Level of charge question

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Blackbelt

Member
Joined
Aug 28, 2023
Messages
15
I have seen several posts suggesting it is bad to fully charge the i and letting it sit. I bought a 2012 last fall with 27K miles on it. I live in Western PA. My garage is currently occupied so the i sits outside. It is currently my wifes main driver, but we are both retired and therefore she doesn't do a lot of driving. We live in the country, so when she does drive, it could easily be a 20-30+ mile round trip. I need to have the battery fairly charged to be able to do that, but don't want to damage it as she loves her EVEE and wants it to last. What is the issue with charging the battery fully? What would be the best compromise for our situation? How do you control the amount of charge goiung into the battery? Thanks in advance for your expertise. My only experience with EV's was a BMW I3, and it had the Rex so range was not a big concern.
 
If you need the full charge (16 bars on the fuel gauge) in order to make your round trips and get back home, then you have no choice but to keep it Full, use it when needed and enjoy it.

But if your 30 mile trips only use part of the "tank", then you can stop charging early such as at 14 or 15 bars, and still have plenty of energy on hand to run your errands.

There were some test done many years ago showing a degradation of the capacity over the long term if a pack was stored fully charged for a long time (1 year). Nobody is gonna do that, but that is how the warning originated.

You can stop charging at anytime by squeezing the trigger and waiting a second for the relays to clack and turn off, then withdraw the handle. Or use a clock timer to notify you when to check on it and cut if off. Or use the charge timer function of the Remote control if your car came with that option.
 
Hi Blackbelt,

My understanding is the I-MiEV software is fairly conservative when charging, with 16 bars only going to about 90% of actual battery capacity.
Our trips are a similar range, and we charge our 2014 to full once or twice a week.
In the winter we only get one trip, in the summer we easily get two.
The battery appears to have close to 95% of its original capacity.

I think your 2012 is fairly similar.

Thanks and good health, Weogo
 
This topic has been beat to death on virtually every BEV forum, and we've had a fair number of discussions ourselves. Best to ignore the early postings.

Yes, every manufacturer has their own version of a safety margin at both the top and bottom end. In the case of our i-MiEV, at the top end, it's limiting the individual cell voltage to ~4.1vdc which is below the theoretical maximum of ~4.2vdc

Battery longevity discussions can be separated into Cyclic Aging and Calendar Aging, with variables (e.g., Temperature) associated with each.

Probably one of the best sources of information I've found is over on the Tesla Motor Club's forum, with a number of quite authoritative posters there with peer-reviewed backup information to support their assertions. I follow a gentleman named AAKEE on many threads there, and perhaps this thread (starting with Post #18 and a summary of links on Post #21) might help answer your question:
https://teslamotorsclub.com/tmc/threads/bestest-idealest-battery-charging-percentage-band.287025/

For myself, I now keep my i-MiEVs SOC a little over half (around 9-10 bars) but charge every day and have no qualms about charging to 100% just before taking off on a longer trip. I use the Remote all the time and wish our i-MiEV had the ability to set our maximum SOC charge level that most (all?) manufacturers have finally come around to doing.
 
Thank you for the responses. Thanks JoeS, the link was very educational. I wish i had a remote but my i didn't come with one. I believe my car has been primarily charged with the 120V trickle charger that comes with the car. The second owner bought it in 2014 and he did not have a level 2 charger. I fully charged mine several days ago and the "guessometer" showed a 63 mile range available. Of course the cold messes with that. LOL. Oh well, spring is almost here.
 
Blackbelt, a Range Remaining of 63 miles is a tribute to your wife's featherfooting (especially in winter) as nowadays that is a very good number for a 2012 i-MiEV with original batteries.

For years we charged our cars using an Intermatic timer.
https://myimiev.com/threads/better-charging-controls.129/page-2#post-2910
This original timer lasted ten years of daily use before conking out, as our i-MiEV drawing 13A@240vac exceeds the timer's maximum specs slightly.

I still have both 240vac and 120vac timers ... now that I think about it, perhaps I should start using them again as they're certainly faster than the blasted Remotes. Nowadays (and reflecting battery degradation), at 240vac my i-MiEV (with >50K miles on its LEV50N) charges 3.5 bars/hour whereas my wife's i-MiEV with original LEV50 and 60K miles zooms up at 5 bars/hour. Originally they were about 3 bars/hour. Unfortunately, we don't know how the preceding owner treated the battery.

Incidentally, whereas when using other vehicles (especially the Leaf where the term originated) and derisively refer to guessometer or 'GOM', our i-MiEV's algorithm is well established and reflects a moving average of the car's consumption over the past 15 miles (24km), excluding HVAC. I prefer to call it 'RR', for Range Remaining. We just have to mentally integrate the information to compensate for altitude or speed or wind or... effects that differ from what was just driven. :)
 
For years we charged our cars using an Intermatic timer.
https://myimiev.com/threads/better-charging-controls.129/page-2#post-2910
This original timer lasted ten years of daily use before conking out, as our i-MiEV drawing 13A@240vac exceeds the timer's maximum specs slightly.

