heat does kill a 12V battery over time... but a 12V battery resides in the *hot* engine bay of an ICE car and doesn't die within 2+ yrs either. And those engine bays are hotter than even a Model 3 parked in the Texas sun will get under the hood
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"Proactive" 12v battery replacement - good idea or overkill?
- Thread starter joebruin77
- Start date
That's astoundingly short lifespan for a car battery. Could it be that Tesla used a cheap battery for earlier cars?
Lots of ICE batteries are not under the hood. I had a BMW whose original battery lasted 13 years and was still going when I sold it. It was in the trunk. Plus, it's continuous heat that kills them. 1 hour at 150F under the hood is not worse than 12 hours at 100F just because it's 100F out. So the overall ambient temperature in the place you live matters a lot.
You're assuming it's the battery quality, but you can kill the most expensive battery in one day if you over charge it or over-discharge it. The most likely reason for the short lifespan is the way Tesla used and managed the batteries, not the manufacturing quality of the battery. This is supported by the fact that they appear to have highly increased the life of the battery via firmware updates. Remember, a Tesla doesn't use the 12V battery in a way that is similar at all to an ICE car. The reason the 12V battery is there is to allow you do do things like unlock your car via an app, so it's used all the time at a low level, and recharged constantly vs an ICE battery that really doesn't do anything until you are cranking the engine and is only recharged while the engine is running.
But we're all also assuming the story of "they all only last 1.5 years" is universally true, which it isn't. Lots of people have 5+ year old batteries in their Teslas, and even 50% of the batteries described lasted 2.5 years, it was just supposedly "surprising" that it did.
FloridaGary
Member
My personal average for Non EV 12v batteries in Florida has been 3 years which of course heat plays a factor. I never received a reason why Tesla's batteries were only getting 1-1/2 years, but it may have something to do with the 12v battery cycling more frequently. I believe this issue goes back to 2012, but my first Tesla was a 2015 Model S. It also had 2 batteries within 3 years. I was glad to see Tesla now placing 12v Lithium Ion batteries in their vehicles.
Ahh yes, because a tiny, mismanaged Li-Ion couldn't be killed in a year either.
You can kill a Li-Ion in one charge if you charge it below 0F. They are much more complex to manage.
The 12V lead-acid batteries having a low lifetime seems to be a common problem among many EVs, not just Tesla. Definitely the case with BMW i3. I suspect the Teslas incur an even higher accessory battery load than other EVs because of the computer demands and features.
Maybe the reality is that lead-acid batteries just aren't very good and the normal EV use as accessory is draining them much more than a conventional ICE car, particularly if HVAC and computers are used when car is not "on". Also I read somewhere that the intermittent high discharge for lead-acid, as used in ICE starting, can be good for their chemical longevity unlike lithium ion.
if HVAC is running - main battery pack is actively "on" and car doesn't sleep. Same with sentry mode which requires the computer to constantly run - battery pack is also "on".
I did, at four years, now coming on 8 years on my MS.
Also getting familiar with front 12v hookup opening procedure and carrying a 12v jump starter
permanently plugged into an USB in car can only help things in case xxxx, as Chris Rock said.
Also getting familiar with front 12v hookup opening procedure and carrying a 12v jump starter
permanently plugged into an USB in car can only help things in case xxxx, as Chris Rock said.
I am in Texas, my 2017 MS 12V still works fine. SC says wait till warnings to replace it, though I am thinking replacing it proactively.
I replaced mine a few months back and it gave me plenty of notice. I think I got both a you should replace soon and a its bad some things wont work message before I did it. That said I couldnt get a replacement through normal auto shops and ended up having mobile service do it. I lost a day of work but at least they did it for no charge.
Nosken
Active Member
My 2015 P85D, two year and 56,000 miles-No battery replacement when turned in on lease. 2016 90D My battery final went out after 5 years and 120,000 miles, all in HOT Sacramento Summers and COLD Tahoe Winters. I attribute the longevity to consistently having the car plugged in.
metroplex
Gearhead
I've never had a 12V flooded lead-acid battery give ample warnings when it failed in the past 25+ years. They'd always just give up the ghost straight away. The higher the probability of me being stranded, the higher the chance it will fail, without question!
There were only 2 exceptions. One was my 2014 SHO with its factory battery dying after about 1.5 years of use. I went to remote start it in the garage and it just clicked flashing some lights. Turns out the battery died. Luckily I had a second vehicle and pulled the dead battery to get a new one on the spot.
The other time was my 2009 Cobalt SS turbo with its factory trunk mounted Group 90/T5. It was the original factory battery from 2008 and the year was 2020, so 12 years on the original factory battery wasn't too shabby. I had driven it 30 miles and it was fully warmed up. Shut it down on the driveway to cool off a bit, then went to do a hot restart. BOOM. Something in the trunk exploded with enough force that I could feel it through the seats. I popped the trunk and battery acid fumes were everywhere. Soaked the trunk area big time. Case was cracked and I could see the plates. Went to replace it, and cleaned the area with baking soda and water. I believe this battery failed due to the desulfating charger I had on it for a few years prior. Normally I just stick with Deltan's Battery Tender and in retrospect should have just stuck with it instead of experimenting with different brands. The Battery Tender maintains a 12V flooded battery at 13.1-13.2 VDC at 50mA-150mA. This is totally safe to leave indefinitely. Other brands tend to cycle up to 14.2 or maintain at 14.2!
