Pathetic charging of i3 compared to B Class Electric

I have had an i3REX for a few months now and picked up a MB B Class Electric two days ago.

I have a current monitoring system from "The Energy Detective" installed in my circuit breaker for the EVSE (BMW Wall Box Pure, rated at 7.2KW).

The power consumption curve when charging the BMW, even when cool, goes up only to about 5.9KW. My measured voltage is 238V. After the car is charged to 85 SOC, the power take up is reduced exponentially so that the remaining 15% takes another 75 to 90 minutes.

When charging the MB, the power take up is close to the rated 7.2KW and stays there all the way till the last two minutes when it ramps down to shut down.

I know about the KLE issue, but right now the BMW charging system is pathetic in comparison.

:evil:

hamgolfer said:

I know about the KLE issue, but right now the BMW charging system is pathetic in comparison.

:evil:

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If you know about the KLE issue then you know that your charge rate has been turned down until the new parts are installed. At 5.9Kw you are charging at better than 70% which is right in line with expectations. Once the new KLEs arrive on the scene you and all the rest of us will be charging at 7.2.

Then there is also the big tail off, where the last 15% takes 90 minutes instead of the 30 min it would take if the power uptake were not reduced.

I suppose one can also excuse that as being better for the battery.

But, the Tesla supplied system in the MB B class Electric does not seem to need it.

The temperature makes a big difference in how fast the car charges...it's been cool here and I'm seeing nearly 7Kw at the beginning of my charging and yes, I do have the temperature dependent KLE s/w in my vehicle. Keep in mind that managing the temperature of the battery pack is quite important to longevity. What is the battery warranty on the MB? They may not care about long-term reliability. That, plus they have a bigger battery pack (and possibly bigger charging unit) could easily account for a bigger charging rate. That may not mean it reaches full charge faster, since it is bigger. It's all about heat management and only time will tell which pack lasts longer. My bet is on BMW's. MB's entry was a me-too thing, and not built from the ground up as electric.

These seem like legitimate complaints about the i3 charging via L2, but it's worth mentioning that there's no DCFC option for the MB, which is much more significant to me than a slight reduction in L2 speeds (given that I normally charge on L2 at home, where an extra 45-60 minutes rarely matters). If BMW is indeed making this option standard on 2015 models, as has been stated, then that makes the absence even more significant on the MB.

The way the i3 reduces the rate when the battery is almost full does seem overly conservative - I wonder if this behavior will be the same once the full charging speed is restored?

How long does the MB take to charge from ~5% to 100% on a 7.2kW EVSE? Based on the larger battery, I'm guessing it's at best similar to the i3, even at the reduced rate.

jadnashuanh said:

My bet is on BMW's. MB's entry was a me-too thing, and not built from the ground up as electric.

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Right, because Tesla doesn't know what they are doing right?! You know the MB uses a Tesla battery pack and motor right?

The Mercedes B ED has a superior 10kW charger built in, about 40% better than the BMW charger today, and at least 30% better after BMW fix their charger issues.

Say what you want, but the AC charger for the MB is more powerful and adds electrons faster than the BMW does.

Then again, the BMW is a far more efficient car, so even with the lower AC recharge rate, the km added per hour is likely very similar.

One thing that is different too is that MB offers a battery pack range extender which you have to pay extra for if you want it enabled. The battery is the same size no matter if you buy the option or not. If you did not pay the extra usable capacity then it is not enabled (acts as a bigger buffer for battery life) and that is not used, that bigger buffer would in principle allow the charging to continue at a faster rate up to the apparent end of capacity as compared to the BMW.

hamgolfer said:

Then there is also the big tail off, where the last 15% takes 90 minutes instead of the 30 min it would take if the power uptake were not reduced.

I suppose one can also excuse that as being better for the battery.

But, the Tesla supplied system in the MB B class Electric does not seem to need it.

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That's because in the MB you are not charging to 100% unless you push the optional button on the dash.

While there may be one, the MBUSA website does not list s separate battery warranty on their B-class (not shown in their brochure or the specs page)...you get the standard 50K miles/4-years. At least with the BMW, you get a known threshold at where they will replace the battery - at least 70% at 8-years/100K miles.

Neither Tesla (nor the BMW) have been around long enough to really know how well their batteries will hold up. The Tesla batteries have LOTS more connections than the BMW batteries internally (BMW uses larger cells), so a failure of a single cell on the Tesla (and MB) could have more of an issue on the ability to hold a charge since so many of them are in series. Time will tell.

Everyone's threshold for waiting to recharge is different...it is entirely reasonable to use a bigger charging unit when there is a bigger battery pack. It's all about cost/benefit. Keep in mind that most public EVSEs will not take advantage of the MB's larger charger - most of them max out at about what the i3 chose...and, if you really want to take advantage of it, that means spending a lot more money on your own because of the larger gauge wiring and more expensive unit you'll need to purchase.

FWIW, since things have cooled off here, I have not noticed ANY degradation in the max charging rate on my i3...I do not know the temperature thresholds where it begins to decrease, but I have not seen it, and expect by early next year, that to be fixed so once it does warm up again, the issue will be non-existent.

