Impact of battery life/capacity on daily distance...

[strider]

Good to hear guys, that pack degradation seems to be far less than I hypothesized. I was just taking an example from other Lithium-ion experiences (not from Tesla's experience).

I've been through this argument. You cannot compare battery degradation in a cell phone, laptop, or digital camera to a Tesla. Those devices have zero thermal management of the battery and with tight packaging are routinely exposed to high heat. High heat trashes Li-Ion batteries fast. Tesla keeps their batteries within a temperature range which greatly increases life.

I daily drive my Roadster ~55 miles/day. I've had it for 18 months and 18,000 miles and I've lost 4.5% of capacity (just did a range mode charge this morning and it settled to 234 miles).

 

[strider]

Even for that trip to Costco?! Toilet paper rolls in the lap, anyone?!

I get your point, Bonnie, but, I do suspect that the Model S will take a bigger 'beating' from a much broader demographic of drivers and usage patterns. School carpool runs, those Costco trips, 3+-member-family weekend trips and so on.

So, it's very conceivable that the battery pack behavior over time might be significantly different from that seen on the Roadster on average... for that reason, the 40 kWh pack could be a non-starter for a large cross-section of folks who definitely wouldn't want to end up with a 'Leaf' after a few years.

But I don't see how that's any different from miles driven and time owned? I'm driving my Roadster 1,000 miles/month which is pretty average (I always heard 12k-15k miles/year is average) so I'm not sure how much more "beat-up" Model S will be. Four 5-mile trips are the same as one 20-mile trip per day.

 

[strider]

In what way?

I don't have a definitive answer but my assumption is that, especially for warm climates, Model S will have more cooling capacity and so will be able to keep the pack cooler than the Roadster. I don't live in a hot place but a couple times a year as I'm driving the A/C in the cabin will cut out in order to shunt all available cooling to the battery. Therefore it's possible that the Roadster's A/C isn't able to keep the battery as cool as Model S will be able to. We also assume that Tesla has improved the car's internal monitoring and management capability for Model S over the Roadster so Model S would be able to take care of the battery better.

 

[Doug_G]

Even for that trip to Costco?! Toilet paper rolls in the lap, anyone?!

Been there, my wife has done that (she's the one that bought too many rolls!).

One great advantage of the Roadster is, if you have to carry two passengers, you get to do the trip twice! Model S will have a serious disadvantage there... :tongue:

 

[Dan5]

Got some information from Panasonic concerning the batteries

It looks like for the first few months, the degradation is 1% per month and then it looks linear at 0.15% per month.

Keep in mind, I don't know if Tesla has them stored and already factored the initial degradation in for the 85 kwhr battery.

Is the Tesla numbers a "fully charged new battery"- probably not, if the batteries were a few months old, that's "as advertised".

The batteries are not airlifted off the Panasonic assembly line and popped into the car that day so there is already some "age" and degradation to the batteries when Tesla gets them

 

[SCW-Greg]

Got some information from Panasonic concerning the batteries

It looks like for the first few months, the degradation is 1% per month and then it looks linear at 0.15% per month.

Keep in mind, I don't know if Tesla has them stored and already factored the initial degradation in for the 85 kwhr battery.

Is the Tesla numbers a "fully charged new battery"- probably not, if the batteries were a few months old, that's "as advertised".

The batteries are not airlifted off the Panasonic assembly line and popped into the car that day so there is already some "age" and degradation to the batteries when Tesla gets them

That's really encouraging news. So if true, that assumes around 9+% in the first few months, but then just slightly more than 14% over the remaining 8 year warranted life.

 

[Dan5]

Actually it's a 10% loss in the first 36 months, in the first 5 months, you see a 5% drop total, then the rest it's very linear in terms of degradation, the next 31 months you see a 5% drop total also. If you can keep the batteries around 25 C you are fine. I would really avoid prolonged exposure to 45 C and 65 C though, that seems to degrade the batteries more drastically. Luckily Tesla has a cooling system so I see no problem keeping it around 25 C

 

[richkae]

Actually it's a 10% loss in the first 36 months, in the first 5 months, you see a 5% drop total, then the rest it's very linear in terms of degradation, the next 31 months you see a 5% drop total also. If you can keep the batteries around 25 C you are fine. I would really avoid prolonged exposure to 45 C and 65 C though, that seems to degrade the batteries more drastically. Luckily Tesla has a cooling system so I see no problem keeping it around 25 C

Roadsters have not seen this pattern at all. There are 3 year old Roadsters with almost no battery degradation.
Maybe the batteries are aged before they go into cars, maybe Panasonics testing ( probably successive deep cycles from full ) is not relevant to real world use ( many shallow cycles without charging to full )

 

[wycolo]

I daily drive my Roadster ~55 miles/day. I've had it for 18 months and 18,000 miles and I've lost 4.5% of capacity (just did a range mode charge this morning and it settled to 234 miles).

Is the miles estimate on the TC an actual test of battery condition?

I've never used Range Mode but now considering it since my regular long trip of 180mi is marginal/scary. Might I better use Range Mode but STOP the charging @210, say, and then never have to actually use the 'bottom 10%' at all? Thus no 'damage' to the battery plus elimination of range anxiety?
--

 

[NigelM]

I've never used Range Mode but now considering it since my regular long trip of 180mi is marginal/scary. Might I better use Range Mode but STOP the charging @210, say, and then never have to actually use the 'bottom 10%' at all? Thus no 'damage' to the battery plus elimination of range anxiety?

It's been said before in other threads: Charge in "Standard", drive in "Range"

 

[dsm363]

Is the miles estimate on the TC an actual test of battery condition?

I've never used Range Mode but now considering it since my regular long trip of 180mi is marginal/scary. Might I better use Range Mode but STOP the charging @210, say, and then never have to actually use the 'bottom 10%' at all? Thus no 'damage' to the battery plus elimination of range anxiety?
--

You have a Roadster and travel 180 miles on a regular basis? That's got to be tough since that is cutting it close even in range mode charge if you're traveling at 65mph. I agree driving in range mode is a smart idea. You getting a Model S? That 85 kWh pack would make your trip much easier.

 

[SCW-Greg]

Yeah I've heard that keeping the battery between 20 and 80% is optimal, while minimizing charge cycles. It will be interesting to see how the S battery cells/technology will perform compared to the Roadster.

 

[SCW-Greg]

Here is an excellent and detailed thread from Tesla on battery states (SoC), and maximizing longevity.

Tesla Roadster Battery Care