Battery Voltage in the Morning

[Maine Sail]

Originally Posted by ramblinrod

When a charge voltage is applied to a battery, it most certainly is being "charged".

But a "charge voltage" can only be applied when you have charge current flowing INTO the battery. If the battery is seeing a -1A load it is still a discharge voltage reading.

The terminology charge or charging does not apply to a discharging battery. The solar system is only applying current to offset the load the battery sees but the battery is still physically discharging not charging. There is no "charge voltage" in a discharging battery. A charge voltage increases terminal voltage it does not allow it to decrease...

Originally Posted by ramblinrod

If the load is high enough, the rate of discharge may be greater than the rate of charge.

With a discharging battery there is no charging happening. The PV just throws current onto the bus and so does the battery. The PV and battery are sharing powering the load. For the PV this is not a charge current or charge voltage it is simply supplying load current. It will not become charge current or charge voltage until it can drive current into the battery and begin increasing terminal voltage.

Originally Posted by ramblinrod

Therefore, the battery will eventually discharge completely, but it will take longer, and at any time, the battery terminal voltage will be higher, than if the charger were not connected.

Precisely, this is because the battery is not charging and is physically discharging. Using the term "charging voltage" to a battery being discharged is the disconnect folks are having with your description.

A battery with a -1A load is not charging it is discharging. The current supplied by the PV is only feeding the loads and reducing the load on the battery but the battery is still not being "charged". We need current flowing into the battery, not out of it, before we can technically describe it as being "charged"..

Still 12.6V on a 460Ah bank under a -1A load -30Ah's down is a perfectly reasonable loaded voltage reading...

[Maine Sail]

Originally Posted by sailorboy1

BTW - you are still the only one who says and I quote "with the solar charger connected and operating, that your battery voltage would read higher than if it were not". Everyone else only believes that the battery voltage will be higher if the supplied solar power is acturally charging the battery.

In Rod's defense that is actually a 100% accurate & correct statement.

Your PV was supplying 2A to the DC systems -3A load. This leaves the battery to supply the remaining 1A of current to the DC system load.

If you killed the solar (flip the switch off) the battery voltage would have dropped lower than 12.6V, not by a lot, but it would have dropped lower now that the battery was supplying all -3A vs. just -1A. So the current supplied to the bus by the PV, while not enough to charge the battery, allows the terminal voltage to be slightly higher than if that 2A were not being supplied onto the DC bus by the PV..

In either discharging scenario you are still discharging the battery not charging it. The rate of discharge when we compare -3A vs. -1A will change the terminal voltage but in neither case can a discharge load on the battery be considered "charging".

It is the use of the word "charging" being applied to a "discharging" battery were the confusion was.

[Cadence]

Originally Posted by sailorboy1

Really, that's what you got and you spend time looking for a way to make it sound that way.

I think you were so excited to be an "expert" that you couldn't even understand what was written in a post. For example post 19 says the solar was supplying the "system", it doesn't say it was charging the battery.

Now of course you are looking for a way to prove you really are an "expert".

BTW - you are still the only one who says and I quote "with the solar charger connected and operating, that your battery voltage would read higher than if it were not". Everyone else only believes that the battery voltage will be higher if the supplied solar power is acturally charging the battery.

You are being rude. Rod was right and only trying to be helpful. He didn't say anything demeaning as did you. I am being rude, get all your **** in one sock before attacking someone that has. JMHO

[ramblinrod]

Originally Posted by sailorboy1

Really, that's what you got and you spend time looking for a way to make it sound that way.

I think you were so excited to be an "expert" that you couldn't even understand what was written in a post. For example post 19 says the solar was supplying the "system", it doesn't say it was charging the battery.

Now of course you are looking for a way to prove you really are an "expert".

BTW - you are still the only one who says and I quote "with the solar charger connected and operating, that your battery voltage would read higher than if it were not". Everyone else only believes that the battery voltage will be higher if the supplied solar power is acturally charging the battery.

I'm sorry buddy, but you are mistaken, both on your understanding and what you believe others think.

I am quite confident that anyone here that has a solar charging system, and understands how it works, would agree that if you have a load on the battery, and measure the battery voltage, and then apply a solar charging system that is operating, you will most definitely read a higher voltage.

