Which Charging Method is Best for Battery Health? Conflicting Information...

[GoldDeluxe5e3]

I'm one of those new people who have been reading your posts but have not yet commented.

Now, things have changed, since I just purchased a 2016 SV with just 46k miles on it. So far, I've just been charging it at home on the 110v charger, but I'm making my initial attempts to charge it away from home. I lurked around a set of charge stations at the supermarket today (Concord, CA), and happened to have a conversation with a man who was gingerly backing a huge, white "Lightning" truck into a charge spot.

In our conversation, he told me it's best to use the Chadmo charger instead of the level 2 charger since the Chadmo charger slows charging over 85% and would not harm battery health. That is the exact opposite of everything I've learned about charging methods so far, but by now, I have heard:
- Charging at home on the 110v charger is time consuming, but easiest on battery health.
- Charging on a level 2 charger is better because the shorter charging interval produces less heat, so easier on battery health.
- Now this guy comes along and tells me using my Chadmo port is the best way to go since it doesn't hurt the battery and is faster. Btw, this guy was very nice and sincere, but had a French accent and Iowa plates. Perhaps he was imparting wisdom true in Europe or Iowa, but not in CA. (Insert your jokes about the French, Iowans and Californians here.)

So my first question to this august group is, "what the hell?" What is the best way to charge my LEAF?

 

[Chad E. Mo]

The consensus is that charging from 20% to 80% provides the longest battery health.

In my opinion, the L2 charges at a slow enough rate to get the best cell balancing.

I recently have needed to travel and frequently use rapid DC charging... my cell balancing went from ~12mV difference (between cells) to ~100mV.

I regularly L2 charge to 100%, but use the car within 12hrs of topping up, so the pack does not stay at 100% for long.

Multiple DCFC (chademo) on a continuous trip can excessively heat the battery and shorten its lifespan.

 

[nlspace]

Realize that your HV traction battery pack is sealed and has no airflow or provision for cooling the cells. Charging and driving causes heating of the cells; higher currents cause higher heating.

With that in mind:
AC charging (Level 1 or 2) at the lowest voltage and slowest rate that will still be acceptable to your needs. The 20-80 rule of thumb is a good guideline, but charge higher if needed and don't worry about it, just drive and charge as needed.

Avoid DCQC Chademo (Level 3) unless needed for an emergency, then only enough to get home.

 

[Chad E. Mo]

...then only enough to get home.

Caveat to the OP: don't trust the range meter in the instrument cluster until you know how yours behaves with your particular situation. Until then, charge at least 50% more than it says, especially in the cold weather.

 

[Turbo21]

I wouldn't say consensus , 35 to 65% with a monthly top up to 100 to fully balance the pack seemed like the "best" , 20/80 is a convenient compromise but it depends on the user , if you do a lot of km on the wee car then charging to 100 and using immediately after seems to have little impact in reality. Have a look here on depth of discharge vs number of cycles .. https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries#google_vignette , then look further below at 25C temp charging full vs 40% , then see soh retention further below 75 to 65% discharge and how it impacts total charge cycles possible and SOH. It just depends if you go to the shops or do big Km , its why i would never pick the leaf for big Km general use but love it as a shopping cart. "Jessie" from Breaking Bad had a saying about this sort of thing , something about science etc ... its near impossible to trust anecdotal evidence however when someone has a 24Kwh leaf with a crazy high SOH i ask how and sure enough , slow charge , low charge is the answer. So there is the theory and the practice all lining up .

 

[Wrench7747]

I wouldn't say consensus , 35 to 65% with a monthly top up to 100 to fully balance the pack

I agree that 35 to 65% is optimal, but the monthly full charge is not necessary. Yes, many or most other common li-ion BMSs will only top balance, but the Leaf BMS does constant balancing. It does not need to be charged to 100% to balance the cells. This can be seen in real time with LeafSpy.

 

[Turbo21]

I agree that 35 to 65% is optimal, but the monthly full charge is not necessary. Yes, many or most other common li-ion BMSs will only top balance, but the Leaf BMS does constant balancing. It does not need to be charged to 100% to balance the cells. This can be seen in real time with LeafSpy.

i thought so too until my cells were never balanced on leaf spy , only when charged to 100 were all of them "blue" its the only way to make them blue that i know of , if you know another way I'm happy to learn another new thing for the day.

