Nov 2, 2014
dpodoll Got a warning on the screen to notify service that I had a 12v battery issue. Took it in, and they replaced it. This is my second replacement in about a year and a half. I thought this was something that had been solved, but maybe not. Replacing every year sounds like there is still an engineering or supply issue.�
Nov 2, 2014
EarlyAdopter When was your first replacement done?
Mine was back in April, funny enough the day after they mentioned the problem on their earnings call. At that point they had not yet switched suppliers, so the replacement was a better qualified/tested version of the same battery, from the original supplier. A month or two later all batteries started being sourced from a different, better supplier.�
Nov 2, 2014
tezco I was told the new ones were more of a deep cycle type.�
Nov 2, 2014
dpodoll First one was April or May 2013�
Nov 2, 2014
EarlyAdopter Yep, same here. I'm guessing we both got replacement original batteries.
Haven't been hearing of any failures of the new ones since. You should be good to go with the new replacement.�
Nov 2, 2014
pgiralt I got my car in August 2013 and just had the same issue last month. Warning popped up saying 12V needs service and they replaced it for me. Seems like the battery lasted about a year for me as well.�
Nov 3, 2014
TexasEV My VIN is within a few digits of yours and the service center proactively replaced my 12V battery last month. I didn't get a warning, but they saw something wrong when they were checking the logs about a message that a download didn't complete.�
Nov 3, 2014
AmpedRealtor If it helps, I took delivery in August of 2013 and have had no 12v issues.�
Nov 3, 2014
glhs272 Me too.�
Nov 3, 2014
Cottonwood If you count the swap done just before my delivery, I have had 3 replacements, and am on my 4th 12V battery in a little over 2 years.
Let's face it, the current design of the Tesla is really hard on the 12V batteries. The vampire is literally sucking the blood out of them. Every one of those discharge/charge cycles feeding the vampire sucks a little life out of the 12V battery. Suck enough blood (battery cycles), and the 12V battery dies... It used to be worse, but until Tesla tames the vampire load, the MS will continue to eat 12V batteries.
Does Tesla even use temperature compensation for the 12V charge Voltages? For constant use, deep cycle applications, temperature compensation can add greatly to battery life; charge Voltages on a 12V lead-acid battery change -0.3V/10?C, leading to undercharging in the winter and overcharging in the summer if not compensated.�
Nov 3, 2014
yobigd20 does anybody know the exact 12V battery make/model they use? just curious so I could look up specs. I've been wanted to put an aftermarket amp/sub in but my concern is the affect it would have on the 12V battery and not sure it can handle it another amp sucking juice (though I know many others here have already done this and I haven't heard of any problems yet...)�
Nov 3, 2014
UberEV1 Me three (knock on wood)�
Nov 6, 2014
kevincwelch Sigh..... (again)
�
Nov 6, 2014
yobigd20 nice overall avg Wh/mi. are there any cars you haven't smoked off the line?
�
Nov 6, 2014
kevincwelch I think they all smoke me.�
Nov 10, 2014
yoyodyne another bad 12v
My warning came on last week when I was out of town. Tesla service called to arrange an appointment for replacement. It will be my second replacement in 16 months. I'm not sure the exact date of the first replacement but probably about a year ago..�
Nov 18, 2014
kevincwelch A Tesla Ranger came out to my house to replace the 12V battery today. Was at my door at 7:30 and gone by 9:00a. Totally convenient for me. I was not charged for the Ranger service; it seems as through Chicago has been pretty busy with cars in their service center.
