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Anyone using a LiFePO4 12 volt replacement battery ?

Discussion in 'Model S' started by ejames, Dec 15, 2016.

  1. ejames

    ejames Member

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    Anyone using a LiFePO4 12 volt replacement battery in their MS ? Is there a downside to one of these compared to the standard AGM deep cycle ?
     
  2. ThisIsTrue

    ThisIsTrue Member

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    My thought is, I'm not going to worry about it until I'm out of warranty....

    But I might carry a "jumper" battery just in case, so I can do my own jump start if ever needed.
     
  3. FlatSix911

    FlatSix911 918 Hybrid

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  4. CHG-ON

    CHG-ON Still in love after all these miles

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    I'd be nervous with a Tesla sanction on it.
     
  5. int32_t

    int32_t Tesla Spotter

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    That is a $400 battery. Nasty tactic to put the "deposit" as the price!

    I'd want to know what's in there and have some geek do a teardown and some analysis before I'd commit that sort of money to a battery. 3x the life? The LG spec sheet will indicate that you can get so many cycles out of the cells, which may very well be 3x what you can get from lead, but that's only possible if the lithium cells inside this 12V battery aren't sitting at 100% charge all the time. The Tesla is going to be trying to charge the battery slowly but continuously, which would keep a lead acid battery in good condition. It would take a mighty smart battery management system to take care of making sure the Tesla sees a fully charged 12V battery while simultaneously keeping the actual cells charged to the 80-85% mark.

    I'd be happy to let somebody else go first on this one ... but it really is high time for Tesla to stick something other than lead in there. NiMH is a nice inert chemistry if it's got to be something other than lithium. NiMH is nowhere near as energy-dense as lithium, but it's 3x as energy dense volumetrically and over 2x as dense in terms of mass than lead acid.
     
  6. Snerruc

    Snerruc Member

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    If you read the ad , the battery doesn't exist.
     
  7. FlatSix911

    FlatSix911 918 Hybrid

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  8. int32_t

    int32_t Tesla Spotter

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    The 12V battery in a Cayenne is under the driver's seat, which (I would expect, anyways) would be a good spot to protect it from extreme temperatures. Not sure about either other Porsches or Teslas, but batteries like this last longer when kept cooler (and charged only when above 0C). If the Tesla battery is in the frunk or someplace that heats up lots when the sun beats on it, that's not conducive to a drop-in lithium replacement.
     
  9. FlatSix911

    FlatSix911 918 Hybrid

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    #9 FlatSix911, Dec 19, 2016
    Last edited: Dec 19, 2016
    The Porsche Li-on battery is designed for their sports cars to save weight and is located in the trunk/frunk :cool:
    The starting capacity is limited at temperatures below 32 degrees F or 0 degrees C.

    Porsche offers world's first lithium-ion automotive starter battery ATLANTA, Nov. 23, 2009 - Dr. Ing. h.c. F. Porsche AG, Stuttgart, is the first car maker in the world to offer a starter battery with lithium-ion technology. Weighing less than 13 lb or 6 kg, the new battery is more than 22 lb or 10 kg lighter than a conventional 60 Ah lead battery.

    The new lithium-ion battery will be available as an option as of January 2010 for the 911 GT3, 911 GT3 RS, and Boxster Spyder and is delivered with the car. It is priced at $1,700. The new battery was developed specifically for lower weight. In sports cars designed for superior driving dynamics as is the case with both versions of the 911 GT3 and the Boxster Spyder, less weight naturally means greater agility and driving dynamics
     
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  10. ig_epower

    ig_epower Member

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    I carry a jumper battery in my frunk but the problem is, there is no place I can put it in the car and gain access to it if my 12V battery goes dead. It is a stupid situation that I cannot solve. I have asked the SC and they too cannot offer up a practical solution other than to get a jump from an external source. So my only real practical reason to carry my jump battery around (along with a tire inflator) is to top up my tires in case they need air.
     
