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Tesla is using a new 12V Lithium-ion battery in the Model S Plaid

AlanSubie4Life

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Oct 22, 2018
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My main curiosity here is how this change is done, and whether it will "help." (Helping is defined as a reliability improvement.) I know very little about how things are done on Model S and how this is different than Model 3/ Model Y.

Background:
On Model 3, the HV battery is disconnected entirely from the 12V system (DC-DC (400V->12V) converter is powered down). The 12V battery is about 600Wh or so, and must supply something like 6-7W standby power when the contactors are open. Then about once a day, the contactors are closed and the HV battery supplies the DC-DC for about 1 hour of recharging (at 10A (~120W) perhaps) to max capacity again. So seems like something like 20% depth of discharge on the 12V (which is not an AGM battery on Model 3/Y, though it is somehow specialized I think for this purpose).

This results in about 200-250Wh of drain per day.

So:

How is this going to be done on Model S? Do they have a separate low power output DC-DC that is always on (maybe in the battery pack?) and supplies a constant 12V to this lithium pack? Has it always been that way on Model S (two DC-DCs?)? I've heard claims about that but no idea.

Anyway, my hope is that they're not cycling this 12V. If there's a DC-DC that is always on, they technically don't even need this lithium-ion "12V," but of course it would be good to have some source of last resort (accident, DC-DC failure, doors can still open, etc.) and presumably that is the purpose.

But with 99Wh of capacity, it's not going to last very long, and it must be used only for the most critical tasks. And if it's going to last, it presumably can't actually be used much.

Maybe they have lowered standby power significantly to ease some of these concerns or enable less cycling of the lithium-ion? Would have to be a factor of 10 or more I would think (less than 1W).

It's all very interesting and I wonder how it's done. And whether the result will be higher reliability or not (which seems like what most people care about!).
 
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AlanSubie4Life

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Oct 22, 2018
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New news, old news, fake news. Everytime we click on these articles someone gets paid, and it just encourages more of the same.
Teslarati is such pablum. It is frustrating, especially since people get information from there. It could be so much better.

Anyway it is far from clear to me that this lithium-ion battery will be any better. I guess we will see. Depends on implementation. I sure hope it is, and it is a lithium-ion battery that lasts 10-15 years, and it’s no big deal if it’s at 30% capacity after that time (3x oversized). And most importantly, it gives you warning a few months before it needs replacement (which it would, if it can operate at 30% capacity), and continues to operate the car perfectly during this time. It only has to unlock the car and open the mirrors and whatnot - and as discussed, maybe not even needed for that, normally - in any case, should be easily possible with a few Wh.

And of course I assume it works perfectly at -20C, even at 30% original capacity. Again, should not be a problem if it is not actually needed normally.

It would make sense for it to be technically able to be removed and have completely normal operation (even if this is not allowed) - and it would only be actually relied upon if the pyrofuses blow.
 
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Tam

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Nov 25, 2012
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Visalia, CA
New news, old news, fake news. Everytime we click on these articles someone gets paid, and it just encourages more of the same.

Some info is genuinely new news:

1) The look. I never knew how different it looks until now. If don't see traditional rounded positive and negative posts at all.
2) The specification: I thought the Lithium should be more but the previous one is higher at 33 amp-hour while the new one is lesser at 6.9 amp hour.
 

beatle

Active Member
Aug 31, 2019
1,251
686
Springfield, VA
I wonder how you would add an amp with a proprietary connector like that? Why would they bother designing a battery with a proprietary connector? Maybe to thwart owners from replacing it with a 3rd party battery?

Also, Teslarati (and Tesmanian) are garbage fanboy sites. This statement from the article doesn't make any sense either:

In gas-powered and combustion engine vehicles, the lead-acid battery is a suitable choice because it is only used for starting the engine and minor electrical tasks like powering interior lights. In electric cars, the 12V battery could handle more tasks, thus decreasing the battery life.
I wonder if he forgot about the fuel pump(s), fuel injectors, coil pack, infotainment, O2 sensors, MAF sensors, throttle stepper motor, and ECU that are present in many gas cars. A good number of gas cars are now even using electric power steering and water pumps. The Tesla heater and AC both take HV inputs. I wonder what EV-specific contraption he thinks is stressing the 12v?

Lead-acid batteries are less sensitive to cold than lithium batteries and are waaay less expensive.
 

Tam

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Nov 25, 2012
9,224
7,915
Visalia, CA
...I wonder what EV-specific contraption he thinks is stressing the 12v?...

I think it's about the wear and tear because of more usage.

In the old days, a 12V battery is hardly used when the ignition is turned off.