Thanks, Tesla!�
Nov 18, 2014
SteveS0353
I'm with you. I believe vampire load is certainly the main underlying reliability issue with the 12V battery. A "better battery" (deep cycle, high quality,...) will help delay the eventual wear out, but it's inevitable under the prevailing vampire load. My particular vehicle is losing of the order of 5 to 7 miles per day, which amounts to somewhere between 1 and 2kWh of energy. That�s consistent with other owners on the forums � some more, some less. Taking the low end of the vampire load, that's equivalent to 1,000 watt hours per day / 24 hours per day = 40W continuous. It amounts to 3.5A continuously from the 12V battery to power the electronics. That's HUGE, and frankly, disgraceful, for the high tech marvel of modern engineering that is the Model S. Modern electronics, in a well designed system, with competent software should be able to achieve an order of magnitude less vampire drain than that. Until that is addressed, I believe we'll continue to see premature wear out and replacement of 12V batteries in the field.�
Nov 18, 2014
Nathan Smith I had the 12V battery warning on Saturday... Tesla was out on Sunday to do the replacement :smile:. Unfortunately, we noted some cabin heating problems and plug acting flacky (car wouldn't lock the plug when it was inserted). So they are coming to pick it up Friday - 3rd time my car will be taken away and I will be driving an Enterprise rental. Asked about a loaner, and was told none were available especially since Tesla is busy selling them all.�
Nov 18, 2014
loganss I recently had my 12V battery replaced as well. I don't recall it ever getting replaced before. My car was delivered 2/2013.
Mine was an odd situation. On 11/6 I dropped my car off to get a faulty TPMS sensor replaced and when I get to the service center and they are about to start the car the 12V message comes on and poof the car can't start. They had to push it into the shop. Good thing it happened at the shop. Turns out there was some sort of problem with my main battery pack that caused and issue with the 12V.
Are these recent 12V issues possibly related to Version 6 of the software?�
Nov 18, 2014
techmaven I disagree. A common set top box can be 50-100 watts continuous. The Tesla BMS is always running. I'd rather sacrifice 40 watts continuous rather than have a problem with the $20k big battery due to inattention. Yes, it would be nice for it to be lower. I actually lose <1kWh per day. Also, at the some point, the electronics are supposed to wake up the big battery and charge the 12v battery. It is possible that a bad 12v battery causes the big pack to wake up more often and charge it, which can accentuate the apparent vampire draw. What is embarrassing for Tesla is the failures in the DC-to-DC charging circuitry and the 12v battery quality issues. They should be able to monitor and proactively replace these without waiting until actual failure (preferably through on-board software that detects a bad pattern and alerts the owner).�
Nov 18, 2014
SteveS0353 Lazy design (HW & SW) often leads to power inefficient systems. A STB is wall powered -- who cares how much it consumes. Any battery powered system, albeit with a HUGE battery like the Model S, requires careful attention to detail to minimize power. Yes, the BMS is always running, and that should come under the same scrutiny for power. I agree protecting the big expensive HV pack is the priority, but I still maintain that the vampire load can be 10 times lower and still get the job done.�
Nov 19, 2014
scottm Putting a fresh 12v battery in every year is like what, price of an oil change? Meh.
call it regular maintenance�
Nov 19, 2014
CHG-ON Does anybody have any input on what the best replacement battery would be? Thanks.�
Nov 19, 2014
scottm
Ohh I am just guessing here, but a solar power storage battery or marine deep cycle battery would probably do nicely.
OR, just get a Costco battery in the largest format that fits the space, and get free replacements if she dies within 30 months or whatever the guarantee is, no cost to you. It is a vehicle application, there should be no arguments.
Anybody know the nearest "group size" of Tesla 12 volter?�
Nov 20, 2014
Cottonwood I forgot the brand, but Tesla uses a very good, deep cycle, AGM battery; the vampire still sucks the life out of them in a year or two.�
Nov 20, 2014
Matias Tesla advertises, that Model S needs less regular maintenance than ICE-cars.
- - - Updated - - -
it doesn't need to be. It could go to sleep for 0.9 seconds and then wake up for 0.1 seconds and then go back to sleep for 0.9 seconds during stand by. This is normal behaviour for many battery powered electronics in stand by mode. This would cut stand by consumption by 90%.�
Nov 20, 2014
SteveS0353 Duty-cycling is one of many techniques for reducing power consumption, and the power saving is indeed a linear function of duty cycle. When they are not being used, it's possible to duty-cycle radios, sensors, CPUs, ..., anything really. I don't subscribe to the position that replacing the 12V battery after a year or two is regular maintenance. Those deep-cycle AGM batteries should remain viable far longer, and probably would if the vampire load / recharge cycles were not so aggressive.�
Nov 20, 2014
Jaff A lot of Roadster owners do this...
