Discharge below 50%?

[arnis]

Range gauge (GOM) does show at the beginning that you have godzillion miles left. And then
at less than 40% it starts to be more reasonable. This results of "disappearance" of those
miles that were never really available.
Charging above 50% is recommended for daily usage.
anything below 80% is not really topping off.

Once a month getting down to very low or turtle does have some benefits. But that should not
be done in hot weather. Heavy discharge really heats up the battery.

 

[Reddy]

Seems to be debatable on this board, but I always charge to 100%, in my mild climate my battery has stayed at ~86% SOH since I bought it 6 months ago.

All known studies show that keeping the average SOC of a lithium battery does in fact reduce the rate of capacity loss. I was pretty diligent about charging only to 80% and then topping off as late as possible for the first 4 years of my LEAF and now as a result it appears that I will just miss the capacity warranty when most others around here who were not so diligent (or changed their charging habits sooner) will make the capacity warranty.

So I think there's good evidence that it makes a noticeable difference all else being equal. It just doesn't make as much of a difference as moving the battery to a significantly cooler climate.

+1 Unfortunately, you are absolutely correct.

 

[Reddy]

I think it is healthy to drain the battery to a low SOC from time to time and then do a full recharge cycle. The only thing that I would actively avoid would be topping off the charge when it is already at a high SOC, such as 70% or more.

No! It is not "healthy" for the battery, but actually shortens battery life (slightly). However, it does allow the battery management system (BMS) a chance to "recalibrate" and figure out more closely where zero and 100% are. This might give a slightly better range in the short term, but will result in less range and more battery degradation in the long term.

Lithium ion batteries have the longest lifetime at lower temps and shallow cycling around 40-50% (e.g., cycling from 40-60% is better than 30-70%, which is better than 20-80%, which is better than 0-100%). There are well-documented chemical degradation pathways at both 0% and 100% charge. This degradation increases with temperature.

All of that said, don't worry too much about it. Just drive it as much as you can, keep it as cool as possible, and leave it "near" 50% when you can. Will it make a huge difference? Probably not much. In 5 years most people will have 20-40% degradation (at least that's what we're seeing for the 2011-2012 Leafs). Hot climate Leafs (AZ, TX, etc.) are probably seeing 30-50% degradation. Keeping the Leaf at a lower average state of charge (e.g., 40% most of the time instead of 80%) will probably make less than 5% difference at 5 years, maybe not even until 10 years. If you are leasing, don't worry about it. If you bought like I did, then try to keep the average %SOC lower (my car is sitting right now at 5 bars and I will drain it down to 3 bars by evening, and won't recharge until 1am-5am on L1).

In the end, calendar degradation will eventually destroy all batteries whether they are used or not. Yes, storage at 20% charge at 35 F will slow degradation significantly, but what's the use in that if you don't use it?

 

[tkdbrusco]

I think it is important to note that there's about a 5% buffer at the bottom and close to 4% at the top. It appears that the 2015 batteries have greater hidden capacity than prior cars. What I meant by cycling through was to not keep using the car from 60-90% on a daily basis. Also we should point out that cycle count is an important factor in battery life and a 30kwh battery will cycle though at about 70% of the rate of prior 24kwh packs because you get more range out of it. For this reason your degradation should at least be 30% better than 24kwh packs.

 

[Reddy]

^^^Agreed. Thanks for adding that. I've read that LiON batteries can last easily last 2000 cycles, and maybe up to 10,000 cycles if kept under optimum cycle and temps. This works out to about 150,000 mi on the 24 KWH Leaf and 200,000 mi on the 30 KWH Leaf. The end of life is highly subjective, but most suggest 70% of the original battery. Only one Leaf in the US has reached (or is close) 150,000 mi and that was in Seattle with nearly perfect conditions (135 mi RT commute with L2 on both ends). For the rest of us, higher temperatures and/or calendar time will degrade the battery as much as cycling. I'm down to 10 bars with 30,000 mi. I fully expect my battery to reach the 8 bar level before 40,000 mi and around its 7th year, missing the free battery warranty replacement by 2 years. In the end, I'll probably get less than 100,000 mi out of my Leaf, but I won't know until 2025 (year 14).

 

[LeftieBiker]

I've read that LiON batteries can last easily last 2000 cycles, and maybe up to 10,000 cycles if kept under optimum cycle and temps.

Then there is the confusing term "LiON" or "lithium ion" battery. It actually refers to a bunch of different chemistries that all involve lithium, but which can last from as little as 500 cycles (lightweight high-density electric bicycle batteries and many similar laptop batteries) to tens of thousands. It looks like even within the term "Leaf battery" we may have more than one kind of specific chemistry...

 

[tkdbrusco]

My 2015 has 26K miles on it and is almost 2 years old (based on MFG date) and my max GIDS are at 273 right now, or about 7% degradation from new. This puts me at end of life (70%) at 110-120K miles in about 5 years. Although there's a bunch of variables that could impact this as well.