Best practices for prolonging Leaf battery life?

[prberg]

Ok so here is a real world question: My wife left with ~90% this morning for her 15 mile each way commute. She now has 59%. Is it best to leave it there for tomorrow at 59% and then charge tomorrow night? So basically run it between 80 and 20 or as close as you can to that ideal. Just charge every 2 commute days?

You can do what feels comfortable. Lithium doesn't have a memory, and the L2 charge is very, very easy on this pack. There's no reason why you can't plug in every night and charge to 80%.

I'm often able to charge my lithium motorcycle once a week, but will top it off before a longer ride.

Nissan's done 90% of the hard work already. Being gentle with L3 and not storing the car with a full charge takes care of the next tier (but smaller) factors.

After that, we start fighting over crumbs.

So based on your comments... L1 won't really extend the battery life over L2? If we have the time to just use L1 charging should we do it? Or are we just wasting our time?

-Peter

 

[patrick0101]

L1 won't really extend the battery life over L2?

I have been wondering this too? What is the difference in "wear and tear" on the battery for the different charging levels? Is charging at L2 the same as L1 for battery life or is it 5, 10, 15% worse?

Same question for L3. How many (L1) battery lifespan charge cycles does an L3 charge burn?

I have only heard "don't do it too often" when talking about L3. I would like to know more about the lifespan cost, so I can make up my own mind about how often (or not) to use L3.

~Pat
Blue SLe ETA 2 to 5 months

 

[gasmiser1]

L1 won't really extend the battery life over L2?

I have been wondering this too? What is the difference in "wear and tear" on the battery for the different charging levels? Is charging at L2 the same as L1 for battery life or is it 5, 10, 15% worse?

Same question for L3. How many (L1) battery lifespan charge cycles does an L3 charge burn?

I have only heard "don't do it too often" when talking about L3. I would like to know more about the lifespan cost, so I can make up my own mind about how often (or not) to use L3.

~Pat
Blue SLe ETA 2 to 5 months

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Eventually, L3 charging will become more commonplace. I read that a few "gasoline" companies indicated they will have L3 available. If we can't use L3 too often, I'm not sure what is the point of having the port in the car. Unless, future Leaf resale will be better with it?

I don't plan on using the L3 very often, even though our company budgeted the install by spring or summer of this year.

 

[Coffee_Slurry]

I have been wondering this too? What is the difference in "wear and tear" on the battery for the different charging levels? Is charging at L2 the same as L1 for battery life or is it 5, 10, 15% worse?

L1 and L2 should be absolutely identical for battery life. Both charging levels are far below "stressful". Really, in the battery chemistry sense, they're both 'slow charge'.

Most lithium-polymer, lithium-ion, type cells are fine with a charge speed up to one hour. (One hour to go from 0% to 100% of usable range). That's called "1C" charge rate, and is the threshold of fast charging. "2C" rates would be half-hour, and that's a pretty fast charge for most batteries. Some Lithium chemistry cells can do 5C or more (10 minute charge), but that's pretty extreme and requires careful temp monitoring and good cell balancing. 1/2 C would be a two hour full charge. So our L2 chargers, at an 6 hour charge would be 1/6C.

Unless Nissan has some really unusual chemistry here, L1 and L2 should be so mild as to be identical -- neither will stress the battery as it has four hours to soak up a partial charge. Plenty of time for the cells to internally equalize, for the chemicals to diffuse well into the electrolyte, and for the balancer to do its job.

(I would not prefer L1 over L2 at all. In fact, it's probably a little less efficient just for running the BMS and charger longer.)

 

[charlie1300]

So, L1 vs L2 is a classic time vs money decision. L1 EVSE is free, but takes longer. L2 EVSE costs money, but is quicker. So there is no "right" answer. Depends on your situation - which is the scarcer resource, time or money?

 

[patrick0101]

Thanks GroundLoop!

 

[Randy]

Charlie1300,
There is one additional factor, and that is cost of the energy to recharge. My L2 EVSE will go live early next week, as I passed inspection yesterday (yay!). So I've been charging for 4 days at L1. In rough terms, because of the new SDG&E rate I'm placed in for the EVSE, it will be about 20-25% of the cost to charge from 00:00 - 05:00 (super off-peak), which is my new sweet spot

The L1 price is much higher because of our current tiered whole house rate, and the EVSE energy gets added on to my existing usage at the top (or near the top) tier.