Now, even when the car's ignition is off, there are still other electronic usages including the security system, cameras...
 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
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There have been built-in warmer for 12V lithium batteries but I am not sure how Tesla regulates the temperature for its new 12V battery.
If they don't need the 12V lithium-ion battery to provide very much current or work particularly well, then there should be no real need to regulate its temperature. Lithium batteries kind-of sort-of work, even at very low temperatures. Just not very well. But if the design of this one (specifically the design of the overall system, not the battery itself) has been done carefully, it really doesn't need to work that well at all. The main pack (which will also be freezing) can provide for all major needs, through auxiliary DC-DC or whatever (which would take care of closing contactors and bringing up the main DC-DC, etc.). Lots of questions about bootstrapping and supply domain sequencing abound!

It looks like it is a 4-series cell (no surprise to get about 16V) pack, 1 parallel, maybe. To get 12-14V they could just keep it at 60-80% SoC all the time or whatever. Hopefully they don't cycle it at all - will wear it out - which we definitely don't want!

Not clear what the exact Li-ion chemistry is - that would also impact cold temperature performance. But for a good design, it won't matter - the idea behind removing a 12V battery is to really remove it from having any significant requirements imposed upon it.

Lots of unknowns here about exactly how this will work. It's what I keep wondering about! I really WANT this to be better. But for that, we need an Li-ion battery that lasts 10-15 years, or so (except for the "infant mortality" failures), where the capacity and current sourcing requirements are very relaxed. You may not get there with 1 cycle a day (3650 cycles) - and with CURRENT standby requirements (about 150Wh), this would result in more than one cycle a day (there's every reason to believe that they may have reduced standby requirements, or they aren't cycling the battery at all - the two options I can think of, there may be more). Obviously reducing standby requirements has other ancillary benefits consistent with Tesla's mission of lowering worldwide energy usage.
 
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AlanSubie4Life

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Oct 22, 2018
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. I wonder what EV-specific contraption he thinks is stressing the 12v?

As explained above, at least in Model 3/Y (no idea on the old S), the 12V battery is routinely cycled - at least once a day, since it is the sole power source, for everything except perhaps the BMS, when the car is sleeping (contactors open, HV battery disconnected, DC-DC off). It runs the Bluetooth, mirrors, locks, display, etc., until the contactors close, as I understand it. Those seem to add up to about 6-7W (not including the display of course - the drain is a LOT higher when the display is on and the car is starting to "wake up," but this only lasts a few seconds) on the Model 3. When Sentry mode is active or whenever the contactors are closed (car is "idle") the 12V is either being charged or floated by the DC-DC, so is not being "used" exactly.

This wears out the battery eventually, since it has to be recharged daily as well. I have heard people say that the arrangement is different on the old S, but I don't know exactly how. But there's a 12V battery still on the old S, so I assume it is a somewhat similar setup, though it's probably not exactly the same.
 
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Tam

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Nov 25, 2012
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...there should be no real need to regulate its temperature...

Battle Born Batteries says without the warmer:

Charging stopped at below 25F (internally)
Charging resumes at 32F (internally)

Battery University says:

"Li ion can be fast charged from 5°C to 45°C (41 to 113°F). Below 5°C, the charge current should be reduced, and no charging is permitted at freezing temperatures because of the reduced diffusion rates on the anode. During charge, the internal cell resistance causes a slight temperature rise that compensates for some of the cold. The internal resistance of all batteries rises when cold, prolonging charge times noticeably.

Many battery users are unaware that consumer-grade lithium-ion batteries cannot be charged below 0°C (32°F). Although the pack appears to be charging normally, plating of metallic lithium can occur on the anode during a sub-freezing charge. This is permanent and cannot be removed with cycling. Batteries with lithium plating are more vulnerable to failure if exposed to vibration or other stressful conditions. Advanced chargers (Cadex) prevent charging Li-ion below freezing.

Advancements are being made to charge Li-ion below freezing temperatures. Charging is indeed possible with most lithium-ion cells but only at very low currents. According to research papers, the allowable charge rate at –30°C (–22°F) is 0.02C. At this low current, the charge time would stretch to over 50 hours, a time that is deemed impractical. There are, however, specialty Li-ions that can charge down to –10°C (14°F) at a reduced rate."
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,491
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San Diego
Battle Born Batteries says without the warmer:

Charging stopped at below 25F (internally)
Charging resumes at 32F (internally)

Battery University says:

"Li ion can be fast charged from 5°C to 45°C (41 to 113°F). Below 5°C, the charge current should be reduced, and no charging is permitted at freezing temperatures because of the reduced diffusion rates on the anode. During charge, the internal cell resistance causes a slight temperature rise that compensates for some of the cold. The internal resistance of all batteries rises when cold, prolonging charge times noticeably.

