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12v battery problem and stranded!

JRP3

Hyperactive Member
Aug 20, 2007
23,952
67,279
Central New York
Have not been following the long, long 12V battery saga closely. Does anyone follow why TM let's this bleeding sore go on and on unfixed, instead of switching to a 12V Li Ion battery? They've increased avg prices by thousands this year, so can't claim it's too expensive to get it fixed once and for all.
If the problem is in the DC/DC converter then switching to lithium would not fix the problem, but I agree they need to do something more drastic than just continuously replacing lead acid batteries. I would not advise anyone to try using a lithium battery on their own since the DC/DC is set for lead acid charging, and lithiums cannot handle over charge the way lead acid can. Unless the lithium comes with it's own BMS that completely disconnects it from the DC/DC when fully charged, though that may cause errors for the car.
 

wycolo

Active Member
May 16, 2012
3,120
484
WA & WY
Yes, don't blame the bucket when you've used up all the water. Not the fault of the 12v batt, usually. They replace the batt because it has suffered a 'deep cycle' incident and thus has been weakened somewhat. They should let you take it home to use on your garden tractor.
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brianman

Burrito Founder
Nov 10, 2011
17,618
3,224
Since Tesla mentioned the bad batch of batteries a while back, and new cars are still having 12V problems, I assume they are using new batteries and still having issues.
While one might expect that, I don't think we can safely assume it. We have numerous examples of one branch of Tesla (service) not communicating deeply with the other branch (production). So, for example, some "new" cars might still have been shipped with "old" batteries as a supply was used up. Put another way, do we have any data or anecdotes that support the notion that any "old" style 12V batteries were discarded (returned for $ to the seller or recycled) rather than just used in new vehicles to get them out to customers more quickly / "on schedule"?

Regarding this particular left/right hand potential mismatch (service and production) there's always the possibility that they are following Elon's "large phrasing" direction in a "clever" way -- production is concerned with profit (so they use all 12V batteries they have rather than delaying vehicle deliveries and scrapping some "old" batteries) while service is not concerned with profit (aggressively replacing "old" batteries regardless of cost implications).

Just thinking out loud. :)
 

jerry33

(S85-3/2/13 traded in) X LR: F2611##-3/27/20
Supporting Member
Mar 8, 2012
20,833
29,908
Texas
Does anyone follow why TM let's this bleeding sore go on and on unfixed, instead of switching to a 12V Li Ion battery?

Is there any reason to think that LIon batteries would be better? The problem seems to be using cheap batteries rather than quality ones (aka Odyssey). There were also some problems with the 12V DC connector. A battery change won't help that. The 12V battery is a problem in all cars that have a big battery. The forums of those cars are full of "My 12V battery died and now the car won't start".
 
Two 12 volt batteries in parallel would be a simple solution to start with. Maybe parallel DC/DC converters too. The odds of both failing at the exact same time is small enough to warrant the safety benefits of not failing when needed the most. Building redundancy into products can be used for more than troubleshooting.
 
Two 12 volt batteries in parallel would be a simple solution to start with. Maybe parallel DC/DC converters too. The odds of both failing at the exact same time is small enough to warrant the safety benefits of not failing when needed the most. Building redundancy into products can be used for more than troubleshooting.
Problem being that if one of the 12v's fails, it will pull the power out of the good one. It may buy you some time, but if a 12v fails, your good one will drain as well. They would need to be isolated, and when one fails, a switch over would need to occur to the good one.
 

wycolo

Active Member
May 16, 2012
3,120
484
WA & WY
> Problem being that if one of the 12v's fails, it will pull the power out of the good one. [islandbayy]

Diode protecting parallel batteries with Schottkys only loses ~0.2v so should be doable. But would have to go on NEG side due to rat's nest on the POS. The real problem with MS is there is just no more room for another or bigger DC-DC since it needs to live near rocker panel 400v feed. Seems quality of DC-DC is improving else there would be more 12v tragedies reported. Press on; stiff upper lip and all that.
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