  11. ejames

    ejames Member

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    I am going to try to find a space behind the nose cone for this booster . Amazon.com: Arteck Car Jump Starter Auto Battery Charger and 8000mAh External Battery Charger Car Jumper for 12V Automotive, Motorcycle, Tractor, Boat, Phone with Clamps, LED Flashlight, 300A Peak 2.5L Gas Max: Automotive
     
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  12. ElectricLove

    ElectricLove Member

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    Hey guys, just to jump in here. I am the guy behind BattMobile Batteries.

    To answer some questions/concerns;

    1. The batteries do "exist" (I just added photo of an ES battery to website); I have several Engineering Samples and have installed several in test vehicles around the country. I also have a batch going through manufacturing now and will be delivering to customers with deposits in early January. I have left the eBay posting and my website posting as "deposit-only" for now in order to ensure folks don't buy them with the belief it'll be there in a few days; presently if one were to place a deposit I have a couple still available from the January batch but worst case is they would get them in March. If one were in "dire" need I would send an Engineering Sample battery to them in the mean-time (or they can just keep it since only changes will be cosmetic)

    2. The price being 50% as a deposit; I get it and I agree it feels deceptive to list it that way but I didn't want to list it at full price and have folks pay me 100% up-front and then feel they were cheated b/c I don't have them ready to ship yet; similar to Tesla or other new to market products I am using the "deposit" money to help kick-start the production and get the costs to where they need to be to be viable.

    3. The cells utilized inside of these batteries are Lithium Iron Phosphate prismatic cells, they have a rating of 2,000 100% DOD cycles; my data analysis of the Model S 12V battery (I have monitored my own extensively and a few others to verify) suggests that with the larger available energy of my lithium batteries the battery will never do a 100% DOD cycle, in fact it will be more like 60% with this chemistry (minimum voltage 12.8V up to maximum of 14.4V).

    4. Safety/inert chemistry; Lithium Iron Phosphate is well-known as the "safe Lithium"; you can drill a hole in the side of the battery and it won't respond the way the Lithium-Cobalt/Nickel cells do (the ones used by LG that I mention in my "custom batteries" page, I use them for non-12V applications), they are more resilient to temperature extremes, etc.

    As far as a "geek tear-down"; I've obviously done this myself and I am a geek and can vouch but I'm the wrong person to do that since I'm also the one selling them, haha! I have one production unit pegged for the folks at Teslarati to review and do a bit of a "tear-down" on... That will be a month or two out I'd guess at this point. And I am happy to work with any other "snarky-reviewers" who are interested as well!

    Sorry, hope this post doesn't come off as an advertisement or anything like that, I just wanted to clarify to you guys since I got excited that folks are talking about my batteries!!!
     
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  13. FlatSix911

    FlatSix911 918 Hybrid

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    #13 FlatSix911, Dec 21, 2016
    Last edited: Dec 21, 2016
    Thanks for your reply. Can you tell us more about the expected lifespan the 12V Li-Fe-Po batteries? :cool:

     
  14. ecarfan

    ecarfan Well-Known Member

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    I hope no one who reads that ebay ad thinks that the battery is in any way approved or sanctioned by Tesla, because obviously it is not.

    Also, it is my understanding that LiFePo batteries are not effective as temperatures approach freezing.
     
  15. ElectricLove

    ElectricLove Member

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    Fortunately for TESLA vehicles, cold-cranking Amps aren't super important, the battery doesn't have to be as super effective in the ultra-cold in a tesla as it would in other vehicles where the vehicle won't get enough amps to turn over the stupid old engine... Now, this is a "young" battery business, obviously, so I don't have mounds of cold-weather data but I do have laboratory data and testing which allow me to be relatively confident in the batteries at "low" temperatures; I mean, if we are talking <-30F I have no idea and it would behoove one to consider a battery warmer in those climates anyways... Actually, if one is concerned a small and very low power battery warmer could help a ton in this department (assuming it is low ~1A draw off of the 12V itself, that wouldn't add a significant load to the system and the additional capacity will make up for the draw)...

