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40 Leaf
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Discussion Starter #1
Hi I’ve had a Leaf 40 for a month now, my daily driving uses around 50% of the battery.

Every night I charge to about 80% and running it to 30% during the day.

My questions are is 80-30 the ideal or should I be doing something different and how often should I charge to 100% to allow the battery to balance properly?

My battery has been scanned with leaf spy and appears to have a low cell on it.

This doesn’t however seem to have affected my range at all so I’m not sure it’s too much of an issue, I asked the dealer about it and got fobbed off with a battery health check report, but it still has 6 years warranty on the battery so not too concerned.

But how often should I top balance?
 

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For a while, charge it to 100% daily, see if it rebalances that cell. Might have not been used much/recently.

If all balanced and well, 30-80 is fine, 100 every so often helps keep the balance.
 

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NISSAN LEAF 62Kwh
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The charging routine that I follow is similar to your self, although I charge to 90% if I am going to use the car the next day, I rarely let the battery go below 20% and always charge to 100% and balance the cell at the end of every month.
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With a good charging routine you will probably find the lower cell will come back up, avoid running the battery really low as this puts a lot of stress on the cells especially if they are weak.

Let the BMS control the battery, don't get obsessive about it, and just enjoy the car.
 

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40 Leaf
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Discussion Starter #4
For a while, charge it to 100% daily, see if it rebalances that cell. Might have not been used much/recently.

If all balanced and well, 30-80 is fine, 100 every so often helps keep the balance.
This was a very low miles car I purchased it when it was 2 years old and it had only 3700 miles on the clock.

I’ll try charging to 100 daily for a couple of weeks and see if it improves.

From the research I’ve done the BMS seems pretty weak when shunting cells for a large imbalance.

It will be interesting to see if it will self correct.
 

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This was a very low miles car I purchased it when it was 2 years old and it had only 3700 miles on the clock.

I’ll try charging to 100 daily for a couple of weeks and see if it improves.

From the research I’ve done the BMS seems pretty weak when shunting cells for a large imbalance.

It will be interesting to see if it will self correct.
Even more so you need to do repeat recharges to 100% for a while.

Drop below 50% or so if you can before 100% recharges.

If you have a current/power monitor, keep an eye on it at the point it is almost fully charged, the current will drop away. The longer it takes between dropping from its maximum to stopping altogether, the more it is trying to balance. Hopefully, over time, that will get shorter and shorter and you will know the pack is coming back into balance.

If it is already very short, then you might have a weak cell. Lower mileage seems worse for EVs of a few years than higher mileage, in this regard.
 

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40 Leaf
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Discussion Starter #6
Even more so you need to do repeat recharges to 100% for a while.

Drop below 50% or so if you can before 100% recharges.

If you have a current/power monitor, keep an eye on it at the point it is almost fully charged, the current will drop away. The longer it takes between dropping from its maximum to stopping altogether, the more it is trying to balance. Hopefully, over time, that will get shorter and shorter and you will know the pack is coming back into balance.

If it is already very short, then you might have a weak cell. Lower mileage seems worse for EVs of a few years than higher mileage, in this regard.
I use a commando portable charger (I installed the 32a cform as it just seemed cheaper and easier)

it has an amperage readout on it itseems to currently spend around an hour on the last 2% of the charge and cycles between 0 and 5 amps several times
 

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I use a commando portable charger (I installed the 32a cform as it just seemed cheaper and easier)

it has an amperage readout on it itseems to currently spend around an hour on the last 2% of the charge and cycles between 0 and 5 amps several times
That sounds quite positive, actually. Just let it do this many times, you'll see that 'hour' drop over time, I am sure, and the low cell will vanish.

The cell may be perfect, but it might actually be the monitoring circuit itself!

It's often the actual BMS that causes more cell imbalance than the cell itself! Just takes a very small, but constant, current draw across a component out of tolerance and unless you're using the car daily and topping off at 100% frequently, then it might become significant. I'd wager 9 parts in 10 this is the case for yours and your car is fine, but for a bit more frequent use.
 

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40 Leaf
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Discussion Starter #8
The charging routine that I follow is similar to your self, although I charge to 90% if I am going to use the car the next day, I rarely let the battery go below 20% and always charge to 100% and balance the cell at the end of every month.
.
With a good charging routine you will probably find the lower cell will come back up, avoid running the battery really low as this puts a lot of stress on the cells especially if they are weak.

Let the BMS control the battery, don't get obsessive about it, and just enjoy the car.
Thanks that’s reassuring, I never let my SOC drop below 30% in daily use.