Many battery users are unaware that consumer-grade lithium-ion batteries cannot be charged below 0°C (32°F). Although the pack appears to be charging normally, plating of metallic lithium can occur on the anode during a sub-freezing charge. This is permanent and cannot be removed with cycling. Batteries with lithium plating are more vulnerable to failure if exposed to vibration or other stressful conditions. Advanced chargers (Cadex) prevent charging Li-ion below freezing.

Advancements are being made to charge Li-ion below freezing temperatures. Charging is indeed possible with most lithium-ion cells but only at very low currents. According to research papers, the allowable charge rate at –30°C (–22°F) is 0.02C. At this low current, the charge time would stretch to over 50 hours, a time that is deemed impractical. There are, however, specialty Li-ions that can charge down to –10°C (14°F) at a reduced rate."
Yeah you generally can't charge a Li-ion battery below freezing (discharging it is fine). But you don't need to charge it if you're not using it! I would think it would make sense to not bother charging it when it's below freezing (this could go on for months). Just don't ever use it, except in emergencies, and you don't have to worry about charging it up again. After the battery emerges from permafrost and temperatures go above freezing, if it's discharged a little bit, top it up.

No idea where it's located, either...it could be in the vicinity of pack heating loops which could elevate the temperature, but if the car's not being used for months, those also wouldn't be active, unless they've implemented methods to wake up the car and heat the HV battery solely so they can warm up the new 12V battery, so they can recharge it (which seems like a lot of work for very little return - just don't use the new "12V" battery, except in emergencies, seems easier, which could be accomplished with a DC-DC "always-on" domain, with minimal standby power, running directly off the HV).

Lots of unknowns, no information. Just discussing the tradeoffs here of how it COULD be done. I don't actually know HOW it's done. If they're using the 12V and need it to be recharged, treatment of cold weather situations would have to be handled carefully of course. But I guess in the case of it "starting to run down" (I'm assuming they are using it now) in cold weather, they could just turn on the DC-DC and just not recharge the battery (take it out of circuit?) until it has warmed up (somehow). But if you have a DC-DC with minimal standby current, why not just use it all the time?
 
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mark95476

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Jun 21, 2020
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I want this new 12V battery for my MY LR. Lighter and Tesla produced instead of some 3rd party OEM where quality is somewhat dubious.

Getting a replacement will be a headache as it is now, but the Li-ion one should be more resilient and have a longer life.

I was watching Bjorn's acceleration tests on a Shanghai-built M3 SR+ and it charged fast and maintained ~6s 0-60 all the way down to 10% SoC. I think it was more resistant/impervious to cold-gating as well. That was amazing! The cells being used in that vehicle probably should be used for this 12V battery.
 
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AlanSubie4Life

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Oct 22, 2018
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Li-ion one should be more resilient and have a longer life.
I doubt it, as a drop-in to the Y (into a completely redesigned subsystem it might well be much more resilient). With a 99Wh capacity, it'll be cycled about twice a day by the car (the car is assuming a lead-acid chemistry, and is looking for a drop below 12.8V, and then charges the battery to near 14V, at something like 10A). How many cycles do you think one of the Li-ion batteries has in it? Depth of discharge matters for cycle count, as does the chemistry. But seems to me to not be a clear win.

The OEM 12V seems fine in most cases, and it is super cheap ($85 from Tesla). It does kind of suck that it provides little warning before failure sometimes, and it's a big problem if you're not living near Tesla service centers. And a huge bummer if it goes out on a road trip (worth thinking about preventatively replacing). But still, at $85 every couple years assuming preventative maintenance (they routinely last 3 years as far as I can tell, though with plenty of much earlier "infant mortality" failures), it doesn't seem like that big a deal. (But, for sure, a point of failure that should be eliminated - which hopefully the new system does - but the battery and the system work together, they are not independent.)

think it was more resistant/impervious to cold-gating as well.
Discharging is one thing, charging is completely another thing. The LFP packs are probably better I guess (I don’t pay a lot of attention to the subtle chemistry differences). Have you tried to charge or supercharge a battery that has cold-soaked at -20C?
 
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Ostrichsak

Active Member
Sep 6, 2018
3,607
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Colorado, USA
I wonder how you would add an amp with a proprietary connector like that? Why would they bother designing a battery with a proprietary connector? Maybe to thwart owners from replacing it with a 3rd party battery?

