12v battery issue, Tesla unsatisfactory response

[neurocutie]

Hate to repeat myself, but after jumping back into this thread it seems worth it. There is no reason a dead 12V should strand a Tesla owner either. It’s really no different than an ICE. When mine died (after 80k miles) I jumped in my wife’s Volvo and headed to O’Reilly. After educating the kid who worked there (had never heard of Tesla) I bought the battery needed and returned home.

The difference is, with the Tesla, your ARE stranded, i.e. the Tesla won't run until you REPLACE the 12V battery. With ICE, after the jump, the car WILL run, potentially for days or more, but at least enough to get you to where you need to go at that moment. Also, my ICE batteries have lasted 5-8yrs. It doesn't seem the Tesla 12V batteries last half of that...

not saying this is a fatal flaw, but I do think Tesla can do better...

 

[scottf200]

The difference is, with the Tesla, your ARE stranded, i.e. the Tesla won't run until you REPLACE the 12V battery.

So my 12v gave up during an OTA a week or so ago. I jump the car (X), it completed the update. I drove the next day and got the warning Info Console msg. Unclear why you say the Tesla won't run until you replace it. It did run for me so I'm proof of the contrary.

 

[AlanSubie4Life]

not saying this is a fatal flaw, but I do think Tesla can do better

Yeah, they can. But likely not until they fix their phantom drain issue. So...never. The two go hand in hand. If phantom drain were 1W rather than the 7W or whatever it is in sleep mode the 12V battery would probably last 5x as long. Which would be sufficient.

Worth noting that the $25 battery monitor discussed here can perform high quality high data rate Bluetooth low energy interactions while consuming a maximum of 12mW according to its datasheet. So it is not the Bluetooth key that is the problem.

 

[scottf200]

What normally charges the battery?

1. The PCS - Power Conversion System - located in the "penthouse" of the main HV battery (under the rear seat, passenger side, in the 3). The PCS is also known as a "DC-DC converter" which takes the 300-400v of the HV battery and converts it down to 10~15v depending on the state of the system (average 13v at most times). The PCS is connected to the 12v bus through a solid-state switch (a MOSFET or similar; an "E-fuse" or a software-defined fuse) and this is what drives the entire 12v bus any time the car is not in deep-sleep (or just sleep). That is to say - the devices that run on 12v power do not "run on" the 12v battery when the car is awake, driving, or otherwise interacted-with. The 12v battery is just along for the ride.
   
   In fact, the car's software actually charges the 12v battery at a controlled 10-amp rate by modulating the 12v bus voltage while monitoring how much is going into the 12v battery. It's a really clever system, but you'll often observe the voltage coming out of your 12v accessory socket as being 12.5... 13.2... 14.2... varying like that, which is how it manipulates the charging process of the 12v battery. Because 12v systems have a relatively wide operating range (usually anywhere from 11v to 15v), the car takes advantage of that to avoid needing a secondary charge controller on the battery.
   
   The 12v battery merely exists on this 12v bus - it is the one thing that never moves, but exactly what device powers the bus can shift, due to the nature of electricity. Thus, for the overwhelming majority of the car's active existence, it's running on the HV battery, not the 12v battery. The 12v battery is just standing-by, ready to power things in case of an accident, a HV systems failure, or when the car goes completely to sleep.
   
   See also: Controlling Tesla's Sleep Mode ~-or-~ Lucid Dreaming for Robotaxis : teslamotors regarding sleep.

I think there are two charging levels (true in my X with a battery monitor):
From article and quote below: Marine Battery Maintenance 101 - e Marine Systems
*** "taken to 14.2-14.4 VDC before it is fully charged"
*** "Once fully charged, marine batteries should be held at a considerably lower voltage to maintain their charge - typically 13.2 to 13.4 volts."

