New battery pack at 21 months - Las Vegas

We bought our Metallic Raspberry i-MiEV in December 2012, in Palmdale, CA, and had it flatbedded 260 miles to Las Vegas.

My wife, Rosa, loves the car. We have an Aerovironment level 2 charger. She routinely drives 25 miles round trip to work, and two days (50 miles) of use between charges. Made it through the first summer (18 months) with no problems.

June of 2014 we noted the range was falling. At times we were getting 70, 60% charges. I kept, and typed, an extensive record of level of charge (miles and squares), level of charge at the end of the day (miles and squares), gauge indicated miles used, gauge indicated miles remaining, and the odometer actual miles travelled. I recorded for two months. Near the end, the range was at 38 miles. I routinely (every two months) drove the vehicle to 1-2 squares remaining and charged it fully, apparently to calibrate the guages. The vehicle left us stranded once and had to be towed. I started driving it and charging it in mid-errand. Fortunately we have a dozen easy to find chargers along the Las Vegas strip. I drove around, located, and charged the car mid-day at least 10 times that summer to make it home.

Our local Mitsubishi dealer (there are three in Las Vegas, but only one has a technician trained) took in the vehicle and (after the technician returned fron training) diagnosed it as a bad battery. This took two weeks. A battery was ordered from Japan and arived in a giant shipping crate, along with a special lifting jack and forklift. This took 6 weeks. After 8 weeks, we are living with a new battery.

I am a car nut, and there was absolutely no explaination as to why the battery had failed prematurely, or hints from Mitsubishi on how to treat the battery differently. "Just go drive it."

We have 12,600 miles on the odometer.

My explanation is high ambient temperatures. My garage is not air conditioned and reaches as high as 90F in the summer (4 months here). The daytime high reaches 105F regularly, and occaisionally 116F. The multi functional gauge can cycle to read vehicle temperature, and that indicated it could reach 106F, and once to 109F.

I can hardly afford to let the car sit during the summer months (June, July, August, September).

There is absolutely no marketing (print, magazines, TV) for the i-MiEV in our area. The dealership has not had one on the floor or the lot for over a year. Resale for the $32,000 vehicle is $10,000.

I put solar panels on my roof. THAT ended up being a wise decision.

Thank you- yours is the first report I recall of premature battery failure in a hot climate. Sure is aggravating that Mitsu remains silent on the cause and potential effects. You might consider the pack cooling hack discussed elsewhere (manually opening the pack ventilation dampers).

'rosecastillon' - welcome to the forum. We have had another hot-weather failure by someone on this forum, and that was in Phoenix. Pity you hadn't joined the forum earlier, as the symptoms you describe (i.e., not fully charging) were indicative of one or more cell failures within the battery pack and we probably would have suggested getting it to the dealer immediately instead of trying to nurse it along. Glad to hear Mitsubishi took care of you with a new battery pack. Could you describe your normal charging regimen for the car?

I think it very well *could be* related to the Las Vegas temps, but then we have had 2 or 3 other random battery failures which were not from hot climates, so yours could be just another one which we have no idea what the cause was

The battery is warrantied for 8 years and 100,000 miles - I would continue to use the car as you normally do and see if you do eventually have another failure. Mitsubishi should stand behind your new battery just as they did the original one

Don

On our charging habits; during the first year with the i-MiEV we had solar panels and used both "net metering" and "time of use" plans from the Electric company. The time of use involved charging the i-MiEV between 11 PM and 6 AM at a cheaper rate, so it was charged wih the Mitsubuishi Remote charger, set to charge during off hours of 11 PM - 6 AM while we slept, for a whole year. After a year, an electric company manditory audit showed time of use was costing us $200. per year, so that program, and the incentive to charge during the night, was eliminated.

We now charge whenever we want; the rate is the same. We usually charge every other night, as soon as we arrive home, and do not allow a time delay to allow the battery to cool down before doing so. We could, set a delay, by using the Remote. Nothing Mitsubishi says recommends this added step. We always charge full up; Las Vegas is big enough that we cannot drive accross town and back on a single charge. We try to use up the complete charge of the battery, as my understanding is that the limiting factor for the battery is the number of charging cycles. The SCiB battery marketed in Japan is supposed to get 4000 charges, but our more typical Lithium-ion battery sold in the U.S. gets around 2500 (8 years, every night).

We plan to use our i-MiEV every day during the year. We cannot afford to let it sit June, July, August, September.

Instructions on how to use the remote are cryptic and misleading. I have a checklist that gets it done wihout errors.

Happy charging!

It sounds like you don't leave the car with a full charge for long periods of time, so that is good. The other hot climate failure was, I think, caused by the owner leaving the car plugged in for two weeks at high temperatures.

