Battery Voltage in the Morning

[ramblinrod]

Originally Posted by boatbod

Oh but I understand just fine. Unless you have the batteries isolated and doing nothing at all, the voltage reading cannot be relied upon to give much indication of state of charge. Some broad brush information might be discernable once you know your boat's characteristics, but it's entirely dependent on what you are measuring and whereabouts in the circuit the measurements are being taken.

And the original questions was....

"Can this voltage be believed?"

The real answer is, if the meter is reading correctly, "absolutely". The voltage measured is the voltage present at the measuring points, and therefore can be believed with confidence.

If the original question was...

"Does this measured voltage represent the true state of charge?"

The real answer is (as stated very early on in this thread by myself and others), "No, the battery must be at rest, or some method used to simulate residual charge voltage removal, or load voltage recovery, before measured voltage correlates (can be "believed" to reflect) actual state of charge.

It appears to me, that you asked a question, and then completely ignored the correct answers, without just cause.

[Cadence]

Originally Posted by ramblinrod

And the original questions was....

"Can this voltage be believed?"

The real answer is, if the meter is reading correctly, "absolutely". The voltage measured is the voltage present at the measuring points, and therefore can be believed with confidence.

If the original question was...

"Does this measured voltage represent the true state of charge?"

The real answer is (as stated very early on in this thread by myself and others), "No, the battery must be at rest, or some method used to simulate residual charge voltage removal, or load voltage recovery, before measured voltage correlates (can be "believed" to reflect) actual state of charge.

It appears to me, that you asked a question, and then completely ignored the correct answers, without just cause.

[sailorboy1]

just feeding the creatures that live under the bridge, they need to eat like everyone I guess and even if they don't they need to have things to spin

[Polux]

Originally Posted by travellerw

Those voltages should only be used as a VERY ROUGH guestimate of SOC when you are cruising. Since you cannot disconnect your battery and let it rest 4 hours, you can't completely rely on voltage. As per the linked article
"To get accurate readings, the battery needs to rest in the open circuit state for at least four hours"

However.. A battery voltage of 12.6V in the morning is very good.. We are usually 12.3-12.4 in the morning!

The article
Measuring State-of-charge - Battery University
That mentions these values:
State of Charge - 12 Volt battery - Volts per Cell
100% - 12.72
90% - 12.52
80% - 12.42
also say:
"While BCI (Battery Council International) specifies the specific gravity of a fully charged starter battery at 1.265, battery manufacturers may go for 1.280 and higher. Increasing the specific gravity will move the SoC readings upwards on the look-up table."

I have AGM batteries that produce a slightly higher voltage than the flooded equivalent and my equipment reads 12.90 for fully charged batteries. If they go below 12.50 I recharge them but that happens very rarely and in the morning normally I have 12.60 or 12.65.