Another 12v battery bites the dust

[jongt3]

I had the warning pop up this morning. Service center said it will be fine to drive, but they will "pull the logs" and will call back to make an appointment to replace it. The car has 14k miles on it. Took delivery July 2013 and had it's annual service in August 2014.

I was really surprised until I came here and found this thread! Hopefully the replacement battery will last longer.

 

[Cottonwood]

I had the warning pop up this morning. Service center said it will be fine to drive, but they will "pull the logs" and will call back to make an appointment to replace it. The car has 14k miles on it. Took delivery July 2013 and had it's annual service in August 2014.

I was really surprised until I came here and found this thread! Hopefully the replacement battery will last longer.

I don't think there is any cost effective battery that can withstand the current Vampire. (pun intended) Until Tesla drives a stake through the heart of the Vampire, it will continue to suck the life of the 12V batteries. Hopefully, Tesla has the warning messages calibrated, so that no one gets stranded, and 12V batteries are just a consumable for now.

 

[martinwinlow]

Can someone tell me if the 'vampire load' (VL) is supplied by an EVSE if connected or does it always come out of the 12V auxilliary battery? I think I know the answer is 'Yes, it always comes out of the aux battery' but if the car is connected to an EVSE will the VL still drain the aux battery or is it constantly topped up by EVSE power? If it is, surely this would prevent the aux battery failing so quickly? MW

 

[jerry33]

Can someone tell me if the 'vampire load' (VL) is supplied by an EVSE if connected or does it always come out of the 12V auxilliary battery? I think I know the answer is 'Yes, it always comes out of the aux battery' but if the car is connected to an EVSE will the VL still drain the aux battery or is it constantly topped up by EVSE power? If it is, surely this would prevent the aux battery failing so quickly? MW

There is not a separate circuit to the wall outlet, so the path is: Wall -> Charge Port -> Charger -> Traction battery -> DC-DC converter -> 12V battery and Accessories.

 

[JRP3]

The idea of "cycling" the 12V battery seems odd. It should not be getting "cycled" more than over a very small DOD. Keeping it topped off between say 12.7 and 13.2V should take no more energy than letting it go down to 12.4 and charging back up to 13.2V, or whatever Tesla is doing. Shallow cycling and keeping it at a higher SOC should greatly extend the life, essentially like keeping a 12V battery on a trickle charger.

 

[Cottonwood]

The idea of "cycling" the 12V battery seems odd. It should not be getting "cycled" more than over a very small DOD. Keeping it topped off between say 12.7 and 13.2V should take no more energy than letting it go down to 12.4 and charging back up to 13.2V, or whatever Tesla is doing. Shallow cycling and keeping it at a higher SOC should greatly extend the life, essentially like keeping a 12V battery on a trickle charger.

It is a widely held belief that many shallow discharges are less harmful than a few deep discharges. That may be true for starter batteries with thin plates, but at least for the deep cycle battery that had a spec sheet showing cycle life vs depth of discharge, the Trojan T-105RE, it was a wash. See below 4,000*20% = 800*100%, etc.

Tesla uses good, deep-cycle, AGM, lead-acid batteries in the MS. The T-105RE is a flooded, lead-acid, battery, but the chemistry is the same.

 

[JRP3]

Interesting chart. If it holds true for the Tesla battery then it suggests a real need for lithium titanate or LiFePO4.

 

[SteveS0353]

Interesting chart. If it holds true for the Tesla battery then it suggests a real need for lithium titanate or LiFePO4.

Or a significant reduction in vampire load to reduce the stress on an inexpensive 12V lead-acid battery.

 

[bluenation]

excuse my ignorance...why isn't the main batt used in place of the lead acid's functions? is it the fast disrcharge rate?

 

[SteveS0353]

excuse my ignorance...why isn't the main batt used in place of the lead acid's functions? is it the fast disrcharge rate?

I believe it's a safety issue. The traction battery contains dangerous high voltages (HV), and there a high current contactor to isolate the HV inside the pack. The contactor is controlled by the low voltage 12V system. First responders can simply sever the 12V connection to isolate the HV inside the traction pack. The 12V battery is charged by a DC-DC converter from the HV traction battery from time to time, but the 12V runs most of the on-board systems (vampire load = CPUs, 3G, WiFi, BlueTooth radios, key-fob pings, etc etc etc).

 

[caddieo]

I had the warning pop up this morning. Service center said it will be fine to drive, but they will "pull the logs" and will call back to make an appointment to replace it. The car has 14k miles on it. Took delivery July 2013 and had it's annual service in August 2014.

I was really surprised until I came here and found this thread! Hopefully the replacement battery will last longer.

We're in the same boat. I also have a July 2013 car, have almost 15 K miles on it and had my annual service July 2014. The message popped up a couple of days ago and the Longwood SC said I could continue to drive it until the new battery arrives and they call me in for replacement. Based on what I have read in other threads, I have switched from scheduled charging to continuous trickle charge at 10 amps so that there is shore power always available and running. I now keep it plugged in even in between errands. Somebody correct me if I am wrong to do it this way.

 

[glhs272]

We're in the same boat. I also have a July 2013 car, have almost 15 K miles on it and had my annual service July 2014. The message popped up a couple of days ago and the Longwood SC said I could continue to drive it until the new battery arrives and they call me in for replacement. Based on what I have read in other threads, I have switched from scheduled charging to continuous trickle charge at 10 amps so that there is shore power always available and running. I now keep it plugged in even in between errands. Somebody correct me if I am wrong to do it this way.

Not sure how that helps you. The 12 volt battery is charged exclusive through the high voltage battery via the DC to DC converter, regardless if the shore power is on or off.

