Seeking Pack Size VS. Degradation and Cost Analysis/Info

[gkalexdc]

No doubt there is a meeting place, but only if you consider cost in the calculation. Here's the best explanation I've seen about battery degradation.

Re-reading your post and Robert.B's response re memory, I think you're asking if the larger battery would last enough longer than a smaller one to pay for itself (ignoring convenience)? The answer is: Very unlikely. There is no graph like you're asking for because there are just way too many variables to be able to come up with anything remotely accurate. 70 miles/day would be no where near enough miles for the 85kwh pack to pay for its premium over the 40kwh pack by longevity savings. Nobody knows what a replacement 40kwh pack will cost of course, but my guess is that you'd have to be discharging it to near zero at least once a week before it would wear out in half the time of the 85kwh pack.

The main reason to buy a 60 or 85kwh battery is convenience and performance. And BTW, you will charge the larger pack just as often as the smaller one except when taking long road trips.

Why would a larger capacity pack have more cycles? I don't think you understand how these cars work. Or I'm misunderstanding you.
Jerry33's quote said the more shallow cycles of charge make for more longevity, if I understood it correctly.

With respect to the questions you're asking, yes we have a lot of data. Assuming I'm understanding you. The larger battery will last significantly longer than the shorter one even if you drive both of them exactly the same number of miles at the same speed every day of its life.


The return on your investment has much more to do with convenience and performance as I stated above. There will also be a return based on longer life, but a 40kwh replacement pack will be cheap enough in 5 yrs that you could probably buy 2 or 3 of them for the same price as one 85kwh pack in 2012. You would have to really drive your car HARD to wear out 2 or 3 smaller packs in the same time as one 85kwh pack would last. So the 85kwh pack is a bad investment unless you want longer trips and better performance. Hope I explained it better.

These are VERY informative answers !! I feel lucky to have found this forum, and you all are very intelligent. Your explanations are getting the job done here.

[gkalexdc]

No doubt there is a meeting place, but only if you consider cost in the calculation. Here's the best explanation I've seen about battery degradation.

It seems I couldnt get the "Science lesson Quote to copy, See Jerry33's Science lesson above !!

[tennis_trs]

Typo:

...
40 kWh goes 125 miles on a cycle, or 125,000 miles for the life of the battery. Cost is $20K. That's $0.016/mile.
...

Looks like it should be $0.16/mile.

[hcsharp]

It seems I couldnt get the "Science lesson Quote to copy, See Jerry33's Science lesson above !!

That wasn't Jerry's science lesson.

[jerry33]

That wasn't Jerry's science lesson.

I did my best to give you the credit.

[gkalexdc]

This was JUST the explanation I was seeking . Thanks for your analysis. I do wish that a pack was infinite in its shelf life....the operative is WISH. I just would like to be able to drive ELECTRIC to Austin from Houston and/ or not have to drive like grandma in my LEAF, which I have now. The Tesla is superior for sure.