Given the fact that MB is only selling the B-class vehicle in very select markets, and the i3 is available country-wide, I do not think many people will actually have the choice in the near term.

Are you watching your car while it charges? What about your phone?

I don't, so it doesn't matter how long it takes for either of them.

SmartElectric said:

jadnashuanh said:

My bet is on BMW's. MB's entry was a me-too thing, and not built from the ground up as electric.

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The Mercedes B ED has a superior 10kW charger built in, about 40% better than the BMW charger today, and at least 30% better after BMW fix their charger issues.

Say what you want, but the AC charger for the MB is more powerful and adds electrons faster than the BMW does.

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The car will only pull as much current as the EVSE will give it. Most household EVSEs will supply 32 amps from a branch circuit that has a 40A breaker. Or less. And the BMW will charge at a max current of about 32 amps on a Level 2 EVSE. So no, the M-B doesn't really charge faster in most situations. But it does have a charger that's too big for the job it has to do.

In this case, "bigger" is not "better", it's just "bigger".

Scanning the available EVSE public/commercial locations, it is VERY rare to find one bigger than 30-40A, which means even with a larger charging unit, you'd never achieve the recharge rate the vehicle could provide. A 10K load at 220vac is over 45A, then, throw in the US code required 125% factor, you're looking at a likely 60A breaker and related wiring. 60A, or even 45A is likely much more 'spare' capacity of most homes, thus requiring a service upgrade. There is a reason why most charging units are smaller. That, and the increased heat can mean more long-term reliability issues, or if not, more than incremental increases in vehicle resources (bigger cooling capacity, maybe bigger heat sinks, not counting the cost of the thing itself).

There's a reason why the Tesla has nearly 4x the battery capacity and it only gets about 3x the range of an i3...adding more batteries and internal infrastructure, adds weight, and increased weight means more power is required to move the thing, which means those batteries are not going to move you as far...there's a decreasing advantage to more batteries...eventually, more batteries would start to DECREASE range, rather than increase it, unless you take the whole picture into account (such as the i3's use of CFRP and aluminum and plastic).

There are tradeoffs, bigger isn't necessarily better. I haven't looked lots of places, but I have never found an EVSE out in the public that was bigger than 32A, and many are a lot smaller. SO much for getting a bigger battery recharged while out shopping.

Sort of like having a modified car that needs to run on avgas to achieve its performance...really hard to find, and not too useful for general operation. Say your Tesla has the battery run down, and you're no where near a supercharger...use a public EVSE that has 23A, and if left in the morning, come back after supper. The size of the internal charging unit is irrelevant unless there's places that can make use of it. Not as bad as having a FCV and not being able to get any H2 at all along your trip, though. At least there are places you can plug in an EV many places...just have to wait awhile before you can get going again.

jadnashuanh said:

Say your Tesla has the battery run down, and you're no where near a supercharger...use a public EVSE that has 23A, and if left in the morning, come back after supper.

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Agree with all you wrote, except this part - sort of.

The salient point at any time for an EV owner is: "how far do I have to go now and at what SoC is the vehicle".

If you can't get to your next destination, it's highly likely you're 10 or 20 miles short, not 200 miles. There is no need in such circumstance to do an 8 hour charge at 23A - all you need is a 1 hour charge and you will then have enough Joules in your battery to do the job at hand.

I've had my i3 for 6 weeks now and I've never needed a public charge, and I've never had to wait at home to go somewhere for want of a charge. And I lived with the EVSE that came with the car for 2 of those weeks.

People get too hung up on "how long does it take to do a full charge"? Almost never do you need a full charge, and when you do it's very likely that you just arrived HOME, where you can plug in - and at 32A, in an hour you again have 30 miles or more of range.

When I'm asked "how long does it take to charge it up", I answer: "12 seconds - 6 seconds to plug it in, and 6 seconds to unplug it".

wayne325 said:

jadnashuanh said:

Say your Tesla has the battery run down, and you're no where near a supercharger...use a public EVSE that has 23A, and if left in the morning, come back after supper.

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Agree with all you wrote, except this part - sort of.

The salient point at any time for an EV owner is: "how far do I have to go now and at what SoC is the vehicle".

If you can't get to your next destination, it's highly likely you're 10 or 20 miles short, not 200 miles. There is no need in such circumstance to do an 8 hour charge at 23A - all you need is a 1 hour charge and you will then have enough Joules in your battery to do the job at hand.

I've had my i3 for 6 weeks now and I've never needed a public charge, and I've never had to wait at home to go somewhere for want of a charge. And I lived with the EVSE that came with the car for 2 of those weeks.

People get too hung up on "how long does it take to do a full charge"? Almost never do you need a full charge, and when you do it's very likely that you just arrived HOME, where you can plug in - and at 32A, in an hour you again have 30 miles or more of range.

When I'm asked "how long does it take to charge it up", I answer: "12 seconds - 6 seconds to plug it in, and 6 seconds to unplug it".

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I agree, I usually only charge up to around 60 to 70% soc myself. My trips are usually short anyway an this method of charging means I am not leaving the car sit a lot with a nearly full battery(which is not good for the batteries). If a longer trip comes up I can just top up the battery in a short time, usually in about 60 to 90 minutes.