Just based on the difference in energy cost numbers, I'd probably want to buy an L2 EVSE even if I wasn't part of the ECOtality project...

 

[DaveinOlyWA]

my opinion; there is no long term detrimental effects of L3 charging as long as you do not overcharge or overheat your batteries PERIOD.

i think the info we have gotten from Nissan is probably due to the fact that the L3 charging network will be slow to develop and Nissan knows that, so they are doing what they can to make L3 unattractive.

now to make L2 3.3 kw when it seems everyone is doing 6.6 is probably a huge marketing blunder. i doubt there is any technical, safety issues, etc.

now to restrict 3.3 for plug in and portable options, ok. i can see that, but permanently wired home options? strange. but then again, i believe that the extra charge time is really not needed generally.

then again, if i were in a TOU area, i might feel differently

Randy; what is your daily driving mileage and how long is it taking you to charge on L1. i am interested since that will be my only charge option for several months (plan to move then investigate a plug in unit)

 

[JimLovewell]

Rules for optimal prolong lithium battery life and how to measure by using the Leaf 12 bar fuel gage.

Bar Note: there are 12 bars, 2 red (0 to 17%) and 10 white (25% to 100%) on the Leaf. The 2 bottom red bars are not counted in the bar numbers listed below. So, 2 bars is really 2 red bars and 2 white bars.

1) Only charge to 80%, 8 bars.
2) Maximum miles from the battery is obtained by running from 80%, 8 bars, to 30%, 2 bars.
3) Do not discharge to more that 30%, 2 bars if it can be avoided.
4) Charge to 80%, 8 bars, when I get to work. If I am making several stops before going home then start charging to 100% one hour before I leave. The same is true for home. Charge to 80% when I get home. If I am going to make a long trip start charging to 100% one hour before I leave.
5) Do not store for long periods of time at 90%, 9 bars and above (4.1V/Cell). Best storage is at about 40%, 5 bars on the fuel gage.
6) Do not store for long periods of time below 30%, 2 bars.
7) Do not store for long periods of time above 86°F.
8) The Ideal operating range is between 50 °F to 120 °F.
9) The optimal storage temperature (just above freezing) is not the same as the ideal operating temperature.

 

[patrick0101]

1) Only charge to 80%, 8 bars.

I assume you mean 8 white bar + the 2 red bars, for a total of 10 bars out of 12.

3) Do not discharge to more that 30%, 2 bars if it can be avoided.

4 bars (2 red + 2 white) is 33%. The "discharge to more" syntax confuses my simple mind. I'll read this as "If I get down to 5 bars, it is time to plug-in"

4) ...If I am going to make a long trip start charging to 100% one hour before I leave.

This is a very good point that I have not seen a discussion of here. One of the main reasons that notebook batteries generally have a short life, is that they are often kept at 100% when they are docked. Lead acid batteries generally 'like' to be kept at full charge, Lithium ion cells are different, they 'prefer' to be about half-way charged. So, as you point out, it is best to charge up soon before you use it, rather than the day before. Granted, this requires a little more planning.

If the Leaf were charged to 80% already, how long would it take to charge from 80% to 100%? The charging rate usually slows down above 80% so it would be longer than the time from 60% to 80%. I assume it would take about 2 hours, has anyone measured it?

 

[DarkStar]

Rules for optimal prolong lithium battery life and how to measure by using the Leaf 12 bar fuel gage.

Here's what I already posted in the "Ways to preserve battery capacity (besides charging to 80%)?" thread that you also replied in.

Due to the latest firmware update, the SOC bars have no meaning anymore. A bar may not be anywhere close to 10% SOC and charging to 80% may not even be truly 80% SOC anymore...

Unfortunately this is a futile discussion since the best way to preserve battery capacity would be to charge to 50-60% SOC and then park the car and never drive it again...

Until we can pull the raw data to monitor the real-time voltage and amperage, while discharging and recharging over the CAN-bus and the traction battery is dissected, we don't even know how large the battery is and how much of it we are using. We have a lot of assumptions without any processes to test them...