Also, Teslarati (and Tesmanian) are garbage fanboy sites. This statement from the article doesn't make any sense either:


I wonder if he forgot about the fuel pump(s), fuel injectors, coil pack, infotainment, O2 sensors, MAF sensors, throttle stepper motor, and ECU that are present in many gas cars. A good number of gas cars are now even using electric power steering and water pumps. The Tesla heater and AC both take HV inputs. I wonder what EV-specific contraption he thinks is stressing the 12v?

Lead-acid batteries are less sensitive to cold than lithium batteries and are waaay less expensive.
Technically speaking, the 12v battery in an ICE vehicle is primarily to store the energy needed to turn the engine over during the start and for powering 12v devices when the engine/charge system isn't running. It can also act as something to help smooth the power coming off of the alternator (among other things) but in a traditional ICE car the alternator/charge system does the work of keeping 12v devices powered and happy once the engine is running. In an ideal world, the battery serves only to start the car (which can be a TREMENDOUS load far greater than anything an EV needs all-at-once) and power 12v devices when the engine isn't running.

That said, Teslarati is still an untrustworthy source of "information" as they've clearly sold their soul years ago for clicks and care nothing of delivering accurate information that requires actual investigation and education.

tl;dr Teslarati sucks.
 

mark95476

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Jun 21, 2020
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Tesla is spec'ing it in their flagship MS Plaid so I want it as well. I'm certain they've done testing--there's likely a host of automotive standards with requirements they need to meet--and it's good. $85 isn't a big deal as I planned to swap in a $400 Ohmmu just so I would have piece of mind. The Tesla factory battery is likely better.

MS has a bigger battery load than M3 & MY. The old MS had two displays with a larger primary. The new MS has an additional gaming system and 3rd rear display. M3 & MY has a smaller primary display and doesn't have the gaming system. ...etc...

Depth of discharge, charging, discharging, temp sensitivity, ...etc... I think you're well aware of the advantages/disadvantages of LFP vs lead-acid. Bjorn's done a lot of testing and the LFP cells from Shanghai are awesome for cold temps and low SoC.


I doubt it, as a drop-in to the Y (into a completely redesigned subsystem it might well be much more resilient). With a 99Wh capacity, it'll be cycled about twice a day by the car (the car is assuming a lead-acid chemistry, and is looking for a drop below 12.8V, and then charges the battery to near 14V, at something like 10A). How many cycles do you think one of the Li-ion batteries has in it? Depth of discharge matters for cycle count, as does the chemistry. But seems to me to not be a clear win.

The OEM 12V seems fine in most cases, and it is super cheap ($85 from Tesla). It does kind of suck that it provides little warning before failure sometimes, and it's a big problem if you're not living near Tesla service centers. And a huge bummer if it goes out on a road trip (worth thinking about preventatively replacing). But still, at $85 every couple years assuming preventative maintenance (they routinely last 3 years as far as I can tell, though with plenty of much earlier "infant mortality" failures), it doesn't seem like that big a deal. (But, for sure, a point of failure that should be eliminated - which hopefully the new system does - but the battery and the system work together, they are not independent.)


Discharging is one thing, charging is completely another thing. The LFP packs are probably better I guess (I don’t pay a lot of attention to the subtle chemistry differences). Have you tried to charge or supercharge a battery that has cold-soaked at -20C?
 
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AlanSubie4Life

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Oct 22, 2018
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The Tesla factory battery is likely better.

I’m sure it is great for the system it is designed for. The new Tesla battery is 99Wh, the largest Ohmmu battery is 2000Wh. Just for context.

MS has a bigger battery load than M3 & MY

Not clear that that is true anymore. We don’t know how it is done right now. The battery in the Model 3 is 600Wh. This one is 99Wh.

The old MS had two displays with a larger primary. The new MS has an additional gaming system and 3rd rear display. M3 & MY has a smaller primary display and doesn't have the gaming system. ...etc...
These things clearly don’t exactly run off the battery (it is 99Wh, with quite limited ability to source power), though they may all be on the same DC-DC (TBD!), and the battery may be connected to their supply.

We don’t know how it is done exactly but I am confident that these systems run off a DC-DC, so are using the HV battery, indirectly.
 
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AlanSubie4Life

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Oct 22, 2018
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The old Model S uses a 35Ah or so (so about 400-500Wh) battery, for completeness.

I'm not quoting these capacities to impugn the quality of the battery. I don't think because a battery is large it is good, or because it is small it is bad. It's just a piece of information that can be used as a guide for how the battery is used. All else being equal, a higher capacity battery will last longer because it will see fewer cycles, but in this case, nothing else is remotely close to being "equal."

But, a mystery still with Model S Plaid, exactly how this low-capacity battery fits into the picture. At some point the hardware will be looked at and we'll figure out what is connected to what, how many DC-DC converters there are, etc.
 

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