I would recommend letting the pack cool down between driving and charging when you can. I've gotten into the habit of waiting about 5 hours before plugging in. I simply plug in before going to bed, but the same can be done with the remote. When you set a delay timer, the car remembers what time of day it starts charging, so if you get home at different times each day, plug in, and set a delay, the number of hours on the remote change to correspond time until the charging time set before.

If your car has the quick charge port, you'll have a servo in the driver's foot well on the right side, which can be removed to allow manual pack cooling. Just set the controls to the floor to put air into the pack.

I am not sure any of the battery packs that have been replaced on this forum as anything to due with temperature or the conditions the owner charges the pack. We know that the pack will slowly loose capacity over time and the speed of this capacity loose will depend on temperature and charging cycles. But the key word is slowly. That means over many years of time.

The pack failures we have seen have been basically over night with charging levels being different each time the pack is re-charged. This suggests to me that a cell has failed. Think of it like a regular lead acid battery. Overtime the battery will not hold a charge but if it is over or undercharged the battery is junk the very next day. In the case of lead acid battery, the buildup between the plates shorts the cell and the battery is toast.

With lithium batteries there is no buildup but a breakdown in the anode or cathode. Forget which one. This breakdown is at the atomic level and hence the slow lose of capacity.

So my theory of what is happening is either poor quality control of the battery manufacturing process or the poor quality of the BMS circuit board which allowed a cell to be discharged beyond the safe voltage.

I guess what I am saying is that it is not the owners fault as to an overnight battery failure but rather design of the BMS circuit board or manufacturing of the battery cell. Both of which is out of the control of the owner of the car. It would explain why failures seem to be random.

Dave

While we can't be 100% certain, it is a reasonable deduction that extreme cold is the likely culprit behind several battery failures. This stems from research done on lithium batteries that when charging below freezing, lithium plating can occur. This is similar to the sulfation that occurs with lead acid batteries. From batteryuniversity.com:

Summary
The four suspected renegades that are responsible for capacity loss and the eventual end-of-life of the Li-ion battery are:
1. Mechanical degradation of electrodes or loss of stack pressure in pouch-type cells. Careful cells design and correct electrolyte additives minimize this cause.
2. Growth of the solid electrolyte interface (SEI) on the anode that forms a barrier and obstructs the interaction with graphite.
3. Formation of electrolyte oxidation at the cathode that may lead to sudden capacity loss. Keeping the cells at a high voltage and at an elevated temperature promotes this phenomenon.
4. Lithium-plating on the surface of the anode caused by high charging rates. (The elevated capacity loss at higher C-rates in Figure 4 could be caused by this.)

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Also this:

Many battery users are unaware that consumer-grade lithium-ion batteries cannot be charged below 0°C (32°F). Although the pack appears to be charging normally, plating of metallic lithium can occur on the anode during a subfreezing charge. The plating is permanent and cannot be removed with cycling. Batteries with lithium plating are known to be more vulnerable to failure if exposed to vibration or other stressful conditions. Advanced chargers, such as those made by Cadex, prevent charging Li-ion below freezing.

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So, with this, we can see that the following conditions can cause battery failure:

1. Keeping the pack at a full charge for a length of time, especially at elevated temperature.
2. Repeatedly quick charging.
3. Charging with the pack temperature below 32° F.

Once a cell or group of cells develops lithium plates, the vibrations from driving can cause a cell to fail.

For optimum health, it appears that we should try to:

1. keep our packs around 60-75° F
2. resist full throttle
3. ease into regen
4. minimize quick charging
5. Only fully charge the car once a month or when needed
6. Avoid running below 1 bar.

Obviously, we can't all do this (I'm especially guilty of not doing 2, 3, and 5 ), but this appears to be what keeps our batteries happy and healthy.

For my cars, I've adjusted my charging habits with Bear, and with the help of OVMS, have been pretty good at keeping the pack above freezing. Koorz, however, was previously a Michigan car, and only has a range of 45-50 miles. I'm thinking it is a combination of a misbalanced, possibly damaged pack and Yokohama front tires. I'll be switching back to driving Bear for now as the 12 volt battery is almost dead and I already have an EV warning light on Koorz because of that :evil: .

dniemeyer99 said:

I guess what I am saying is that it is not the owners fault as to an overnight battery failure but rather design of the BMS circuit board or manufacturing of the battery cell. Both of which is out of the control of the owner of the car. It would explain why failures seem to be random.

Dave

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Battery failures on the forum have tended to be cold weather cars, but not all. I think there was one car here that was bad from the factory.

