12v battery issue, Tesla unsatisfactory response

[scottf200]

just trying to understand...

It seems like IR around 30milliohm is certainly bad if you are trying to start an ICE: Suppose the starter needs 250A to start the ICE. At 13.2V, 250A means a resistance of 0.053 ohms (53 milliohms). Not counting the resistance of the wiring, etc, adding the 30milliohm to make 83milliohm means that the starter is only going to get 160A instead of the 250A. With added resistance from wiring, switch, etc, only going to be worse.

However, the Tesla (I hope) doesn't need 250A or even 160A out of its 12V battery. I don't know what it needs, but supposing its 20A (about 250 watts).That's 0.66 ohms load, so adding an additional 30milliohm of IR just makes that 0.70 ohm so the Tesla "only" gets 19A of the 20A. I doubt that's a problem: the 30milliohm is just a 0.6V voltage drop at 19A.

So, not sure IR is the right way to test whether a 12V AGM battery for a Tesla is going to be good or not...

30 milliohm with 20A of current is a power dissipation of 12 watts. That's fairly significant inside the non-cooled battery and can pretty easily overheat it if the current stays at 20A for while. So although the voltage drop is small with the small currents, the increased internal resistance is still a problem.

Thanks for both your input. Some of us are using the 12v for dashcams and (worse) for refrigerators so we are 'harder' on the 12v. ie. the HV battery & DC-to-DC converter has to recharge them more frequently. I've only taken one reading on my Xs 12v battery (bit of a pain to get to) but monitoring it over time should give me a warning. Especially good to verify before a long few week road trip!

Here is the Battery University pages on rising IR and how to measure IR with some good information. The how to measure IR indicates that IR should remain flat even when capacity drops. If IR changes it would seem a strong indicator there is a problem with the battery.
Rising Internal Resistance - Battery University
How to Measure Internal Resistance

 

[neurocutie]

My point is that a "high" IR for a battery expected to deliver 250-500amps is different than an acceptable IR for a battery that only needs to deliver 20-40amps. Sealed lead acid (SLA) batteries are also typical for UPS systems for computers, etc. For a UPS to work, it typically needs to deliver moderate/high currents for seconds to a few minutes. Most UPS systems for PCs etc aren't expected to carry their load for more than 15-30minutes tops, usually much less. I often have to replace these batteries every 2-4 years.

But I then can take those "old, bad" SLAs and use them for other things, like running LED lights, etc where I only need 1 amp or less. These spent SLAs will be fine at smaller loads for years, even though their IRs are now too high for UPS usage. So I'm not sure that IR metrics and criteria established for ICE starter usage are applicable to the Tesla usage regime, although certainly IR is an important gauge of battery health.

 

[dhanson865]

I live in the heat of Vegas where 12v batteries fail without warning in any car. I intend to replace the 12v every 2 years, and wouldn't expect it to last more than about 3 years anyway.

I usually get 8-10 years out of a 12v here in TN in ICE vehicles. I found in the Prius it was easy to run a battery down by leaving an accessory on and switched to deep cycle batteries for it. On the hybrids and EVs I've had so far I've not had one more than 6 years since I replaced the 12v with a mid quality 12v. Both Leafs are on the 2nd battery after the OEM only lasted about 4 years. But I've always found OEM batteries to be lower than average quality. It's usually an upgrade when I buy a 12v for one of my cars.

Then again it was easy in those cars to put a CTEK or NOCO smart charger on the 12v several times a year (basically every time I put air in the tires I'd toss a smart charger on the 12v). That won't be so easy on the Tesla.

Also the Vampire drain has been a week spot on Tesla cars in the past (Model S/X), I hope they made the 3/Y more consumer friendly in terms of vampire drain causing the 12v to be cycled more often.

 

[gaspi101]

It’s nit the same

Yep, this has been happening to quite a few 3 owners. Mine was stuck in my garage, dead, and the 12V was HOT and stunk like sulfur. I was able to jump the car and get it out onto the street at least so that if the 12V caught fire, it wouldn’t burn my house down with it.