    I don't think folks would go on eBay and assume a battery that says the brand is BattMobile Batteries is built by tesla; I have gone with a different color/style and don't place the word TESLA or the TESLA logo on the battery at all, but who knows, people are people. Obviously for marketing the thing for what it is intended I do have to use the word TESLA when describing it as that is the intention of the design/battery in the first place...

    I can tell you from testing that the batteries will go for a minimum of 2,000 cycles at 100% DOD, at a lower DOD the number of cycles goes up (and in the Model S/X it will be a lower DOD) and that after 2K cycles they won't be "dead" but will have ~80% capacity remaining. I can also tell you that in running many long-time studies on the Model S and how it is using it's 12V battery the vehicles are regularly "cycling" the batteries (to the tune of ~500-700 times per year); putting these two bits of information together I am confident in providing a 4 years warranty on the batteries but I fully expect them to go for 6+ years...
     
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  16. gearchruncher

    gearchruncher Member

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    Some important facts about LiFePO4 batteries:

    1) In ICE cars, which only use the battery for cranking and short term voltage stabilization, the useful element for a battery is cranking amps. Well, LiFePO4 is pretty good at this, so most batteries are rated "Ah equivalent" which is a marketing term covering up the fact that while they have the cranking amps needed, the actual energy stored is MUCH lower. It's common to see a Lithium battery saying it's the equivalent to a 50 AH car battery and it only has 12 actual AH. So you need to carefully choose.

    The simple way around this? Weight. A LiFePO4 battery weighs 1LB per 90 WH. A Tesla battery is 33AH @ 12V, or 400WH. So if your battery doesn't weigh 6 LBS, it's not as big as the original 12V. And BTW, the stock battery is about 16 lbs. This battery should cost you at least $800 given current LiFePO4 prices.

    2) Charge/discharge cycles in Lithium batteries are not total cycles. It's really about the total power in over the life. So you can charge 100% 1,000 times or 50% 2,000 times. But the smaller the battery, the more times you will cycle it. We know the tesla lets it discharge some and re-charge constantly as you are driving or not driving. A 30AH LiFePO4 can handle about 400KWh total energy over it's life. If you assume the vampire drain in the car all comes out of the 12V system, and vampire is 3 miles a day, that's 1 KWh a day, so a LiFePO4 might only last 400 days.

    Use a smaller battery, like a $300 10AH battery? Might only last 150 days.

    3) Seriously- Tesla is basically the world expert on Lithium batteries, and they used a lead acid in this application. You think you're a better engineer than they are? They could have thrown 40 18650 cells at this problem if it was that simple. There's a reason they went with a $60 Lead Acid in this application.
     
  17. gearchruncher

    gearchruncher Member

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    @ElectricLove,
    Looks like your battery is actually 30AH, for $400? That's impressive. It does look like a great fit for the Tesla.

    How do you handle balance charging the cells? Have you verified the Tesla charges to 14.4V?
     
  18. sorka

    sorka Active Member

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  19. sorka

    sorka Active Member

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    Seems like a good spot if the seat is an ejection seat :eek:
     
  20. ElectricLove

    ElectricLove Member

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    I love your explanation of the misleading term "Lead Acid Equivalent"!

    I appreciate your input; one thing to note though about Tesla doing it themselves;
    They use one type of Lithium chemistry (which they don't manufacture, remember that is Panasonic) and it differs from what I'm using. This is crucial b/c Tesla's chemistry ends up with a nominal voltage around 3.7V per cell, put 3 in series and you have an 11V battery, put 4 in series and you have a 14.8V battery, you can't make a 12V-equivalent battery using that chemistry.

    It isn't as simple as them popping some of their Panasonic cells in a box with a BMS and calling it good to go, it does take some engineering time and that does take resources away from other "primary" objectives for Tesla; selling 12V batteries isn't really their objective and I think they assume the market (myself for example) will fill in the empty holes as they sell cars, its what has been happening in many instances already with these cars...

    I do hope that at some point Tesla does buy my batteries and install them in the vehicles from the get-go, I think it will be a good offering for them and I'll have done all the ground work to make it easy! We will see, a guy can dream, right?
     

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