When is a lead acid battery full?

[Jev88]

I am sure the answers to this may help others too.

Three New Numax batteries installed October.
RV has 200watts solar in storage with Victron controller and battery sense on a network.
EHU over weekend whilst we did some DIY.
Let batteries settle for at least 12 hours with solar off. Batteries reported at 12.58V.
They must be full surely?

But am I misguided as I thought a fully charged battery should be 12.8+

I know the difference is small but I also know small increments can show the state of discharge.

 

[Stealaway]

How are you measuring the voltage?

 

[Jev88]

With the Victron Battery Sense widget connected directly to battery bank

 

[pappajohn]

Use a multimeter.
Onboard meters are unreliable and a waste of time looking at

 

[Tombola]

the victron battery sense is usually quite accurate. Put a meter across the terminals to double check

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[Lenny HB]

As you didn't measure them until after 12 hours it sounds like you have current drain that's discharging them.

I would fully charge them again then disconnect them after about 30-60 min I would expect to see them reading over 12.8. Leave them for 24 hours and read again. If they are holding up start looking for what's draining them.

 

[Jev88]

Use a multimeter.
Onboard meters are unreliable and a waste of time looking at

I agree with onboard meters but this is a brand new Victron meter fitted to battery bank.

 

[pappajohn]

I agree with onboard meters but this is a brand new Victron meter fitted to battery bank.

I would still use a multimeter over any other meter.

 

[donkey]

If battery has top-up plugs then a hydrometer will tell you the correct sate of charge.

Geoff

 

[Barti Ddu]

Two thoughts -
Firstly - Is the on-board charger when you used EHU capable of getting the batteries up to a high enough voltage where they go through an absorption phase. If not they are probably not fully charged. Basic Sargent chargers fitted to lots of British built vans never get to absorption.
Secondly - do you have a Battery Master (or the Votronic or CBE equivalents)? If so, they can drag the voltage down of the leisure battery as they feed the vehicle battery.

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[Jev88]

Two thoughts -
Firstly - Is the on-board charger when you used EHU capable of getting the batteries up to a high enough voltage where they go through an absorption phase. If not they are probably not fully charged. Basic Sargent chargers fitted to lots of British built vans never get to absorption.
Secondly - do you have a Battery Master (or the Votronic or CBE equivalents)? If so, they can drag the voltage down of the leisure battery as they feed the vehicle battery.

On-board charger is American RV so still getting my head around circuitry and functions.
Victron BatteryMaster - yes. But RV was driven about 50 miles on the day before and solar would have been feeding into system whilst in storage (i.e. engine battery wouldn't have been depleted much from full?