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  #11  
Old 03-01-2015, 03:04 PM
okashira okashira is offline
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Default Re: tesla model S module for sale

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Originally Posted by onegreenev View Post
When we have an actual graph of cell capacity after you put on about 1500 cycles then I will consider if they are better than the current available cells.

Id love to have a full Tesla pack but just can't yet get over the price some are trying to sell them at. I don't think they are worth $20k.

Good luck selling them off at that price. I know the price point for these should be higher than the current Leaf modules but until we get actual data Im going to remain skeptical. Remember I have driven a Leaf for nearly 4 years now and I don't live in Arizona and I was getting some serious range loss even after that short of time. Battery pack was warranted for 8 years and no more than 33% loss of original capacity after 8 years. I was at 24% or better loss only after 3 1/2 years. Go figure. This is real world driving in a real electric car. Im hoping the new chemistry will do better. If not Im out of the EV game until the batteries get better. I'll give it a real solid 7 years total of real every day driving. It will be a testament of either a great thing or not.

Bust that price by a 1/3 and I'd be game for the entire pack. I think that would be fair.
I will post some research later. I can promise you they will be WAY better for cycle and calendar life then the Leaf cells. Not to mention it only takes FOUR of these modules to match the kWh of a leaf pack. That's 200lbs, with watercooling/heating ready to go. Leaf pack is what, 650lbs? There is no comparison. :-)
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  #12  
Old 03-01-2015, 06:46 PM
eas eas is offline
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Default Re: tesla model S module for sale

This is intriguing, though unfortunately, a bit out of my hobby budget.

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Originally Posted by Ai! View Post
$30k for 16 modules - nice price for used product. Tesla got each module new for almost the half of this price...
Any evidence at all to back up your assertion that Tesla got each model for half of this price?

Even if you are right, though, Tesla has the advantage of buying in Q100,000,000, with the promise of buying many times more over the coming years. For someone buying hundreds of these cells, I haven't seen better than ~$6/cell for similar Panasonic cells, and no telling exactly how new those are. I've been able to pick up lightly used laptop packs with these cells for ~$3/cell on rare occasions, but more commonly such laptop packs are closer to $5-6/cell.

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Originally Posted by okashira View Post
I got 3.02Ah stopping at 2.55V with 10A load (>3C) That was with a 100ma cut charge, Tesla uses a 50ma cut, so a little more capacity. And 10A load is pushing these cells to the limit.
I did 3 cycles repeated at 10A each and capacity actually increased with each cycle. (By ~0.06%) 10A continuous is a pretty heavy draw for these cells, they do get hot by the end.
If I remember correctly, curves I've seen on similar cells suggest these would have 100mAh or so more at ~6A. Temperature can also make a noticeable impact on capacity.

Quote:
Originally Posted by onegreenev View Post
When we have an actual graph of cell capacity after you put on about 1500 cycles then I will consider if they are better than the current available cells.

Id love to have a full Tesla pack but just can't yet get over the price some are trying to sell them at. I don't think they are worth $20k.

Good luck selling them off at that price. I know the price point for these should be higher than the current Leaf modules but until we get actual data Im going to remain skeptical. Remember I have driven a Leaf for nearly 4 years now and I don't live in Arizona and I was getting some serious range loss even after that short of time. Battery pack was warranted for 8 years and no more than 33% loss of original capacity after 8 years. I was at 24% or better loss only after 3 1/2 years. Go figure. This is real world driving in a real electric car. Im hoping the new chemistry will do better. If not Im out of the EV game until the batteries get better. I'll give it a real solid 7 years total of real every day driving. It will be a testament of either a great thing or not.

Bust that price by a 1/3 and I'd be game for the entire pack. I think that would be fair.
I posted some mediocre notes on a very informative lecture I watched on YouTube called "Why Do Lithium Ion Batteries Die?" by Dr. Jeff Dahn. The video is linked in my post.

