There are no forum members that confuse A and AH.

[noelex 77]

Originally Posted by JBP

1) Another reason is that some people are unable to sail at the moment and are surfing the web for something to talk about, even if it is bickering about typos.

2) "Ahrs is still a useful unit on a boat. Batteries do not store Whrs."
Of course they do. Watt hours is just another way of denoting stored potential. In fact some people don't have 12 Volt systems so Watt hours is more definitive (see point 1!)

Batteries use a chemical reaction to store energy, and Ahrs more accurately reflects the stored energy.

For example, if we are charging with one amp of current for one hour and this is during the bulk phase when the battery voltage is 14.7v, using WHrs would show we have stored 14.7 WHrs. The same one amp of current for one hour when the battery is deeply discharged with a voltage of 12.2v would show we have stored 12.2 Whrs. This is not accurate. The energy stored in the batteries in both cases is similar. If anything, the battery will be less efficient at storing energy at high states of charge. Using the Whrs unit incorrectly suggests the opposite.

Using Ahrs for calculating the batteries gain in energy is much more accurate. We have added 1 Ahr in both cases. Once we allow for the battery efficiency, using Ahrs more accurately reflects the battery’s gain in energy. This is why battery monitors predominately use Ahrs. It is the appropriate unit.

On the other hand, if we are discussing the energy source then Whrs are more accurate. The solar panels will have to put out 14.7 Whrs to put 1Ahr of capacity into the batteries during the bulk phase and similarly they will only need to supply 12.2 Whrs to put 1 Ahr of capacity into the deeply discharged battery. Using Whrs is more accurate.

The above examples show why we need both units depending on the circumstances.

See point 1 .

[s/v Jedi]

Originally Posted by noelex 77

Ahrs is still a useful unit on a boat. Batteries do not store Whrs.

Near the end of the charge cycle when the voltage is higher, batteries are not storing more energy because of this higher voltage. AHrs into the battery more accurately corresponds to the Ahrs that can be withdrawn from the battery than doing the same calculation with Whrs.

Whrs are the official unit for electrical energy and this unit is particularly appropriate when discussing mixed voltages, but Ahrs is still a better unit when dealing with energy storage in batteries. This is why most battery monitors report Ahrs not Whrs.

I think both units can be used to good effect depending on the situation.

I’m sorry but you are very wrong. The energy stored in “batteries” can only be correctly expressed in Wh or Joules. The industry has chosen Wh while science normally uses J. Ah is a measure of current over time, which does not represent the amount of energy because the voltage is missing, which is just as crucial to the amount of electrical energy as the amperage.

We see this misconception over and over again.

[SailingHarmonie]

I think we can all tell the difference between someone who had a slip of the keyboard and someone who is missing basic concepts. I think it is endearingly cute that you actually believe everybody here understands how an Amp differs from an Amp-hour. That's right up there with the Easter Bunny.

I will point out if you look at insurance claims, DC circuits are the leading cause of fires on boats, and fires are the most likely cause of boat loss. I am very comfortable explaining a specific issue to someone who has a clue, and I know I have gotten some answers to esoteric questions here, for which I am grateful.

But I am also NOT going to give advice to someone who has NO IDEA what they are doing. I am not going to write a 10,000 word chapter on electrical standards for someone who hasn't felt the need to read anything on the topic before. If I think someone is in over their heads, I ABSOLUTELY consider the best, safest, and most responsible thing is to tell them, and I will continue to do so.

When someone has no idea what they are looking at, it is virtually impossible for them to give me a description of all the details that might be important, when they have no idea what "important" is. If I don't know how their system is connected, and THEY do not know, how can I give advice?

Sometimes the best possible thing you can say is "hire someone who knows what they are doing."

[markcouz]

Originally Posted by SV THIRD DAY

Science has shown that posting a corrective post online releases endorphins in the poster similar to those released during sex. Once you understand that…so much of the online works begins to make sense.

This is very valuable information, I am definitely going to start looking for more opportunities to post corrections [emoji16]

[team karst]

Originally Posted by s/v Jedi

I’m sorry but you are very wrong. The energy stored in “batteries” can only be correctly expressed in Wh or Joules. The industry has chosen Wh while science normally uses J. Ah is a measure of current over time, which does not represent the amount of energy because the voltage is missing, which is just as crucial to the amount of electrical energy as the amperage.



We see this misconception over and over again.

I might just start using ergs in my future posts about energy. That way this pesky use of capitalization goes away.

[noelex 77]

Jedi, I agree. If we want to accurately reflect the energy a battery can discharge or deliver in specific circumstances (especially when considering different chemistries) Whrs is more appropriate.

I don’t think we should always use Ahrs instead of Whrs, but use the unit that is most appropriate.