I was told on Tesla to just use the high voltage charger and the car has an onboard maintainer for the 12V low-voltage. I see on 2022's Tesla switched to a CATL 15V LFP low-voltage battery (14.8 VDC).
This type of low-voltage battery isn't new. LFP/LiFePO4 batteries for motorcycles have been used for more than a decade, and they generally still last only 2-5 years. Shorai, Anti-Gravity, etc... are popular LFP brands.
There were only 2 exceptions. One was my 2014 SHO with its factory battery dying after about 1.5 years of use. I went to remote start it in the garage and it just clicked flashing some lights. Turns out the battery died. Luckily I had a second vehicle and pulled the dead battery to get a new one on the spot.
The other time was my 2009 Cobalt SS turbo with its factory trunk mounted Group 90/T5. It was the original factory battery from 2008 and the year was 2020, so 12 years on the original factory battery wasn't too shabby. I had driven it 30 miles and it was fully warmed up. Shut it down on the driveway to cool off a bit, then went to do a hot restart. BOOM. Something in the trunk exploded with enough force that I could feel it through the seats. I popped the trunk and battery acid fumes were everywhere. Soaked the trunk area big time. Case was cracked and I could see the plates. Went to replace it, and cleaned the area with baking soda and water. I believe this battery failed due to the desulfating charger I had on it for a few years prior. Normally I just stick with Deltan's Battery Tender and in retrospect should have just stuck with it instead of experimenting with different brands. The Battery Tender maintains a 12V flooded battery at 13.1-13.2 VDC at 50mA-150mA. This is totally safe to leave indefinitely. Other brands tend to cycle up to 14.2 or maintain at 14.2!
I was told on Tesla to just use the high voltage charger and the car has an onboard maintainer for the 12V low-voltage. I see on 2022's Tesla switched to a CATL 15V LFP low-voltage battery (14.8 VDC).
This type of low-voltage battery isn't new. LFP/LiFePO4 batteries for motorcycles have been used for more than a decade, and they generally still last only 2-5 years. Shorai, Anti-Gravity, etc... are popular LFP brands.
You've never had a car before that runs an active, smart, computer controlled charge and discharge cycle on the battery when the car is off though. Everything before is just a dumb alternator. On the Tesla you aren't waiting for the battery to warn you, you are waiting for the battery tester to warn you.
Again, with a dumb, fixed voltage alternator (or even worse on most motorcycles), not a current limited, smart charger. But of course, that smart charger is also much more likely to detect a LFP battery as "broken" because it IS a broken Lead Acid.
metroplex
Gearhead
The alternators I'm using on my Fords are computer controlled. Like the 230A in my Ford Explorer. They may not be the latest and greatest, but the ECU has controls for the regulator and an on-board battery management system. Ford has used this system for well over 10 years now. These aren't your old set-point alternator. You can change the setting for flooded lead-acid or AGM lead-acid. I can also adjust the temperature compensation charging voltage as well. BMS also monitors SOC, time in service, etc... You can't just replace a battery in a Ford now, because after a few months it will give you a low voltage warning. You need to reset the BMS when you replace the battery, etc... Not the latest and greatest tech, but a bit more advanced than a 60A alternator from the 1980s.
I bought a Rick's Lithium MOSFET regulator for my Ducati to run a Shorai LFP. The set-point is lower for the LFP battery (14VDC) instead of 14.5 VDC for flooded. It's not high-tech but the LFP is smaller and lighter, and packs a significant punch for cold starts.
I understand what you're saying about the charge/discharge for the Tesla though, but I've read several reports of Tesla owners with dead batteries that never received any prior warning. I suppose with the new CATL 14.8V LFP, it might be more precise.
Read around thread more. Yes, that used to happen. Tesla significantly updated their detection methods about 6 months ago, which catches bad batteries earlier, and when the detection happens changes how the car operates such that it doesn't need a 12V during that time at the cost of much higher vampire drain. This new algorithm also catches brand new LFP batteries as bad because they don't work like LFP batteries, but that itself is proof the algorithm is working in a way it didn't used to.
There are people that say it's still happening, but they weirdly can't point to any cases of it.
As for smart charging, the charging in a Tesla is limited to 8A, and the voltage of the "12V" battery can be completely independent of the "12V" rail for the rest of the car. That's what I mean by "dumb" alternator- the Tesla DC/DC can completely independently manage the lead acid and current in/out without changing voltage for the whole car.
metroplex
Gearhead
So how do we know if the particular Tesla has the "updated" battery management software? Was it a hardware change, or just software?
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