alohart
Posts: 1537
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Battery capacity issue

Mon Feb 11, 2019 5:19 pm

JLB2 wrote:I wonder what they will do in 2023 when the 2014's are out of warranty and need new batteries. I'm sure many of the cars will still be functioning perfectly but needing new batteries. Will they allow owners to buy battery replacements?

Based on the experience of gasoline-electric hybrids with bad battery packs, 3rd-party battery pack builders offer replacement packs for considerably less than the car dealer's retail price. Battery cell quality would be my main concern. However, there's no reason why a 3rd-party battery pack builder would not be able to buy the same cells used by the car manufacturer. As EV battery pack warranties begin to expire, I expect choices to become available.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

jadnashuanh
Posts: 4339
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Battery capacity issue

Mon Feb 11, 2019 6:17 pm

On a commercial basis, BMW has been retasking replaced battery packs as backup systems. I saw one prototype designed for use in a home they showed in a press release as a possibility, but I've not seen that they ended up offering for sale anywhere. At least the engineering has been done. There is expected to still be a very significant capacity left in a battery pack once it is deemed less than ideal in a vehicle. Personally, I would like the idea...there'd still be enough power to get through probably a couple of days with power out if you conserved some. And if you were really conservative, a lot longer.

What I've heard on the rebuilders is that they disassemble used packs, discard modules that are less than satisfactory, and reassemble from the good ones. The i3 was designed with fairly large cells in easily replaced modules (well, easier than most), so replacing a bad module is likely to be the first line of attack. IMHO, thousands of small cells, like in the Tesla offers more chances of failure than the barely 100 in the i3. The fewer internal and external connections there are , the more reliable it should be.

Seems the battery degradation thing peaks this time of year as the temperatures drop, while once it warms up, people seem to realize their range is going back up again and relent.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

Oleksiy
Posts: 63
Joined: Fri Mar 23, 2018 4:30 am
Location: Kyiv, Ukraine

Re: Battery capacity issue

Tue Feb 12, 2019 1:22 am

We have a huge fleet of used Leafs from the US in Ukraine, a lot of 2011-2013 MY ones as well. Most of these cars have either dead or almost dead packs, quickly approaching or in some cases going below 60% SOH. There's also a burgeoning cell repackaging industry here catering to the needs of these Leaf owners. People can do lots of things. They can easily upgrade 24 kWh packs to newer 30 kWh ones, there have been tries to move to 40 kWh packs as well, although with limited success yet. They install dual batteries, additional packs from Chevrolet Volts and other things. They have developed custom BMS operating systems for Leafs, or rather OS skins providing for a lot of added flexibility, etc.

But, there have been no third party battery pack solutions yet. Also, partial replacement of cells in degraded battery packs proved to be quite a futile exercise. Once done, the packs seem to quickly re-group themselves to degrade a lot faster than previously, and all of a sudden you get the same pack as before but for more money. So, what people do now, they try to replace full packs for the ones taken from salvage cars. This is one of the reasons there's a growing import of wrecked Leafs imported to Ukraine as well.

I follow the Leaf "industry" closely. They are far ahead of BMW in all departments here in terms of serviceability, including the existence of LeafSpy. If the degradation of my i3 's pack going forward is linear, I may see maybe one or two more years in my car until it becomes unusable in winter, so I need to start considering my options today. The most likely one - I'll need to sell the car at a very significant loss (despite my previous thoughts that the notorious EV depreciation had already been captured by the previous owner of the car - I did buy it for 1/3rd of the initial price, a 2.5 year old vehicle in an excellent condition with 15K miles on it).

Oleksiy
Posts: 63
Joined: Fri Mar 23, 2018 4:30 am
Location: Kyiv, Ukraine

Re: Battery capacity issue

Fri Feb 15, 2019 5:09 am

alohart wrote:
JLB2 wrote:My home charger (Chargepoint) gives me the amount of KWH's that was transferred to my i3 during a charging session.

That's not the energy actually used to charge the battery pack due to some of the energy being converted to waste heat during charging. The Idaho National Labs measured a 2014 i3's charging efficiency at various charging powers. The most efficient charging, 93%, was 30 A @ 240 V. Lower charging powers were less efficient.

Whereas, Batt. Kapa. max is the calculated maximum energy that could be added to the battery pack (i.e., excluding wasted energy).

So to make these equivalent, you'd need to correct the Chargepoint energy for energy lost to heat (i.e., at least 7% less than Chargepoint reports).

Just an observation: had to charge at a public charging station today, paid for 9.7 kWh. I took readouts of Batt.Ladung from the hidden menu before and after the session to measure charging losses:
Before: 19% SOC, Batt.Ladung 3.1 kWh (implied battery capacity = 16.3 kWh), Batt.Kapa 16.9 kWh, ambient temperature +1.5C / 35F
After: 69.5% SOC, Batt.Ladung 12.8 kWh (implied battery capacity = 18.4 kWh), Batt.Kapa 17.0 kWh, ambient temperature +1.5C / 35F

Seems the session was effectively lossless - 9,7 kWh metered - 9.7 kWh added to Batt.Ladung. Also, the post-session implied battery capacity didn't translate into significantly higher Batt.Kapa value, as I would have expected. And, if we divide 9.7 kWh by the depth of charge (9.7 / 50.5%), we get one more implied battery capacity value, this time 19.2 kWh. Go wonder...

(for those, who may be interested, the screenshots are under this link: https://www.drive2.ru/l/524031640918296811/).

jadnashuanh
Posts: 4339
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Battery capacity issue

Fri Feb 15, 2019 4:53 pm

One thing that can affect battery life is how well the logic and hardware can handle cell balancing. From what I've read, I think that BMW uses a more sophisticated routine to try to keep the batteries in shape. Leafs also seem deficient in their heat management. Lots of owners in the US southwest had early Leaf battery pack issues. THey still don't do refrigerated cooling...air cooling only (except maybe the newest models?). FWIW, the newest Leafs specify a limit on a single trip of DC fast charges you can do...they can't handle the heat. I do not know if they can preheat the batteries, which helps things in the winter.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

metaflash
Posts: 2
Joined: Mon Feb 11, 2019 12:44 pm
Location: 1724 Center Street Medford, OR 97501

Re: Battery capacity issue

Sun Feb 17, 2019 6:34 am

I almost have the same problem but thanks guys, I'm reading it all the ideas and suggestions, again thanks
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