I have heard the 12V is a regular sort that you can get from a normal store, although I didn’t try that. Had mine towed to Tesla and replaced, but I was still under warranty.

And, yes service is much reduced from 3 years ago. I have just gotten used to having lower expectations.

Not the same as a regular car battery. Car batteries are made for insanely high amp rates for a few seconds to power the starter motor, and then after that, 12v system (lights, radio, etc.) runs off of the alternator. A regular car battery lasts very long largely because it is so seldom used—starting the car, amd the odd case where the car accessories are on but the engine is not. Not the same as a Tesla, which has no alternator...it is the 12v battery’s job to power the entire 12v system, everything, at all times. Its job is different, and accordingly, it’s chemistry is different.

 

[gaspi101]

Not the same as a regular car battery. Car batteries are made for insanely high amp rates for just a few seconds to power the starter motor, and then after that, 12v system (lights, radio, etc.) runs off of the alternator. A regular car battery lasts very long largely because it is so seldom used—starting the car, amd the odd case where the car accessories are on but the engine is not. That’s it. 99.99% of the time, it’s just sitting there without discharging...Not the same as a Tesla, which has no alternator...it is the 12v battery’s job to power the entire 12v system, everything, at all times. It is constantly discharging and charging off of the high-voltage battery pack. It works a lot harder than an ICE batter.

 

[TraumaDoc]

Seems excessive to even think about replacing the 12v unless there's an issue.

I had my last two cars 10 years each and only replaced the 12v on my Ford when the alternator went and took the battery with it.

 

[scottf200]

Seems excessive to even think about replacing the 12v unless there's an issue.
I had my last two cars 10 years each and only replaced the 12v on my Ford when the alternator went and took the battery with it.

Depends where you live and if you have harsh weather. Very hot or (very cold that limits battery output or worse).
Weather spark indicates you have quite mild temps.
Average Weather in Bradford, United Kingdom, Year Round - Weather Spark

 

[scottf200]

My point is that a "high" IR for a battery expected to deliver 250-500amps is different than an acceptable IR for a battery that only needs to deliver 20-40amps. Sealed lead acid (SLA) batteries are also typical for UPS systems for computers, etc. For a UPS to work, it typically needs to deliver moderate/high currents for seconds to a few minutes. Most UPS systems for PCs etc aren't expected to carry their load for more than 15-30minutes tops, usually much less. I often have to replace these batteries every 2-4 years.

But I then can take those "old, bad" SLAs and use them for other things, like running LED lights, etc where I only need 1 amp or less. These spent SLAs will be fine at smaller loads for years, even though their IRs are now too high for UPS usage. So I'm not sure that IR metrics and criteria established for ICE starter usage are applicable to the Tesla usage regime, although certainly IR is an important gauge of battery health.

Are you going to do anything proactives with your Tesal 12v or is your plan to just wait to see if a message shows on your Tesla screen?
How/what do you think they are testing in the 12v system/rail to know to put up a message? Clearly their method has not be accurate in many cases. I plan on monitoring my IR (especially before a multi-week road trip) unless there is a better way.

 

[EnrgyNDpndnce]

No, you'd jumpstart the car, drive to the auto parts store, and replace the battery in the parking lot.

And this is EXACTLY what you’d do in a Tesla as well. And if for some reason the jump start doesn’t work (which btw happens occasionally in all cars) you find other transportation to the auto parts store (friend, uber, etc), buy the battery, bring it home and install it. This is basic problem solving. I can’t for the life of me understand why we have so many threads on the 12V giving up the ghost. They die in all cars, replace it and move on. And if your car is still under warranty when it dies and Tesla says it will be a week before they can get to you, replace it and save the receipt then submit that to Tesla for reimbursement. Maybe they pay for it, maybe not. But we’re talking about a $200 part not a $2k part.