Why Marine Batteries Fail -- When a lead-acid battery is discharged, a soft lead sulfate material forms on the battery plates. During the battery's recharge, this material is lifted off the plates and recombined into the battery's electrolyte solution. If, however, the battery is left in a partial state of discharge for as short as 3 days, the lead sulfate material will begin to harden and crystallize, forming a permanent insulating barrier. As this barrier becomes thicker and thicker, the battery's ability to accept a charge or deliver energy is diminished, resulting in the perception that the battery is no longer usable. The accumulation of such deposits, otherwise known as sulfation, is the most destructive process in the life of any lead-acid battery.

Multi-stage Battery Charging -- A typical 12-volt lead-acid battery must be taken to approximately 14.2-14.4 VDC before it is fully charged. (For 24 volt systems, double these figures.) If taken to a lesser voltage level, some of the sulfate deposits that form during discharge will remain on the plates. Over time, these deposits will cause a 200 amp-hour battery to act more like a 100 amp-hour battery, and battery life will be considerably shortened. Once fully charged, marine batteries should be held at a considerably lower voltage to maintain their charge - typically 13.2 to 13.4 volts. Higher voltage levels will "gas" the battery and boil off electrolyte, again shortening battery life.

 

[FalconFour]

Most of what you say is very informative... But these statements, as has been pointed out, are somewhat inconsistent. A well-behaving car is sleeping for the vast majority of its life. So that's the mode that is the most common. So the 12V battery receives a LOT of use.

So, for the majority of the car's active existence, it's running on the 12V battery, and the contactors are open. From what I understand it's usually just drawing a few watts (less than 10W?) from the 12V, but there are transient increases in load just prior to contactor engagement, presumably (like when you open a door and turn on the headlights and ambient lights prior to the contactors closing).

Okay, but in my experience that's absolutely not been the observed behavior of the car. It's really tricky to get it to go to sleep. It stays awake for hours, sometimes even overnight. Sleep mode has been a constant source of headache for me. Hours and hours, it'll sit there spinning the water pump, churning away a hundred watts, doing nothing. Third party apps turned off, trying to get it to sleep. It doesn't sleep.

About 3/4 of the mornings I go out to it, yeah, it's finally gone to sleep at some point during the night (open the door and the MCU stays blank for a moment, mirrors extend with a slightly lower pitch sound, "clunk-clunk" from the battery pack). But more than half the times I go back to the car during the day, after a long period of sitting idle, it'd never gone to sleep (MCU instantly comes up, mirrors extend with a higher pitch sound). Hours sitting there in the garage or in the parking lot... never slept.

Pair that with the fact that charging time is 100% active time as well - and you can start to see how little time is actually left for sleep, when sleep is so hard to achieve (thus my thread on Reddit).

So I honestly suspect that maybe half the car's existent life is spent in sleep, while the other half is spent awake, per hour-by-hour basis.

Maybe my car just has insomnia, but it's definitely a real thing. It legit bugs me how much I can't get the car to sleep.

And somewhat exhausted that all the stuff I wrote about is now going to get buried halfway down the 14th page as this thread goes on towards infinity Maybe oughtta bookmark it or something. At least my write-up on logging-in to YouTube has stayed relevant

 

[neurocutie]

So my 12v gave up during an OTA a week or so ago. I jump the car (X), it completed the update. I drove the next day and got the warning Info Console msg. Unclear why you say the Tesla won't run until you replace it. It did run for me so I'm proof of the contrary.

yes, you're "proof" that sometimes you *can* jump a Tesla and have it run, just like someone else will say: I tried to jump my dead ICE and *couldn't* get it started. But what is the *average, typical* behavior? Seems like I'm reading mostly that when their Tesla 12V battery dies, often without warning, the car is dead until the battery gets replaced, no?

 

[EnrgyNDpndnce]

The difference is, with the Tesla, your ARE stranded, i.e. the Tesla won't run until you REPLACE the 12V battery. With ICE, after the jump, the car WILL run, potentially for days or more, but at least enough to get you to where you need to go at that moment. Also, my ICE batteries have lasted 5-8yrs. It doesn't seem the Tesla 12V batteries last half of that...

not saying this is a fatal flaw, but I do think Tesla can do better...

