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POLL: Have you had to have your 12V battery replaced?

Have you had to have your 12V battery replaced?

  • No

    Votes: 269 49.4%

  • Yes, once

    Votes: 213 39.2%

  • Yes, more than once

    Votes: 62 11.4%
  • Total voters
    544
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#141
efusco said:
No suggestion of a "major design flaw"--very few cases like this, perhaps the battery itself was bad. the vast majority of us have only had to have the battery replaced after many miles--for me it was 70k miles and 4 years into ownership...does that suggest a major design breakthrough?
Click to expand...
I love how the logic on this forum works. If you (and many other people) went to 70k miles before a replacement, good for you. That doesn't mean there isn't a design flaw for a subset of people who need to replace them every 12-24 months.

I think I got to 18 months and maybe 35k miles before the notice to replace the battery came on. I was told I could drive another 1-2 weeks with no problems. But I'm not saying it's a design flaw, I don't know if it is or is not; but frequent replacements are definitely happening with at least a subset of owners.
 
#142
Max* said:
I love how the logic on this forum works. If you (and many other people) went to 70k miles before a replacement, good for you. That doesn't mean there isn't a design flaw for a subset of people who need to replace them every 12-24 months.

I think I got to 18 months and maybe 35k miles before the notice to replace the battery came on. I was told I could drive another 1-2 weeks with no problems. But I'm not saying it's a design flaw, I don't know if it is or is not; but frequent replacements are definitely happening with at least a subset of owners.
Click to expand...
I'm not saying it's not a design flaw either, but an annecdote isn't evidence of a design flaw any more than my annecdote is evidence that they have an improved design. There's a bell shaped curve and without much more data and control for all the relevant variables there is no way to imply anything one way or the other..that was the point I was trying to make...which is, btw, quite logical.
 
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#143
This is flawed thinking.

Flaw

1.a feature that mars the perfection of something; defect; fault:
beauty without flaw; the flaws in our plan.
2.a defect impairing legal soundness or validity.
3.a crack, break, breach, or rent.

verb (used with object)
4.to produce a flaw in.
verb (used without object)
5.to contract a flaw; become cracked or defective.
Click to expand...

The perfection of the Tesla is to have no 12v battery, then it can't be a problem.

Have everything run off the tractor pack: a fused line coming out to a 12v step-down converter that runs all the 12v electronics in the car... and operates main contactor that connects HV pack to drive unit and/or on-board chargers. When you source power to the car for charging, it also splits off to the 12v step-down converter so contactor will work to charge a dead-dead battery.

Not doing this way was a design choice, for carefully considered reasons, probably not flawed thinking.
 
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  • Funny
Reactions: GSP
#144
The point to having a 12V battery is to be able to cut off all HVDC outside of the pack when the car is off. You need 12V to keep the electronics in standby and engage the contractor to energize the HVDC bus and power the DC-DC converter.

You could eliminate the battery by moving the DC-DC converter inside the main pack (or at least a smaller one for standby loads)
 
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#145
efusco said:
No suggestion of a "major design flaw"--very few cases like this, perhaps the battery itself was bad. the vast majority of us have only had to have the battery replaced after many miles--for me it was 70k miles and 4 years into ownership...does that suggest a major design breakthrough?
Click to expand...

There absolutely is a design flaw. The DC-DC converter is unable to keep the battery on a 'float' charge. The battery is typically cycled on average 5 times per day. That's insane. This is equivalent to the alternator on an ICE letting the 12v battery get to 11.5v then charging it to 14.4v then letting it get to 11.5v before charging it again. No battery can survive that treatment for long... especially a lead-acid battery. Tesla needs a way to keep the 12v battery at a constant ~12.4v. Given the ~$200 cost of a replacement even a separate AC powered float charger like 'Battery Tender' to maintain the 12v battery would be worth it....

I'm on my 3rd 12v battery...
 
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#146
nwdiver said:
Given the ~$200 cost of a replacement even a separate AC powered float charger like 'Battery Tender' to maintain the 12v battery would be worth it...
Click to expand...

This is exactly what I do. I plug in the front of my car at home, which prevents discharge cycles on the 12v. And in doing so... the main pack also stays at the % charge that I parked the car. The Ctek charger draws about 21 Watts from the wall all the time when connected to the Tesla 12v.

So, it's not fair for me to comment on how long my 12v lasts in this poll, although I did vote and polluted the result... as my 12v will "unfairly" outlast most any other Tesla.

To connect the Ctek, I used the lighter socket fuse position in the panel under the hood to back-feed the 12v battery (wherever it is in the car, don't need to know) and also rigged it so the lighter socket is powered all the time by pulling the relay and inserting a jumper. (This is still all fused, using an adapt-a-fuse piggyback thing at the panel.)

I am considering using the Ctek at work too... wherever the car sits for 8 hours or more would be worth stopping the discharges. To this end, I have made a recoiling 120v extension that I plan on mounting inside the frunk area with plug end hanging out from under the grill somewhere.. just grab it and pull enough out to plug into nearest 120v. Which would be the same 120v pedestal that I use the mobile charger for trickling the main pack all day.. gain about 20% charge in a work day.

If some of the glass on top of the car was converted to solar cell.. This would be a tremendous use for that energy... trickle the 12v battery. Of course it doesn't help at night, in the garage, etc.. but lots of cars spend a lot of parked time out in the daylight. Maybe as an order option, at least have the choice.
 
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#149
2015 P85D @7,500 miles, I had to replace the cheap C&D 12v due to heavy sulphation. Installed a much higher capacity, far longer-lasting (and lighter) LiFePO4 and haven't looked back.

HSOtxzu.jpg


(I had to make the stainless strap as the battery is deeper)
 
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#155
Just had the battery replaced this morning. Dec 2014 build P85D with 58.7k miles.
I got the Battery Needs Service message last night. Called roadside assistance this morning and they said to bring it in as soon as I could.
Service center charged me $144 for the battery, $35 labor.
 
#158
Just see a warning my 12V battery needs service.
My car was delivered 17 Jan. 2017 and I have now 36,666 km or 22788 mi.
I will call the Tesla service Center in Brussels and see what they propose
no pro-active attitude here yet.
 
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