12V battery State of Change (SOC)

[DcnPat]

Our ‘23 f150 Powerboost is the 1st car/truck with a non lead acid battery.....just the same I’ve installed a a battery charge connection…..leveraging a NOCO intelligent battery charger (set to AGM (actually didn’t even need to set it - it automatically detected the AGM).

I have forscan and will start monitoring the SoC.

just for clarification, the AGM battery IS a lead-acid battery. The acid electrolyte is contained in a glass mat between the lead plates so it doesn't spill. That also means it can't mix or stratify like a liquid electrolyte battery can.

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[PaulGrun]

These trucks appear t be electric sinks.
I put my PowerBoost to bed last evening at 85%.
I checked today- 77%

The key was in the house, so I was not periodically waking from a snooze.
Some have suggested locking- does that really make a difference?
I have a lot to learn about the battery dynamics.

Something to keep in mind is that generally SOC is a derived number meaning that it is a calculated value driven by measured voltage based on tables possibly combined with some measurement of current movement (so-called coulomb counting). SOC isnt a value you can measure like you can how much gas is in the tank. It is very difficult to measure SOC.
As I understand our Ford trucks (and I don't...go read he loooong running thread on this topic from guys like @Snakebitten and @Jersey Jim who have put a TON of effort into experimentation and analysis into understanding these beasts), but the running SOC number being reported is derived from an industry standard family of tables based on voltage measuments and a crude estimate of current flow based on the voltage drop across a shunt resistor. The problem is that the tables are based on a "resting voltage" which only occurs after the battery has been at rest for a number of hours, like overnight. So as I understand it, the truck resets its idea of what constitutes SOC after re-aligning itself overnight using the tables and based on the resting baery voltage. So it seems unsurprising to me that the SOC would vary from end of day to the next morning after the system has recalibrated its SOC.
That's the problem that a company like Ford faces in giving us too much info without the background to understand what that info means.
One other minor point about SOC: I read a Ford patent application from a couple of years ago which describes SOC as being the value above which the system will try to draw the battery down. So if "target SOC" is set to say 80%, anytime the truck 'calculates' that the current SOC (based on voltage) is *above* that target SOC it will atte mpt to 'burn off' the excess voltage until it gets down to the target.
I suspect but don't know that the 80% default target is a balance between having an adequately charged battery and battery life, given the chemistry.
@Snakebitten, you've been deep into this - care to offer any corrections?

 

[wrgrimes]

Paul
Thanks for the information.
Like I have tried to relate, I am ignorant and trying to learn.
Having been burned by a bad battery and having the truck not start (after 2hr of rest it started). I am a little anxious like every time I push the start button.
Everyone's kind information is appreciated.

 

[bushpilot]

just for clarification, the AGM battery IS a lead-acid battery. The acid electrolyte is contained in a glass mat between the lead plates so it doesn't spill. That also means it can't mix or stratify like a liquid electrolyte battery can.

yeah I understand its not a conventional (old skool) "flood" battery.....I say AGM as a matter of differentiation from a historically conventional battery.

 

[Snakebitten]

@PaulGrun

Why would I add any to something so well said?
I especially like the point you make regarding the perils of having so much information at hand these days. We used to be limited to an Alternator idiot light, are if it was fancy, a voltmeter that told us that the alternator must be working since we are showing more than 12Volts!

What we don't have, nor likely ever be privy to, is a real life official on the record explanation (or documentation) of Ford's battery management system and why it's designed the way it is.

But I'm convinced that more often than not, some really smart folks come up with this stuff and we forum folks are left to ponderings that are short of the whole story. At the least I declare that we oversimplify?

A small excerpt from an article regarding Ford's engine management logic:

Think about that.
Have you seen what one table might contain?
Stack more than 100 and imagine how granular and precise, whether you would agree or not, the strategy is. And it's being calculated perhaps many times per second.

We just want to know why Ford isn't providing more charging current while we head to the office.

 

[Gros Ventre]

The AGM Battery not only has the glass mats, its plates are thinner, these plates are packed together more tightly than the flooded cell battery. Chemically it is a classic lead acid battery. One of the features of the lead acid battery is that terminal voltage is proportional to state of charge but should be measured with no current in or out. I suppose that waiting for several hours of rest gives a more accurate state of charge measurement, as a practical matter the terminal voltage with zero current is close enough. One of the advantages of the AGM battery is there is far less volume of electrolyte to be diffused as a charge/discharge is going on. One weakness of the battery is there is so little active plate material in it, that overcharging warnings need to be taken seriously. When the battery reaches near full charge, gasses are developed on the plates and if that is too active small bits of active material will be flaked off the plates. On the other hand the amount of electrolyte is so much smaller and the plates closer together the internal resistance is lower providing greater burst of power capability.

 

[PB2021]

These trucks appear t be electric sinks.
I put my PowerBoost to bed last evening at 85%.
I checked today- 77%

The key was in the house, so I was not periodically waking from a snooze.
Some have suggested locking- does that really make a difference?
I have a lot to learn about the battery dynamics.

Regarding locking, my short term findings suggest it does make a difference. I can only gather that possibly some of the systems are put to sleep when locked versus holding in some standby mode when left unlocked. My SOC readings have dropped more if left unlocked for hours or overnight vs locked.

 

[Snakebitten]

Regarding locking, my short term findings suggest it does make a difference. I can only gather that possibly some of the systems are put to sleep when locked versus holding in some standby mode when left unlocked. My SOC readings have dropped more if left unlocked for hours or overnight vs locked.

I would NOT be surprised. And thanks for mentioning because it's an interesting data point to look into.

Anyone with a 986/987 era Porsche learns that if he locks the doors when he gets home, the odds he'll find it needing a jump the next day, or couple of days, diminishes substantially.
(if it's going to sit for several days, it's better to put it on a trickle)

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