 

[toolman335]

And this is EXACTLY what you’d do in a Tesla as well. And if for some reason the jump start doesn’t work (which btw happens occasionally in all cars) you find other transportation to the auto parts store (friend, uber, etc), buy the battery, bring it home and install it. This is basic problem solving. I can’t for the life of me understand why we have so many threads on the 12V giving up the ghost. They die in all cars, replace it and move on. And if your car is still under warranty when it dies and Tesla says it will be a week before they can get to you, replace it and save the receipt then submit that to Tesla for reimbursement. Maybe they pay for it, maybe not. But we’re talking about a $200 part not a $2k part.

This^^^^^
This guy got 79k out of a 12V battery? That's better than any car I've ever owned. I just had to replace my wife's battery AND alternator at 73,000. Do you think I'd rather pay for that or simply swap out the 12V in a Tesla?
I feel awful for those who have had these batteries die without warning and not many miles on the cars. Buy a cheap battery monitor and plug it in until the software update that includes 12V health is installed in the near future.
If you own a Tesla, you have to have a battery to open the frunk and have a portable jumpstarter. I have portable jumpstarters in all of my vehicles anyway(along with tire patch kits with mini air compressors).

 

[toolman335]

The portable jumpstarters weight nothing and don't take up any space(same with 9v battery to pop the frunk).

 

[cwerdna]

The portable jumpstarters weight nothing and don't take up any space(same with 9v battery to pop the frunk).

They may or may not work to actually get a Model 3 "started". I learned the hard way that the small cheap li-ion pack I mentioned at cheap 12 volt li-ion packs verified to jump start Bolt... (no longer at Amazon but is at DJS 40 DBPOWER 300A Peak 8000mAh Portable Car Jump Starter (Only for Gas Engine up to 2.5L) (Yellow) - Power Your Life and manual at https://avada.oss-us-west-1.aliyunc...wp-content/uploads/2018/07/DJS40-Manual-1.pdf) was NOT able to jump start my Leaf w/a dead 12 volt, despite its modest power demands to get it into READY mode.

I had to fall back to a large lead-based heavy 12 volt pack.

Given that, I'm not that confident it'll work when my Bolt's 12 volt bites the dust.

 

[webbah]

It’s nit the same

Not the same as a regular car battery. Car batteries are made for insanely high amp rates for a few seconds to power the starter motor, and then after that, 12v system (lights, radio, etc.) runs off of the alternator. A regular car battery lasts very long largely because it is so seldom used—starting the car, amd the odd case where the car accessories are on but the engine is not. Not the same as a Tesla, which has no alternator...it is the 12v battery’s job to power the entire 12v system, everything, at all times. Its job is different, and accordingly, it’s chemistry is different.

Tesla doesn't have an alternator in the classical sense, but it does have a DC-AC Inverter to power and charge the 12v battery when the car is awake, driving, etc.

I bought myself a bluetooth 12v battery monitor on Amazon with an iOS app that notifies me every time I approach the car within range the status of the 12v. And viewing the app I can see the state (charging, volts, etc).

I knew the issues with the OEM 12v's and planned on installing several 12v accessories that I run quite often even when the car is sleeping. Both of these pull ~5 watts. These are a Blackvue 900S HD dual channel dashcam with wifi remote viewing and also a Teltonika RUT850 automotive wifi router with LTE.

So I purchased an Ohmmu as it maintains a higher consistent voltage and lower drain rate vs the OEM lead acid. I'm fortunate in that I have not experienced any of the errors for 12v battery with my Ohmmu, but they have recently announced that updated revision 2 batteries will be ready in early October AND they will replace all existing batteries for owners. Stellar customer service that Tesla should take note of. ;-)

 

[RedModel3]

I keep a small portable jump starter in the unused tow hitch door of my 3 just in case this happens to me one day. I will pull it out, open my frunk, charge the batter, drive home.

They have waterproof ones but I just stuck mine in a plastic bag.