Do yourself a favour before you post disagreement. With your refrigerator running and solar charging system connected. Measure the terminal voltage. Then throw beach towels over all of your solar panels. What happens to the terminal voltage? Answer: it will most certainly go down. It has to, battery terminal voltage is inversely proportional to the current drawn from it, and the net current drawn from it is most definitely less, when the solar
system is supplying a charge current (meaning there is a charge voltage connected).

[sailorboy1]

Originally Posted by Maine Sail

In Rod's defense that is actually a 100% accurate & correct statement.

Your PV was supplying 2A to the DC systems -3A load. Leaves the battery only to supply 1A of current to the DC system load.
.

I will agree that a battery discharging at 3 amps will have a lower voltage than one discharging 1 amp.

That's the only part above I agree with.

[anotherT34C]

...not an expert...

my understanding, it works (an example) like this;

Battery with no load: reads 12.8V
same battery with 3A load: reads 12.5V
add in a solar panel that supplies +1A: reads 12.6V (battery still discharging 2A)

Adding the solar panel raises the read voltage, even though the bank is still discharging.

Otherwise, it looks like an argument over semantics.

[sailorboy1]

[QUOTE=ramblinrod;2201251

Do yourself a favour before you post disagreement. With your refrigerator running and solar charging system connected. Measure the terminal voltage. Then throw beach towels over all of your solar panels. What happens to the terminal voltage? Answer: it will most certainly go down. It has to, battery terminal voltage is inversely proportional to the current drawn from it, and the net current drawn from it is most definitely less, when the solar
system is supplying a charge current (meaning there is a charge voltage connected).[/QUOTE]

Not a freaking to do with the question. No one has even tried say that higher battery discharge rates don't result in lower terminal voltage.

Do yourself a favor and read a question before being an expert on it.

[SV THIRD DAY]

When threads get off track with egos, sometimes it's best to go back to the start and remember what the question was before the battle of Egos started.

Originally Posted by Original Poster Asked

The other morning my solar panel was supplying about 2 amps into the system, the battery was discharging about 1 amp, the batteries were 30 AH out of a 460 AH bank, the voltage was reading 12.6V.

Can the voltage be believed?

The Consensus answer from multiple well respected experts in the field along with nice explanations as to "why" say, Yes to the question. This isn't a Cruising budget thread where different opinions matter, Science is Science and true even if someone doesn't believe it or want to accept it.

Originally Posted by anotherT34C

...not an expert...

my understanding, it works (an example) like this;

Battery with no load: reads 12.8V
same battery with 3A load: reads 12.5V
add in a solar panel that supplies +1A: reads 12.6V (battery still discharging 2A)

Adding the solar panel raises the read voltage, even though the bank is still discharging.

Otherwise, it looks like an argument over semantics.

But arguments over semantics are the best kind on chat forums...ha ha ha

[ramblinrod]

Originally Posted by sailorboy1

Not a freaking to do with the question. No one has even tried say that higher battery discharge rates don't result in lower terminal voltage.

Do yourself a favor and read a question before being an expert on it.

Excuse me. I did read the question.

Here is the question you posed in post #19...

So you don't feel that the solar supplying power into the "system" should affect the battery voltage, since the battery was still discharging?

I don't feel it should...

I interpreted this as you declaring your position that the connected solar charging system would have no impact on the battery voltage you were reading.

That is incorrect, and what I attempted to help you with.

You seem to be changing your position now to a correct one. So I guess my response had a positive influence on your understanding. My work is done here.

[sailorboy1]

whatever, you can win

you didn't help me at all other than the weak entertainment value

[ramblinrod]

Originally Posted by sailorboy1

whatever, you can win

you didn't help me at all other than the weak entertainment value

Well, this sometimes happens when one tries to help another. Good thing I have pretty tuff skin, and will keep trying to help others.

[sailorboy1]

better luck with them

[Panacea2183]

Originally Posted by ramblinrod

Incorrect, the solar charging system was providing a charge voltage.

A load on a battery reduces the terminal voltage.

A charge on a battery increases the terminal voltage.

If you apply a load to a battery, the voltage goes down from the "at rest" terminal voltage. With that load applied, if you then apply a charge voltage, the voltage at the battery terminals goes up. Where it lands, with respect to "at rest" voltage, depends on the load and the charge voltage, but make no mistake, when the charge voltage is applied, the battery terminal voltage increases from where it was before the charge voltage was applied. (Which is exactly what the OP questioned about.)

