L1 / L2 and Battery Life

I'm trying to understand the advantages/disadvantages of L1/L2 charging in terms of battery life. (Are there any?)

More specifically, I was planning on Level 1 charging--at work, no cost--for 80-90% of the power needs for my 2015 Leaf S w/QC. However, "Nissan recommends using normal (L2) charging for usual charging" and, also according to Nissan, "Trickle (L1) charging is not recommended for regular use." (2015 LEAF OWNER'S MANUAL, p. CH-7)

Is Nissan implying that L1 will be detrimental to battery life? Why would they caution against using L1 for "regular use"?

Can anyone direct me to the appropriate thread here and/or online?

Thanks!

Answered yesterday.
See http://www.mynissanleaf.com/viewtopic.php?f=4&t=18789&hilit=convenience&start=20#p405198" onclick="window.open(this.href);return false;.

Here is the response:

Using 120V EVSE is not bad for the LEAF battery.
Occasional charging to 100% at a very slow rate is actually good for cell balancing as the cell pair shunts are more effective at balancing near 100% charge level.
It is less efficient and will put more usage on the LEAF coolant pump but I doubt that would ever be a problem unless you put 200,000 miles on the LEAF.
The 2013 on LEAF charging protocol is better than 2011 and 2012. It spends a lot of time at low charge rate doing cell balancing the last hour.

Why Nissan recommends 120V EVSE for only emergency convenience use is safety.
Most garage outlets are not a good idea.
You really need to be certain.

There are risks with 120V :shock:

As I have advised many people considering use of 120V EVSE that comes with the LEAF and other plug in vehicles:

TimLee said:

A repeat of my input from previous questions on 120 V EVSE use:
Note that Nissan recommends the 120V EVSE for limited emergency use only.
Some people have used it for a long time without problems yet, but in general that is a bad idea unless you have a newly properly installed dedicated circuit with high grade receptacle using properly tightened screw connections.

Previous info from another thread:

mikelb said:

...
Trickle charging should be safe, though, right? I wouldn't necessarily need to have the circuit certified for it or anything, should I? If I were to go to a friend's house, would I be safe plugging into their outlet?

Click to expand...

How safe 120V charging is depends on how lucky you are.
Very few garages have the correct properly installed high quality single outlet supplied by a single breaker.
Code only allows using 80% of the circuit rating for a long term continuous load.
So on a 15 amp circuit nothing else should be on the same circuit while the car is charging.
And a lot of 120V gets put in poorly using push in connections.
One person had a bad fire most likely from staples that had damaged the cable in the wall.
http://www.mynissanleaf.com/viewtopic.php?f=27&t=15784&hilit=+fire#p352567" onclick="window.open(this.href);return false;

Click to expand...

[TimLee beat me to it, but I'll post this anyway...]

That question comes up periodically and the answer is scattered among many threads (difficult to search for it) such as this one:

http://www.mynissanleaf.com/viewtopic.php?f=4&t=18789&start=20" onclick="window.open(this.href);return false;

In short, using L1 charging won't hurt the battery. I believe that Nissan put that statement in the manual because L1 charging is so slow that it makes it difficult to get a full charge overnight and that will lead to a poor user experience for owners, as compared to the much quicker L2 charging. They also may have been concerned about people using substandard 120 V outlets that can heat up if not properly wired or trip a breaker if other devices are using the same circuit. Ideally Nissan would like the LEAF drivers to have an electrician install an L2 EVSE for a better and safer charging experience.

Some other factors to consider:

1) L1 charging is less efficient than L2 charging because the charge/cooling system runs for hours longer for a given amount of charge put in the battery. We think L1 is about 75% efficient whereas L2 should be around 86% to over 90% efficient depending on the charger speed (3.3 kW or 6.0 kW) and the ending charge level ("100%" is less efficient than a lesser charge level because the charge speed tapers as it approaches 100%, leading to higher overhead losses).

2) If you preheat, L1 charging may not supply enough power to do it effectively, especially in very cold conditions (been there, done that). That isn't likely to be important in Chico, CA.