�
Nov 20, 2014
SteveS0353 The cost and inconvenience of regularly changing the 12V battery is not the issue. My biggest beef with the vampire load / 12V battery issue is that I would have expected a much more elegant design for a vehicle which sets new standards in just about every category. It's not that the Model S is otherwise perfect, there are certainly many opportunities for improvement, and they will be doing that with software releases over time, but the engineer in me cringes when I know the vampire load can be tamed.�
Nov 20, 2014
techmaven Well, maybe Tesla should put together a lithium ion based 12v battery that has far higher cycle life. There are a lot of AGM 12v batteries that are really not designed for a high number of duty cycles - most car batteries for instance. They are designed to have a large burst of energy but almost never cycle down very far. Tesla's 12v application lifecycle is much more like solar batteries. If you tried to stick an automotive 12v battery on an off-grid solar system, you'd have dead batteries pretty quick. At this point, Tesla should be putting in batteries that can last years, even with significant vampire drain. After all, that is basically what a lead acid off-grid solar system does and those batteries will last for more than a year.
Yes, it would be *very* nice if Tesla lowered the vampire drain even further. I suspect the wake up procedure is a nightmare. Of course, we have no clear idea of the what exactly is the big power draw while "asleep" and the various people I've spoken to at Tesla about this situation haven't exactly known the answers. BMS was a frequent response.
This is also one of the reasons why I think we should be able to have a solar panel on the car. Most people think I'm talking about charging the main traction battery - no... I'm talking about helping out the 12v battery to power the BMS and run the systems that allow the Tesla app to function. Maybe, if there is extra juice, to run a fan to reduce cabin heat. At the very least, if the 12v system can be charged through the 12v accessory plug, we can add a solar charger there. However, that 12v outlet gets cut when the car goes to sleep.�
Nov 20, 2014
Oyvind.H Many norwegians have reported the "12V batteri problem - replace soon" message. Seems like a factory pushed message to a group of cars? I too have changed 12V battery little less than a year ago. Never had any problems, so the only issue has been the message in the dash�
Nov 20, 2014
kevincwelch Heh.
My Model S has been serviced more times in 2 years than my Honda Accord and Civic were combined for a total of 10 years.
S is way more fun to own though.�
Nov 20, 2014
CHG-ON That totally sucks and is my big fear. After owning Acuras for years, I am totally used to NEVER having a problem. They need almost no maintenance at all and nothing has ever gone wrong in them. I don't know how they do it. I just hope my new girl is a good girl! And YES, much, much more fun in every way.�
Nov 20, 2014
scottm It is easy to find out what drains the battery.
put an amp meter on the whole battery to get an idea of total draw over time and plot it. Then pull each fuse and run branch circuits through the amp meter and plot over time, repeat for each branch.
Then you know what is taking power.
Is everything necessary?
Duty cycle branches of your own choosing when the car is off by brutally interrupting the branch at the fuse box, using some timer. Close all branches when "IGN" is detected for drivability.
Or, what if you just power down the whole car nightly after a full charge? Wonder if that really means power down dead or vamps still draw? I guess something has to be listening to power back up again. Does this take the key on the window trick... Ive never powered down.�
Nov 24, 2014
carrerascott Argh. We were planning to take the Tesla on our Thsnksgiving travels tomorrow. The 12v warning light came on today. Tesla service said don't drive it. No loaners available by tomorrow and I'm 3 hrs from service center. Have to drive gas car now. Boo.......�
Nov 24, 2014
sgblank Add another March 2013 Model S that just got the 12V battery needs service message.
Ranger coming out next week to replace it.
I'm wondering if the first cold(ish) night in Northern California had anything to do with it.
When I called service they said the voltage looked OK now (13 volts).
I wonder if low temps are triggering a temporary under voltage flag.�
Nov 24, 2014
EarlyAdopter Oh, bummer!
Did you let them know about your upcoming trip? Maybe they can send a service tech down to your house to swap the 12V battery. Took a tech less than 30 minutes to swap mine in the parking lot at work.