I still have both 240vac and 120vac timers ... now that I think about it, perhaps I should start using them again
vaguely recalled a discussion about possible damaging to the on-board charger by abrupt AC disconnect ? may be it is no longer the final verdict, it was during the early days of a host of inverter/charger failures
 
possible damaging to the on-board charger by abrupt AC disconnect ?
It's still real. Mechanical disconnect: bad, electronic disconnect: good.

It's because you are disconnecting a large inductor carrying significant current, with nowhere for the magnetic energy to go except arc the contacts (not so bad, timers and switches are relatively cheap), and/or zap the expensive on-board charger (not so good, replacement OBC is US$4000++).
 
I do have a remote, but don't like the interface. I would rather have some simple outdoor timer that could be easily set between 1 and 24 hours. I searched for such a thing and found nothing that matched. I just found ones that go to 8 hours max, or that can be set to come on and off at certain times of the day.
 
It's still real. Mechanical disconnect: bad, electronic disconnect: good.
It's because you are disconnecting a large inductor carrying significant current, with nowhere for the magnetic energy to go except arc the contacts (not so bad, timers and switches are relatively cheap), and/or zap the expensive on-board charger (not so good, replacement OBC is US$4000++).
Coulomb, thank you for this and your point is well taken. I get the science and am not concerned about the cheap timer's contacts; however, once inside the OBC I thought that the rectified input filter network had large enough capacitors (800µF 450vdc?) to ameliorate the sudden disconnect surge. Nevertheless, I will heed your advice as one can never be too conservative in attempting to prolong the life of our expensive i-MiEV Achilles' Heel OBC and will dutifully continue using either the manual J1772 plug switch or Remote when charging our i-MiEVs and abandon using timed switches on the input side of our EVSEs.
 
Thanks again for the most recent replies. I had thought about how to connect/disconnect the standard charger and wasn't sure the best method. If not using a timer, what would be recommended. Last thing I want to do is wreck the OBC. When connecting, what should occur first, inserting the the charger into the car or plugging the charger in? Same question when disconnecting, which happens first, pull it out of the car or disconnect the plug from the wall receptacle? The term "Guessometer" is left over from my time on the BMW I3 forums. That was a common reference there.
 
The EVSE unit either level 1 or 2 (120 or 240vac) needs to be plugged in first and removed last. The EVSE must communicate with the car so it has to be powered up to do that. After powered up then insert the J1772 handle [ref: https://en.wikipedia.org/wiki/SAE_J1772] into the charge port of the car, and if the comm is working then charging should start after you hear the relays and contactors in the car clacking.

When done or want to stop charging, then squeeze the trigger on the handle and wait to hear the relays clack off, then remove the J jack.
 
get the science and am not concerned about the cheap timer's contacts; however, once inside the OBC I thought that the rectified input filter network had large enough capacitors (800µF 450vdc?) to ameliorate the sudden disconnect surge.
Those big capacitors come after the Power Factor Correction stage, which uses some paralleled transistors (IGBTs, from poor memory). Typically after the bridge rectifier there is a small (e.g. 2.2µF) capacitor, which I think is to improve power factor during the grid zero crossings, when the bridge rectifier won't conduct at all. It will absorb only a small part of the inductor's energy. The bridge rectifier (actually 4 separate diodes in most iMiEV on board chargers) are hardy but will eventually succumb to repeated transients.

That 2.2µF capacitor is one of the parts in the iMiEV OBC that commonly fails, often oozing out its innards. That could be from interrupted charges.

The cheap timer's contacts, while not terribly expensive, could end up high resistance and become a fire hazard.
 
Incidentally, whereas when using other vehicles (especially the Leaf where the term originated) and derisively refer to guessometer or 'GOM', our i-MiEV's algorithm is well established and reflects a moving average of the car's consumption over the past 15 miles (24km), excluding HVAC. I prefer to call it 'RR', for Range Remaining. We just have to mentally integrate the information to compensate for altitude or speed or wind or... effects that differ from what was just driven. :)
To supplement Joe the RR is only accurate if the car's consumption doesn't change from the moving average. The primary factor determining the consumption is the speed. The consumption in Wh/km or Wh/miles is proportional to the square of the speed times the air resistance so it increases quickly as the speed increases.

And now a bit of advertising. OBDZero shows the range together with the speed at which this range is accurate. This shown on the app's Drive screen.

Screenshot_20220903-134310_OBDZero-001.jpg

When the top number is 0, the middle number is the range as shown on the dashboard. The bottom number is the speed corresponding to the range. Almost all of our driving is in town at low average speeds such as 39 km/h, therefore we often have a fully changed range of more than 100km. This is true even though the car is 13 years old. (On the other hand it has only done 40,000 km.) As long as we drive in town we usually get 100km on a charge. On highways we are lucky if we get more than 70 km. We don't try driving on motorways.
 
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