His lab has developed a testing method based on a theory of cell aging that seems to make good predictions about long-term cell life based on the results of much shorter tests. The use very precise instruments to measure the coulombic efficiency of cell charging cycles. Li-ion batteries should return one electron in discharge for every electron pumped into them during charge, and any difference is due to parasitic reactions that lead to cell aging and capacity loss.

They've looked at a variety of cell chemistries, under a variety of charging rates and temperatures. What they found is that, basically, the panasonic cells that Tesla uses have low levels of parasitic reactions at "normal" temperatures AND they only increase slowly with temperature. On the other hand, the choices Nissan made for the Leaf's pack were absolutely terrible. Both chemistries they chose tend to have higher levels of parasitic reactions at normal temperatures, and the rate of parasitic reactions for both grows rapidly as temperatures increase. This, combined with the lack of active pack cooling adds up to a sure recipe for premature pack wear.

The other thing Tesla packs have going for them, besides their choice of cell chemistry, and their use of active temperature control, is that they a much larger than the leaf packs, which means that the relative load during typical driving cycles is less.

Time will tell, but I think todays Tesla packs are going to have extraordinarily long lives, and wouldn't be surprised if next gen packs from other manufacturers have considerable improvements in their own durability.
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Last edited by eas; 03-01-2015 at 07:25 PM.
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  #13  
Old 03-01-2015, 07:09 PM
okashira okashira is offline
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Default Re: tesla model S module for sale

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Originally Posted by eas View Post
This is intriguing, though unfortunately, a bit out of my hobby budget.



Any evidence at all to back up your assertion that Tesla got each model for half of this price? Even if you are right, though, Tesla has the advantage of buying in Q100,000,000, with the promise of buying many times more over the coming years. For someone buying hundreds of these cells, I haven't seen better than ~$6/cell for similar Panasonic cells, and no telling exactly how new those are. I've been able to pick up lightly used laptop packs with these cells for ~$3/cell on rare occasions, but more commonly such laptop packs are closer to $5-6/cell.



If I remember correctly, curves I've seen on similar cells suggest these would have 100mAh or so more at ~6A. Temperature can also make a noticeable impact on capacity.



I posted some mediocre notes on a very informative lecture I watched on YouTube called "Why Do Lithium Ion Batteries Die?" by Dr. Jeff Dahn. The video is linked in my post.

His lab has developed a testing method based on a theory of cell aging that seems to make good predictions about long-term cell life based on the results of much shorter tests. The use very precise instruments to measure the coulombic efficiency of cell charging cycles. Li-ion batteries should return one electron in discharge for every electron pumped into them during charge, and any difference is due to parasitic reactions that lead to cell aging and capacity loss.

They've looked at a variety of cell chemistries, under a variety of charging rates and temperatures. What they found is that, basically, the panasonic cells that Tesla uses have low levels of parasitic reactions at "normal" temperatures AND they only increase slowly with temperature. On the other hand, the choices Nissan made for the Leaf's pack were absolutely terrible. Both chemistries they chose tend to have higher levels of parasitic reactions at normal temperatures, and the rate of parasitic reactions for both grows rapidly as temperatures increase. This, combined with the lack of active pack cooling adds up to a sure recipe for premature pack wear.

The other thing Tesla packs have going for them, besides their choice of cell chemistry, and their use of active temperature control, is that they a much larger than the leaf packs, which means that the relative load during typical driving cycles is less.

Time will tell, but I think todays Tesla packs are going to have extraordinarily long lives, and wouldn't be surprised if next gen packs from other manufacturers have considerable improvements in their own durability.
Thank you thank you for your informed post.
We did not buy this pack because these cells are crap. They are amazing cells. We bought to make ebike packs, for my personal plug in hybrid vehicle project, sell individual cells, and we're looking to offload a few modules to offset the $$$ invested as well for those who want to use modules as is.

The pack these were in were from a car with 3200 miles, which I personally verified. The car pack had been sitting for 2-3 months with the car DEAD at 0 miles, yet the cells all read ~3.305 volts +/- .010 V, amazing lack of self discharge considering they were powering a (in sleep mode) BMS the whole time. 3.3V is an ideal storage voltage for these cells, too. Oh, and it was a cold weather car...


