Optimum Charging Strategy - 2012 Leaf

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mwilliams

Member
Joined
Mar 31, 2016
Messages
13
Hi All,

First special thanks for the guidance in the past from this forum as I acquired a 2012 Leaf with 22 months left on the battery warranty with 10 bars in Texas. We fell to 8 bars in February and had the new warrantied battery put in.

So, I want to now optimize the new battery to last as long as possible. Trying to formulate the charging strategy. I've hear about only charging to 80% to extend the life, but then I have also read in recent post that should take to 100% once in a while to balance battery load.

Is there a more specific recommendation/best practice? Like if this is correct, then how often I should charge at 100%.

I appreciate your help.

Thanks,
Marc
 
keep it cool.

now the key thing to remember with everything below is how convenient it is do whatever I suggest. sometimes its easy, sometimes not. The real thing is the car is meant to haul your butt around. that is the highest priority.


minimize time at full charge especially when its hot. So plug it in just before bed if you leave first thing in the morning. Or plug it in first thing in the morning if you don't. Get a 240 volt EVSE. This allows you to "cut it close" because a recharge will be much quicker so you don't always have to know exactly what your future holds.


minimize time at very low charge. those warnings the LEAF spits out is not to keep you entertained. If any are active when you get home, plug it in for an hour.

Get a Fitbit and park in the shade. Biggest advice ever for people in hot climates. I see it all the time. People park next to the building because they don't want to walk when there is a covered parking garage a block away... Around here it rains... a LOT and people will walk 100 feet in the rain over walking a block from a covered parking area while staying dry. that is how lazy we have become!

Make sure you have enough range to cover your day along with a bit extra in case something comes up. It is better to charge to 100% and only use half your charge then it is to charge to 80% and run it down to 30%. May not seem like a huge difference but in reality, battery management is really a whole bunch of little things. I can guarantee you, getting caught short ONE time will be more than enough to blow out any goodness you had with several months of diligent battery management.
 
Good advice from Dave, but I suggest parking where the ground is cool(er) is more important than shade. Often these two things go hand in hand, but not always. E.g., parking on dirt in the sun is probably better that parking on hot black asphalt that has just recently been shaded.
 
It is better to charge to 100% and only use half your charge then it is to charge to 80% and run it down to 30%.

Unless you're talking about the benefit of having a reserve when parked, this doesn't matter - at least not for battery health. The OP has the right idea: charge to 80% normally, and to 100% right before use occasionally. You do have it right about not letting the pack get hot or stay hot.
 
LeftieBiker said:
It is better to charge to 100% and only use half your charge then it is to charge to 80% and run it down to 30%.

Unless you're talking about the benefit of having a reserve when parked, this doesn't matter - at least not for battery health. The OP has the right idea: charge to 80% normally, and to 100% right before use occasionally. You do have it right about not letting the pack get hot or stay hot.

1) minimal (if any) evidence 80% helps

2) Top end balance required for maximum range and "once in a while" has not been proven to be effective. Its more like 4-5 days in a row at a minimum.

3) If you plan to use at least 35% of your capacity, there is no drawback to charging to 100%

4) if your life is that predictable, you don't need my advice.
 
All you're doing is replacing my unproven assumptions with unproven ones of your own. ;-) Since there is no 100% confirmed data, anyone wanting to play it safest would be best not charging to 100% if the car won't be used immediately, and not letting the packs get or stay hot. I've been doing that for three of the last four years, and still have about 87% SOH after three hot summers. I believe I lost most of that in the first year, before I understood the heat issue.
 
Here where I live there are dozens of Leafs for rentals. All of them are being raped on daily basis
by a) keeping at 100% for long periods and b) discharged to dead often c) are ONLY charged at DC (as those
rentals do not have home, they are only charged with DC stations).
And not a single action does enough harm to lose lots of bars, since 2011.

Therefore the biggest thing is constant heat (and not even the peaking heat as those rentals are often
driven 200 miles in one shot with multiple DC-charge cycles).
Trying to slow down degradation with all kinds of things except keeping average battery temperature low
has not worked. Some have tried, some have not. And they all lose bars too fast in hot climates.

Forget everything and get a) underground garage b)cooled garage c) white/aluminium vehicle tent (NOT cover!)