 

[caddieo]

Not sure how that helps you. The 12 volt battery is charged exclusive through the high voltage battery via the DC to DC converter, regardless if the shore power is on or off.

OK. Thanks.

 

[Jaff]

Many Roadster owners replace their 12v battery every year when the annual service is performed...it gives you "peace of mind " at a relatively low cost...

Bottom Line: Be sure TM installs a NEW Battery every 12 months since there will be no magic 12v solution appearing any time soon.
--

 

[Zzzz...]

excuse my ignorance...why isn't the main batt used in place of the lead acid's functions? is it the fast disrcharge rate?

Well, it is possible to make a compartment within main battery pack consisting of few dozens cells that would produce close to 12V. Or simply replace lead acid battery with the one based around cells that are used in main battery.
It would be cheaper, and Tesla owners will forget about replacing 12V battery.
Problem is that such battery would have voltage range slightly different from lead acid battery. Even if li-ion cells would be cycled between 2.9V-3.5V max output voltage(4x) would be 14V instead of 12V. This itself is not a huge problem, but Tesla buy parts from automotive suppliers that are designed and certified to operate at voltage supplied by 12V lead acid batteries. Think of windshield wipers motors, HVAC electronics, car control electronics, power windows etc etc. There are many dozens parts that are mass produced and rely on 12V range. Most parts would work but without certification Tesla would not get warranty coverage / would run into potential problems with liabilities etc.

Tesla volume is too miniscule to update big part of automotive supply chain to make such battery a reality. Reward is a nice one: lighter weight, cheaper and way more reliable low voltage battery. But obstacles are very real unfortunately.

 

[JRP3]

That's not accurate. All "12V" car accessories operate at alternator output voltage, which can be between 13V and 15V. Up to 16V is probably not an issue for 12V accessories, which 4 NCA cells would hit if charged to 4V, (of course they could be under charged further), but 4 LiFepo4 cells or lithium titanate cells would operate around 12-14.4V.* As I type this I'm charging 5 "12V" batteries each made up of 4 LiFePO4 cells using "12V" lead acid chargers.

*Actually I misspoke about lithium titanate, you'd need 5 or 6 cells, depending on how close you wanted to get to 12V or 14V.

As for tapping into "12V" worth of cells from the traction pack, it's a bad idea since that group of cells would cycle more heavily, go out of balance, and experience more wear, leading to even more imbalances.

 

[omarsultan]

Add me to the list - July 2013 build, this is the first real service issue I have had in 43K miles. I called my SvC - they said once the warning comes up, you have a couple of weeks to get it fixed. Nonetheless, they sent a ranger out the next day and swapped it out - no drama.

I wonder if this was the battery swapping Elon was really talking about? :wink:

 

[Zzzz...]

That's not accurate. All "12V" car accessories operate at alternator output voltage, which can be between 13V and 15V. Up to 16V is probably not an issue for 12V accessories, which 4 NCA cells would hit if charged to 4V, (of course they could be under charged further), but 4 LiFepo4 cells or lithium titanate cells would operate around 12-14.4V. As I type this I'm charging 5 "12V" batteries each made up of 4 LiFePO4 cells using "12V" lead acid chargers.

As I said, QUOTE: "...Most parts would work but without certification ..." <--- notice certification part. And yeah, I agree with you, hardware itself most likely would NOT need to be changed. But automotive suppliers are/would be VERY reluctant to give same price for volume produced parts if even slight deviation from certified mode of operation is taking place.

Problem is not technological possibility, but inertia of an industry. Besides, only in recent years price of li-ion became comparable to lead-acid. Yes Tesla would benefit from switch financially right away (getting high specific energy cells in high volume already), but for the rest of the industry switch is not an obvious one.

PS. lifepo4 or titanate could not compete with NCA or lead acid on price basis. But I'm sure you quite aware of that.

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As for tapping into "12V" worth of cells from the traction pack, it's a bad idea since that group of cells would cycle more heavily, go out of balance, and experience more wear, leading to even more imbalances.

I agree, making physically separate low voltage battery instead of separate and totally independent part of main pack most likely makes more sense. But I'm not quite sure that those cells cycle more heavily. But you could be very well right about it.

 

[JRP3]

As I said, QUOTE: "...Most parts would work but without certification ..." <--- notice certification part.

I'm suggesting they may already be certified for that voltage.

Problem is not technological possibility, but inertia of an industry. Besides, only in recent years price of li-ion became comparable to lead-acid. Yes Tesla would benefit from switch financially right away (getting high specific energy cells in high volume already), but for the rest of the industry switch is not an obvious one.

PS. lifepo4 or titanate could not compete with NCA or lead acid on price basis. But I'm sure you quite aware of that.

Upfront costs, no, but actual lifetime costs, I think at least LiFePO4 is already cheaper than a good AGM battery.
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But I'm not quite sure that those cells cycle more heavily. But you could be very well right about it.

Since they would see traction loads as well as 12V loads they would have to cycle more frequently and under greater load than the rest of the pack.

 

[TexasEV]

Add me to the list - July 2013 build, this is the first real service issue I have had in 43K miles. I called my SvC - they said once the warning comes up, you have a couple of weeks to get it fixed. Nonetheless, they sent a ranger out the next day and swapped it out - no drama.

I wonder if this was the battery swapping Elon was really talking about? :wink:

Me too. July 2013 build, all was good at annual service (a few weeks late, in August), then when I had error message the following week that a software update didn't complete the service center checked the logs and said they needed to replace my 12V, which they came out to do the next day.