Or if the service center is in your direction of travel, maybe you could stop off there for a short pit stop.�
Nov 24, 2014
carrerascott Ours happened today when it was 74 out.... Can ranger do this on site or does it need to go to service center?�
Nov 24, 2014
jerry33 A Ranger can do it on site. They just did mine last week. (21 months, 35,000 miles)�
Nov 24, 2014
kevincwelch Interesting that they told you jot to drive it. Tesla told me that when the warning light came on it wasn't necessarily urgent. I went about 2 weeks with the warning before the Lt came out to replace the battery. Maybe they are playing it safe with you.�
Nov 24, 2014
carrerascott Maybe because ours was flashing? Or they logged in and saw how bad things were? Can't say. I do know his words were "I would recommend not taking the Tesla, there is a chance the car will be fine with no issues but I would not want you to get stuck trying to leave the airport." -- a chance that the car will be find doesn't sound too confident.
- - - Updated - - -
Thanks. Nothing scheduled yet so hopefully they can come while i'm in Iceland! (I have a housesitter who can give them access).
I'm at 37,400 miles and 20months old. Very similar...�
Nov 26, 2014
Joe My car is a Dec 2012 model. Tesla swapped out the 12V battery preemptively in April of 2013. The message to service the 12V battery came on last thursday - called and Tesla could only set it up for this tuesday. Interestingly, they too told me that its better to sit in the garage. The service coordinator actually asked me "don't you have another car as a backup?". Ranger came by yesterday and the replacement was pretty quick. As per the ranger, its the same manufacturer (not the original one, but the same as my first replacement) - looked the same, but forgot to take a picture.
I have the same experience as kevincwelch - I've had my Tesla in for more service visits (and Ranger visits) than I've had to do with my 2004 LS430�
Dec 1, 2014
carrerascott Pretty disappointed in Tesla service. 12v light comes on 11/24. They tell me not to drive it. Soonest a ranger can come? Dec 4. Yes it's during the holidays, but 10 days with my car dead in the garage is not acceptable.�
Dec 1, 2014
wycolo If I should see a '12v battery light' or a screen msg re 12v batt, I would simply hook up a good 12v battery to the frunk posts and drive car to nearest service center. This 2nd battery can be any good motorcycle or physically larger 12v battery, just be sure it is good i.e. holds a charge. And be sure the weak battery (the car) is not shorted out such that the 2nd battery is being depleted. In this case you cannot drive car at all. But from what I gather shorting out is not the usual failure mode re the 12v battery, so this ploy should get you to the Service Center asap. A voltmeter plugged into the console outlet will allow you to monitor: normally it should indicate approximately 14v. When 12.1v becomes 12.0v the car is DEAD!!
PS: They replaced my 1.5 year old 12v battery last week during annual service. It tested 'borderline'. The ModelS really operates this battery in ways not previously anticipated by the battery industry, but progress is being made with more deep-cycling capable batteries being sourced by Tesla nowadays.
--�
Dec 1, 2014
clea ... that is strange as my light came on last Thursday and they swapped it out right away but that is only because they had a cancellation the same day and told me that I would've been able to drive it for a few weeks still. I was told that the light is more of a warning that it should be addressed soon rather than immediately.�
Dec 1, 2014
carrerascott I am 3 hours from the nearest service center. This is not something I should need to do on a $100k+ car where I paid the additional $8,000 service plan.
- - - Updated - - -
I was told not to drive the car. The soonest Ranger service date is Dec 4th, so they say. But what if I didn't have other cars??
�
Dec 1, 2014
Lifeguard(ret.) I was reassured by both the service center and Tesla Ownership that with normal driving the 12v would be OK for at least 2 weeks. The Service Center called me about 5 days before the warning appeared on the dash - the Model S sent a distress call back to the mother ship before the warning actually showed up. This was about 2 weeks after the annual service at 15 months, about 13500 miles. The Service Center was waiting on a shipment of 12v. Ranger replaced it at home last week - about 10 days after the warning appeared. No issues during the interim.�
Dec 1, 2014
carrerascott No pre-emptive call here. Called them when the warning came on and they basically said if I drive it I "might make it where I'm going."
So it's been sitting in the garage since Nov 24.
�
Dec 1, 2014
Cottonwood I would probably do something like wycolo suggests if I really needed the car.
