BMW i3 REX - Taking too long to charge on Maximum Setting

[AviatorMan]

Some pedantry:

kWh (kilowatt hour) and kW (kilowatt) are regularly confused on this forum. This is akin to confusing miles with miles per hour. If someone asks what the i3's top speed is, you wouldn't answer "93 miles".

The rate at which a charger provides power is measured in kilowatts. Since watts are amps times volts, an EVSE (charger) providing 30 amps at 240 volts is providing 30 x 240 = 7200 watts or 7.2 kilowatts. The total amount of energy provided during a charging session is measured in kilowatt hours. Charging at 7.2 kilowatts for 2 hours provides 7.2 x 2 = 14.4 kilowatt hours of energy (assuming perfect efficiency).

I work in a related field, and have found it interesting when dissimilar items can be directly and accurately converted. Example, a watt is ultimately a unit of heat, it is 3.41 btu's of heat. So an i3 battery is carrying 22kw/75,000 btu's of energy. About 18kw/61,000 btu's is usable. Gasoline contains 115,000 btu's per gallon so the i3 battery holds 1/2 gallon of gas, basically.

 

[Bunter]

This picture shows the start time, and how long it took to charge exactly. We are using a Chargepoint charger, rated at 6.7kw/h. With the vehicle set to Maximum charge setting via the iDrive

This vehicle is a brand new i3 just off the truck, with 15 miles remaining before dead battery.

It took 5 hours and 10 minutes to charge to full.

This is pretty standard from what i've seen on all of the i3's that I have PDI'd so far. Is there a problem? I dont know.

I'd say they is definitely a problem if you're using a 6.7 kW charger and only getting ~3.5 kW of charging out of it.

But where the problem is is harder to be sure about.

Bill

 

[noakey]

See this thread - http://www.mybmwi3.com/forum/viewtopic.php?f=10&t=1295

It appears that the current software patch lowers the charge rate to protect KLEs. If you've taken delivery in the past two weeks or so, or you've brought an older one in for service, you likely have it.

I made an enquiry into bmw uk and received tge following reply..

" I have spoken to technical about your query and you are correct, the new software installed on your vehicle has stricter temperature modelling built in. When the parts detect higher temperatures they de-rate the charging power. BMW AG are looking into this and it is possible that future software will reduce the affect of the temperature modelling but currently your vehicle is at the current solution."

 

[hamgolfer]

Some more pedantry: there is a thermodynamic aspect as well. A much smaller fraction of energy in gasoline compared to energy in a battery is available for moving the vehicle. Given current technology, it is probably less than 10% conversion efficiency via ICE versus closer to 90% for that in the battery.

Some pedantry:

kWh (kilowatt hour) and kW (kilowatt) are regularly confused on this forum. This is akin to confusing miles with miles per hour. If someone asks what the i3's top speed is, you wouldn't answer "93 miles".

The rate at which a charger provides power is measured in kilowatts. Since watts are amps times volts, an EVSE (charger) providing 30 amps at 240 volts is providing 30 x 240 = 7200 watts or 7.2 kilowatts. The total amount of energy provided during a charging session is measured in kilowatt hours. Charging at 7.2 kilowatts for 2 hours provides 7.2 x 2 = 14.4 kilowatt hours of energy (assuming perfect efficiency).

I work in a related field, and have found it interesting when dissimilar items can be directly and accurately converted. Example, a watt is ultimately a unit of heat, it is 3.41 btu's of heat. So an i3 battery is carrying 22kw/75,000 btu's of energy. About 18kw/61,000 btu's is usable. Gasoline contains 115,000 btu's per gallon so the i3 battery holds 1/2 gallon of gas, basically.

 

[Zzzoom3]

Some pedantry:

kWh (kilowatt hour) and kW (kilowatt) are regularly confused on this forum. This is akin to confusing miles with miles per hour. If someone asks what the i3's top speed is, you wouldn't answer "93 miles".

The rate at which a charger provides power is measured in kilowatts. Since watts are amps times volts, an EVSE (charger) providing 30 amps at 240 volts is providing 30 x 240 = 7200 watts or 7.2 kilowatts. The total amount of energy provided during a charging session is measured in kilowatt hours. Charging at 7.2 kilowatts for 2 hours provides 7.2 x 2 = 14.4 kilowatt hours of energy (assuming perfect efficiency).

