Rapid battery loss

Hi,
I'm seeing my battery health decline much more rapidly than it was a month or so ago. Just wondering if I've hit some point in the normal degradation curve or something else going on?

A couple of charts in this spreadsheet, table also here:
I bought the car 2nd hand at about 22000km (13700mi) and drove it 80km a day for a month before getting an OBD reader and starting to take readings. At that point (24500km) it was reading 99% SOH and looking good.
The last few days I'm seeing SOH drop by almost 0.5-1% every day. I also noticed for a few days that most of the cells were showing the shunt active, where normally I only see <5. That has since returned to normal.
I'm charging on timer to 100%, timed to finish an hour before I drive to work. It has been pretty warm lately, getting to 6 temperature bars on most drives (around 24-27°C or 75-80°F). Parked outside in the shade during the day, so trying to keep it cool.

Wondering really if running for 22000km and only dropping 1% and then dropping 5% in 2000km is to be expected, or am I really abusing this battery right now? I did try charging to 80% but then if I do a shopping run I may get home with only 1-2 bars left, which I figured was worse than charging to 100% (is it?).

thanks for any suggestions!
chris

Probably heat issue. Several folks have reported increased degradation in summer vs winter, although below 80 F I wouldn't expect much degradation.

Looking back at your posts, you have a 2012 LEAF that was imported from Japan, right? (I presume that it didn't have a new battery installed.) 65 Ah for a 2012 LEAF seems much too high to me, so my guess is that the battery capacity measurement was reset before you bought the car.

After that resetting it takes some time for the battery management system to return to normal and give accurate capacity data. During that time the capacity will seem to drop rapidly. Eventually it will settle at a number that is the actual capacity and then decline gradually after that as the battery continues to age and lose capacity. (But in cold weather the measured decline will stop and resume again when the battery warms up in warmer weather. Below a battery temp of about 12ºC the capacity decline seems to stop. At battery temperatures of 20ºC or more it will continue to decline, albeit with a lag of weeks or months.)

Since it is summer in NZ I would expect the capacity to continue to drop even after the capacity measurement settles down at the new number. Unless your weather is very cool where you live.

Anyway, that's my guess as to what's going on. I also have a 2012 LEAF (manufacture date October 2011) and my battery capacity is 56.3569 Ah in a moderately cool climate but with additional battery heating due to mountain driving.


It would be helpful with answering future questions if you would add details about your car to your forum "signature".

Thanks dgpcolorado, good to know the capacity is higher than expected, although I'm a bit surprised in that I can just about do 120km which seems to be in line with expectations.

I'm doubtful there's a new battery in the car, but it also seems odd that somebody would have reset the measure. Mind you, we used to have a problem here with odometers being wound back on Japanese import cars, so I guess this could be the new thing the dodgy importers are doing.

I'll keep a close eye on things anyway, see if it settles down at a new level. Sounds like I need to move somewhere much colder to make it last well. Norway looks nice...

thanks again for the great advice, and I've added a sig with some basic details.

gaddman said:

...I'm doubtful there's a new battery in the car, but it also seems odd that somebody would have reset the measure. Mind you, we used to have a problem here with odometers being wound back on Japanese import cars, so I guess this could be the new thing the dodgy importers are doing...

Click to expand...

Two possibilities: the battery management system was deliberately reset to obscure the degradation of the battery (we are beginning to see a bit of this here in the USA; it is plain fraud) or the BMS was accidentally reset while the car was being given a health check at a dealer or exporter. It has been reported that the service manual says that the reset is not to be done unless a new battery is installed, but it might have been done by someone who didn't realize what would happen if that software "button" was pushed.

It will be interesting to see where your battery capacity finally settles. As long as the range suits your needs, especially in cold weather, it appears that the car will serve you well.

If the LBC/BMS was reset, the Hx would have dropped pretty much with the first reading as it responds very quickly in comparison to the Ah/GID readings, but it pretty much follows the Ah/GID readings.

So I simply suspect that the pack is fairly new, or originally used in a very cool climate.

Curious. If the online registration info is accurate then it was imported in May 2013 with just 4000km on the clock - that may well have been in a cold area of Japan. But then it was driven for 18000km and even if it was replaced just before I got it it still managed 2000km before really degrading.

I'll baby it for a while and see what effect that has. Maybe it is just the recent good weather having an impact.

Since my last post I've been charging to 80% and generally taking it a bit easier on the hills with more use of eco mode. Pretty abrupt change in where the health was heading, things have levelled off considerably. I think the temperature must be a big factor as well, since I can't otherwise explain why it was trucking along fine for the first few months.
My feeling is that once the max daily temperature gets above about 20degC the impact of charging to 100% becomes much more significant, but keen to hear other views on what the data shows or your own experience. Charts and data here and selected charts below:





Max daily temperature from nearest weather station:

gaddman said:

Since my last post I've been charging to 80% and generally taking it a bit easier on the hills with more use of eco mode.

Click to expand...

I must say those charts are the first ones I have seen that indicate that perhaps 80% charging really DOES reduce the rate of battery degradation. Of course your driving style changes may also be a factor, but the charts can't show that information.

Regarding your original post, I think it was pretty normal for the MY2011/2012 LEAFs that the SOH would stay up around 100% for a year or two before it started dropping. I believe this was simply a result of the BMS ignoring capacity above nameplate on some vehicles which came from the factory with higher-than-nominal capacity. And, as you and others have said, temperature does impact the rate of degradation.

It occurred to me there was another change I made - parking the car in the shade while at work. So I guess 3 things that together appear to have stopped the loss: 80% charging, driving style, temperature. Which has the biggest impact I don't know.

Interestingly enough, the SOH has actually increased a couple of days ago. That's a pleasant surprise.

I should get my late 2012 Gen 1 Japanese import later this year, also with similar km on the clock. It shows 12 bars but the general story is that these cars are being serviced in Japan and are reset before leaving the country. I presume it looks good when auctioning them off.

How are you findings since, Chris?

Certainly stabilised since then, if you check my signature I'm still tracking performance. The rapid drop bottomed out at a SOH of 94, and I'm down to 89 now, so dropping about 1% for every 4000km.