I was looking in the service menu today and noticed that I only had 17.5KWh battery capacity. This was with the battery at 20 degrees C. Yesterday the capacity was at 17.4. Several weeks back it was at 18.2. Any ideas? My miles per kwh hasn't changed yet either with the weather beginning to get colder.
Lost a whole KWh
- Thread starter sdobbie
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alohart
Well-known member
Discharge your battery pack as far as you can without risking being stranded, then charge it fully leaving the EVSE plugged in for at least a couple of hours after the battery pack seems to be full. The charge levels of the cells in your battery pack might have become unbalanced over time which has the effect of lowering the battery pack's usable capacity. Charging from near empty to full and then allowing the lower-charged cells to continue charging to "catch up" to the higher-charged cells for at least a couple of hours could result in a greater usable capacity. It's certainly worth a try and won't damage anything or cause any problems.
If you try this, please report the results.
If you try this, please report the results.
i3atl
Well-known member
Do you have the March software update? If not, go get it - it will help, as they "unlocked" a bit more of the battery.
It is my understanding it will vary based on recent charging habits as well as weather. Mine showed 19.2 the first time I checked it (2500 miles) and at 3500 showed 19.7. I think like another person responded, discharging as much as you can without being stranded (not really a problem with REx) followed by a full charge helps to recalibrate the computer and show a more accurate reading. Even though it is not needed/required I have been trying to do this once per month, I work a rotating 4 week schedule and charge at work for free as much as possible; there is a point in my schedule where it is easy to remember to do this every 4 weeks.
This morning I got a puncture. The tire seal didn't work and it got taken to Edinburgh for repair. I spoke to them about the battery issue and they say a software update will be performed to correct the problem and restore range to 90 miles. They offered me a 3 series and I said no danger and got an I3 with range extender. It had much better range than mine. My I3 was showing a fully charged range this morning of 68 miles and a capacity of 16.9 KWh It then went down to 16.4 after a short charge session.
michaelbmw
Active member
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The US Department of Energy has fleets of electric cars and they perform periodic tests of battery capacity.
http://avt.inl.gov/fsev.shtml
They have four I3s in their fleet. Three of them were tested after approximately 4000 miles of use and show battery fade ranging from 2% to 4%. The fourth one doesn't yet have a 4000 mile test.
This is typical of what's experienced with EV batteries....fade of about 10% over the first 12,000 miles and year of operation.
http://avt.inl.gov/fsev.shtml
They have four I3s in their fleet. Three of them were tested after approximately 4000 miles of use and show battery fade ranging from 2% to 4%. The fourth one doesn't yet have a 4000 mile test.
This is typical of what's experienced with EV batteries....fade of about 10% over the first 12,000 miles and year of operation.
alohart
Well-known member
If true, and if this rate doesn't decrease significantly in future years, BMW might be replacing a lot of i3 battery packs under warranty. I'm sure that BMW knows the typical degradation rate and has taken measures to avoid the apparent 30% capacity reduction during the first 8 years/100,000 miles that would trigger a battery pack replacement under warranty in the U.S.michaelbmw said:
The i3 having a 15% low charge/high charge buffer when new (18.8 kWh/22 kWh = 85%), BMW could gradually reduce this buffer via software so that it could avoid a battery pack replacement under warranty as long as the usable battery pack capacity doesn't decrease more than 45% during the warranty period (45% - 15% = 30%). This may already be occurring as some have reported increased battery pack capacity (and thus, a reduced buffer). Apparently, Chevrolet is doing something similar with the Volt, but the Volt battery pack's initial low charge/high charge buffer was considerably larger than that of the i3, so decreasing the buffer size would not be as potentially harmful.
A serious problem with this approach for long-term i3 owners who charge to full and/or discharge to low charge levels regularly is that doing so would increase the battery pack degradation rate. This is another motivation for me to manage the charge level of my battery pack between an indicated 20% and 80% when possible so that even if BMW has reduced the low charge/high charge buffer, I would not be damaging my battery pack by charging and discharging to extreme levels.
Good advice. I try to avoid fully charging and discharging by charging the car at night on the lowest power setting which is 1300 watts. It isn't fully charged by morning and I also charge for 30 minutes after my journey to work in order to keep the battery as close to 50% as possible. Another benefit of not fully charging is that the regenerative breaking can work at full power. I have noticed that when fully charged I can hear the normal brakes slowing the car down too.
MikeS
Well-known member
Anyone got the details of the BMW nomenclature for the ‘March Software Update’ that apparently released extra battery power for use by the car?
i3atl
Well-known member
MikeS said:
Are you looking for the version info, or some official note regarding the increased usable capacity? I don't think they provided anything about the capacity, even internally.
Jeffj
Well-known member
Annecdotally, the changes include adjusting the charging voltage by a millivolt or two to "unlock" more capacity. This is apparently a normal practice with Li-Ion batteries as they age (according to some literal rocket scientists on the Facebook group who work with Li-Ion batteries in space probes), and changing the GOM algorithm to us the actual Max capacity of the battery for estimates, rather than 18.8 kWh as a max. So many have reported seeing higher range estimates as a result. Fewer have actually done testing to see if the additional range is actually real.
MikeS
Well-known member
i3atl said:
Im looking for the official name or term that BMW use for this upgrade such as - i3.2015v3 - or whatever format they use. Im after it as BMW in UK don’t think any such software upgrade from March exists or even that there is one that improves range.
i3atl
Well-known member
ISTA/P 3.55.0 (I-level I001-15-03-501)MikeS said:
I001-15-07-501 is the latest release, though.
jadnashuanh
Well-known member
One should realize that the i3's software is not the same country-to-country, so features and updates in one country may not be the same or even available in other markets. This is one reason why, at least in the USA, that the dealers do not have the software updates as a package available locally...the car is hooked up to their computer, and BMW in Germany assesses what software needs to be updated then sends it to the car directly (this is based on the VIN). The local country branch likely knows if there is a generic version to address some local issue, but it may or may not be the same as in a different country.
MikeS
Well-known member
I3atl - thank you.
Jadnashuanh - yes I do appreciate that, but if there is an update to improve battery performance/range why would it be restricted to a country/countries?
Jadnashuanh - yes I do appreciate that, but if there is an update to improve battery performance/range why would it be restricted to a country/countries?
jadnashuanh
Well-known member
A specific build is likely a market specific thing to address local issues. Some (maybe all) of those issues may also be addressed in other markets, but trying to base the release date and version number between say a USA and a UK vehicle is unlikely to result in anything useful as they are likely not compatible, especially in the release date. BMW tends to only alert people to updates when it is either a safety or major issue, and apply other updates on an as needed, or upon normal maintenance schedules. IOW, don't try to correlate a US release with one from anywhere else.
MikeS
Well-known member
True what you say. But BMW in UK say there are no updates for my car - it was Dec last year when it had any updates!