The last one will have limited effect but at least removes the direct heat from the sun/pavement.

So the answer for the topic " Optimum Charging Strategy" actually won't give meaningful results.
It does work if one has normal degradation speed (1-3% per year) - optimum charging strategy might slow it down 1%.
But getting 1% slower degradation while having 10% per year - not actually helping.
I would recommend keeping away from going below 30% as it heats up the pack more than anything above that.
And as heat is the main enemy, everything that keeps the average annual pack temperature down helps.

Yes, you actually have to do something big to get less degradation. Switching between 80% 100%, avoiding DC or 110V wont help!
12951da3643eeae5fa835b646408edb7.jpg
 
If those rentals are being charged with DC fast charge stations, they must leave them on them for hours to get a full 100% charge. Are you sure they aren't charging them to 80 or 90% and then leaving them at that? No one here claims that DC charging is bad for Leafs in any context other than when the pack is hot. As for 80% vs 100%, there is no harm in playing it safer by usually charging to 80%.
 
People just leave them at the DC-station. Vehicles charge for up to 59min59sec and then stop
IF nobody takes them for next ride before charging ends. ChaDeMo protocol never continues
for longer than an hour. Yes, vehicles charge above 90%. I can see stats online*.
I personally, when leaving my own vehicle unattended in DC station, usually find that
charge state is between 97-100% after 1h charging session. Most likely same with rentals.
Demonstration of one of my 58min unlimited charging session, I arrived few seconds before the end of the
session and was able to see the current on the screen (preheating was activated, so around 2kW draw
due to PTC heater). https://goo.gl/photos/Up87P7oqghCXrjzE9



No one here claims that DC charging is bad for Leafs in any context other than when the pack is hot.
And even that is not true. Like I said, people just rent those vehicle and never care about temperatures.
Even in our summer packs get to 10 bars easily. Nobody cares, still normal DC charging with no extreme consequences.

*
https://rent.elmo.ee/
click on the Earth icon upper right corner, select English. Click on any green icon on the map to see SOC.
 
The two Leafs I found were at 50% and 69%. I think you are overestimating average rental Leaf SOC and how long it lasts. A rental is likely to be near empty when connected, so they are probably in the low to mid nineties after an hour, which is much better than 100%.
 
I wouldn't call 2 readings a reasonable sample size :lol:
Also there is actually almost no difference in cell voltage from the moment
charging speed is reduced. Charging speed is reduced as highest
cellpair reaches predefined voltage limit, around 4.1V. This voltage is kept until
the end of the charging cycle. 80% SOC is 4.0V.

Definitely people tend to finish with less than 1/3 charge left.

There is almost no difference between mid nineties and 100%.
As 100% is actually far from 100%. On the absolute scale of things
mid-nineties and 100% is something like 89%SOC and 93%SOC.
There is a reason why Leaf has 24kWh pack and around 22kWh is usable.
Usable capacity of that 24kWh is between 0.4kWh and 22.3kWh.

My phone charges up to 4.4V :lol: That is way closer to absolutely 100%.
 
Definitely people tend to finish with less than 1/3 charge left.

So your claim that those rental Leafs are sitting around with 100% (indicated) SOC is hyperbole? I'd much rather let mine sit at 90% or even 95% indicated SOC than 100%.
 
100% on the instrument cluster is just a number. It is definitely healthy and safe. Like I said, it is actually not 100%, it's
less than 95%.

Last 1-3% take an hour so charging on DC will hardly give actual indicated 100% (though the 100% might be shown
it is not actually 100% indicated, first 3-4% vanish twice as fast).

Can't argue that 90% (indicated) is more healthy than 100% (indicated) - we know that ideal is around 30-50%.
But hassling with it gives nothing meaningful in return. In EU a lot of Leaf owners always charge to 100%.
And, as they have 2-4% degradation per year, Why continue massive discussion about 80-90-95-100% (indicated) charging?
Yes, 80% charge by default would slightly reduce degradation.
Question - is it worth to hassle so much to have 1% less degradation per year? That's 10% per decade.

Or is it worth hassling with 5-15% degradation per year due to hot pack? Decade estimation not possible.
 
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