There are items in the Model S that are very Tesla centric and Tesla may be justified in wanting to do their own work, but replacing a lead acid battery is 100 year old technology that any reasonable mechanic can do.
If you did not have another car available, then Tesla should provide a loaner or rental car in this situation.
When the Ranger does show up, please try to take a picture of the replacement battery, getting a clear view of the manufacturer and model number. Thanks ahead of time for that info.
Tesla really needs to do an update on its processor designs and supervisory, offline functions to drive a stake into the Vampire's heart. Until the Vampire is vanquished, it will continue to suck the life from the 12V, lead-acid batteries.�
Dec 1, 2014
rogbmw My 12 V Battery needs service notice came up this morning. I called the Orlando center, and they said I could drive it and be fine. After checking the schedule, then they were able to work the car in today, and then they called me back and a Road Ranger came at noon and installed the new 12 V battery here at my work. I hope we don't have another round of bad 12 Volt betteries. This will make my 3rd one, but to Tesla's credit, they have been excellent at replacing them.�
Dec 1, 2014
Cottonwood If possible during one of these Ranger visits, would someone please take a picture of the battery that Tesla is using for the replacement? Please get the manufacturer and model number.
Thanks!�
Dec 1, 2014
Modelxvin1365 I am glad to hear that they are replacing them so expediently and taking proactive measures but i can't help but think that known more reliable suppliers would be a better solution such as. Lead acid batteries are not hard to make we have had them for a century and then some, AcDelco is just one of many reliable brands�
Dec 1, 2014
Cottonwood Even the time tested, lead-acid battery has a limit to its total charge-discharge cycles. A very good deep-cycle battery, used in a lot of small, off-grid systems it the Trojan T-105RE. It is limited to about 800 cycles, 1,600 half cycles, 4,000 20% cycles, etc, or 800 cycle equivalents.
Let's do some round number math on the Tesla lead-acid battery. Assume about 4 rated miles per day vampire load or 1.2 kWh per day vampire cycling, and a 60 Amp-hr battery at 12 Volts for 0.72 KWh lead-acid battery capacity; then the Tesla goes through 1.2/0.72 or 1.67 cycle equivalents per day. If the life of the battery is 800 cycles, then that is a 480 day life, or about 16 months. It seem obvious to me that the vampire cycling of the 12V battery due to the Vampire load is sucking the life of the 12V batteries.
The reason that I am asking for the manufacturer and model number info is to look up the exact capacity and other specs on the current Tesla Model S 12V battery.
Here is the life curve for the Trojan T-105RE from http://www.trojanbattery.com/pdf/datasheets/T105RE_TrojanRE_Data_Sheets.pdf:
�
Dec 1, 2014
SteveS0353 Agreed 100%. The vampire load must be tamed before any 12V battery has a hope of being reliable long term. The 1.2kWh per day is equivalent to ~50 Watts running continuously, even when the vehicle is parked and "off". That's enormous! It needs to come down by an order of magnitude, which in this day and age, should be easily possible with attention to engineering detail.�
Dec 1, 2014
qwk The vampire drain should have been adressed a long time ago, but the Tesla software department has better things to work on, like the ability to name your car.�
Dec 2, 2014
wycolo The MS 12v battery has a single cable to the Negative terminal as you would expect. BUT it has 5 or 6 cables siamesed onto the POSITIVE battery post. To observe this in your car you really have to remove the tubular aluminum half-crossmember and peer carefully at all angles, or use a dental mirror. So replacing the battery or even just checking all the cables for tightness is a difficult job. Hence the suggestion to simply jumper in a second battery using the posts behind the nosecone (but more on this below).
Those 5 or 6 cables on the POS symbolises Tesla's problem here: every engineering team wants their project hooked into the 12v batt. Its an addiction. For a lame symbolic example take the radio - it cannot be turned OFF. I want to turn mine OFF permanently so there are no more voices appearing when I accidently hit one of the steering wheel switches. I know the radio is likely a miniscule load, but give me a switch or a separate fuse!
TM is thrashing this poor battery but they *are* charging it properly with pulsed input to retard sulfation (as posted here some time ago). If you jumper in a fresh battery it likely will NOT be able to supply enough amps for the heavy users: pumps and the like. So you better pray you make it to the Servive Center. Bottom Line: Be sure TM installs a NEW Battery every 12 months since there will be no magic 12v solution appearing any time soon.
