Why does Mitsubishi recommend fully charging every 2 weeks?

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acensor

Well-known member
Joined
Mar 15, 2013
Messages
371
Location
Southern Oregon
On page 1-19 of the owners' manual it reads:
"Fully charge the vehicle by regular charging every 2 weeks?"

Seems that everything I've read about TLC for the batteries would loosely translate as "if you don't really need to for the range it's best to never ever fully charge these batteries for longest life."

I note that sentence is a few parapgraphs below the suggestion that repeatedly quick charging isn't such a great idea..... So maybe it's in THAT context?

Alex
 
Alex, we already have plenty of threads discussing battery charging regimens. 'Twould have been better to tack this question onto one of them instead of starting a new thread (you'll understand why when you try to retrieve some prior information).

The Owner's Manual was superseded by the February 2012 letter from Mitsubishi which addresses the battery scheduled maintenance. Wee John posted the letter here.

The letter recommends fully charging the battery (from 2 bars) in the first year, and every two years thereafter. I suspect all of us end up fully charging the battery more frequently - for example, I do it just before embarking on a long trip. I now normally try to keep my fuel gauge somewhere between 5 and 12 bars and certainly avoid full charge + high temperatures.

Question for recent iMiEV purchasers: is there any newer information provided by Mitsubishi?
 
JoeS said:
Alex, we already have plenty of threads discussing battery charging regimens. 'Twould have been better to tack this question onto one of them......

....The [Mitsubishi update] letter recommends fully charging the battery (from 2 bars) in the first year, and every two years thereafter. ........
.......Question for recent iMiEV purchasers: is there any newer information provided by Mitsubishi?
'm
I was kind of torn between posting on an existing thread (in part because there were, IIRR, several that meandered into the battery chargin turf, and in part because I thought having a specific subject line might be MORE helpful if others later search. But as moderator I'll defer to you.

Thank for the link to the Mitsubish update letter.

I'm a very new owner (barely more than a month). Only info I got was the clearly older gray owners' manual. I'm even a registered-with-Mitsubishi owner and they have not contacted me with any supplementary info.

Alex

Alex
 
acensor said:
... and in part because I thought having a specific subject line might be MORE helpful if others later search...
No worries, as there's certainly much merit to your approach. I've been a little too touchy lately and perhaps need a vacation...

In re-reading Mitsubishi's letter, I find it interesting that the stated reason for the full charge routine is for instrument calibration ("...maximize accuracy of SOC indicator..." - i.e., the 'fuel' gauge), and eliminating the need for routine maintenance. The battery itself is not addressed.

Somehow, I would have thought that Mitsubishi would want to test the traction battery capacity, if for no other reason than to garner feedback. As it now stands, we have no quantitative measure of pack state of health. Perhaps just as well, as we won't experience the Leaf community obsession and paranoia with that capacity number. :lol:
 
JoeS said:
acensor said:
...
In re-reading Mitsubishi's letter, I find it interesting that the stated reason for the full charge routine is for instrument calibration ("...maximize accuracy of SOC indicator..." - i.e., the 'fuel' gauge), and eliminating the need for routine maintenance. The battery itself is not addressed.

Somehow, I would have thought that Mitsubishi would want to test the traction battery capacity, ....

I wondered a bit too about their stated rreason . Wondered is in part it had to do with wiping out undesirable battery "memory" which was/is the bane of nicads but which I thought was a nonissue with lithium.
But I guess having a reasonably calibrated SOC indicator is important.

Alex
 
acensor, I hope this helps. The car is actually never charged to 100% of the battery capacity. It could have been, but Mitsubishi intentionally limited the amount of voltage each battery can take. I'm sure this is specifically to ensure a long life and limit the rate of pack degradation.

So good news. Charge the car as much as you want! :)

I had my annual maintenance done about 4 months ago. Everything was fine, Mitsubishi dealer hooked the car up to a computer and checked the voltage on each Cell. Here's a picture of the printout. As you can see, the Cells are limited to 3.955 Volts, rather than the 4.25 they are capable of. So no matter what, you're only ever charging to 92% of "full". Pretty cool!

CAM00231.jpg
 
iDriver said:
.... The car is actually never charged to 100% of the battery capacity. ....Mitsubishi intentionally limited the amount of voltage each battery can take. .... to ensure a long life and limit the rate of pack degradation.

So good news. Charge the car as much as you want! :)

I had my annual maintenance done about 4 months ago. ..... only ever charging to 92% of "full". Pretty cool!.....

Thanks iDriver,

Yeah, I think most of us here knew that the onboard charger is configured to protect the battery longevity that way. Not sure your calculation of 92% is right. Think it might be a bit less than that we're capped at as the total kilowatt-hours stored isn't exactly proportinal to voltage level charged to.
Still everything I read and think I understand suggests that for maximum life ideally you'd keep the battery charged somewhere in mid capacity, not fully charged.
I realize that's not always practical, and no, occassional or even modertely frequent fully charging isn't a cardinal sin. But if your driving style permits you'd be better off for long life never charging to more than two bars short of full.

