Battery Life

Battery Life

This is not about range, but rather how long the battery will live or battery longevity. A Tesla FAQ states: The Tesla battery is optimized for nightly charging: topping off frequently enhances the longevity of your battery. I'm asking about this because this runs counter to other things I've read. is devoted to maintenance of lithium ion batteries, and they suggest that the number of discharge cycles affects battery life. I've had a Nissan Leaf for 1.5 years. (My Model S is being delivered March 22 - April 5, and yes, I am very excited :) Nissan engineers have suggested that battery life is enhanced by charging LESS often, and by keeping the charge between 20-80% of capacity. Don't run down to zero. Don't charge to 100%. Obviously these things happen sometimes, but the less often they happen the better. Even with the Leaf's limited range of 75 - 100 miles, I usually charge three times a week. I had assumed that with an 85Kw battery (the Leaf only has 24.4Kw) I would only be charging once a week.

Is the Tesla battery that different? Does the much larger battery react differently? Is this just a religious war between different engineers?


KendallPB | March 9, 2013

First, a general site may not know just how Tesla's batteries are made. But second, most of this isn't contradictory (maybe none is). Tesla also recommends against letting run down to zero and says that doing a max charge (to 95% or 100% or whatever it is) reduces battery life.

The devices I own nowadays also say to keep them topped off (iPhone, iPad, etc.) and I believe they use lithium ion batteries as well.

I suspect your confusion comes from "number of discharge cycles"--that's full cycles. So discharging from 80% down to 60% is not using up one of those precious cycles. So keeping it topped off does not contradict what says. Heck, they even have a chart showing that you can get more smaller discharges than if you do a full 100% discharge:

300-500 100% discharges but if you're doing 50% discharges you, not 600-1000, but rather 1,200-1,500. "A partial discharge reduces stress and prolongs battery life."

So I don't think this runs counter to what Tesla says at all. I wouldn't take Nissan's recommendations for Tesla's batteries, BTW...not the same batteries, I'd trust each automaker to make smart recommendations for their own cars--it's in their own best interests to give good recommendations. ;-)

negarholger | March 9, 2013

The design philosophy is different: the Tesla battery is a web of 8000 small batteries and if one fails it has only little effect on the performance of the entire battery pack. Traditional batteries like the the one in your ICE (12v) or Boeing are big cells in series - if one cell fails the entire pack fails.
All batteries have a natural degradation over time. How fast depends on the environment. E.g. in the leaf the cells are air cooled and stacked vertically. During charging or discharging heat is created and rises - meaning the top cell is always hottest. In contrast TM cells are in a horizontal sheet and liquid cooled or heated.
It is not "a religious war between different engineers", but completely different battery pack strategies. The TM pack is designed with cell failure in mind, traditional designs ignore cell failure.

Brian H | March 9, 2013

A test engineer told me he is astonished at what Tesla has achieved. In a remote test range, cars have been supercharged hundreds of times serially, full, without detectable loss of capacity, so far.

No, P_D, I am not making anything up. P_D-off.

Pungoteague_Dave | March 9, 2013

Good question and points. I don't think anyone knows the answers except TM, which advises in the manual to plug in when not in use, thereby always topping up to the standard charge limit. it would be nice to have a better handle on the impact of charging less often, max range vs standard charging, and Supercharging on battery life. We are told that max range and SC use reduces life, but some say that is just engineers being conservative, and that both practices have no real deleterious impact on the battery system.

It may be that no one will know for years. We have been surprised by the battery life in our daughter's 2004 Prius with 225k miles, which seems good as new after nine years and hard use. The Toyota dealer in Annapolis tells us that they have never replaced a Prius battery, despite lots of anticipation that this would eventually impact all hybrids. Maybe battery technology took a leap ten years ago, and we re just now learning that they are more resilient than we think?

Pungoteague_Dave | March 9, 2013

Brian H. Wtf?

My5bAby | March 9, 2013

12,000 miles multiple use of the supercharger and no degradation what so ever. I try not to let the batter get below 50miles range and have only range charged twice.

My5bAby | March 9, 2013

Pungoteague Dave did you see my post regarding a charger in Onley ?

Paul1839 | March 9, 2013

Hay Pungoteague_Dave are you in Annapolis?