--�
Dec 2, 2014
glhs272 My 12volt battery is still original. 16 months of ownership, 36K miles, and winter.... I am getting nervous. During my last annual they didn't replace it, at least according to the paperwork.�
Dec 3, 2014
wycolo See if they tested it during your annual. It might have passed with flying colors. Next time for sure though! Its a $100- item so why push your luck.
--�
Dec 3, 2014
glhs272 They performed "Courtesy Inspection and pulled logs" so I expect they did test it and it tested fine. It's still working so it seems like it was a valid test. I am just going to keep whistling past that graveyard until it's ready for it's next annual and recommend to Tesla that they proactively replace it. It just has to last until May 2015....�
Dec 3, 2014
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.�
Dec 3, 2014
Cottonwood 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.�
Dec 6, 2014
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�
Dec 6, 2014
jerry33 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.�
Dec 6, 2014
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.�
Dec 6, 2014
Cottonwood 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.
�
Dec 6, 2014
JRP3 Interesting chart. If it holds true for the Tesla battery then it suggests a real need for lithium titanate or LiFePO4.�
Dec 6, 2014
SteveS0353 Or a significant reduction in vampire load to reduce the stress on an inexpensive 12V lead-acid battery.�
Dec 6, 2014
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?�
Dec 6, 2014
SteveS0353 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).�
Dec 6, 2014
caddieo 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.�
Dec 6, 2014
glhs272 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.�
Dec 7, 2014
caddieo OK. Thanks.�
Dec 7, 2014
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...
�
Dec 7, 2014
Zzzz... 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.�
Dec 7, 2014
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.�
Dec 7, 2014
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:�
Dec 7, 2014
Zzzz... 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.
- - - Updated - - -
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.�
Dec 7, 2014
JRP3 I'm suggesting they may already be certified for that voltage.
Upfront costs, no, but actual lifetime costs, I think at least LiFePO4 is already cheaper than a good AGM battery.
- - - Updated - - -
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.�
Dec 7, 2014
TexasEV 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.�
Dec 7, 2014
Zzzz... They are not. Certification for li-ion voltage curve is totally different beast.
Current NCA li-ion pack designed to last lifetime of the car, Tesla Model S. If LFP could last 100 or 1000 times longer than the Model S itself - that would not change a thing for an automotive application of it. So upfront cost is what matters. Comparing it to AGM makes no sense at all - AGM are not used in Tesla Model S or Model X and most likely(read 0 chance) would not be used in Model 3.
If in your imagination AMG batteries will be used in automotive world - we got a principal disagreement.
Sure I meant cells that are separated from traction loads. I could not imagine how one cell could participate at both loads simultaneously. And this is why I wrote QUOTE: "separate and totally independent part of main pack" <--- but with your selective reading skill I see how in your mind cells in separate and independent parts of main pack could see both traction loads as well as 12V loads....
In reality I meant only possible savings from assembly of battery pack - same cells that designed to last for the life of the car will make sense to place into same case.�
Dec 7, 2014
JRP3 The "curve" is irrelevant, components only need to be certified for the maximum voltage they will see.
Not sure what you're on about since Tesla uses an AGM battery for their 12V battery, which is what we've been talking about this entire thread.
"My mind" was directly addressing another comment regarding using part of the main traction pack for 12V loads, which you addressed as well, though maybe didn't actually understand the question. It is theoretically possible but not a good idea for the reasons I outlined. You probably should not be attacking my reading skills and just stick to the topic at hand.�
Dec 8, 2014
tliving I think that the 12V warning comes on for different reasons. Some may just be a dropping voltage level on the 12V indicating its near end of life. If thats the case you can keep driving for a while until you can get it into a SC. I think another cause may be when the DC-DC inverter fails and the 12V is getting no charge. In that case its going to die quickly and potentially leave you stranded. The best bet is to call Tesla Service (24x7) and get their advice. I don't think they're giving inconsistent advice, I think it depends on what actually caused the warning.�
Không có nhận xét nào:
Đăng nhận xét