HYBRID 12V Battery Mystery SOLVED

[Bob The Builder]

Wow!! Great thread. Kudos.

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[2024_xl_hybrid b&w]

Great discovery! That's awesome and it makes sense. Thanks for sharing your findings!!!

 

[Finnster]

HOT DIGGITY DAMN! Thanks Mavster Mechanic!!!!
Simple workarounds to an enigmatic and long-standing Maverick puzzle.
Simply amazing!

 

[El Kabong]

Fact: 2022 Hybrid (and others) actively drain a 12 volt battery to the computed 80% charge level.
Then do not try to add charge to the 12 volt battery until a computed 60% or lower charge is reached.

Holy crap that's amazingly dumb! An entire team of engineers designed that, there must have been a reason for this as a specification.

I need to dig up my old 12v power socket test thingamabob and see if the '26 does this.

 

[Glen Baker LLC]

Holy crap that's amazingly dumb! An entire team of engineers designed that, there must have been a reason for this as a specification.

I need to dig up my old 12v power socket test thingamabob and see if the '26 does this.

One down. One to go.
While it charges the battery better.
We still have parasitic drain issue.

 

[El Kabong]

Well it charges the battery better it still does not address the issue of the parasitic drain problem.

I scratch my head over that one too. There is a rather large alternative power source available nearby in the hybrid, why not tap that for power when the vehicle is otherwise off?

Of course, I'm not an engineer, so maybe I'm just ignorant.

 

[Glen Baker LLC]

I scratch my head over that one too. There is a rather large alternative power source available nearby in the hybrid, why not tap that for power when the vehicle is otherwise off?

Of course, I'm not an engineer, so maybe I'm just ignorant.

SAME HERE.

 

[MakinDoForNow]

Oh - mine's different then, right now.
I'm always at 14.x - 15.x.
No matter initial seconds of 15 A down to float 0.5 A.

But that's probably because my battery is currently no where near 12.8V resting.
When it was, I did see that effect of draw.
Oh those carefree days! Literally - only lasted a few days...

I'll see what happens on drive home tonight - plan on letting the initial high amp drop to float level - then I'll test with fan and headlights.
And video it.

Glenn - aren't you coming up on the season that testing a 12V resistance heater would work well.

Be sure to compare the amps of current into the 12v with lights & fan on and off.

 

[HeyBales]

Excellent work trying and documenting different theories.

Am I correct you're working on the premise:

A) These things cause a higher state of charge​

B) Which is independent of a parasitic draw. However a higher state of charge will hold off the parasitic draw issues longer.​

From the normal posts from those having that B issue - the parasitic drain was going to kill ya in 1 or 2 nights anyway.
Fully charged would give a few more hours.

What it would do though - is having your battery in normally healthy state, that a full drain isn't as detrimental.
Drain an already sulfated battery a couple times - likely need a new battery shortly.
A good healthy battery though - with a good recharge, just keep moving.
Until the intermittent bugs strike again!

 

[MakinDoForNow]

I scratch my head over that one too. There is a rather large alternative power source available nearby in the hybrid, why not tap that for power when the vehicle is otherwise off?

Of course, I'm not an engineer, so maybe I'm just ignorant.

The "large" (HVB) power source would only normally have only that capacity between 30-40% soc (=0-100% of 1.1kw) available to maintain 12v. Might be enough? I think Ford would resist placing any load at rest on the 8 year warranted battery.

 

[HeyBales]

I scratch my head over that one too. There is a rather large alternative power source available nearby in the hybrid, why not tap that for power when the vehicle is otherwise off?

Of course, I'm not an engineer, so maybe I'm just ignorant.

It appears for safety in the vast majority of EV's and others - off needs to be off.
HVB needs to be disconnected from everything a tech might be touching, or emergency responders.
I thought I heard in a post 1 vehicle that could do 12VB charging from HVB.
But other makes/models seem to confirm the same principle.

 

[Mavster Mechanic]

A.I. Overview

"Are there any good reasons to keep a flooded lead acid battery partially charged?"


Generally, there are no good reasons to keep a flooded lead-acid battery partially charged; it is harmful to their lifespan. Leaving them undercharged leads to sulfation (hard sulfate crystals on plates), significantly reducing capacity and causing premature failure. Always aim to keep them fully charged to maximize battery life.
Midtronics +4

• Damage from Partial Charging:Failing to fully charge a battery causes sulfation—hard sulfate crystals form on the plates, which cannot be removed easily.
• Optimal Storage Condition: For long-term storage, the battery should be fully charged (approx. 12.7–12.8 volts) to prevent sulfation, rather than partially charged.
• Only Exception (Specific Controlled Conditions): Some studies show that in specialized, highly optimized operational setups, operating in a strict, controlled Partial State of Charge (PSoC) can marginally increase energy efficiency. However, this requires advanced, consistent management and is not recommended for typical use, as it risks hard sulfation.

 

[Mavster Mechanic]

Same question for AGM


There are generally no good reasons to intentionally keep an AGM (Absorbent Glass Mat) battery partially charged. Unlike some lithium-ion chemistries that benefit from being stored at a partial state of charge (SoC), AGM batteries—like all lead-acid types—are designed to be kept at a 100% full charge whenever possible.
Battery Stuff +2

Why Full Charge is Necessary

• Preventing Sulfation: This is the primary risk. When an AGM battery is left partially discharged, lead sulfate crystals begin to form and harden on the plates. This "hard sulfation" is often permanent, reducing the battery's capacity and eventually preventing it from holding a charge at all.
• No Memory Effect: AGM batteries do not have a "memory effect" like older nickel-cadmium batteries. You do not need to discharge them before recharging; in fact, doing so frequently can shorten their lifespan.
• Capacity Retention: Repeatedly charging an AGM battery to only 60-80% can cause it to "lose" the ability to reach its full 100% capacity over time, effectively reducing its overall service life.
  Discover Battery +6

When Partial Charge is Unavoidable (But Not Recommended)

• Active Cycling: During normal use (e.g., in an RV or off-grid system), the battery will naturally be at a partial state of charge. However, experts recommend never discharging below 50% SoC to avoid significant damage.
• In-Transit Limitations: Sometimes a vehicle's alternator may not provide the high voltage (typically 14.4V to 14.8V) required to fully top off an AGM battery during short trips. In these cases, using a dedicated AGM smart charger periodically is advised to reach 100%.
  BRS Battery +4

Recommended Maintenance

Condition	Target State of Charge	Recommended Action
Storage	100%	Store in a cool, dry place and use a smart trickle charger.
Active Use	50% to 100%	Recharge to 100% as soon as possible after use.
Emergency	> 12.4V	Never let resting voltage drop below 12.4V to avoid early failure.

 

[Mavster Mechanic]

This:

Does this:

But at the same time this:

I don't have Forscan and I've never used it. Can it set "headlamps" to always on? Not just DRL but full lamps? I bet so. That would keep the battery 100% probably 100% of the time.

Now tell me the downside. Burn out bulbs faster? Anything else?

 

[Finnster]

AI Overview:
LED headlights typically last between 30,000 to 50,000 hours, roughly 10–15 years of normal driving, making them much longer-lasting than halogen (500–1,000 hours) or HID (2,000–3,000 hours) options. OEM factory-installed LEDs often exceed 30,000 hours, while aftermarket bulbs commonly last 5,000–20,000 hours, depending on quality.

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