It's also my understanding that if 8 year from now you come into a dealer complaining that your maximum ranges is down 20% and that's intolerable they can reprogram it to allow 100% charging to stretch your useful full range life a bit further down the calendar before you have to ditch those batteries.

Finally: Three questions which I will post under the cost of operation topic (so please don't answer here):
1) You didn't show the price on what you were charged for your annual inspection. What was it?
2) Is there an "annual inspection?" I only see offhand something due at about 15,000 miles.
3) Anyone know if you don't bring it in on the required schedule can and will Mitsubishi use that to wiggle out of covering something that otherwise would be on warrenty coverage?

Alex
 
So just to be clear on this subject, I should never or rarely fully discharge or fully recharge my battery?

My understanding of InfoLithium batteries was that to optimize it's life you should fully discharge and fully charge the battery once a month and then charge it from 90% then 80% then 70% then 60%...so on and so forth until you reach 10%. Then you repeat the process.
I've always done this with my iPhones and seems to have worked as my battery life is always so much greater than that of my friends.

Now I know I probably shouldn't compare the battery of an iPhone to our i-MiEV but can anyone confirm what is the absolute best way to ensure a long healthy life of my battery pack and why?

Also is the Battery pack a Toshiba SCiB or not? There's a lot mixed info on the forum and according to Wikipedia and Toshiba the battery is SCiB..
 
Definitely never fully discharge if you can help it. I've been fully recharging nearly every day that I drive the car for a year and a half now and haven't noticed any difference in range.

The i-MiEV takes the cells to 4.1 volts (CaniOn), and I believe their max is 4.2 volts. My laptop takes its cells to 4.3 volts, though they may be a different chemistry. My cell phone goes to 4.325 volts.

The regular i-MiEV battery is a standard lithium chemistry, not SCiB. Japanese i-MiEVs have an optional SCiB battery (at 14.5 kWh capacity) since they are much more tolerant to repeated quick charging, which is in no short supply in Japan.
 
mixmike6 said:
So just to be clear on this subject, I should never or rarely fully discharge or fully recharge my battery?
I don't think we know that for sure - Lots of what you read on this subject is opinion based on whatever research the poster has read somewhere else

No question though that keeping the battery pack charged between 20 or 30% and 60 or 70% is probably best for it, but that's not always practical to do - It turns a 75 mile range car into a 30 mile car for one thing. It also builds in some range anxiety no matter how carefully you calculate your usage

I would try (and I do in actual practice) to do partial charges as much as is practical, but an occasional 'full' charge (whatever percentage Mitsu has limited it to) is probably not a bad thing either - Occasionally balancing the cells in the pack is probably a good thing

There are many, many owners who do a full recharge every single day and quite a few of those with longer commutes are doing full recharges twice per day, so for you and me to do a full recharge once or twice per month can't be a bad thing, can it? It remains to be seen 5 or 6 years from now who has the most pack capacity left and that will modify our 'assumptions' and opinions further

Long story short - You bought the car to commute from place to place. Use it as you need while partially charging it whenever possible but fully whenever you need and 5 or 6 years from now you're bound to be near the top of the heap ;-)

Don
 
Good point - I doubt it would be good a good thing to constantly charge the car between 20% to 80% as the cells outside that range would get little activity.
I'm going to continue with my gut feeling of charging the car fully about once a week and also using it from 100% to almost 0% at least once every two months.
Also I'm sure charging it using 120V instead of a Level2 240V will prove to be much better in the long run for the battery pack.
 
Doing full charges since two years, battery State of Health like the first day.
Below see link to calibration record with the help of seclog data from canion when below two bars.
I rarely go below two bars.
http://myimiev.com/forum/viewtopic.php?p=18067#p18067
Range will be more accurate and cells balance will be more equal. See graph Cells Umax -Umin.
The number of charges might have an influence on the lenght of the battery life and also the Depth of Discharge, so full charge is a good optimisation.
Anyway, the main killer is temperature, :mrgreen:
http://myimiev.com/forum/viewtopic.php?p=18559#p18559
 
mixmike6 said:
Also I'm sure charging it using 120V instead of a Level2 240V will prove to be much better in the long run for the battery pack.
No, it won't. Really, really, REALLY it won't. To repeat comments I made in a post last year, I've seen no technical support for the suggestion that L2 charging is "harder" on the battery than L1; that assertion should be regarded as folklore, anecdotal or at best "extrapolated common sense." There have been plenty of discussions about this elsewhere in the forum, but I think any newcomer reading through this should be aware that this is not a universally accepted truth.