Using Whrs to estimate the amount of energy a battery is storing is fraught with problems for the reasons I outlined in post #16. To eliminate Ahrs from our vocabulary and always use Whrs is not helpful.

[boatpoker]

I don't pay much attention to amps, amp hours, joules or kilowatts other than trying to track down an issue.

I know that if I go to bed with 12.7V showing I'm good for the next day unless it's totally overcast then I may have to run the generator for an hour.

[Chris31415]

Ah and kWh and Coulombic potential. Seriously?

We all know the proper unit for energy is Joules, let’s use Joules.

[thomm225]

Actually I like the voltage reading best and have always troubleshot live circuits, batteries, electrical using voltage readings (for the most part) unless I'm using an O'scope which we rarely use anymore these days and never on the boat.

Most computer techs rarely touch a voltmeter or amp meter for anymore.

For 14 flight and tactical simulators, we have 4 Fluke 87 Meters and 2 O'scopes (calibrated) and that is it.

[rslifkin]

Originally Posted by thomm225

Actually I like the voltage reading best and have always troubleshot live circuits, batteries, electrical using voltage readings (for the most part) unless I'm using an O'scope which we rarely use anymore these days and never on the boat.

Most computer techs rarely touch a voltmeter or amp meter for anymore.

For 14 flight and tactical simulators, we have 4 Fluke 87 Meters and 2 O'scopes (calibrated) and that is it.

Voltage is useful to know (and having a meter is good for troubleshooting). But voltage is nearly useless for knowing how full your batteries are if they're under load, and voltage alone tells you nothing about how much power you're consuming.

[team karst]

Originally Posted by Chris31415

Ah and kWh and Coulombic potential. Seriously?

We all know the proper unit for energy is Joules, let’s use Joules.

Sorry. Joules have been defined as one Newton force moving one meter. Not even Jedi will have that meter on board [emoji3]

Luckily for us working with electricity, someone defined Watt-hr as Joule/3600.

[JBP]

Originally Posted by noelex 77

Batteries use a chemical reaction to store energy, and Ahrs more accurately reflects the stored energy.

For example, if we are charging with one amp of current for one hour and this is during the bulk phase when the battery voltage is 14.7v, using WHrs would show we have stored 14.7 WHrs. The same one amp of current for one hour when the battery is deeply discharged with a voltage of 12.2v would show we have stored 12.2 Whrs. This is not accurate. The energy stored in the batteries in both cases is similar. If anything, the battery will be less efficient at storing energy at high states of charge. Using the Whrs unit incorrectly suggests the opposite.

Using Ahrs for calculating the batteries gain in energy is much more accurate. We have added 1 Ahr in both cases. Once we allow for the battery efficiency, using Ahrs more accurately reflects the battery’s gain in energy. This is why battery monitors predominately use Ahrs. It is the appropriate unit.

On the other hand, if we are discussing the energy source then Whrs are more accurate. The solar panels will have to put out 14.7 Whrs to put 1Ahr of capacity into the batteries during the bulk phase and similarly they will only need to supply 12.2 Whrs to put 1 Ahr of capacity into the deeply discharged battery. Using Whrs is more accurate.

The above examples show why we need both units depending on the circumstances.

See point 1 .

Interesting. I'm curious how that would change with modern lithium batteries. However point 1 no longer applies to me so it'll have to wait.

[s/v Jedi]

Originally Posted by noelex 77

Jedi, I agree. If we want to accurately reflect the energy a battery can discharge or deliver in specific circumstances (especially when considering different chemistries) Whrs is more appropriate.

I don’t think we should always use Ahrs instead of Whrs, but use the unit that is most appropriate.

Using Whrs to estimate the amount of energy a battery is storing is fraught with problems for the reasons I outlined in post #16. To eliminate Ahrs from our vocabulary and always use Whrs is not helpful.

Yes, for state of charge counting Ah is the way to go. Unfortunately many use a voltmeter to tell their SOC.

[thomm225]

Originally Posted by rslifkin

Voltage is useful to know (and having a meter is good for troubleshooting). But voltage is nearly useless for knowing how full your batteries are if they're under load, and voltage alone tells you nothing about how much power you're consuming.

The voltage reading of my batteries has always allowed me to know about how much power my batteries are consuming that is over the last 12 years anyway.

Before I got 6 Volt Golf Cart Batteries, I knew that if my batteries were reading 12-12.2 volts in the morning first thing they were working about right.

If they were in the red on my Battery Power Gauge which is below 12 volts, it was time to be a little concerned even though I have gone months like this in the past.

[s/v Jedi]

Originally Posted by JBP

Interesting. I'm curious how that would change with modern lithium batteries. However point 1 no longer applies to me so it'll have to wait.

As battery technology evolves, the difference becomes less. With lithium we can almost take it as an ideal storage medium but for SOC we still need to count Coulombs.

I have the Peukert’s factor at 1.00 though