanSeaSpray]

Note that unless you have TWO shunts and you separate loads from charging sources, you are not measuring everything (which was my question to Erik earlier). All power does not go through the battery, a standard battery monitor doesn't see everything.

Originally Posted by Ip485

I dont entirely follow.

Your solar panels are producing 10A, you are presently using 6A running your fridge or whatever, the other 4A are going into the battery:

Your BMV-thingy is reporting that you are charging at 4A, because the shunt is between the battery and everything else. You can't see the other 6A that are flowing directly from the panels to the load. In other words, some of your consumption is hidden and unaccounted for, because you are only monitoring the battery, not the whole system.

If you want the full picture, you need two shunts: for example, a battery shunt and a load shunt. In this case, the battery shunt would read charging 4A and the load shunt would read consuming 6A in the same time, so you can then deduct that you are producing 4A+6A=10A to achieve this.

The battery history does not reflect your total energy consumption at all when you produce and consume in the same time.

[44'cruisingcat]

Using the input from the solar regulator, we use around 150-170 amp hours most days at anchor.

We run 100 litre fridge, 100 litre freezer, a watermaker, breadmaker, washing machine, and the usual lights, fans etc. On overnight sails the power use doesn't change much, because while the autopilot uses power, we don't run the watermaker, breadmaker etc..

[cyan]

Originally Posted by john61ct

That would have to be AH (amp hours) for a quantity of power used over time, or stored.
Amps are an instantaneous measure of flow rate.

Originally Posted by KRMS

Whoops you don’t mean Power you mean Energy! When ‘correcting’ another forum member, particularly when we all knew what he meant, it pays to be ‘correct’.

Not so fast with the double-snark, there...

Sure, John COULD have meant: (bold added by me)
"That would have to be AH (amp hours) for a quantity of power [WHICH IS THEN] used over time, or stored."
That would be incorrect, as you say.

OR, he COULD have meant: (bold added by me)
"That would have to be AH (amp hours) for a quantity of [SOMETHING DEFINED BY] power used over time, or [SOMETHING] stored."
John would be correct here. (in his 12V world)
No "Whoops" needed at all, as I knew he meant this.

You nailed it, though, KRMS, I'll give you that:
When ‘correcting’ another forum member, particularly when we all knew what he meant, it pays to be ‘correct’.

HOW MUCH DOES IT "PAY"??

Ok, sorry for the triple-snark detour... this is a REALLY good thread outside of all of the correcting corrections correctly.
-Cy

[StuM]

Originally Posted by cyan

Not so fast with the double-snark, there...

Quadruple snark alert!

Ashley, john61ct was correct.

Amps are a quantity of power.
Amp hours are a quantity of energy, or power used over time.
Perhaps a different placement of the comma would have helped clarify:

That would have to be AH (amp hours) for a quantity of power, used over time or stored.

[cyan]

Originally Posted by StuM

Quadruple snark alert!

Ashley, john61ct was correct.

Amps are a quantity of power.
Amp hours are a quantity of energy, or power used over time.
Perhaps a different placement of the comma would have helped clarify:

That would have to be AH (amp hours) for a quantity of power, used over time or stored.

Except that no, "Amps" are NOT a quantity of power without specifying the voltage too. Current, sure.
But yes, I agree that john61ct was essentially correct.
The comma would have worked and that's all I was attempting to say earlier.
Sorta like saying:
Seven plus three, times two equals twenty. (7+3)*2=20 Yes.
Seven, plus three times two equals twenty. 7 +(3*2)=20. No.

No snark intended, really. Just smiling at the poster who DID use some snark to incorrectly "correct" someone who was already correct, then suggest that he should be correct before correcting someone. Such unintentional humor is good for everyone provided we don't take ourselves too seriously.
(crap, sorry, I do see a white flag)

Back on topic, I see that the watt meters are much cheaper now than they used to be. I have some overly expensive old gear that could use an upgrade. Thanks to those who posted links!

[StuM]

Originally Posted by cyan

Just smiling at the poster who DID use some snark to incorrectly "correct" someone who was already correct, then suggest that he should be correct before correcting someone. Such unintentional humor is good for everyone provided we don't take ourselves too seriously.