 

[pearlyleaf]

Accelerate as gently as possible.

Don't recharge until remaining charge is below 40% - but don't let it go down below 20%.

Keep the car from baking in the sun - especially with a full or near full charge.

Can you cite where you got that information?

 

[DaveEV]

Accelerate as gently as possible.

Don't recharge until remaining charge is below 40% - but don't let it go down below 20%.

Keep the car from baking in the sun - especially with a full or near full charge.

Can you cite where you got that information?

It's all basic lithium battery management techniques. The faster your draw power out of the pack, more time the pack spends at very low or very high states of charge, and the more time the battery spends at high temperatures (especially at full states of charge), the faster capacity will deteriorate.

 

[patrick0101]

Accelerate as gently as possible. Don't recharge until remaining charge is below 40% - but don't let it go down below 20%. Keep the car from baking in the sun - especially with a full or near full charge.

Can you cite where you got that information?

drees is correct. keeping the batteries in the middle ~50% is where it is easiest to move energy in and out without generating much heat. heat is the enemy. I am not too sure that you have to let it go below 40%, but that does reduce the times that you are going up to 100%. you can get your battery learning on here.

 

[garygid]

Although these "rules" about general types of Li batteries MIGHT still apply to the Nissan chemistry and construction, it is NOT a GIVEN that each of these "rules", charge limits, and temperature limits are correct for the Nissan LEAF's battery pack.

Until we have more info, we are just GUESSING, I believe.

If you have data on the Nissan batteries, please present the studies. Data from LiFe..., Polymer, Cobalt, and even other LiMn... cells is only suggestive, but MIGHT NOT apply significantly to the LEAF's battery pack.

But, generally not over-stressing something is correct. We just do not yet know what "over" means in this case.

 

[cwerdna]

How about general practices to try to keep battery temps down?

On Priuschat.com, it seems there might be a correlation between premature NiMH battery failure and those who live in very hot areas and/or who have hilly areas that end up causing the HV battery to be discharged "fully" on climb and charged "fully" in descent). (Prius SoC actually only goes from ~40% to 80%.)

With my Prius, if there's no covered parking available, I tended to park it in a spot where it'd get less exposure to sunlight and be in shady area more hours of the day (e.g. blocked by other things like buildings). I also use a front windshield sunshade. If it's warm out, when there was no chance of rain, I'd also leave the windows open a crack instead of letting the heat buildup inside.

If keeping the battery temps down (esp. w/high SoC) does matter, perhaps the above is a good idea w/the Leaf?

edit: Also, on my Prius, at my apartment covered parking, when it's hot out, I back in so that the rear hatch area is always shaded (since the HV battery and 12 volt is in that area) and only the hood of my car (where there are no batteries) gets any exposure to sunlight.

 

[planet4ever]

I doubt if reducing the cabin temperature with techniques like windshield shades or windows open a crack will have any significant effect on the battery temperature. More important might be whether you park on hot asphalt. (i.e. already hot before you park. The car will shade the asphalt, keeping it cooler than its surroundings after you park.)

Ray

 

[Herm]

Nissan has mentioned that heat will shorten the life of the battery.. This type of chemistry is very efficient when operated within an 80% SoC (from 10% to 90%), very little heat is generated.. but outside those limits using the battery produces more and more heat.. and heat is bad.

High voltage, and permanent keeping the battery there, speeds up degradation of the electrolyte.. thus the recommendation to only charge to 80%.

 

[DaveinOlyWA]

the Prius battery pack is much different that the Leaf pack and its not so much do to chemistry as position and possibility of thermal management. the Leaf pack being in the floor has a better option for better air flow. the Prius pack was basically enclosed in the trunk with only a few vent fans.

also we have to look at the fact that there has been a very small percentage of Prius pack failures in any temperature conditions

 

[GaslessInSeattle]

Herm, I think you have nailed it. That's the most succinct explanation I've heard yet!
G

Nissan has mentioned that heat will shorten the life of the battery.. This type of chemistry is very efficient when operated within an 80% SoC (from 10% to 90%), very little heat is generated.. but outside those limits using the battery produces more and more heat.. and heat is bad.

High voltage, and permanent keeping the battery there, speeds up degradation of the electrolyte.. thus the recommendation to only charge to 80%.