Could you post which one it is? Thx

 

[one2many]

And this is EXACTLY what you’d do in a Tesla as well. And if for some reason the jump start doesn’t work (which btw happens occasionally in all cars) you find other transportation to the auto parts store (friend, uber, etc), buy the battery, bring it home and install it. This is basic problem solving. I can’t for the life of me understand why we have so many threads on the 12V giving up the ghost. They die in all cars, replace it and move on. And if your car is still under warranty when it dies and Tesla says it will be a week before they can get to you, replace it and save the receipt then submit that to Tesla for reimbursement. Maybe they pay for it, maybe not. But we’re talking about a $200 part not a $2k part.

I do agree perhaps a little too much drama. I dated girls on hills for a long time because
my starter did not work, the old push start dates. Yes on very cold days the battery would die.
Had a shorted spark plug once, bearing froze on A/C unit, ate the fan belts, points, electronic
ignition units, bad seal shorted out my Mecerdes S class, broken gears on the rear end of a BMW,
had to use a hair dryer on the carb in cold weather (auto choke), flat tires, engine fires, timing belts,
and the list goes on. The best of all was the German fire department was called in because my gas
tank was leaking so they took my gas out of my tank and left me a note that I had no gas.

 

[scottf200]

... I bought myself a bluetooth 12v battery monitor on Amazon with an iOS app that notifies me every time I approach the car within range the status of the 12v. And viewing the app I can see the state (charging, volts, etc). ...

Thanks for that idea. It looks like this is the common one out there and it seems it is rebranded and sold but others (often at higher cost!).
https://smile.amazon.com/QUICKLYNKS-Battery-Monitor-Bluetooth-Device/dp/B01MT4583U

 

[webbah]

Thanks for that idea. It looks like this is the common one out there and it seems it is rebranded and sold but others (often at higher cost!).
https://smile.amazon.com/QUICKLYNKS-Battery-Monitor-Bluetooth-Device/dp/B01MT4583U

Yeah, that's the one. I bought one from AEG but it uses the same app and is essentially the same device. Easy to setup with the exception that the positive lead on the 12v is a little tricky to connect the clip and then put the red rubber cap/seal back. I bent the clip in an L shape and managed and also used some waterproof electrical tape to make sure it would stay in place.

 

[TheRFMan]

And how would you get to the latch if you are locked out of the car?

My understanding is that the car rolls down a window in cases of 12V failure, specifically so that you can get in-out of the car using the "emergency" door releases.

 

[Tjhappel]

@Tjhappel
How is this any different if your two ICE cars were blocking the driveway with a dead battery and you couldn't get the Tesla out ?? Would you send an "emergency roadside assistance" note to Toyota or BMW, or Honda and demand they rush over and change your dead 12v battery that was out of warranty ??

I could actually buy a battery and change it, when you call around to ALL local part suppliers and ask for a Tesla 12v battery they have no options. Do you not see the difference? I’m not trying to be bitchy here at all it’s just crazy 1- the difference from a few years ago with service and 2- that you get zero warning and your car in not movable.

I have owned a ton of cars and non perfect, tsla has been amazing it’s just really bad and weird when you can’t fix something yourself. And yes I know there’s a lot of people who can fix their own 12v and are super smart etc etc. I am apparently not

 

[Tjhappel]

That's a good question... Does AutoZone care what type of car it is?

Re: BMW, over-engineer yes, perhaps. Dealer's overcharging for "programming/registering a battery", sure. But my last BMW battery lasted 8-9 years, so maybe the engineering helps...

This is true in theory but in practice engineers are lazy. No one would buy an ICE vehicle that drained the 12V battery after parking for a day. With EVs you can just recharge it from the main battery when it gets low.

The real question is whether battery makers will honor their warranties when a battery is installed in a Tesla? AGM batteries seem to have 4 year free replacements.


No, you'd jumpstart the car, drive to the auto parts store, and replace the battery in the parking lot. On the BMW you'd hook up a scan tool to "register" the battery and curse BMW's ridiculous over-engineering of everything.

dan next time call me back man!