See Muphry's Law

[Ip485]

Your BMV-thingy is reporting that you are charging at 4A, because the shunt is between the battery and everything else. You can't see the other 6A that are flowing directly from the panels to the load. In other words, some of your consumption is hidden and unaccounted for, because you are only monitoring the battery, not the whole system.

Thank you.

OK, so under load, no charging, the gauge tells me the batteries are discharging at say 10AH shown as -10AH. With the charger on, the load the gauge is now reporting is -4AH. By deduction the panels are charging at 6AH. Which of the numbers is wrong and by how much?

Chaps, generally as the starter of this thread could we keep the discussion about the Colregs elsewhere please, as it is such a different topic and ends up being difficult to follow this tread - PLEASE!

[rom]

Originally Posted by Ip485

Thank you.

OK, so under load, no charging, the gauge tells me the batteries are discharging at say 10AH shown as -10AH. With the charger on, the load the gauge is now reporting is -4AH. By deduction the panels are charging at 6AH. Which of the numbers is wrong and by how much?

Chaps, generally as the starter of this thread could we keep the discussion about the Colregs elsewhere please, as it is such a different topic and ends up being difficult to follow this tread - PLEASE!

10A (@12V I believe) without any load is a lot of current loss. You have to investigate where that current is going. I believe there actually is a load connected that you don't suspect (e.g. inverter ON without any load will pump a few amps)

Many here have been trying to explain you are talking A, not Ah (correct spelling is Ah not AH or ah BTW). You should take some time to make sure you understand the difference. good luck !

[Ip485]

Thanks Rom.

No these are hypothetical figures, not mine, from the poster I was quoting.

Yes, i think I have got to grips with the difference and the spelling although sorry I havent been consistant.

I am also I think better to grips why amp hour counters are essentially inaccurate -

Keeping Your Battery Monitor More Accurate Photo Gallery by Compass Marine How To at pbase.com

so I realise if your gauge says you have drawn x and put back x in fact the battery will not be at the same state of charge - but may not be too far adrift with for example new Lifeline AGMs. The article also gives some approximation of the amount of drift.

[john61ct]

You do not need "two shunts" to accurately audit all charge sources and all loads.

A shunt only measures the current passing through it, and it does measure all of it.

A BM shows everything going in **and out** that bank, so if that is the only active source when you are measuring loads, that's fine.

If you want ultimate flexibility, insert appropriately sized Anderson style connectors at all the strategic points where you want to measure amps as they fluctuate or count AH over time, and move the shunt around as needed.

[Mr B]

May I enquire what you mean by moving the shunt around,
I thought the shunt stayed in the same place all the time,

[john61ct]

In a bank monitoring scenario it usually does.

With the APP connection approach I describe it can be more mobile, used to meter specific loads or charge sources.

As you would with a clamp ammeter, but more accurate, and counting AH flow over time.

[Ip485]

With my set up it has (for some reason) just occurred to me that there are battery isolation switches for each of the four banks of batteries (house, engine, bow thruster and Genset). With the isolator turned off to the house bank and the charger switched off the batteries are completely in free float, but the BMV is still connected and will still show voltage. As it happens my house batteries are a real pain to get at in terms of isolating each battery and checking the voltage of each. So it occurred to me as an approximation of the 20 hour test and the shorter test referred to there in lies a solution. I appreciate the limitation that you are testing the whole battery bank but it seems to me it is a reasonable solution to monitor how it is doing.

How many of us do one of these tests and recalibrate their battery gauge every so often? Is it a real hassle when you are cruising or do you just accept a without battery day. For me on mains power (either from the Genny or shore) I can get on with life pretty much ok without the batteries, except my main fridge and freezer are battery only (the other fridge is mains or battery).

[john61ct]

The real tests are a major PITA for most, require equipment on mains power and hardly anyone bothers.

Most BM's are wildly inaccurate, and that's just one reason why.

[sailorboy1]

amazing how complex some can make a sailboat