Your point is not based on facts as Teslas can and have been jump started just like an ICE. There is, as I said, no difference. And my Model 3 battery lasted 80k miles which for most people (driving 15k per year) would be 5+ years. So far I have seen nothing but anecdotal evidence showing Tesla has a real issue with premature 12V deaths. If anyone has any statistical data showing Tesla suffers from early 12V issues at a significantly higher rate than other manufacturers, I would love to see it.

 

[FalconFour]

yes, you're "proof" that sometimes you *can* jump a Tesla and have it run, just like someone else will say: I tried to jump my dead ICE and *couldn't* get it started. But what is the *average, typical* behavior? Seems like I'm reading mostly that when their Tesla 12V battery dies, often without warning, the car is dead until the battery gets replaced, no?

there is no technical reason that could be the case, that a discharged battery would *NEED* to be replaced before the car would start again. A 12v battery is a 12v battery. It's not like an ink cartridge with a sense chip in it saying "I'm spent". However, knowing how the 12v system works, there's generally not going to be any case where the car will go into an OTA without a fully charged 12v battery - at least, as fully charged as a defective 12v battery can be (that holds 100mAh and drops dead almost instantly).

Honestly, a lot of this does seem like paranoia response and "it's such a weird car let's just tell people to do the Most Correct thing and make up hand-wavey excuses as to why this must be the case". Karen and Ken owners of Teslas could easily be the cause of this, causing nightmare scenarios for service centers.

I've heard some 12v horror stories - of bloated and legitimately f*cked-off 12v batteries pulled out of Teslas at SCs and 3rd-party shops - and of course those would have to be replaced. Batteries on the edge of failure would probably be weeded-out by an OTA that fails.

It still baffles me how 12v batteries in Teslas can fail. In an ICE car, they're drained down (BMWs probably draw more sleep power) then stabbed in the neck with a surge of starting current multiple times a day, then rammed back with unlimited charging power again. In a Tesla, the worst they ever get is a slow trickle of sleep power and a Google Nest alarm clock gently lifting it awake when it comes up. By comparison, Tesla 12v batteries are living life on a cloud cushion their whole life. However, I suspect whatever their problem is, something probably seriously changed recently with 2020.28, so that's worth sticking a milestone in the ground and gauging from there, if anyone's paying attention to that.

 

[neurocutie]

Your point is not based on facts as Teslas can and have been jump started just like an ICE. There is, as I said, no difference. And my Model 3 battery lasted 80k miles which for most people (driving 15k per year) would be 5+ years. So far I have seen nothing but anecdotal evidence showing Tesla has a real issue with premature 12V deaths. If anyone has any statistical data showing Tesla suffers from early 12V issues at a significantly higher rate than other manufacturers, I would love to see it.

I don't think that it is fair to equal miles driven to years of 12V battery life -- why not just state how many years you have been running your 12V Tesla battery.

I agree that I'd love to see real statistical data on whether 12V Tesla battery failure 1) means that the car cannot run til replaced (jumping doesn't get them running), 2) the average life span of a Tesla battery. It's my perception that there are many more reports of dead means dead (unjumpable) for Tesla, but perhaps it isn't reality...

But given that (lack of real statistical data), it also means that your statement of "no difference" is also unsupported by real data ("facts" as you say).

 

[neurocutie]

there is no technical reason that could be the case, that a discharged battery would *NEED* to be replaced before the car would start again. A 12v battery is a 12v battery. ...
It still baffles me how 12v batteries in Teslas can fail. By comparison, Tesla 12v batteries are living life on a cloud cushion their whole life.

Indeed, it just means that many of us (myself probably included), don't really know what's going on as it doesn't make sense, why 1) so many unjumpable failures, 2) Tesla 12V batteries dying after only 2-3 yrs instead of 5-8 yrs. Many ICE 12V batteries are *guaranteed* for 5yr life spans. Is there any reason that Tesla 12V batteries couldn't also be guaranteed for 5 yrs?

Are they really "living life on a cloud cushion" or being constantly drained with heavy loads over long periods of time? Are they even AGMs?