The BMU could use some tweaking. It should be more protective of the cells in low temperatures and bring in cool air when the battery is hot. Thermal management is almost non-existent.

I'm about to sign the dotted line and buy a sight unseen i-miev SE with 4,900 miles to Michigan.
We have had frigid temps here and I've no garage. Any advice on minimizing potential harm to the battery?
My experience with a car shared Nissan was it liked charging in the winter better immeiately after I had driven it rather than before.

The dealer I spoke to said the SE had an active cold/heat package to protect the battery. How true was/is this
OR are there things I can do to help the car?

Ben (hoping this wasn't another ev mistake.)

I've adjusted my charging habits to keep the battery above freezing. What I do is use the slowest charging rate that allows for a full charge by the time I need the car. Since the car can get a full charge in 12 hours on level 1, 12 amps. I rarely need level 2 in the winter except for pre-heating.

Usual scenario:

I get home around 5 PM with a usual 8-11 bars left. I plug the car in when I get home, but I have the EVSE turned off by a switch inside the garage (car is parked outside and cord is run under garage door). Around 10-11 PM before going to bed, I go out to the garage and turn the EVSE on. The car usually finishes around 5 AM, and I start preheat at 7 AM, leaving at 7:30. I use the EVSEUpgrade cable, so it can do both 120 volt and 240 volt charging, which I can switch between easily. I charge on level 1, and switch to level 2 before preheating, and since the car is done charging, the Charge light is off.

I drive 10.5 miles to work at 45-50 mph on a fairly level road, the car sits outside for 8 hours, then the same drive home. With this, I have been quite successful at keeping the battery not only above freezing, but around 40-50° F, even when the outside temperature was in the teens. Single digit temperatures were more difficult, with the battery dropping to 25° F. If you need to boost the temperature of the battery, drive on the highway for about 20 miles, then charge soon after. Driving back and forth 30 miles one-way to Pittsburgh on the highway with level 2 charging in between got my battery better than 65° F in 5-20° F. I could feel the regen getting stronger the further I drove. :lol:


The car's battery warmer (from reading the service manual) apparently only activates when below 5° F and when "Heat" is triggered from the remote, but that may be inaccurate. The biggest help is actually being able to see battery temps, which can be done with the help of Android app CaniOn and the OBDLink MX, or with the Open Vehicle Monitoring System (OVMS).

rosacastillon said:

…We always charge full up; Las Vegas is big enough that we cannot drive accross town and back on a single charge. We try to use up the complete charge of the battery, as my understanding is that the limiting factor for the battery is the number of charging cycles. The SCiB battery marketed in Japan is supposed to get 4000 charges, but our more typical Lithium-ion battery sold in the U.S. gets around 2500 (8 years, every night)…

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The number of charge cycles is a laboratory standard that is largely irrelevant in an EV application as the vehicle is constantly undergoing partial charging and discharging and almost never experiences a complete 'cycle'. The consensus seems to be that it is better to charge more frequently to keep the battery in its SoC midrange rather than charge less frequently and allowing the battery to fully deplete.

BenBrown said:

I'm about to sign the dotted line and buy a sight unseen i-miev SE with 4,900 miles to Michigan….

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No worries, assuming you're getting it for a good price, go for it! If the battery truly fails, you will be rewarded by Mitsubishi with a brand-new pack. If it is only diminished range then, if you are like the vast majority of US drivers, the car will still be fully usable for years to come.

In addition to PV1's discussions, you'all might peruse this forum, as over the past three years we have had many discussions regarding prolonging battery life. To continue beating this topic to death, a few generalizations have emerged:

1. Lithium chemistry batteries like to operate at around 50%SoC and not be subjected to large SoC excursions. For this reason in my everyday driving I normally keep my pack between three and thirteen bars, only fully charging if I'm just about to set off on a longer trip.

2. To emphasize previously-posted comments, high power charging at very low temperatures and keeping the pack fully charged at high temperatures should be avoided if at all possible.

3. If stored long-term (weeks-months) keep the pack in the 25% - 40%SoC region.

Finally, when driving below about two bars, be VERY easy on the accelerator pedal to avoid drawing high currents. This is subjective on my part, based on having murdered a number of unprotected Lithium cells in my other EVs. Although the i-MiEV BMS should protect the pack, CaniOn has shown us that large cell voltage disparities can exist at low SoC and I would rather not apply high currents and risk an excessive individual cell voltage drop.

PV1 said:

...Since the car can get a full charge in 12 hours on level 1, 12 amps. I rarely need level 2 in the winter except for pre-heating...

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Doesn't level 1 take a looooonngg time to keep the cells balanced (maybe months)? Just a curiosity question.
Thanx,
-Barry