As I have educated many boaters for many years, the most accurate (voltage) assessment of SOC is with the battery:

1. Topped with fluid.
2. Fully charged.
3. At rest (no load and no charge voltage) for several hours.

However, when this is not practical (rarely is on a cruising boat in use), a reasonable SOC assessment can be made, based on terminal voltage, as follows:

1. Remove charge voltage.
2. Apply a load (~5% of capacity) for 15 minutes and remove.
3. Wait 15 minutes and read the terminal voltage.

If you do this consistently (same load, same timing) each reading, you will have a repeatable method of assessment and relative measurement results.

0 amp flow = rest voltage
+ amp flow = higher voltage
- amp flow = lower voltage
The charge voltage has to be high enough to "push" current (amps) into battery
To raise the voltage
Negative amps = lower voltage
Positive amps = higher voltage
If the amp draw is negative (power comming out of battery) voltage will go down

[ramblinrod]

Originally Posted by Panacea2183

0 amp flow = rest voltage
+ amp flow = higher voltage
- amp flow = lower voltage
The charge voltage has to be high enough to "push" current (amps) into battery
To raise the voltage
Negative amps = lower voltage
Positive amps = higher voltage
If the amp draw is negative (power comming out of battery) voltage will go down

When a load is on a battery, and a charge voltage (voltage from a charger) is applied to the battery, the current flow out of the battery is reduced, and the battery terminal voltage rises.

Example:
1. At rest battery voltage = 12.6 A
2. Battery with 5 amp refrigerator load at 12.4 A
3. Sun comes out and solar starts pumping 3 amps into battery at 12.5 V

Is the charger "charging"? It is functioning properly, per design intent, and exactly as it is supposed to, it is outputting a voltage, which can be described as a charge voltage. It is inducing a current which can be described as a charge current. So loosely, yes it is charging, if "charging" is defined as a charger working properly.

If one wishes to not refer to the charger output voltage as a "Charge Voltage" or the induced circuit current as a "Charge Current" or to refer to the charger as "Charging" unless the battery SOC is increasing, then by this definition, the charger is not "charging".

It's like the issue, is a "saw" "sawing" if a carpenter is drawing back and forth across a piece of wood. Yes? What if no wood fibres are being removed? Well loosely, yes the carpenter is still "sawing" but if your
definition of "sawing" requires the wood to actually being cut, then "No".

But all the smoke and mirrors aside. In response to post 19, if the solar (or
any charger for that matter) is connected to the battery, and is producing current, it is impacting the terminal voltage.

If one follows the steps I posted previously, removing the "charge voltage" applying a 5% capacity load for 15 minutes, and then rest for
15 minutes, it will give a fairly accurate representation of the SOC based on voltage, without having to wait several hours.

Leave the load on, the charger on, or both, and the voltage does not give an accurate SOC.

[ramblinrod]

Originally Posted by SV THIRD DAY

The Consensus answer from multiple well respected experts in the field along with nice explanations as to "why" say, Yes to the question. This isn't a Cruising budget thread where different opinions matter, Science is Science and true even if someone doesn't believe it or want to accept it.

Here we go.

The very first question was, "Can the voltage be believed".

If this means, "Is the voltmeter reading the terminal voltage properly", my answer is "maybe". (I can't say "Yes" because the voltmeter could be out of calibration, have a high impedance issue with a test lead, a weak battery, be affected by a source of EMI, or any number of issues that would make it inaccurate, ie "can't be believed".

If the original question means, "Does the voltmeter reading accurately represent the battery state of charge, when the solar panel charger is connected", (which was my interpretation) my answer is "NO" (assuming there is substantial current flow in the charging circuit, as described by the original poster). Even if it is lower, than the load current, the current flowing through the charging circuit (I have called this "charge current") induced by the voltage produced by the charger (I have called this "charge voltage") is increasing the battery terminal voltage, so the battery terminal voltage "does not" accurately represent the battery state of charge.

That is the science. This post (and any terminology I have used) can be refuted by anyone, but it is absolutely correct (in my opinion), and can be easily confirmed by controlled scientific experiment.