Anyways, there is a big difference in comparison to ICE in that when you jump start and ICE, you are using the other guy's battery to start the engine, after which, your half-dead 12V battery doesn't really do too much til you try to start your engine again. Presumably what this means is that with ICE, you get a clear "warning", your car can't start, can't deliver the cranking amps, but otherwise the car runs fine. But with Tesla, when the 12V battery fails, its because it can no longer do what it needs to to run the car, so, yeah, the car can't run anymore...

 

[SageBrush]

Anyone who is reasonably good at problem solving should have zero difficulty finding a proper replacement and making the switch. Most of us know better than to trust the opinion of some kid making $10 an hour with anything important.

I found it difficult to locate right sized 51R, deep discharge battery replacements

So for now I would say
Replacement to not get stranded -- sure.
Good replacement that will last years -- not so simple outside of Tesla

 

[brkaus]

@Daniel in SD exactly. If autozone said they had a match in the catalog, I would have jumped the car and driven right over.

I was cautious because of little experience, a smell of sulfur (my truck did that too, but this has more electronics), and no direct part match (I’m not even clear here if it’s a flooded lead acid or a AGM battery).

I asked the tow driver about getting it on the truck. He said they nearly all jump just fine and the AWD let’s him drive it right up on the truck!

My typical ice battery has lasted 3-4 years. My truck has two, so it’s twice as much to replace each time

 

[EnrgyNDpndnce]

I don't think that it is fair to equal miles driven to years of 12V battery life -- why not just state how many years you have been running your 12V Tesla battery.

Fair enough, I suppose we can disagree as I believe miles driven is a fair assessment of battery life. For the record, my Model 3 will be 2 years old next week. So the battery lasted under 2 years but as I said, 80k miles. At the rate I put miles on my car, to get 5 years the battery would have to last ~ 200k miles. To me that’s an unreasonable expectation.

But given that (lack of real statistical data), it also means that your statement of "no difference" is also unsupported by real data ("facts" as you say).

Sure but I’m not going to attempt to prove a negative. Your assertion is that Tesla batteries are dying early at a rate that exceeds the industry norm. My response is that we have no real evidence of that. The burden of proof lies with you to prove the assertion, and until we find data to prove it my opinion stands. And again for the record, if that data exists and I see it and it seems to support your assertion, I’ll readily admit there’s a problem. I just don’t like people jumping to conclusions based on anecdotal forum complaints.

 

[EnrgyNDpndnce]

I found it difficult to locate right sized 51R, deep discharge battery replacements

So for now I would say
Replacement to not get stranded -- sure.
Good replacement that will last years -- not so simple outside of Tesla

Well you could be right. I’m not one of those “it must be an OEM part or die” guys so I easily found a good match at O’Reilly and popped it in there. So not stranded, check. As for lasting years, only time will tell. I have 12k miles and counting so far on the O’Reilly battery, which for most people is close to a year.

 

[mspohr]

Your point is not based on facts as Teslas can and have been jump started just like an ICE. There is, as I said, no difference. And my Model 3 battery lasted 80k miles which for most people (driving 15k per year) would be 5+ years. So far I have seen nothing but anecdotal evidence showing Tesla has a real issue with premature 12V deaths. If anyone has any statistical data showing Tesla suffers from early 12V issues at a significantly higher rate than other manufacturers, I would love to see it.

FWIW (another anecdotal point), my 2015 Model S with 86,000 miles has the original battery. I've never had a problem or a warning about the battery. I do have a jump charger which people have reported works well but which I've never had to use. However, with the Model S, there is usually a warning that the 12v battery needs service.

 

[neurocutie]

Sure but I’m not going to attempt to prove a negative. ... I just don’t like people jumping to conclusions based on anecdotal forum complaints.

Its not "proving a negative", like Aliens don't exist. Its a simple question of data: What is the MTBF of the Tesla 12V battery? What is the proportion of successful Tesla jumps? I agree that all we seem to have is anecdotal data and that is not a good basis for conclusions...

