Battery & Charging primer

[ironmanco]

I know there are lots of threads (stickies included) on this subject but I was wondering if there is some definitive information out there that I can use as a guideline/reference? Most of the threads include banter back and forth and not that I'm not game for some good debate, I'm thinking there is some pretty strong guidelines for this subject that can be generalized.

I'm looking for some information about charging guidelines for my leaf. I know the general rule of thumb is not to charge from a high SoC (>80%) but I was wondering what drives this. Also, does that mean I can do a fast charge to 75%, pause then charge the rest of the way to 100% without issue? Is there a difference in how I should approach charging when doing a L1 vs. L2 vs. fast (CHAdeMO).


Thanks,
Andrew

 

[LeftieBiker]

It would be nice to have FAQs of these subjects, but the site isn't set up that way. To answer your question: lithium batteries are kind of like balloons filled with water. They can hold much more energy than is good for them. That means that the capacity above 75-80% should be used for short-term storage, and not kept full for long periods. You can charge from 75% to 100% with no problem, as long as you use the car shortly after reaching 100% - within a few hours. This is more of an issue in hot weather than in cold, but I wouldn't leave a pack sitting at 100% indicated for days in any weather...

 

[ironmanco]

It would be nice to have FAQs of these subjects, but the site isn't set up that way. To answer your question: lithium batteries are kind of like balloons filled with water. They can hold much more energy than is good for them. That means that the capacity above 75-80% should be used for short-term storage, and not kept full for long periods. You can charge from 75% to 100% with no problem, as long as you use the car shortly after reaching 100% - within a few hours. This is more of an issue in hot weather than in cold, but I wouldn't leave a pack sitting at 100% indicated for days in any weather...

Yea - that's what I was kind of looking for. Even if there is a site outside of mynissanleaf.

Thanks for that info. I almost never wind up with a 100% charge since I typically charge in town then drive home. Sometimes I'm in the 90% range but not that often.

 

[RegGuheert]

Good questions, ironmanco!

While there is excellent information on LI-ion batteries at Battery University, there are so many subtle differences between different implementations of even the same Li-ion chemistries and their charging and cooling systems (e.g. LEAF versus Volt) that generalizations from external sites do not help much.

As far as what we have learned through our collective efforts over the years, Stoaty has done an excellent job of compiling that information in the Battery Capacity Loss Wiki. While there is not a concise table of charging recommendations to be found there, the information should help to guide charging behaviors to minimize capacity loss. Unfortunately, at the end of the day it appears that our behaviors do not influence capacity loss as much as we would like to think.

Finally, I will say that you have purchased a LEAF with a different battery chemistry (NMC) than most of the rest of us own. NMC should have more capacity and better capacity retention than the LMO chemistry the rest of us own. As such, your experience should be significantly different than what was previously the norm. In a sense, you will be a part of the new generation of LEAF owners to collect the data and inform the world about what works and what doesn't in terms of LEAF charging habits.

 

[ironmanco]

Good questions, ironmanco!

RegGuheert - thanks for the info. That's EXACTLY what I was looking for. Pretty much that this is a whole new ball game with this version of battery and though the overall guidelines still probably apply, this version of the Leaf battery will produce a completely new profile.

So....what can I do to help provide data for the profile? I know there is leafspypro connect via the obd port....but my Leaf is new and I'm not sure what I should be capturing to create this new battery "profile".

 

[RegGuheert]

So....what can I do to help provide data for the profile? I know there is leafspypro connect via the obd port....but my Leaf is new and I'm not sure what I should be capturing to create this new battery "profile".

I collect the following information from LeafSpy in a Google spreadsheet following each drive (but not as much lately), having turned off climate control and letting the car sit for a few seconds before shutting off the vehicle:

- Date
- Odometer
- Capacity (Ah)
- Hx
- SOC
- VBatt Min
- VBatt Ave
- VBatt Max
- Temp 1
- Temp 2
- Temp 3
- Temp 4 (I don't think your car has four temperature sensors)
- L1/L2 Cycles
- QC#

I also try to capture the following:
- OAT from dash just before shutdown
- Nimber of bars shown on Carwings following shutdown, but before charging

From the above information, I calculated other values, such as:
- Capacity %
- VBatt Diff
- Cell Voltage Loss Inspection (CLVI) - This is the number Nissan uses to determine if there is a bad cell or not.
- Hx/Capacity % - (Not really needed, but I find this value tracks Capacity % closely. In other words, Hx is approximately (Capacity %)^2.)


If there is certain information about the trip which might be useful, I also add this in notes:
- If this was a particularly long drive, I will record the details of the trip.
- If I did something unusual, such as a QC, I record that.
- Did I pass LBW? If so, at what SOC did that occur and how many miles before this reading?
- Did I pass VLBW? If so, at what SOC did that occur and how many miles before this reading?
- Did I see the Turtle? If so, at what SOC did that occur and how many miles before this reading?
- Did the battery shutdown?

Others may have more parameters that they track, but this is what I do.

Here is a link to my Google spreadsheet in case you would like to make a copy to help get started.

 

[lpickup]

lithium batteries are kind of like balloons filled with water

I like that analogy...I have been using a rubber band wound up tightly (like on a toy car or plane), of course that has the negative connotation of a toy car, and the balloon analogy is actually physically close.

I collect the following information from LeafSpy in a Google spreadsheet following each drive

While I've had LEAFSpy for years, I've only recently started doing this once I realized how LEAFSpy actually makes this super simple (well, actually it does it for you) if you take the time to make sure that it connects to the dongle at the beginning of the drive (somewhat of a complaint that LEAFSpy, while it runs in the background the whole time, will only connect to the OBDII dongle if you bring it to the foreground, at least in my case).

Anyway, I've noticed that my AHr and SOC% have actually climbed recently. I think I've seen a brief mention of this behavior. Can someone explain what would cause this? I think the reference I saw said that it's typical behavior in the winter as temps get colder (but I can't quite recall).

On 1/4, my AHr/SOH bottomed out at 47.186 / 71% and has generally been climbing since then. Today it is at 48.045 / 73%.

Is this due to colder temps? Is there an adjustment that I could make based on pack temp (doesn't look like that data is captured in the LEAFSpy trip log, maybe it should be)

 

[ironmanco]

totally unrelated thread hijack (feel free to PM me) - how do I change my icon/avatar? That functionality is not available to me.