 

[GentleGiant]

I agree that 35 to 65% is optimal, but the monthly full charge is not necessary. Yes, many or most other common li-ion BMSs will only top balance, but the Leaf BMS does constant balancing. It does not need to be charged to 100% to balance the cells. This can be seen in real time with LeafSpy.

i thought so too until my cells were never balanced on leaf spy , only when charged to 100 were all of them "blue" its the only way to make them blue that i know of , if you know another way I'm happy to learn another new thing for the day.

The Leaf has been through several iterations over the last 14 years, it may be that different versions of the BMS do things differently; certainly the advice was always to do a monthly 100% charge to cell balance on the early cars - just as it is for my early Kia Soul; and on the Soul at least, even this balancing ONLY occurs when charging to 100% using an AC charger, not a DC rapid charger.

Now, I dont know if these differences between your two experiences are due to software updates or actual hardware differences between different model years/BMS versions, or battery sizes.... It might be worth comparing specs, rather than argue.

 

[Wrench7747]

its the only way to make them blue

Making them all blue is not a need for a balanced healthy Leaf battery, and does not need to be done on any regular schedule in the Leaf. As long as the difference in top to bottom cell voltage is low, like 10 to 20 mV, then the battery is balanced. Anything more minuscule than that is overkill.

It's like reading that you should drink a liter of water per day, and then using an eye dropper to make sure you dispense exactly one liter. Or going to the barber to get a haircut, and insisting on them shaving your head completely every month, as the only way to make sure every hair is exactly even.

If you're going to go to that extreme, then why is keeping the pack SOC between 35% to 65% good enough? Why not keep it at 40% to 60%? Or 45% to 55%? Or 49% to 51%? Recharge every kilometer you drive. We don't do that because this is all about optimal tradeoffs and practical usage versus battery health.

Yes, you can charge to 100% to the point that the BMS has absolutely nothing possible for it to do (all showing blue in LeafSpy). But nobody needs to do that for good battery health.

 

[jc2024Leaf]

A fairly good summary and scientific discussion (video) was posted here: https://mynissanleaf.com/threads/battery-best-practices-interesting-research.34956/
The video doesn't directly address DC charging (if I remember correctly) or whether slow charging is beneficial. Also some of the presenter's thinking is based on cars with active thermal control of the batteries which the Leaf is lacking.

Having taken Thermal Dynamics many moons ago for my engineering degree, I suspect that it would be better to charge at a slower rate if you have to replenish more charge. I would think this would produce less heat than if you tried to pour in electrons quickly.

My R/T daily commute is ~50 miles M-Th. Base on my research so far, I plan to try to charge to ~75% (have to guess since the Leaf can't control) and add charge after every use. Bump up the charge Thursday night if we have a trip planned for the weekend. I would like to charge at 240V/10 or 12A, but I only have the Nissan OEM EVSE, so far.

It would be really nice if we had solid science behind all this, and EVSEs that communicated with the vehicle and took into account how far you want the vehicle charged to, what the temp is, vary the current based on what is best for the battery for the given time you have to charge. Then the darn EVSE might actually be worth half a grand to buy and so much more if you pay to have it installed.

 

[WetEV]

If you're going to go to that extreme, then why is keeping the pack SOC between 35% to 65% good enough? Why not keep it at 40% to 60%? Or 45% to 55%? Or 49% to 51%? Recharge every kilometer you drive. We don't do that because this is all about optimal tradeoffs and practical usage versus battery health.

Extreme pack protection would be 35% to whatever you need to do your trip. Recharge ending just before the trip.

Would be a lower range of SOC if your trips are not frequent, or if temperatures are high.

Ideal charge rate would be about 0.1C, for a 60kWh battery that would be 6kW, a typical L2 rate. L1 would be better at very low or high temperatures.

High SOC increases the rate of "calendar" loss, as does high temperatures. So keeping the average SOC as low as possible will extend battery life. Oh, but not too low of SOC, as "cycling" loss increases at low SOC. The exact "best" you could do would be to minimize both types of loss, while meeting availability goals.

If you are designing a gadget that has fairly predictable usage, you might code all this into the battery controller. The Failure Analysis department might give you a gold star two decades later, long after you left the company. 20% longer life saved the company money.


But for humans with a car? Mostly don't bother with details. Get mostly good, and stop there. Charge to 100%? Sure, on a timer. Avoid 100% by setting a timer window too short? Sure. Keep an eye on the pack balance, a weak cell might be babied along with more frequent 100% charges to keep the pack in balance. Maybe. But if the pack is close to balanced, no point.

Practical considerations need to be considered as well. What if there was a big storm or an earthquake or whatever, and you needed to drive 50 miles to a hotel or a hospital? This implies you should have more charge in the battery than ideal for battery life.