Tesla uses 97% DOD (they charge to 4.2, with a 50ma cut (about as 100% as you can get), and they go down to 3.3V resting voltage (which is 4% or less)
And these should be good for 2000+ cycles or 20 years. I will find some links later. (have them on my work PC)

Yeah I am well aware of Dahn's research. He found regular LiCo is the best out of the once he tested, and NCA is even better, which his video does not touch on.

One of the worst? Lithium Manganese type in the Leaf... and they only use ~80% DOD, and still get lots of degradation in the heat. On the other hand, these Panasonic NCA cells LOVE the heat. They really open up in performance.

Last edited by okashira; 03-01-2015 at 07:12 PM.
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  #14  
Old 03-02-2015, 02:09 AM
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Default Re: tesla model S module for sale

these cells need to be active cooled/heated and this will add weight. Leaf module weights about 3.8 kg and this is not 3 times more than compared nca cells, I see around 15-20%. And one big difference that leaf cells will not catch fire... nca, on the other hand will shine like the sun. Remember those burned Teslas?
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  #15  
Old 03-02-2015, 02:51 PM
eric1565 eric1565 is offline
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Default Re: tesla model S module for sale

Update 5 modules are left.
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  #16  
Old 04-04-2015, 10:01 PM
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Ai! U are a wrong on your statements. The tesla cells are heated and rarely cooled. Here are the specs and the weights include that

Tesla entire pack is 14lb/kwh including the aluminum case.
Tesla modules (includes heat and cool parts) are 9.4 lb/kwh (no aluminum case)
Leaf pack is 27 lb/kwh

I have never bought a leaf pack so i dont know what the individual modules weigh but right now the leaf battery is at least double the lb/kwh of the tesla if not closer to 2.5X

Eric
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  #17  
Old 04-07-2015, 05:38 AM
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Default Re: tesla model S module for sale

I have 2 complete Leaf battery packs and the batteries themselves weights around 420 lbs, and this is ~17.5 lb/kwh INCLUDING alum casing. Tesla modules are WITHOUT liquid, it will add more weight and the final rating difference will be, as I've mentioned before, around 15-20%. But I'm ok with that, cos leaf batteries are much much safer.
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Old 04-07-2015, 07:41 AM
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Default Re: tesla model S module for sale

Ai! The weight of the cooling fluid is about 6 oz. Go weigh 6oz of water and that is the weight increase from the cooling fluid.
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  #19  
Old 04-07-2015, 11:15 AM
Hollie Maea Hollie Maea is offline
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Default Re: tesla model S module for sale

I was under the impression that everyone was in agreement that gen 1 Leaf cells, while fairly cheap, are terrible.

I have friends who have Leafs who have driven 3x,xxx miles who have less than 80 percent of their original capacity left. Meanwhile, I have seen zero degradation in the range of my Think City after 34,000 miles. And that's here in Portland where it's not very hot.
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  #20  
Old 04-07-2015, 12:27 PM
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Default Re: tesla model S module for sale

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Originally Posted by Hollie Maea View Post
I was under the impression that everyone was in agreement that gen 1 Leaf cells, while fairly cheap, are terrible.

I have friends who have Leafs who have driven 3x,xxx miles who have less than 80 percent of their original capacity left. Meanwhile, I have seen zero degradation in the range of my Think City after 34,000 miles. And that's here in Portland where it's not very hot.
leaf 2011-2012 MY have many problems: miscalibrated bms sensors in the battery pack, no battery heater and many other. I have 2013 leaf and got no battery degradation at all, but the car has only 20+k miles. And of course You must pay attention to the battery usage in the ev. I'm talking about charging to 80% and avoid fast charging stations. 12kW charger is ideal for leaf users, charging at 0.5C for Leaf is the best to prolonge life of the batteries. So not in every case degradation of the battery is the battery fault.
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