I work in a related field, and have found it interesting when dissimilar items can be directly and accurately converted. Example, a watt is ultimately a unit of heat, it is 3.41 btu's of heat. So an i3 battery is carrying 22kw/75,000 btu's of energy. About 18kw/61,000 btu's is usable. Gasoline contains 115,000 btu's per gallon so the i3 battery holds 1/2 gallon of gas, basically.

Power and energy can be represented in a number of different units. Typically the units are related to the type of energy (Thermal, Electrical, Mechanical, etc.). Electrical power is typically expressed in "watts" or kilowatts (1000 watts) and electrical "consumption" is expressed in watt-hours or kilowatt-hours (1000 watt-hours). It is pretty much that simple.

Expressing electrical power in terms of thermal energy units is interesting but not germane to a discussion about electrical power me thinks ...

 

[CarlT2000]

Maybe there should be a thread talking about kilowatt vs killowatt hour, instead of hijacking this thread.

 

[Zzzoom3]

Some more pedantry: there is a thermodynamic aspect as well. A much smaller fraction of energy in gasoline compared to energy in a battery is available for moving the vehicle. Given current technology, it is probably less than 10% conversion efficiency via ICE versus closer to 90% for that in the battery

If you want to talk about energy efficiencies, have a look at the link below and see where all the energy used in a vehicle goes and where it is lost in your typical hybrid vehicle. No more than 40% of the energy actually goes to power the vehicle! This analysis comes out of the U.S. EPA.

Probably best to start a new thread if folks want to chat this up.

https://docs.google.com/file/d/0B5L...WtoNU1qWjJ0T1RLWGhLa1FJ/edit?usp=docslist_api

 

[jadnashuanh]

FWIW, at least with an ICE, when you need heating, it's essentially 'free'...not so with the EV's.

 

[TomMoloughney]

Unfortunately the i3s are having onboard charger failures and it sounds like you have experienced it (as I did). The car has two 3.7kW chargers which combine for the ability to charge up to 7.4kW. On many cars, one of the chargers fail so the car will only charge at about 3.5kW max which is why your car is taking so long to charge. Here is my post from another thread about the issue:

Notice: Onboard charger replacement and temporary reduction of charge rate

Over in the i3 Facebook group there have been some discussion here regarding the charge rates of some cars that have been returned from service once they had a new onboard charger(KLE) installed. Some people have reported that their car is taking longer to charge than it did before they had the service. I now have the real facts on this from BMW NA and it will be officially communicated through them soon. I just wanted to get this out there now before anyone else wonders why their car may be charging slower after service.

Unfortunately the lower charge rate is indeed going to be the case, but it is only a temporary measure. The problem is some i3s (BEV and REx) are having a failure of their onboard charger and the result is the car will only charge at half the usual rate (roughly 3.5kW instead of around 7kW). BMW has identified the cause and is in the process of developing a permanent fix for this which I believe will be a new KLE. In the meantime, if your KLE fails and you bring it in for the service, they will install a new KLE(the same one as the one you have), and then reduce the charge rate by about 20% (you should see about a 5.8kW draw instead of the ~7kW draw the car can take now). This will help to prevent the new unit from failing again but it is only a temporary measure until the new, permanent unit can be installed. What this means is instead of charging at about 23 miles per hour, you'll be charging at about 18 miles per hour (of course, YMMV) and instead of a 3.5 hour full recharge, it will be about 4.5 hours.

I don't have any time official frame, but I expect this to be a short stint of perhaps a couple months, that's all. Many of you won't even be effected, as long as your KLE doesn't fail. One suggestion I have that will prevent any failure is to set your charge rate to minimum if you don't need to charge faster, like if you are recharging overnight. The lower charge rate will prevent the KLE from failing and you won't be inconvenienced by having to bring it in for service just yet. No, I realize it's not ideal, but BMW does indeed have a permanent fix and the cars will indeed have the 7.2kW charge rate we were promised. I'll update more as I get information on this.

I'm not sure if the European i3 owners have been experiencing the same onboard charger issues as we have been here in the US, but I'd like to hear about it if you have. I'm not sure exactly why it would only affect us here, but I do know the KLEs are failing at a pretty good rate and many of the i3 owners that I know have had the problem, including me.