To put this issue in context, let's consider that Level 3 charging at 50kW falls well within this battery chemistry's specifications; indeed, Mitsubishi has made no secret of their assessment that the GS Yuasa batteries are more tolerant of L3 charging than Nissan's (the Toshiba SCiBs that Mitsu offers in Japan are a whole other thing, definitely being able to handle multiple L3 charging sessions per day, but we can't get those here).

Keeping that in mind, let's also remember that our L2 chargers are QUITE low powered, only 3.3kW, barely more than 1/16 of L3 charging levels. The difference between this and L1 is negligible when either is compared against L3, so I don't think it's something that people need to be concerned about.
 
BlueLightning said:
Doing full charges since two years, battery State of Health like the first day.
I think all lithiums lose some capacity as they age. In our car, that loss is hidden below the turtle - A new battery might go 15 or 20 kms after the turtle appears while a 2 or 3 year old one might only do half of that and eventually it will get to where the car stops moving shortly after the turtle appears . . . . or do you have some evidence to the contrary?
I've seen no technical support for the suggestion that L2 charging is "harder" on the battery than L1; that assertion should be regarded as folklore, anecdotal or at best "extrapolated common sense."
Agreed that L1 charging won't do anything to lengthen the life of the battery - I used to think the same thing, but it's been proven that L2 recharging is actually very slow when compared to the recharge capability of our 50 amp cells. Even if we had a 6.6 Kw charger, L2 recharging is harmless to the cells . . . . and it's actually a little more efficient, so you're be using less energy recharging L2 compared to L1

Don
 
mixmike6 said:
I doubt it would be good a good thing to constantly charge the car between 20% to 80% as the cells outside that range would get little activity.
?! Maybe I misunderstood what you wrote. All cells in the battery pack are connected in series, so the current passing through all cells during charging and discharging is identical. Therefore, all cells participate in discharging and charging equally leaving no cells with little activity if the battery pack's charge level range were limited to 20%-80%. Limiting the charge level range like this would likely extend the life of the battery pack compared with repeatedly using a greater operating range, but as Don states, doing so is not practical for all owners.
 
I, too, have learned quite a bit about our i-MiEV and our batteries and have played quite a bit with various Lithium cells over the last couple of years, which has altered my perspective considerably. High temperatures and, as we are now finding out, low temperatures are to be avoided. The heating effect of L2 vs. L1 is negligible and charging using L1 is more inefficient than L2 due to the vehicle's fixed loads being utilized over a longer period of time.

I still use L1 occasionally, as my Remote is too erratic with my SPX L2 EVSE. I basically adjust my nightly charging to (1) allow the car to cool down for most of the night before commencing charging and (2) have the car reach about 14 bars just before it's needed in the morning. This last summer, this often means ignoring L1 and turning on L2 after getting up in the morning. I have a mechanical turn-off timer on my L2 EVSE. and can pretty well predict and set either L1 or L2 to turn off at 14 bars; nevertheless, I do indeed fully charge the car every few weeks, just before taking longer trips.

This thread addresses what I think is the SoC recalibration issue and that area continues open for discussion, and I'm leaning towards Don's explanation. Since I've never seen turtle, I have no idea how my turtle range has changed over time.
 
Vike, the only common sense I had was based on what I already knew of batteries: Higher voltage = Higher stress and temps = Not great for battery.
I also have many sources to cite this. It's not just anecdotal.
Yes I'll agree that 3.3kW vs 1.44kW probably seems negligible compared to 50kW but your missing the point. I want to keep my battery as healthy and as long as possible. I want to do everything I can to optimize the lifespan of the battery pack.
I've been charging my car once or twice a week with the L1 charger and so far see no use in an L2 for my kind of usage. THUS I don't mind the car charging at a slower rate or not being at 100% all the time.

You say that the battery from the Japanese version differs from that of ours, where did u read this and can it be confirmed officially?
Wikipedia says otherwise and I can't find a reliable source that confirms that there are any differences.

 
mixmike6 said:
Vike, the only common sense I had was based on what I already knew of batteries: Higher voltage = Higher stress and temps = Not great for battery...
Mike D., higher pack voltages using more cells results in less stress on individual cells than lower voltages. It's current (amps) that is deleterious to a battery's health and the higher the pack voltage the lower the current in a series pack such as we have in the i-MiEV. The maximum voltage each cell is charged to (4.091v resulting in a fully-charged pack voltage of 360v) is managed at the cell level. Even though this voltage is set by Mitsubishi already to be below the maximum (4.2v?) that each cell is comfortably capable of handling, limiting our charging to an even lower voltage (as you are doing) will hopefully result in an extended battery life. For our family use putting on over 1000 miles/month, I find it rarely necessary to fully charge the car for 'longer' trips more than a couple of times a month.
 
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