I’ll keep charging to 100 and monitor how long it spends balancing as Donald suggested and scan with leaf spy again in a couple of weeks, fingers crossed. 😃
 

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40 Leaf
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Discussion Starter #9
So, quick update.

I have completed 6 charging cycles from below 50% - 100% and according to leaf spy the battery seems to be about 5mV less imbalanced after 6 cycles.

At this rate (provided the rebalancing continues) it will take about 12 weeks of charging to 100% 6 times a week to even the imbalance.

Does anyone have any insight?

Is this what you would expect to see?
 

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All sounds fine and as expected to me (as mentioned previously).

If you are also noticing lesser balancing time at the end of the charge sequence, then all is well and getting better. When that balancing time stabilises to some given period (it'll probably come down to about 20 mins or so) then you can move to a 30~80% charge regime, with an occasional 100% to provide 'that' balancing opportunity once in a while. I think all that has happened before is a lack of sufficient such 100% cycles, and your case demonstrates why to do that.
 

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We've had our leaf for 2 months now and really love it.
Just had a podpoint installed but it's more of a pain than the Granny charger. With the Granny I could stop charging using a WiFi plug easily. Now with podpoint I have to unplug it ?
Unless there's something I've missed.


Wouldn't be a problem if charging to 100% every night was fine to do but I believe it's not the smartest idea ?

Or am I doing this all wrong ?
 

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40 Leaf
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Discussion Starter #12 (Edited)
We've had our leaf for 2 months now and really love it.
Just had a podpoint installed but it's more of a pain than the Granny charger. With the Granny I could stop charging using a WiFi plug easily. Now with podpoint I have to unplug it ?
Unless there's something I've missed.


Wouldn't be a problem if charging to 100% every night was fine to do but I believe it's not the smartest idea ?

Or am I doing this all wrong ?
Hi what kind of leaf do you have?

If it’s a 40kW and your charging at 6.6 kW/h to 80% you will find it charges at 17% per hour. (or about 3% every 10min)

You can then set the charge start and end timer on the dash to charge to 80%.

E.G. if you start at 35% is will take 2hr 40min to hit 80%. That’s the easiest way.

You should charge to 100% once every 2-3 weeks to prevent your battery going out of balance,

Have you purchased the car new?

If not have you ever scanned the battery with leaf spy?
 

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Even more so you need to do repeat recharges to 100% for a while.

Drop below 50% or so if you can before 100% recharges.
If you're just trying to give the cell balancing time to work and get the pack balanced in the shortest amount of time (weeks) there's no reason to go below as low as 50% as the car won't be balancing until near the end of the charge so you're just cycling the battery more and taking more time to recharge.
 

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It is a 40kw leaf and two years old. Going to have to read the manual aren't I ?😃

No not used leafspy on it. Will investigate that. Thanks.
 

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Other than Tesla no EV battery is actually full when it shows 100%. This paranoia about charging and that you need to do weird charging patterns needs to stop or widespread adoption of EVs just won't happen.

A big benefit of an EV is a "full tank" (or 85% in case of our Tesla) every morning and the simplest approach, (for those who can) is to just plug in every night, especially as that allows preconditioning in the morning if you need to leave for work (less common right now I appreciate). Me and OH don't have a "backup ICE" so need our cars to have sufficient range in the morning for an unplanned longer journey (work or family related).

There is no field data to support that fully charging every night is any worse for the batteries - lab tests of single cells (or laptop batteries) with rudimentary battery control are not relevant.
 

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If you're just trying to give the cell balancing time to work and get the pack balanced in the shortest amount of time (weeks) there's no reason to go below as low as 50% as the car won't be balancing until near the end of the charge so you're just cycling the battery more and taking more time to recharge.
Op says he runs it to 30% daily, so was just clarifying some number for confidence.

I would resist topping back up too much higher than 70% or so, though, TBH.
 

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Other than Tesla no EV battery is actually full when it shows 100%. This paranoia about charging and that you need to do weird charging patterns needs to stop or widespread adoption of EVs just won't happen.

[...]

There is no field data to support that fully charging every night is any worse for the batteries - lab tests of single cells (or laptop batteries) with rudimentary battery control are not relevant.
And your evidence for this is ? Wishful thinking perhaps ? Absence of evidence is not evidence of absence.

