12v second battery overcharged after using ODB port battery tender?

[zymolysis]

Hypersensitivity to vampire drain. That is the motivation.

That is not the only motivation. Extending 12V battery life would be my primary motivation, and I think there is plenty of reason to think that a trickle charger, especially one with a desulphation cycle, will keep the batteries healthier.

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[Riviot]

From another thread, here's RiDE stats on my 12V system. Mine spiked at 19V at some point... I also have never used a battery tender so

It also bottomed out at 3V... This was likely when it died in the SC, they forgot to do 12V tender during a wiring harness service.

While using, I kept battery tender on 24/7 (it was plugged to a LifePo4 battery), even while driving vehicle.

I do think it's unnecessary and unusual to leave it plugged in while driving, less is always more, but I agree it wouldn't kill your battery.

 

[Audiotek]

When I park I turn off the headlights.
I also turn off the Radio, Vents Heat/AC, Seat Heat/AC.
Set camp mode display off and vehicle to stay off.
41K miles and 2+ years later no issues.
Also, have Baja Squadron ditch lights connected to switch pro with DCE hood mounting kit therefore I treat the Rivian like a laptop and shut it down when not in use.
Hopefully these steps can help other Rivian owners with drain concerns.

Edit: too many other electronics connected to my switch pro controller to name. However, Vampire drain post always seems concerning because it's not normal for me.

 

[Electrified Outdoors]

Post of the month right here

 

[ndmiller]

This EV 12V battery discussion occurs on many forums. Same for ICE forums, many many threads on 12V battery heath, how to extend the life, etc. Same for motorcycle forums, 12V battery failure, how to extend life, etc.

I've had dozens of vehicles, Auto/Cycle, ICE and EV and found there is no way to avoid the fact that 12V batteries fail. I found no way in 4 decades to consistently increase their lifespan or somehow not have one fail and last forever.

The answer is simple. Like adding washer fluid, checking your oil (ICE), check you state of charge (EV), walking around the vehicle, rotating or changing your tires, its about accepting that 12V batteries can and will fail.

Now that it's an accepted possibility, start looking for the signs and when you see them just replace the battery, problem solved. I've spend more time writing this than worrying about 12V batteries in our current 4 vehicles and 8 previous in the last decade.

For example, bought a Ford Maverick for my daughter to take to college. The forums consistently talked about 12V failure from the OEM battery. I bought and installed an Odyssey battery and haven't thought about it for a couple years until just now.

 

[Zoidz]

It's entirely possible to overcharge. When the chemistry is full up on electrons and can't take any more, that surplus force feeding... i.e. energy... has to go somewhere. Heat. Gas, i.e. chemical reaction and irreversible change to chemical composition; a "cooked" battery.

Physics does not work that way…if your battery is, say, already 15v and your charger can only supply max 14v, there is no way to “force” the electrons into the battery, no matter how powerful the charger is.

@UnsungZero_OldTimeAdMan is correct. It is entirely possible to overcharge if a modern smart charger fails, or an old school linear charger (those big heavy transformer/rectifer based units) is left connected too long.

Lead Acid batteries have a charge profile curve, and once the battery is fully charged, the voltage must be decreased - otherwise, heat and plate oxidation damage can occur.

A dead battery does not have any more, or less, electrons than a fully charged battery. The number of electrons in the battery/circuit is essentially constant (physics demands that). Charging increases the energy level of the exisitng electrons in the chemistry.

Since the charger is increasing the energy level of the electrons, that energy gets transferred into electrons in the battery. When the battery is fully charged, due to resistance, a small current will continue to circulate. The electrons can't absorb any more energy, so that energy gets dissipated as heat and can damage the battery. By reducing the voltage to float level, it maintains the proper energy level.

 

[Zoidz]

From another thread, here's RiDE stats on my 12V system. Mine spiked at 19V at some point... I also have never used a battery tender so

It also bottomed out at 3V... This was likely when it died in the SC, they forgot to do 12V tender during a wiring harness service.

