12 volt battery dead

mikeg561 · Jul 10, 2015

Today marks my 2 week anniversary of having my car. Go out to the garage this AM and there is a warning message. "Car needs Service" "12 volt batter low"

Car will not go into gear. Call service and they are bringing me a loaner car and a flatbed truck to take the car into the shop.

Based on searching this forum, I thought the 12 volt battery issues were behind Tesla.

Anyone else having this issue lately?

Now I need to see how long I will be without my baby. :-(

Mike

mknox · Jul 10, 2015

I have never had a 12v issue, but Tesla has at least twice now proactively replaced my 12v battery at various servicing intervals.

Barry · Jul 10, 2015

I had the "12v battery low" warning after about 2 months of ownership (last month) and 2000 miles. Due to a backlog at the Denver SC, they gave me an appointment 4 weeks out for replacement and assured me the car would be fine in the meantime. They were right - it never died on me.

martinwinlow · Jul 11, 2015

I am wondering if this issue is in any way related to whether or not people leave their MS' plugged into the mains permanently whilst not driving. Has a poll on this been done yet?

Q "If your MS has suffered a 12V auxilliary battery failure, do you park your MS with a live mains connection; a/ always, b/ mostly, c/ half the time, d/ not much or e/ I only use SuCs to charge."...?

I understand that the MS will charge the auxiliary battery from the main pack when it gets low if left disconnected from the mains long enough. Is this extra cycling to blame for premature auxiliary battery failures or is it just poor auxiliary battery manufacturer quality-control?

I was mildly surprised to see that the auxiliary battery is only about 35Ah - same size as my i-MiEV. MW

Barry · Jul 11, 2015

When I'm home, I'm always plugged it. When I'm out during the day, I'm not plugged in while parked. I haven't taken the car on any overnight trips, so it's been plugged in every night.
IIRC, I was away on a 4 day trip (without the car), and when I came home, I saw the low battery warning message.

jerry33 · Jul 11, 2015

My speculation is that Tesla purchases these batteries in very large quantities to get a price break and some of them sit too long before being installed.

martinwinlow · Jul 11, 2015

Barry said:
IIRC, I was away on a 4 day trip (without the car), and when I came home, I saw the low battery warning message.

Left plugged in? MW

apacheguy · Jul 11, 2015

OP - Can you please post back with Tesla's disagnosis? I strongly suspect the 12 V was not the root cause.

Lex · Jul 11, 2015

In another thread it is suggested that the Model S uses the 12V 1000x more than an ICE vehicle. This just might be a "consumable" to add to the cost calculator once the warranty is gone as there doesn't seem to be any easy alternative / replacement to lead acid.

It's also a single point of failure that scares me, eg. may just need to push / pull if dead, and need to access the controls so I've put a backup battery jump-start pack (that also is has an air pump) in my trunk. Yep it adds weight but I think we have a real engineering dilemma on our hands here for the Tesla team as they plan the mass production model.

mikeg561 · Jul 11, 2015

Good thoughts from everyone. I will post the final results when I get them. I talked to service this AM, and they said they are replacing the entire battery pack. Did not get any more info yet. i.e. what really failed, what caused the failure, is the 12 volt also dead?

FWIW, when home, I always plug the car in. I have not taken any long trips yet.

Mike

AndY1 · Jul 11, 2015

Replacing all these 12V batteries every year or so on every Model S is very enviromentally friendly.

jerry33 · Jul 11, 2015

AndY1 said:
Replacing all these 12V batteries every year or so on every Model S is very enviromentally friendly.

Batteries are the most recycled products and have been recycled for the longest time (I recall that they were recycled in the 1950s). In addition, they are almost 100% recyclable. I don't see a problem here in terms of environmental friendliness.

Cottonwood · Jul 11, 2015

jerry33 said:
Batteries are the most recycled products and have been recycled for the longest time (I recall that they were recycled in the 1950s). In addition, they are almost 100% recyclable. I don't see a problem here in terms of environmental friendliness.

I agree. Here is a good reference: Lead Acid Battery Recycling - Battery Council International

Barry · Jul 11, 2015

jerry33 said:
My speculation is that Tesla purchases these batteries in very large quantities to get a price break and some of them sit too long before being installed.

My speculation is it's a design flaw. Either the 12V battery is too small and/or being cycled too much, or there are issues with their charging algorithm that's killing them early. This has been going on for too long to be one huge batch of bad batteries. Tesla doesn't have the cash flow position to buy years-worth of batteries for inventory.