It's a fundamental fact that Lithium Ion cells do degrade faster at high SoC and high temperatures and especially when the two are combined. Arguing against this is like arguing against the sky being blue. Go read any number of data sheets for the cells from the companies who actually design and manufacture the cells and it's all laid out, complete with graphs that show expected age related degradation at different combinations of temperature and state of charge. This information helps car manufacturers decide on warranty periods for their batteries etc...

So the burden of proof is on you to prove that this high SoC degradation which the cell manufacturers themselves document in detail would not happen in cars. Where is the carefully controlled study proving your position ?

You're also repeating the myth that Tesla batteries charge to 100% and everyone else doesn't as if all other cars leave a huge buffer at the top. That's nonsense, and I can't find where this myth started. Full charge voltage for most Lithium Ion cell chemistries is around 4.1 to 4.15 volts and varies slightly with chemistry.

My Peugeot Ion charged the cells to 4.1 volts which is typical for Lithium Ion. My Leaf seems to charge the cells to 4.12 volts. (At which point the raw reported SoC in Leafspy is just under 98%, for 100% shown on the dashboard - so hardly a "huge" top buffer) The exact maximum standing cell voltage on Tesla's seems to be difficult to find on a quick search but the best figure I can find is 4.16 volts, someone can correct me if this is wrong.

There is only about 10% of the total energy of a cell available between 4.2 volts and 4.1 volts in most Lithium Ion cells and it is fairly linear over this small range so comparing 4.16 and 4.12 volts you're talking about a difference of at most about 4% in the raw SoC between the Tesla and the Leaf at "full" charge. 4% is insignificant vs charging to 80%.

I do charge my Leaf to 100% on a week day for the daily commute but only because Nissan have given me no other option. Not only is there no charge limit setting, if I do deliberately set the charge end timer later than the departure time to cause it to not be fully charged, if I then enable the climate control timer it completely overrides the charge end timer and ensures the car reaches 100% charge 2 hours before the climate control timer. :rolleyes:

But I do at least use the charge timer to delay charging for as long as possible and don't charge on a weekend unless I'm going to need the range before Monday. No way would I charge the car to 100% as soon as I get home each night. If I had a long range car which also has a charge limiter like the e-Niro I would absolutely limit my commute charging to 80% and just use 100% once a month or before a long trip. Even if the reduction in degradation is modest there's no good reason not to do it if the car lets you and doesn't actively fight you like a Leaf does.
 

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Discussion Starter #18
What I have found with the BMS on the 40 leaf is that the only way it seems to correct any significant imbalance on the cells is by charging to 100% and allowing it to top balance.

Even then it only seems to correct by 1mV per balance if you have a low cell.

I think my imbalance was caused by lack of use for its first 2 years, however if I only charged to 100% once a month I could see that over time a major imbalance could occur.

This morning I climatised the car on battery then drove it half a mile to work with all the heating on and heated rear screen, I arrived showing 98% and then plugged it in at work and allowed it to do a top balance cycle again which took an hour.

Sure enough when I scanned it again after the balance the imbalance had dropped by another 1%.

By top balancing twice a day I should be able to correct my current 71mV imbalance in about 5 weeks, until I started charging to 100% daily it just wasn’t coming down.

It seems Nissan have designed to battery balancing system to be charged to 100%.

Once I have rebalanced the battery I intend to charge to 100% once a fortnight and scan at that frequency to make sure that it isn’t going out of kilter again.

I can’t see that 5 weeks of top balancing 12 times a week is going to do that much harm, after that I will return to charging to between 80-90% depending on how much driving I need to do the following day.
 

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I used to be a bit paranoid about charging when I bought my first Ev. Now I am just blasé - I won’t be keeping my car more than 3 years so if it needs charging I charge to 100%. If it should only go to 80%then Nissan should have provided that facility - as they did I believe on the original 24 kw.
 

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I am not going to get into a big debate over charging, but just one post to clarify my point above...

If an EV has an EASY facility to limit charging to the (contingency) range I need, I am happy to use that as (IMO) it may improve the battery life or usable capability for a future owner.

We use that facility on our Tesla to ensure we have around 250 miles range in the morning. As the Zoe does not have such a facility, if the range is below 150 miles we usually plug it in and let it fully charge overnight.

I believe that in years to come, field data will show that our (no-CCS) Zoe being charged (several days a week) to "full" on a home 7Kw charging point will suffer less battery degradation than one (owned by someone without home charging) regularly taken to a rapid and charged to 80%. I suspect this is why Renault charge £1000 for CCS. It clearly doesn't cost that to add it, but will result in more cost of warranty claims against battery loss in the 8 years.

Finally, unfortunately there are not many public reports based on field data, but here is one
 
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