I do think it's unnecessary and unusual to leave it plugged in while driving, less is always more, but I agree it wouldn't kill your battery.

This could be some evidence here connecting to the bigger problem of 12 volt battery failure. Rivian (to my knowledge) has never told us the exact cause of the 12 volt battery failure. We have assumed manufacturing defect or failure to recharge leading to damaging discharge. I can't help but wonder if the root cause of the battery failure is overcharging at 19.2 volts due to a hardware or software bug in the DC to DC converter/logic?

If I were going to trickle charge, I would most certainly not do it while the vehicle is in use. Rivian's 12 volt battery monitoring/charging algorithm is not expecting another source of charging current while the vehicle is in operation. It's impossible to know what effect this could have.

 

[flaky]

I was explaining why it's not possible to "overcharge" the battery to 19v. While your explanation is mostly true, still does not explain how that's possible. Assume the charger is faulty, energy got dissipated as heat, or gas due to chemical reaction, or whatnot, but won't increase the voltage to 19v.

@UnsungZero_OldTimeAdMan is correct. It is entirely possible to overcharge if a modern smart charger fails, or an old school linear charger (those big heavy transformer/rectifer based units) is left connected too long.

Lead Acid batteries have a charge profile curve, and once the battery is fully charged, the voltage must be decreased - otherwise, heat and plate oxidation damage can occur.

A dead battery does not have any more, or less, electrons than a fully charged battery. The number of electrons in the battery/circuit is essentially constant (physics demands that). Charging increases the energy level of the exisitng electrons in the chemistry.

Since the charger is increasing the energy level of the electrons, that energy gets transferred into electrons in the battery. When the battery is fully charged, due to resistance, a small current will continue to circulate. The electrons can't absorb any more energy, so that energy gets dissipated as heat and can damage the battery. By reducing the voltage to float level, it maintains the proper energy level.

 

[MacO512]

This EV 12V battery discussion occurs on many forums. Same for ICE forums, many many threads on 12V battery heath, how to extend the life, etc. Same for motorcycle forums, 12V battery failure, how to extend life, etc.

I've had dozens of vehicles, Auto/Cycle, ICE and EV and found there is no way to avoid the fact that 12V batteries fail. I found no way in 4 decades to consistently increase their lifespan or somehow not have one fail and last forever.

The answer is simple. Like adding washer fluid, checking your oil (ICE), check you state of charge (EV), walking around the vehicle, rotating or changing your tires, its about accepting that 12V batteries can and will fail.

Now that it's an accepted possibility, start looking for the signs and when you see them just replace the battery, problem solved. I've spend more time writing this than worrying about 12V batteries in our current 4 vehicles and 8 previous in the last decade.

For example, bought a Ford Maverick for my daughter to take to college. The forums consistently talked about 12V failure from the OEM battery. I bought and installed an Odyssey battery and haven't thought about it for a couple years until just now.

Problem is where do you buy a rivian 12v battery? Service center won't sell them, no auto parts store has them. Yeah you can spend the $800 to have rivian swap them but when I can spend $100 to put in a larger 12v battery on an ICE vehicle it's pretty ridiculous you cant buy one for a Rivian.

 

[Zoidz]

I was explaining why it's not possible to "overcharge" the battery to 19v. While your explanation is mostly true, still does not explain how that's possible. Assume the charger is faulty, energy got dissipated as heat, or gas due to chemical reaction, or whatnot, but won't increase the voltage to 19v.

?
Nobody posted here that their battery was overcharged to 19 volts nor was I implying as such. What they said was that the charging voltage was recorded by Rivian's logs as 19v. The battery had 19 volts applied to it during charging. That's considered overcharging - the recommended charge voltage/rate/duration for a 12 volt lead acid battery was exceeded.

Overcharge: The forcing of current through a cell after all the active material has been converted to the charged state. In other words, charging continued after 100% state-of-charge is achieved. The result will be the decomposition of water in the electrolyte into hydrogen and oxygen gas.

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