How long do batteries last?

[Hillhater]

That certainly shows the potential extended life benefit of using a oversize pack .
...but it does mean you have been carrying around a lot of unneccessary excess cell weight and have had extra cash tied up in unused capacity ..for 7 years !
..In effect you bought double the capacity you needed and with such light use the pack has had little more than storage conditions to cope with, so long life should be solely a function of cell quality/ calander life expectancy.
It would be interesting to see exactly how much of that 20Ahr capacity they can still deliver ?

 

[redilast]

That certainly shows the potential extended life benefit of using a oversize pack .
...but it does mean you have been carrying around a lot of unneccessary excess cell weight and have had extra cash tied up in unused capacity ..for 7 years !
..In effect you bought double the capacity you needed and with such light use the pack has had little more than storage conditions to cope with, so long life should be solely a function of cell quality/ calander life expectancy.
It would be interesting to see exactly how much of that 20Ahr capacity they can still deliver ?

A larger pack I guess is a luxury, which is why we see 200+ mile ranges in Teslas, when 99% of the owners are probably not doing more than half that in an average day. I think there is a good balance between oversizing the pack way too much, and oversizing it slightly to get the best cycle life out of it. For example, at a minimum of I was designing a pack for say a 30 mile commute I would probably oversize it by at least 30-35% (10-15% for cell capacity deterioration) then 20% because I would charge the pack regularly to 4.00v per cell in order to quadrupedal cycle life.

 

[dogman dan]

I'm still amazed that sitting in a shed in San Antonio fully charged hasn't killed it. I'm fairly sure it has less than 80% capacity now, but still plenty since you never need more than 10 ah.

Carrying more than he needed was not stupid, as we can see..

 

[jimw1960]

It's hard to tell what the range is now. My round trip commute is about 10 miles. A few months ago, I used it on three consecutive days without a recharge and it didn't cut out. So still has at least 30 mile range.

I'm still amazed that sitting in a shed in San Antonio fully charged hasn't killed it. I'm fairly sure it has less than 80% capacity now, but still plenty since you never need more than 10 ah.

Carrying more than he needed was not stupid, as we can see..

 

[SniperGaulois]

I have heard that Tesla have stated 50,000 cycles would be possible with their battery packs if they were kept in between 30 and 70 percent capacity... It's perhaps 10 times longevity than can be achieved with LiFePo for the same weight...

So that leads to an interesting prospect... we can fine tune the DOD to make the batteries live 2500 cycles by only using 80 percent of their capacity?

It's complex because there are three factors: charge current, discharge current and DOD... that all three play a role in the longevity of the battery... The only way to know is to have some small cells and send them through 1000ds of cycles and see what is the best for achieving 2000 and 10,000 cycles.

There should be a scientific paper published on the matter, for the sake of ecology and the environment, except that it's probably not something battery manufacturers want to research because it can decrease our need for new batteries constantly...

I want to know because 18650 is made for the 3rd world, how to make 18650 packs that last 5000 cycles for rickshaws and things.

 

[SniperGaulois]

Chevy volt use 65pc of the battery only. would be interesting to see graphs from chevy and tesla. here is a good graph, i definitely dont know why we charge to 4.2 volts!!! bad idea!!! it's trading 5 percent more power for 500 more uses!


some graphs here:
http://www.electricvehiclewiki.com/Battery_Capacity_Loss