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"Proactive" 12v battery replacement - good idea or overkill?
- Thread starter joebruin77
- Start date
ODWms
Member
They changed mine out, under warranty, just on the strength of the battery warning less than a year ago.
I just don’t get it. 12v battery is a consumable on every car I’ve ever owned. I can’t tell you how many ICE cars I’ve owned have had batteries crap out unannounced. Why would we expect Tesla to upgrade? I know that they often replace as warranty or goodwill… but to me that is above and beyond.
2018 Model 3 owner here, my 12V died pretty gracefully recently and it seems tesla has done serious software tweaks to account for previous failures they saw. I got in the car in the morning and it said something along the lines of "12V battery failure energy consumption increased, contact service" so the car was basically no longer allowing itself to go into sleep mode and use the 12V system to disconnect the high voltage system. Coming from my previous ICE cars that consumed a 12V about every 2-4 years I went to the nearest AutoZone after doing some research on the 12V battery type and purchased a new 12V battery and swapped it myself. The only issue I ran into was the car refusing to power down since it was trying to keep the 12V system active (Even without the 12V battery present). Once I got the car powered down and HV to fully disconnect I did the swap and returned the old battery to get the core charge back. So far no issues and the car wakes up from sleep way faster now. I honestly am surprised Tesla will even do the battery swap for free seeing as it is a consumable item.
danarcha
Member
What type of battery did you purchase from AutoZone. Was it a deep-cycle battery or just any 51R type?
Well for me, I've never had a car battery last less than 6 or 7 years, so a failure at 2 (or within the 4 year warranty period) is unacceptable to me.
At least for ice cars I have owned, high heat kills 12v batteries. Lived in Dallas Tx and mine and friends batteries all died within 2 years. Living in Seattle with moderate temps, last 4 to 5 years. Posted this on another battery thread, and a reply said the Tesla 12v battery was AGM and this didn’t apply. Seems like conflicting info on this. Is it AGM or regular leaf acid? Either way, see plenty of responses here saying died after 2 or 3 years.
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android04
Active Member
It's unknown for sure if it's AGM, but it likely is not because the manufacturer's catalog lists it with a part name that does not follow their convention for AGM batteries. The way they list it has "MF" in the name, which means that it is likely a conventional maintenance-free battery. I know that I plan on opening mine up when it dies in order to find out for sure (coming up on it being 4 years old).
Well, they did swap mine out under warranty (2018 Model 3).
Yeah, all my previous cars typically made it 5-7 years as well before dying.
But the loads that Tesla is putting on the 12V battery is actually pretty harsh because lead-acids do not like sitting around partially charged and there seems to be a decent amount of vampire drain to keep the cellular and wifi radios / microcontrollers on. AGM batteries do better than flooded, but it's still hard on them. Lithium batteries are far better here since they last longest at lower states of charge. Even if it only makes it 10 years between replacements, that's a lot easier to digest and it should be easier to predict the death of it as well.
stopcrazypp
Well-Known Member
Yeah, heavy vampire loads are not good for lead acid batteries. They much rather sit close to fully charged all the time and then occasionally do a discharge (basically like for traditional car starting applications). They also can fail suddenly. Lithium-ion batteries tend to die more gradually, so much easier to warn the user. But lead acid batteries are much cheaper compared to lithium ion, so purely on parts, they typically still end up cheaper (although if you add in costs of inconvenience and labor, it might not be).
It'd be interesting to analyze Tesla's cost of it's lithium battery replacement - it's tiny at 99 Wh compared your typical lithium lead-acid replacement. The cost could be comparable with Tesla's manufacturing scale. I see some 120 Wh LFP batteries down around $85/ea in bulk retail, pretty comparable to lead-acid.
I swapped mine out about a month ago. Didn't want to risk having a problem where I'm left stranded. Like others have said, cheap insurance. Walked into my nearest SC service bay and asked for a battery, paid my $8x.xx, it was that simple. Swapped it out at home in about 10 minutes.
I'm the type that proactively replaces batteries in my ICE cars as well. After about 2 years, I do some homegrown "load tests" involving cranking the engine after leaving lights and other stuff on for 30-45 minutes. If it still sounds healthy, it gets fully re-charged and stays in the car, if it slow cranks or sounds weak, it gets recharged then its off to the store to get it tested properly. More often than not, I leave with a warranty/prorated replacement because the old battery is considered bad. Yes, it probably would've held on for another year or more, but why risk it? For the record, no car of mine has needed a jump in 20+ years. I just consider battery testing/terminal cleaning/replacement part of the deal and never wait until the day it doesn't start. Plus, your car battery is also your backup power in the event your alternator fails. It *SHOULD* be able to run your car, headlights and all, for up to 2 hours to get you home. Can't do that if it only has enough juice to crank the motor for short while.
For the record, I did a discharge test on my old Tesla 12V and was able to extract 90%+ of the rated Ah's out of it (20 hour rate) before I stopped the test to protect the battery, so the battery is still good. I recharged it and am hanging on to it as a spare for now. So some would say I wasted time and money replacing it. I'd say I bought myself the confidence to drive my 3 another 2.5 years without thinking about the 12V battery going bad. All for the price of a tank of gas.
I'm the type that proactively replaces batteries in my ICE cars as well. After about 2 years, I do some homegrown "load tests" involving cranking the engine after leaving lights and other stuff on for 30-45 minutes. If it still sounds healthy, it gets fully re-charged and stays in the car, if it slow cranks or sounds weak, it gets recharged then its off to the store to get it tested properly. More often than not, I leave with a warranty/prorated replacement because the old battery is considered bad. Yes, it probably would've held on for another year or more, but why risk it? For the record, no car of mine has needed a jump in 20+ years. I just consider battery testing/terminal cleaning/replacement part of the deal and never wait until the day it doesn't start. Plus, your car battery is also your backup power in the event your alternator fails. It *SHOULD* be able to run your car, headlights and all, for up to 2 hours to get you home. Can't do that if it only has enough juice to crank the motor for short while.
For the record, I did a discharge test on my old Tesla 12V and was able to extract 90%+ of the rated Ah's out of it (20 hour rate) before I stopped the test to protect the battery, so the battery is still good. I recharged it and am hanging on to it as a spare for now. So some would say I wasted time and money replacing it. I'd say I bought myself the confidence to drive my 3 another 2.5 years without thinking about the 12V battery going bad. All for the price of a tank of gas.
I have a few friends who complain about the cost of a 12 volt battery.. same guys that have spent several thousand on suspension upgrades like Coilovers and such to feel like a track car.. I also had a friend who was bragging about his ti bolts for his bike that cost a few hundred bucks.. to save a few oz. whereas losing a pound or two would have been easier and cheaper. Misplaced priorities. Pretty human failing 
A tank of gas! Oh, right, you're in California.
I just paid $4.03 a gallon here in my part of Maine for ethanol free gas to power my snow blower. It was around $3 early last year the last time I bought gas.
smatthew
Active Member
To a lithium ion? No way.
Requires a new wiper fluid pump. and replacing part of a harness.
ODWms
Member
I can attest to 2 years being the case for me. Luckily I got the warning, scheduled the appointment and Tesla replaced free of charge. My understanding is that they have improved the battery and tech even more, so maybe it’ll last longer this time?
smatthew
Active Member
I replaced the 12V before my winter holiday trip in December. 12V was 3 years old, and I was going to be spending two weeks in Oregon and Washington with decently cold weather. Decided it wasn't worth the risk, so $85 later.....
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