The temporary charge rate does not effect level 1 charging or DCQC, just level 2 charging.

 

[Bunter]

This doesn't really explain why CarlT had been PDI'ing i3s for 3 months and only getting about 3.5 kW charging (6 hours to charge) on brand new vehicles.

Bill

 

[jadnashuanh]

This doesn't really explain why CarlT had been PDI'ing i3s for 3 months and only getting about 3.5 kW charging (6 hours to charge) on brand new vehicles.

Bill

It does if one of the charging units is DOA. While probably even less likely, but possible, is that they did not change the charge setting to maximum, since they come from the factory set to minimum.

 

[Zzzoom3]

Unfortunately the i3s are having onboard charger failures and it sounds like you have experienced it (as I did). The car has two 3.7kW chargers which combine for the ability to charge up to 7.4kW.

Are you referring to the AC/DC converter in the convenience charging electronics (KLE) and the electrical machine electronics (EME)? I think I read that each takes single phase AC and outputs the necessary DC voltage to the battery. Each is capable of delivering 3.7 kW. I understand that there is a control unit also called a KLE. Would you happen to know which of the power electronics modules is failing or is it also a control unit problem?

 

[i3Panda]

Hi everybody,

A little update on my REX. It was in BMW service from July 31st to August 8th for the following:
1) Taking 6 hours to charge vs. 3 hours.
2) Unable to connect to DC Fast Charger.
3) Received control error message "Increased battery discharge."

After a week of "we don't know" and "we're in contact with BMW" they were able to determine that there was a fault in the negative battery cable which was ordered and replaced. Since then, I have experienced none of the above and am able to charge my vehicle in roughly 3.5-4 hours. It connects to DC Fast without any problems (charging takes closer to an hour vs 20-30 min as quotes from BMW), and all error messages are gone.

This thread got very technical. Sorry if I was not perfectly clear on the issues. I am a girl , but I have another electric car and as soon as I saw a huge difference the car went back in for service. I hope that anybody else having the same issue mentions the negative battery cable (don't ask me for specifics because I don't know :lol: ) because that was the fix for my REX and she is now working just fine.

In the meantime, I have learned that the standard Level 1 charger is somewhat "smart" and you will notice changes in the charge times dependant on how much power you are using overall in your house. I may plug it in and it says 9:20 AM and then 30 minutes later once we are ready for bed (and have turned off appliances) it will say 5:45AM. It regulates itself somehow.

Hope this helps also.

Have a great one and enjoy your i3's!

 

[i3Panda]

Maybe there should be a thread talking about kilowatt vs killowatt hour, instead of hijacking this thread.

lol. Much to my surprise when I came back to read up on the thread I started. "What are they talking about?!" I posted an update as to what was presumably wrong with my REX.

 

[KurtEndress]

In the meantime, I have learned that the standard Level 1 charger is somewhat "smart" and you will notice changes in the charge times dependant on how much power you are using overall in your house. I may plug it in and it says 9:20 AM and then 30 minutes later once we are ready for bed (and have turned off appliances) it will say 5:45AM. It regulates itself somehow.

I've noticed the same sort of change in estimated completion for a 120V level 1 charge.

My current theory is that initially the car battery and electronics are still warm from driving and that the cooling system is still working to get the temperature down. Operating the cooling system takes a larger percentage of the level 1 charge than a higher power charge so would cause a greater variability in charge time. After a while the battery cools down and the cooling system isn't using as much of the charge power so the estimated finish becomes earlier.

Or maybe the system simply overestimates level 1 charging time and as it gets closer to finished the time becomes more accurate.

 

[jadnashuanh]

BMW states 20-minutes with the DC fast charger to 80%...once it reaches that charge level, it slows down the charging rate quite a bit, so yes, it often will take close to an hour to get 100%, but note BMW does not advertise 100% on the DC fast charging...they specifically state 80%, and the timing is accurate for that (IF you have the max rate unit the car can accept - just like not all level 2 units are created equal, neither are the DC units).

 

[kevinb61]

In the meantime, I have learned that the standard Level 1 charger is somewhat "smart" and you will notice changes in the charge times dependant on how much power you are using overall in your house. I may plug it in and it says 9:20 AM and then 30 minutes later once we are ready for bed (and have turned off appliances) it will say 5:45AM. It regulates itself somehow.