 

[Turbo21]

Yes as mentioned above its generally practical to charge 80/20 as real humans with lives etc , i have a timer so when i plug in at 35% ish it cuts off before full charge for me , i dont have to lift a finger or even program anything each time. charging to 100 is based on exp of a lack of full balancing on my Leaf 40kw 2018 , for sure other models might attack the balancing problem differently. I can sleep well knowing im doing what i can within reason , i'm only 5k from a friends with Solar so power cuts , even long term are not a bother to me , of course you would struggle to pump fuel in a cut too , i doubt garages have manual pumps these days . Each to their own but its good for people to know alternate approaches , the reasons behind them and then have their own free choice to do as they please. i still have an old gas car so a bet each way in an earthquake that reminds me i should start it up today , its been a while.

 

[jc2024Leaf]

Extreme pack protection would be 35% to whatever you need to do your trip. Recharge ending just before the trip.

So I've read that it is better to delay charging immediately after driving. Is it better to end charging just before a trip or is it better to have a cool down interval between charging and driving. I'm thinking daily commute here.

 

[Drew21]

So I've read that it is better to delay charging immediately after driving. Is it better to end charging just before a trip or is it better to have a cool down interval between charging and driving. I'm thinking daily commute here.

It probably depends on your specific driving and weather conditions. If your battery temperature is "in the red" when you finish a drive, you probably want to delay charging until it cools as much as possible.

If you just finished a moderate drive on a moderate day, and your battery temperature gauge is right in the middle, it probably doesn't matter.

 

[frontrangeleaf]

My 2 cents - the recurring advice *not* to over-optimize your charging habits is well-taken. Don't over think this.

It's natural to want to avoid making "the dumb mistake" and EV's do represent a new technology for folks just getting into them, so the concern is understandable.

"Get mostly good and stop there" is sage advice.

To summarize:
- "Live in the middle," i.e., avoid leaving the car at 100% or very low charge for long periods, 20-80% is a useful guideline. Adjust as you see fit.
- Avoid DCFC unless necessary. Charge at L2 or L1 rates if you can. L2 is a useful intermediate solution for many, meaning 6.6kW for most of us.
- Watch your battery temperatures. If the battery is very hot, let it cool down some. Likewise, avoid charging a stone-cold battery near freezing.
- Battery temps ≠ ambient temps. The battery is large and very heavy - it has a lot of thermal inertia. Parking overnight in the cold is fine, unless you get some pretty extreme weather.

In 5+ years driving our Leaf in town, I have never seen the battery temp outside of the normal range limits, either hot or cold. Under normal circumstances at least where we live, that's not as big a concern as one might fear. Our Leaf lives outside year round. There was one extreme weather event where we saw temps in the mid negative teens, Fahrenheit. I pulled it into the garage that night. Otherwise, not so very worried about it.

Enjoy your car. It's a competent little vehicle.

 

[Turbo21]

The battery university link i posted earlier also shows battery temp vs life span and you are correct in wanting to avoid extreme high temps. There is science behind all of the general advice given and it shows you fairly precisely what the consequences are of ignoring them , no need to guess. Many people have habits formed loosely around this advice and throw a pinch of salt over their shoulder if in doubt and carry on . It's a great idea if you come home from a long trip running warm to delay the charge start as long as you can before it starts to impact your future plans, heat is the single greatest enemy of long life from these packs

 

[hradek]

I think it is pretty simple. Avoid charging when it is very hot. Can't recommend this car to anyone who has to drive in the heat but I would like to hear back from those up north.

 

[RPaulThomas]

Hello all, sending my 2c from 'up north', but actually I am south of most of Michigan and Wisconson. North shore of lake Erie.

Anyway, the first winter with my 2018 I charged to 100% almost always. Then I switched in 2nd year to 80% max unless full range was needed. In 5 years it went down to about 91% and now at 6.5 years its about 89% SoH. So as far as I can tell it isnt much differing than other climates, minus the hot southwest.

For range its harder to say. My driving habits altered a lot a year ago. It was mostly urban and some highway, about 80/20. Now its flipped to about 30/70 and I still get 235-240 kms full range in summer (40kWh pack). Winter of course loses but thats very temperature dependent.

So, my conclusion is the battery is right in line with others and my range gets hit in winter but not permanently. I cant say the colder weather has harmed the battery.

I would like to hear back from those up north

I expect I see all the same limitations as anywhere. A DCFC was done in summer some years ago on a hot battery. Not in the red but close. Charge started at 45 kW but within 10 minutes the BMS dropped the feed to about 25 kW, to not stress the battery I assume.