Electric Car Battery Packs and Longevity

It’s 2016.  We’ve all messed around with lithium battery powered devices.  Cell phones, laptops, tablets, GPS units, smart watches, hoverboards… whatever.  After a few years worth of use, they all have absolutely terrible battery life, and you need to either replace the battery (if that’s even possible) or buy a new one (with the manufacturers, obviously, preferring you to buy a new one).

This is a companion discussion topic for the original entry at https://www.sevarg.net/2016/01/03/electric-car-battery-packs-and-longevity/

(Comments from Blogger)

2016-01-03 by stevejust

I have a 2008 Tesla Roadster that you managed to ignore. It’s on it’s original battery pack. In 7 years it has lost about 26% ish of it’s original range. I find that totally acceptable, since it’s still got easily twice the range it needs to have.

2016-01-03 by Unknown

What about Mitsubishi or Kia? I understand that they are thermally managed as well. Mitsu is so much so that they don’t put a temperature gauge.

2016-01-03 by Russell Graves

The Roadster isn’t being produced anymore, so it’s not something people in 2016 are likely to care about that much. As near as I can tell, it’s a lithium cobalt oxide chemistry, with some sort of liquid cooling, but I wasn’t able to find detailed information. It seems like it was fairly well done, but they’re using a bad chemistry for longevity since that’s what was available.

I’d expect to see less loss on the Model S than 26% in 7 years. How many miles do you have on it?

2016-01-03 by Russell Graves

I’m not familiar enough with them to really speak with any authority - though you should be able to use what I’ve written to determine how they’re likely to hold up.

Mostly, I picked electric cars I’m familiar with through talking to owners regularly.

2016-01-03 by Unknown

Well, I’ve had one in the Caribbean for a year now. Its held up well, but I haven’t done a diagnostic since its been here. No authorized dealers. I’m also leasing my second Leaf in DC. Battery issues on that are exactly how you discussed. Its a business expense BTW.

2016-01-03 by Unknown

To be clear, I have a i-Miev in Saint Martin.

2016-01-03 by Russell Graves

The i-Miev, at least in some countries, is using a lithium titanate battery, which has poor energy density (so range will be less than you’d get with a different chemistry), but is otherwise nearly indestructible. That’s a pack I’d be perfectly happy with no thermal management on beyond perhaps an extreme cold weather heater, because it just doesn’t seem to die.

2016-01-03 by Unknown

I’ve got an electric conversion with a 40-cell, 160Ah LiPO4 battery pack. My question regarding battery pack longevity is what changes when the capacity goes down. Does the practical amp-hour rating of the pack go down (i.e. my pack will really have 120Ah in 5 years) or does something else go down? Part of the reason I’m wondering is because I have a meter that measures the amp-hours used, so in 5 years, will my pack die when I’ve used 120Ah? If so, is there any way for me to know when it’s going to be dead when the amp-hour rating isn’t accurate? Would the voltage still reflect the energy level of the cell (i.e. 2.7V is at the bottom of the charge curve and means the battery has very little energy)?

2016-01-03 by Russell Graves

The usable amp-hours are what decay over time. So your 120Ah pack may only have 100Ah of capacity at some point in the future.

The voltage curve will remain the same (so, basically useless for anything involving LiFePO4 except when it’s stone dead). The voltage will continue to reflect the energy level of the cell.

The answer is to run the pack down to your specified cutoff voltage every now and then, see how many Ah you get out of it, and then recalibrate any range gauges you have based on that.

2016-03-28 by EvPositive.com

At EvPositive we are putting battery degradation knowledge into the hands of the EV owner. Our Apps feed battery degradation statistics to our website so owners can compare their EV to other owners of the same vehicle, and if necessary change driving or charging strategy. More info here www.evpositive.com/battery-history.html

2017-05-03 by badijet@gmail.com

Thank you for your analysis. I live in rural Canada, and am thinking of getting a Leaf. I do not think longevity is as much of a consideration as you imply. Who knows what batteries will cost, even after next year when Tesla’s huge battery factory comes on line? Even now, you can get a replacement battery for a Leaf for less than $5k. If I buy a new leaf, in ten or twenty years when it needs a new battery, I will be happy to upgrade the battery. It will be like getting a whole new car. Here, where roads are salted, it is rust that will destroy the car, not the life of the battery.