But like aliens and Mulder, The truth is out there... certainly Tesla knows and knows precisely what the demands are on the 12V battery and how it is being used relative to its optimal load and duty cycles.

 

[SageBrush]

Well you could be right. I’m not one of those “it must be an OEM part or die” guys so I easily found a good match at O’Reilly and popped it in there. So not stranded, check. As for lasting years, only time will tell. I have 12k miles and counting so far on the O’Reilly battery, which for most people is close to a year.

I was not talking about OEM

Did you find a deep cycle replacement ?

 

[FalconFour]

Presumably what this means is that with ICE, you get a clear "warning", your car can't start, can't deliver the cranking amps, but otherwise the car runs fine. But with Tesla, when the 12V battery fails, its because it can no longer do what it needs to to run the car, so, yeah, the car can't run anymore...

Well, at risk of "ackshuelly"-ing again...

When one ICE jumps another, it's probably because it was bled down to nothing, and so there's nothing left. Jumping it gets it running again, and the dead battery immediately starts getting charged off its running engine once again. The cycle continues as usual and it regains its charge over time. That's the case when someone just left something on in the car with the engine off - like if someone left it in ACC and listened to the radio and then realized O poop I Can't Start my Car. A jump just brings it all back to normal operation, no harm done.

When a Tesla dies, well... there's no "listened to the radio in ACC too long". It's always running off the HV battery. There is no big load. There never is. The 12v battery is only used in sleep, and in sleep, everything is off - because the car controls everything. If you're sitting in the car, it's running on HV, not 12v. That's why I say it's running on a cloud cushion - that 12v battery is literally never given any big loads, except maybe a higher-than-normal tickle (woo, 10 amps instead of 0.5 amps) when it wakes up, for a split second, then it goes from a 10-amp load to a 10-amp charge instantly. That, to me, is living on a cloud.

Meanwhile, ICE batteries get stabbed in the neck with a 500-amp cranking discharge, then slapped back with 50 amps of recharging or so.

Legitimately cooked batteries exist. The cause of that still doesn't make sense, other than deep discharges not being caught by the controller (which should wake things up and recharge the battery, then go back to sleep). It's simple enough to fix that, so they probably worked towards fixing it with 2020.28 FW.

When a legitimately cooked battery is encountered, weird things can happen. There just isn't enough storage capacity, between "fully charged" and "an inert brick", to get it through a sleep-and-wake. So that'd surface as a bad battery. But you'd only know it when the car sleeps... so you go out to the car one day and woop it just doesn't work. Many people seem to attribute it to voodoo, because the behavior of the car is so very vastly different from how a ICE car uses its 12v battery... but really, I wonder how many batteries just had defects out of the gate that were masked by how the car uses it. Also, curious how the 12v failure stats compare between Tesla and others...

Also, another fun fact I hadn't mentioned before: the charge is controlled by the PCS output voltage, but that is also intelligent - it charges at 10 amps until it reaches 14.4v, lingers there for a little while, then stops and drops to 13.5-ish. What's odd, though, is that it doesn't hold a stable 13.5. It drifts around a bit, almost like the car is intentionally lowering the PCS voltage to let the 12v battery discharge and be tested. Strangely, this actually puts a little (controlled and intentional) load on the battery, then it recharges it, cycling it. I dunno why they do this, but I suspect it's got something to do with the "UPS battery effect" - that UPS batteries stay fully charged their whole life, and in that "optimal" environment, they become some of the most f*cked up batteries I've ever seen. So, being fully charged isn't optimal, and neither is being fully cycled... so what is? Maybe Tesla is trying to find that out... and lead batteries - even being a 100-year-old technology - still have lots of room to improve.

(it does beg the question of why in the sweet hell are we still using lead batteries and trying to solve problems of an obsolete battery technology... I dunno that either, but that's why I run a lithium 12v in mine! lol)

 

[neurocutie]

When a Tesla dies, well... there's no "listened to the radio in ACC too long". It's always running off the HV battery. There is no big load. There never is. The 12v battery is only used in sleep, and in sleep, everything is off - because the car controls everything. If you're sitting in the car, it's running on HV, not 12v. That's why I say it's running on a cloud cushion - that 12v battery is literally never given any big loads, except maybe a higher-than-normal tickle (woo, 10 amps instead of 0.5 amps) when it wakes up, for a split second, then it goes from a 10-amp load to a 10-amp charge instantly. That, to me, is living on a cloud.

