There are no forum members that confuse A and AH.

[noelex 77]

Originally Posted by JBP

Interesting. I'm curious how that would change with modern lithium batteries.

The error is less when using Whrs to estimate the energy gain for lithium batteries. This is because the charge and discharge voltages are more similar than with lead acid batteries.

Counting Ahrs in and Ahrs out (after allowing a small constant for battery efficiency, Peukert's law etc ) is still more accurate than counting Whrs in and Whrs out with lithium.

If we charge a lithium battery with 1 amp for l hour at a charging voltage of 14.4 v (14.4 Whrs) that does not mean we can later draw 1.16 A for one hour (also 14.4 Whrs) when the battery has dropped to 12.4v and remain at the original SOC.

Batteries don’t work like this.

We can put 1 Ahr into the battery and later draw out 1Ahr and remain close to the same state of charge (although even here there is a small loss due to battery inefficiency that should be factored in).

Ahrs are better than Whrs when estimating the energy balance of batteries.

[rslifkin]

Originally Posted by thomm225

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.

Voltage gives you a decent idea if you have minimal to no load on the batteries. But it's otherwise a poor indicator. If I pop some food in the microwave and fire up the coffee maker at the same time, I can easily pull the batteries down to 11.8 - 12 volts even if they're just about full. Of course voltage will recover when the load reduces, but in that moment a voltage reading would lead me to believe the batteries are quite low when in reality, they may be 99% full. And with LFP batteries having a flatter voltage vs SoC curve, all bets are off for using voltage as an indicator.

[thomm225]

Originally Posted by rslifkin

Voltage gives you a decent idea if you have minimal to no load on the batteries. But it's otherwise a poor indicator. If I pop some food in the microwave and fire up the coffee maker at the same time, I can easily pull the batteries down to 11.8 - 12 volts even if they're just about full. Of course voltage will recover when the load reduces, but in that moment a voltage reading would lead me to believe the batteries are quite low when in reality, they may be 99% full. And with LFP batteries having a flatter voltage vs SoC curve, all bets are off for using voltage as an indicator.

Doesn't matter.

If you pay attention to the voltage you can pretty much predict your battery power usage, but you cannot come in cold with no experience of your boat and know by the voltage reading.

You have to know your boat and your system and if you are cruising you should know it very well in a few weeks.

I also have my Victron Display but usually the old Altus Battery Power Gauge tells me all I need to know.

[s/v Jedi]

Originally Posted by thomm225

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.

Don’t you realize that this is due to a strict daily regime and observation over time rather than the voltage representing SOC?

[thomm225]

Originally Posted by s/v Jedi

Don’t you realize that this is due to a strict daily regime and observation over time rather than the voltage representing SOC?

Sure but I have always troubleshot circuits and electrical with voltage (or continuity) readings so it seems the natural way of doing it.

This method since around 1976 or so

On rare occasions, I have used the current attachment on a meter, but this has occurred maybe 5X in 50 years or so that I needed to do that

Now days many techs don't troubleshoot at all with meters, scopes, or with voltage or current checks as most systems at least here are so computerized

Some techs are lost say if the power doesn't come on. Computer, Cyber, or Software Techs/Engineers

Luckily I have a few old school guys on staff for that.

[s/v Jedi]

Originally Posted by thomm225

Sure but I have always troubleshot circuits and electrical with voltage (or continuity) readings so it seems the natural way of doing it.

This method since around 1976 or so

Ha! I can do that too: people have been using chiromancers to troubleshoot and fix their lives since the beginning of time!

[Stu Jackson]

Originally Posted by Fuss

We have this endless point that some of us don't know the difference between Amps and Amp Hours. It consumes many pages of many threads.
>>>>>>>>>>>>>>>

But that's not the point.


Whether people know or don't know, the point is that many keep using and typing the wrong unit of measurement.


That's the only point.

[gonesail]

but do we know the difference between lumens and watts?

[thomm225]

Originally Posted by s/v Jedi

Ha! I can do that too: people have been using chiromancers to troubleshoot and fix their lives since the beginning of time!

Like I said troubleshooting with voltage has always worked for me and for cruisers on their own boats especially those of us with an electronic background we have a general idea of how our systems are doing just with a glance at the voltage.

Remember though in my case my Battery Monitor displays voltage so you get used to it being at a certain voltage at certain times and in certain conditions.

Of course, you also have to know what the gauge is telling you when it is say at 1/2 tank. (I say tank because it reminds me of a fuel gauge in a car)

For example, when my Victron is in Float Mode the Battery Power Gauge indicates in the middle of the Red Over Full section. If it's lower than that, first thing is to tap the gauge a few times!!

Volage is about 13.1 - 13.2 volts if you get out a phone and check the Victron on Bluetooth.

[Sand crab]

Originally Posted by team karst

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

Isn't erg what a pirate says?

[team karst]

Originally Posted by gonesail

but do we know the difference between lumens and watts?

Light measurements. Another ridiculously complicated measurement.

[team karst]

Originally Posted by Sand crab

Isn't erg what a pirate says?

Give it time. Someday pirates will use optical weapons. [emoji15]

[boatpoker]

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.

If go to bed with 12.7V and wake up to 12.5% or 12.6V My batteries are fine.
If I wake up to 12.3V or 12.4V I know I need to dig deeper. It's worked for me for 30 years.

[team karst]

Originally Posted by boatpoker

If go to bed with 12.7V and wake up to 12.5% or 12.6V My batteries are fine.
If I wake up to 12.3V or 12.4V I know I need to dig deeper. It's worked for me for 30 years.

I have not gone to bed with batteries, but if i did they would NOT be FLA.

[wholybee]

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 .

This is incorrect.

Ah = Amperage x hours
Wh = Watts x hours
W = Voltage x Amperage
Wh = Voltage x Amperage x hours

The ONLY difference in accuracy between the two units, is that Ah doesn't include Voltage. In your example, at the lower voltage, there really *is* less stored energy, because the voltage is lower. The stored energy is *not* close to equal. It might be "1 Ah" at both high state of charge and low state of charge. But if you are running a windlass for one hour at 1 Amp at both times at the lower voltage less work is done(the windless runs slower). So, the lower state of charge has less stored energy, even if you figure 1 Ah at both charge levels.