I've noticed the same sort of change in estimated completion for a 120V level 1 charge.

My current theory is that initially the car battery and electronics are still warm from driving and that the cooling system is still working to get the temperature down. Operating the cooling system takes a larger percentage of the level 1 charge than a higher power charge so would cause a greater variability in charge time. After a while the battery cools down and the cooling system isn't using as much of the charge power so the estimated finish becomes earlier.

Or maybe the system simply overestimates level 1 charging time and as it gets closer to finished the time becomes more accurate.

+1 to the idea that maybe temperature is playing into the calc.

 

[sradcliffe77]

BMW has throttled down the L2 charging rate due to heat issues with the "KEL". the KEL being the German term for onboard charger. My i3 Rex takes 4h23m from zero to full. BMW plans to either change out the onboard chargers by the end of 2014 or fix it with some software/firmware update. Very disappointing to say the least.

 

[M2140]

Unfortunately the i3s are having onboard charger failures and it sounds like you have experienced it (as I did). The car has two 3.7kW chargers which combine for the ability to charge up to 7.4kW. On many cars, one of the chargers fail so the car will only charge at about 3.5kW max which is why your car is taking so long to charge. Here is my post from another thread about the issue:

Notice: Onboard charger replacement and temporary reduction of charge rate

Over in the i3 Facebook group there have been some discussion here regarding the charge rates of some cars that have been returned from service once they had a new onboard charger(KLE) installed. Some people have reported that their car is taking longer to charge than it did before they had the service. I now have the real facts on this from BMW NA and it will be officially communicated through them soon. I just wanted to get this out there now before anyone else wonders why their car may be charging slower after service.

Unfortunately the lower charge rate is indeed going to be the case, but it is only a temporary measure. The problem is some i3s (BEV and REx) are having a failure of their onboard charger and the result is the car will only charge at half the usual rate (roughly 3.5kW instead of around 7kW). BMW has identified the cause and is in the process of developing a permanent fix for this which I believe will be a new KLE. In the meantime, if your KLE fails and you bring it in for the service, they will install a new KLE(the same one as the one you have), and then reduce the charge rate by about 20% (you should see about a 5.8kW draw instead of the ~7kW draw the car can take now). This will help to prevent the new unit from failing again but it is only a temporary measure until the new, permanent unit can be installed. What this means is instead of charging at about 23 miles per hour, you'll be charging at about 18 miles per hour (of course, YMMV) and instead of a 3.5 hour full recharge, it will be about 4.5 hours.

I don't have any time official frame, but I expect this to be a short stint of perhaps a couple months, that's all. Many of you won't even be effected, as long as your KLE doesn't fail. One suggestion I have that will prevent any failure is to set your charge rate to minimum if you don't need to charge faster, like if you are recharging overnight. The lower charge rate will prevent the KLE from failing and you won't be inconvenienced by having to bring it in for service just yet. No, I realize it's not ideal, but BMW does indeed have a permanent fix and the cars will indeed have the 7.2kW charge rate we were promised. I'll update more as I get information on this.

I'm not sure if the European i3 owners have been experiencing the same onboard charger issues as we have been here in the US, but I'd like to hear about it if you have. I'm not sure exactly why it would only affect us here, but I do know the KLEs are failing at a pretty good rate and many of the i3 owners that I know have had the problem, including me.

The temporary charge rate does not effect level 1 charging or DCQC, just level 2 charging.

I'm starting to see this issue myself. We used to charge in 3.5 hrs and now at 4.5 hrs and today saw as high as 5.5 for a full charge. i also can't get fast charging to work, the car constantly has an error about "reduced" charging! and I'm constantly loosing communication with the car and the app.

I'm taking mine to the dealer and asking for a fix to all of it or my money back. The car has already stranded me twice.

 

[jadnashuanh]

The charge rate varies depending on the temperature. The fix for the KLM is known, but it takes awhile to actually make the new ones, then it will be awhile to get them installed. I've learned over the years that even something with the same part number may not be consistent from batch to batch, so something that worked great during testing, may exhibit issues when you then buy what you think is the same part in bulk. The only way to ensure nothing changes is to build everything yourself, and in today's world, that's nearly impossible.