I wonder why they just didn't build a Lithium-based 12V battery pack. Cost?

martinwinlow said:
Left plugged in? MW

Yes. Tesla says keep it plugged in when not in use. You seem surprised...

Cottonwood · Jul 11, 2015

Barry said:
My speculation is it's a design flaw. Either the 12V battery is too small and/or being cycled too much, or there are issues with their charging algorithm that's killing them early. This has been going on for too long to be one huge batch of bad batteries. Tesla doesn't have the cash flow position to buy years-worth of batteries for inventory.

The problem is that the batteries are being cycled too much.

This is caused by the excessive thirst of the Vampire, called the control circuitry that stays powered up even when the car is "off." The control circuitry design draws about 1kWh (3 rated miles) per day or about 42 Watts, even with the most power conserving settings. The lead acid battery 100% capacity is 12V*35Ah or 420 Wh. This means the lead acid battery is cycled about 2.5 times its capacity per day. Even the best deep cycle batteries are only good for about 1,000 cycles, or about 400 days. That is about how long the lead acid batteries last on average in a Tesla Model S.

To solve this problem, Tesla needs to reduce the power draw of the "off" control circuitry, increase the capacity of the lead acid battery, or go to a battery chemistry with more cycles available.

sorka · Jul 11, 2015

martinwinlow said:
I am wondering if this issue is in any way related to whether or not people leave their MS' plugged into the mains permanently whilst not driving. Has a poll on this been done yet?

Q "If your MS has suffered a 12V auxilliary battery failure, do you park your MS with a live mains connection; a/ always, b/ mostly, c/ half the time, d/ not much or e/ I only use SuCs to charge."...?

I understand that the MS will charge the auxiliary battery from the main pack when it gets low if left disconnected from the mains long enough. Is this extra cycling to blame for premature auxiliary battery failures or is it just poor auxiliary battery manufacturer quality-control?

I was mildly surprised to see that the auxiliary battery is only about 35Ah - same size as my i-MiEV. MW

The when is about 6 times day. The systems, with more recent software, unless they've fixed it, draw about 100 watts of power continuously. Was about 70 watts but it jumped a few updates ago. It's like having 3 hid headlights on continuously. Lead acid batteries were not designed to be discharged over and over again. They're meant to stay charged.

kuttakamina · Jul 11, 2015

Cottonwood said:
To solve this problem, Tesla needs to reduce the power draw of the "off" control circuitry, increase the capacity of the lead acid battery, or go to a battery chemistry with more cycles available.

The newest Model S's use gel based batteries. (Atleast thats what I was told)

Cottonwood · Jul 12, 2015

kuttakamina said:
The newest Model S's use gel based batteries. (Atleast thats what I was told)

Gelled-electrolyte, lead-acid batteries are less expensive than absorbed glass mat (AGM), lead-acid batteries, and it looks like they will have a little longer life in this application.

See Gel vs. AGM vs. Wet Cell Batteries | Solarcraft for some info on the various types of lead-acid batteries.

To really solve this problem, Tesla needs to greatly reduce the the power draw of the "vehicle-off" control circuitry.

Barry · Jul 12, 2015

Cottonwood said:
The problem is that the batteries are being cycled too much.

This is caused by the excessive thirst of the Vampire, called the control circuitry that stays powered up even when the car is "off." The control circuitry design draws about 1kWh (3 rated miles) per day or about 42 Watts, even with the most power conserving settings. The lead acid battery 100% capacity is 12V*35Ah or 420 Wh. This means the lead acid battery is cycled about 2.5 times its capacity per day. Even the best deep cycle batteries are only good for about 1,000 cycles, or about 400 days. That is about how long the lead acid batteries last on average in a Tesla Model S.

To solve this problem, Tesla needs to reduce the power draw of the "off" control circuitry, increase the capacity of the lead acid battery, or go to a battery chemistry with more cycles available.

This agrees with my previous comment about it being a design flaw - the 12V system is under-engineered for its demand requirements, as it currently exists.
It still doesn't explain why some recent batteries (like mine) in new cars, needed to be replaced after 6 weeks/1500 miles.

mikeg561 · Jul 12, 2015

Tesla chose to swap out the entire battery pack. There was an intermitted problem with one of the connector among the 7,000 batteries.
They picked up my car Friday about 10:30 am. Diagnosed and had a new battery pack in the car (based on looking at android app) around 4:00 pm Saturday. That included time needed to get a new pack sent from Fremont to Costa Mesa. Should get me car back on Monday.

I guess the 12v was not the issue in this case.

12 volt battery dead

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