HYBRID 12V Battery Mystery SOLVED

[Mavster Mechanic]

Some of you will laugh.
Some of you will cry.
Some of you will say "Holy Crap that's amazing!"
Some of you will say "Holy Crap that's dumb."

Here goes.

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. God only knows why.
For 3.5 years my 12v battery has been "maintained" at about 60% charged. Always a resting voltage of 12.1 or 12.2.

Fact: running your headlamps will force the 12v battery to be 100% charged given enough time. (DRL will not do it. Parking Lamps only will do it.)

Fact: running your vents blower at speed 6 or 7 will force the 12v battery to be charged to 100% given enough time.

Fact: attaching a trailer, 4-pin or 7-pin will force charge the 12v battery to 100%.

Theory A: the truck needed to detect 12 volt demand, and above a certain wattage to trigger 12 volt charging.

Why would fan level 6 trigger battery recharging and fan level 5 would not? Why would full headlamps trigger battery recharging, but DRL would not?
Did the truck detect demand to run my camper fridge and coach battery?

I tested this last part. From Amazon I ordered a $10 LED brake light for the 2" hitch receiver with 4-pin connector.
Wow! The LED brake light pulling no power when not braking, and only 4 or 5 watts when braking DOES TRIGGER 12 volt battery recharging to 100%.
It's not the electrical demand that triggers recharging. It is simply thinking a trailer is there that triggers recharging.

Theory A shot down.

But this explains a lot.
This explains why some people have more 12v battery issues than others.

Those that drive at night a lot have more battery charging by happenstance.

Those that use fan speed 6 or 7 have more battery charging by happenstance.

Those who connect trailer wiring (and you don't even need a trailer!) have more battery charging.

Not a permanent fix. But a work around. Some of you may prefer running your headlamps more often over plugging into a home charger.

My 12v battery has been 100% for ten days in a row now. And is maintained at 12.7 or 12.8 volts. But I need to do one of the three "triggers" above or it rapidly starts to decline.

More to come...

UPDATE: running headlamps or one of the other tricks will recharge your 12v about 8% in an hour.

Recommend using lamps full time. But at a minimum, 2 hours per week.

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[Mavster Mechanic]

Watch this video.

12.x volts and discharging to 14.x volts and charging. All I did was manually turn on my headlamps.

 

[HeyBales]

Ugh - I'd be happy if my SOC% and Volts were matched like that - 60% & 12.1V.
After 4 hr drive yesterday - got up to 65% SOC (float level started after 20 min about), from 52% IIRC.
This morning resting - 63% (ya it held!), and 11.9 V (boo it didn't). (bad battery at this point)

Thanks for observational skills with your different setups.

I haven't attached my trailer hitch yet, and don't think it came with wiring kit, but had for so long I don't recall. Time to get busy.

Or per the EB poster that found the rear AC outlet with night light was enough draw (he has inverter) to prevent AS/S from kicking on - perhaps I can find a high draw powerpoint light.

Does your scanner have these PID's available for cumulative charge/discharge?
Curious what level of matching you have?
This pic was day after a drain usage of doors open - BMS motivated to get it matching again - which it did - currently 32 Ah matching.
I've observed how close these are determines the BMS willingness for rate of charge too.

 

[Glen Baker LLC]

THANK YOU. David, @Mavster Mechanic

 

[Glen Baker LLC]

I wonder if putting a night light with an incandescent bulb in the bed AC outlet would also work?
I would totally go with the plug-in trailer hitch light except, I believe it deletes cross traffic warning sensor.

 

[Mavster Mechanic]

I now think long drives have nothing to do with it.

Other than long drives may have involved more headlamp use and/or more high speed fan use.

My 12v will fully charge from -90% to 100% in under 1 hour. Then maintain 100% and 14.x volts indefinitely IF my headlamps are on OR my trailer is attached.

Drive 10 hours Sunday with my trailer behind me. Voltage stayed 14.x and 100% SOC the entire trip.

The DC/DC "downshift" to 12.x never happens when headlamps are on or one of the other things mentioned.

 

[Mavster Mechanic]

I wonder if putting a night light with an incandescent bulb in the bed AC outlet would also work?
I would totally go with the plug-in trailer hitch light except, I believe it deletes cross traffic warning sensor.

Umm.... my statement above was my "minimum load" theory failed the test with my LED hitch light. The "computer" just needed a bit set that there was a trailer. It didn't matter if the trailer was pulling a little power, a lot of power, or none. But worth a shot what you want to try. Try it. I can try in about.....6 hours.

And yes, trailer plug deactivates blind spot and cross traffic alert in 2022 to 2024 models but there is a work-around for the 2025+ where it won't.

In newer models you input trailer length and you can input zero. If not, 1 foot for your trailer and your sensors stay on.