All that said, there are a number of people here who don't drive many miles per day and charge only at L1 and find that it suits their needs fine. If the 120 V outlet used is in good condition, wired correctly, and not shared with other devices, charging at L1 is perfectly safe.

TimLee said:

Answered yesterday.
See http://www.mynissanleaf.com/viewtopic.php?f=4&t=18789&hilit=convenience&start=20#p405198" onclick="window.open(this.href);return false;.

Here is the response:

Using 120V EVSE is not bad for the LEAF battery.
Occasional charging to 100% at a very slow rate is actually good for cell balancing as the cell pair shunts are more effective at balancing near 100% charge level.
It is less efficient and will put more usage on the LEAF coolant pump but I doubt that would ever be a problem unless you put 200,000 miles on the LEAF.
The 2013 on LEAF charging protocol is better than 2011 and 2012. It spends a lot of time at low charge rate doing cell balancing the last hour.

Why Nissan recommends 120V EVSE for only emergency convenience use is safety.
Most garage outlets are not a good idea.
You really need to be certain.

There are risks with 120V :shock:

As I have advised many people considering use of 120V EVSE that comes with the LEAF and other plug in vehicles:

TimLee said:

A repeat of my input from previous questions on 120 V EVSE use:
Note that Nissan recommends the 120V EVSE for limited emergency use only.
Some people have used it for a long time without problems yet, but in general that is a bad idea unless you have a newly properly installed dedicated circuit with high grade receptacle using properly tightened screw connections.

Previous info from another thread:

mikelb said:

...
Trickle charging should be safe, though, right? I wouldn't necessarily need to have the circuit certified for it or anything, should I? If I were to go to a friend's house, would I be safe plugging into their outlet?

Click to expand...

How safe 120V charging is depends on how lucky you are.
Very few garages have the correct properly installed high quality single outlet supplied by a single breaker.
Code only allows using 80% of the circuit rating for a long term continuous load.
So on a 15 amp circuit nothing else should be on the same circuit while the car is charging.
And a lot of 120V gets put in poorly using push in connections.
One person had a bad fire most likely from staples that had damaged the cable in the wall.
http://www.mynissanleaf.com/viewtopic.php?f=27&t=15784&hilit=+fire#p352567" onclick="window.open(this.href);return false;

Click to expand...

Click to expand...

Somehow, Tim, I knew you would know the answer to this.

At work I there are parking/charging spaces that have EV-charging-dedicated, professionally-installed, 120V/15A outlets. These have been in use for a number of years, so I'll assume that these are okay.

At home--the house we rent was constructed around 2000--we have a grounded, 120V/15A outlet in the garage that has its own (15A) circuit breaker. I won't charge much at home, but I did give it a 8-9 hour trial during the day so I could keep an eye on it. There were no problems as far as I could tell: nothing became hot (or even very warm) and the charging rate was about 5-6 range miles per hour of charging.

THANKS, Tim and everyone else who has or will respond to my new-Leaf-guy questions!

What about this post that references a study that says charging at C/2 is optimal? For the leaf this is 12 Kw. Slower charging shows 3% more degradation after 800 cycles. Has real world experience of Leaf owners negated that study? Not a huge difference so I guess all this confirms is that there isn't a significant detrimental affect either way.

Look at the bottom of the "Factors Affecting Battery Capacity Loss" section:
http://www.electricvehiclewiki.com/?title=Battery_Capacity_Loss" onclick="window.open(this.href);return false;

Nfuzzy said:

... Slower charging shows 3% more degradation after 800 cycles. Has real world experience of Leaf owners negated that study? Not a huge difference so I guess all this confirms is that there isn't a significant detrimental affect either way.

...

Click to expand...

One: The report is 13 years old and they were not LEAF batteries.

Two: 3% is a tiny difference. How would you ever see that amongst the noise from other significant variables?

Correct conclusion, there is no significant difference between L1 and L2 on capacity degradation.