If the demand on the 12V battery is really what you say, 10A for just a short time, then all that is needs are two $20 7AH 12V SLAs and a crossover switch (automatic transfer switch). When one SLA goes weak, it draws from the 2nd one and reports that the 1st needs replacing at your leisure. Somehow I don't think its quite as easy as you say... something really doesn't add up... (I agree UPS battery life doesn't make sense either... Curiously, in my experience they also last about 2-3 years, again half that of an ICE battery, even though they also have that cloud cushion life)

 

[AlanSubie4Life]

That's why I say it's running on a cloud cushion - that 12v battery is literally never given any big loads, except maybe a higher-than-normal tickle (woo, 10 amps instead of 0.5 amps) when it wakes up, for a split second, then it goes from a 10-amp load to a 10-amp charge instantly. That, to me, is living on a cloud.

I don't really get this. To me it seems like running 7W from a battery 80% of the time (and I think we all agree it's something like that) seems pretty stressful.

That would be 49kWh per year! The battery is 576Wh nominally (48Ah at 12V approximately) so that's 85 full cycles minimum per year. Obviously these would be shallow cycles, so under reasonable circumstances, since 168Wh is the daily draw, you probably do a 10% DoD 3x a day (so 3 discharges of 56Wh). So you're looking at 1100 10% DoD cycles each year!!!

That's a lot of cycles. And I think this is a conservative estimate, since I suspect there is more than 7W load (that would be 0.6A) on the battery at times.

If you do an arbitrary search on the internets, you find all sorts of pictures, which make me think shallow cycles may not be... that great.

This is for a NON deep-cycle battery (like in the Model 3 - it's likely not an AGM battery).

Using a battery is bad! Even with shallow cycles! It wears away the positive electrode material over time, from what I understand. Because of entropy and such.

This is why I claimed (without evidence) that Tesla battery longevity is likely inversely related to the level of vampire drain.

Meanwhile, ICE batteries get stabbed in the neck with a 500-amp cranking discharge, then slapped back with 50 amps of recharging or so.

Pretty sure a lot of ICE alternators have fairly sophisticated regulators these days...probably to optimize battery life, safety, etc.

And I'm not even sure whether the starting requirements and idling (engine off) requirements on an ICE vehicle would exceed the cycle count that the Tesla sees, except for heavy duty (lots of on/off) applications. It just does not take that much energy to start an ICE engine. It just takes a lot of current (and power), briefly. 500A*12V*2seconds/(3600s/hr) = 3.3Ah per start, and that's probably on the high side for a vehicle in good condition. My guess is you draw less than 40Wh from the battery each day with the typical two starts per day. 3x less than the Tesla. Consilience! (Lol, that's an inside COVID joke.)

I don't know whether we should be using BMW as our benchmark, BTW, but you said their standby power is as high as Tesla's? That seems...highly improbable. If it were, and the BMWs draw 7W just sitting there, the 12V battery would invariably be dead on BMWs after just a few days. I know BMW owners are long-suffering, but I'm pretty sure they would not be ok with that. I suspect the standby power is substantially less than 0.5W in most ICE vehicles that are operating correctly (would allow the car to sit for two months and still probably start - a typical safe period for most ICE vehicles with 12V batteries in good condition). (0.5W/12V = 40mA, 40mA*24hr/day*60days = 60Ah)


By the way, what is the Ah capacity of the Ohmmu battery (it's 48Ah for the Model 3 OEM battery)? I looked up their website but I could not find that information anywhere. If it's not ~500Wh (48Ah) or so, that would explain why you have problems getting your car to sleep. If it's just 150Wh or something your car would wake up more than 3x as often. But I have no idea. I assume it's a true replacement with equivalent capacity.