 

[Glen Baker LLC]

Umm.... my statement above was my "minimum load" theory failed the test with my LED hitch light. The "computer" just needed a bit set that there was a trailer. It didn't matter if the trailer was pulling a little power, a lot of power, or none. But worth a shot what you want to try. Try it. I can try in about.....6 hours.

And yes, trailer plug deactivates blind spot and cross traffic alert in 2022 to 2024 models but there is a work-around for the 2025+ where it won't.

More than likely anything that's plugged into the AC plug at least lightwise would have to be an incandescent to draw enough power. LEDs just won't do it as you found out with your trailer light.
Hmmmm.

 

[not null]

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.​

 

[Mavster Mechanic]

The DC/DC converter is the only thing that can charge a 12v battery.

But it's variable. It can output any voltage it's programed to within design limits.

For whatever reason, it's being told to output only 12.3 or 12.4 volts much of the time.

Doing one of the "tricks" mentioned forces it to put out 14.4 to 14.8 volts ALL OF THE TIME.

 

[HeyBales]

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.

 

[MakinDoForNow]

Some of you will laugh.
Some of you will cry.
Some of you will say "Holy Crap that's amazing!"
Some of you will say "Holy Crap that's dumb."

Here goes.

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. God only knows why.
For 3.5 years my 12v battery has been "maintained" at about 60% charged. Always a resting voltage of 12.1 or 12.2.

Fact: running your headlamps will force the 12v battery to be 100% charged given enough time. (DRL will not do it. Parking Lamps only will do it.)

Fact: running your vents blower at speed 6 or 7 will force the 12v battery to be charged to 100% given enough time.

Fact: attaching a trailer, 4-pin or 7-pin will force charge the 12v battery to 100%.

Theory A: the truck needed to detect 12 volt demand, and above a certain wattage to trigger 12 volt charging.

Why would fan level 6 trigger battery recharging and fan level 5 would not? Why would full headlamps trigger battery recharging, but DRL would not?
Did the truck detect demand to run my camper fridge and coach battery?

I tested this last part. From Amazon I ordered a $10 LED brake light for the 2" hitch receiver with 4-pin connector.
Wow! The LED brake light pulling no power when not braking, and only 4 or 5 watts when braking DOES TRIGGER 12 volt battery recharging to 100%.
It's not the electrical demand that triggers recharging. It is simply thinking a trailer is there that triggers recharging.

Theory A shot down.

But this explains a lot.
This explains why some people have more 12v battery issues than others.

Those that drive at night a lot have more battery charging by happenstance.

Those that use fan speed 6 or 7 have more battery charging by happenstance.

Those who connect trailer wiring (and you don't even need a trailer!) have more battery charging.

Not a permanent fix. But a work around. Some of you may prefer running your headlamps more often over plugging into a home charger.

My 12v battery has been 100% for ten days in a row now. And is maintained at 12.7 or 12.8 volts. But I need to do one of the three "triggers" above or it rapidly starts to decline.

More to come...

I had a 2012 Honda crv that ate 12v battery in 18-24 months. Could increase life to 36-42 months if drl's and fan speed 3 were set to come on at key on. Then to 60+ months life if noco g5 was put on three times a year. (Crv 12v logic did not start 12v charging until about 15 minutes of operation or when 12v soc was about 11.5 volts).

 

[Glen Baker LLC]

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.

The battery charger idea didn't work. The charger didn't energize / turn on. No light whatsoever.
Before I removed Maya's heating pad from her seat. I plugged it in and made sure that the outlet was working fine. After taking out the heating pad. I put in the driver side rear window sun shield.

 

[SafetyGuy]

Well done, this is indeed interesting to read...where we need to demand a bit of power for the charging system to kick in and charge the 12 volt battery properly.

It kinda makes me think that I have been unknowingly doing your newly suggested procedure following my normal safe driving habits.

I almost always turn on my parking lamps (in daylight) in normal driving conditions and then move up to headlights as soon as we have any snow/fog etc going on.

In doing so, it provides an explanation why my 12 volt battery charge indication (on my inexpensive cigar lighter 12 volt power port plug-in indicator) is always showing a very good charge level.

Couple that with normal every 1-2 month external battery recharging process, this is a definite move in the right direction.

Whenever we arrive home and park, I look through the drivers window and good charge levels indicated (every time I enter my garage).

Now I can compare the 2 situations (trucks normal-no load charge level versus my normal lights on and better charge condition), just using my little 12 volt plug-in indicator!

Thanks again, @Mavster Mechanic for probably solving what the 12 volt issue is!

Have a great day,

Andy

 

[Mavster Mechanic]

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.

Same here. As high as 15.3 or 15.4 volts with a really undercharged battery. But 14's only with a charged or mostly charged one.

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