Keep in mind that the i3 disconnects from the EVSE once it reaches full charge (and in the scheme of things, that is NOT the full charge of the battery), and will only start charging again if you ask it to precondition or the SOC drops a fairly significant amount (someone said about 5%, but I've not verified that). IOW, it manages things itself...you do not need to worry about it sitting on the charger for long periods of time...it will disconnect all by itself. You still need to pull the plug out when you want to go somewhere, but the relay in the EVSE has long since been opened, removing all power from the vehicle.

jadnashuanh said:

Keep in mind that the i3 disconnects from the EVSE once it reaches full charge (and in the scheme of things, that is NOT the full charge of the battery), and will only start charging again if you ask it to precondition or the SOC drops a fairly significant amount (someone said about 5%, but I've not verified that). IOW, it manages things itself...you do not need to worry about it sitting on the charger for long periods of time...it will disconnect all by itself. You still need to pull the plug out when you want to go somewhere, but the relay in the EVSE has long since been opened, removing all power from the vehicle.

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I agree with the 5% figure (95% soc) or start precondition in order to charge again after a full charge, I tried it.

jadnashuanh said:

Scanning the available EVSE public/commercial locations, it is VERY rare to find one bigger than 30-40A, which means even with a larger charging unit, you'd never achieve the recharge rate the vehicle could provide. A 10K load at 220vac is over 45A, then, throw in the US code required 125% factor, you're looking at a likely 60A breaker and related wiring. 60A, or even 45A is likely much more 'spare' capacity of most homes, thus requiring a service upgrade. There is a reason why most charging units are smaller. That, and the increased heat can mean more long-term reliability issues, or if not,

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It's odd that you'd mention charger issues, when the smaller i3 charger already have issues, and the Tesla chargers that have been in use since June 2012 do not.

The limit on public charging is typically 30 amps. Period. Not 40.

The Tesla charger pulls 40 amps max, not 45, and requires a 50 amp circuit breaker, not 60.

The smaller capacity 30 amp charger on the BMW requires a 40 amp circuit breaker, however code allows for a 50 amp breaker to be used, since 40 amp ones are hard to find.

The North American standard household electrical voltage is 120 / 240, not 220.

Commercial voltage is typically 120 / 208.

Sort of like having a modified car that needs to run on avgas to achieve its performance...really hard to find, and not too useful for general operation. Say your Tesla has the battery run down, and you're no where near a supercharger...use a public EVSE that has 23A, and if left in the morning, come back after supper. The size of the internal charging unit is irrelevant unless there's places that can make use of it. Not as bad as having a FCV and not being able to get any H2 at all along your trip, though. At least there are places you can plug in an EV many places...just have to wait awhile before you can get going again.

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Just plugging into to any 50 amp circuit, like those found at RV parks, provides full 40 amp power. Tesla cars come with a portable charger cord that allows full 40 amp charging. BMW does not.

TonyWilliams said:

jadnashuanh said:

Scanning the available EVSE public/commercial locations, it is VERY rare to find one bigger than 30-40A, which means even with a larger charging unit, you'd never achieve the recharge rate the vehicle could provide. A 10K load at 220vac is over 45A, then, throw in the US code required 125% factor, you're looking at a likely 60A breaker and related wiring. 60A, or even 45A is likely much more 'spare' capacity of most homes, thus requiring a service upgrade. There is a reason why most charging units are smaller. That, and the increased heat can mean more long-term reliability issues, or if not,

Click to expand...

It's odd that you'd mention charger issues, when the smaller i3 charger already have issues, and the Tesla chargers that have been in use since June 2012 do not.

The limit on public charging is typically 30 amps. Period. Not 40.

The Tesla charger pulls 40 amps max, not 45, and requires a 50 amp circuit breaker, not 60.

The smaller capacity 30 amp charger on the BMW requires a 40 amp circuit breaker, however code allows for a 50 amp breaker to be used, since 40 amp ones are hard to find.

The North American standard household electrical voltage is 120 / 240, not 220.

Commercial voltage is typically 120 / 208.

Sort of like having a modified car that needs to run on avgas to achieve its performance...really hard to find, and not too useful for general operation. Say your Tesla has the battery run down, and you're no where near a supercharger...use a public EVSE that has 23A, and if left in the morning, come back after supper. The size of the internal charging unit is irrelevant unless there's places that can make use of it. Not as bad as having a FCV and not being able to get any H2 at all along your trip, though. At least there are places you can plug in an EV many places...just have to wait awhile before you can get going again.

Click to expand...

Just plugging into to any 50 amp circuit, like those found at RV parks, provides full 40 amp power. Tesla cars come with a portable charger cord that allows full 40 amp charging. BMW does not.

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Actually I have a portable 30 amp charging cord, not provided by BMW but still readily available from Clipper Creek for a measly
wait for it $590. So I don't see that the Tesla is that much better and I don't know what KOA camp grounds would charge me for a quick charge vs renting a space over night. Probably price prohibitive as compared to charging at a real level 2 charging station vs using my portable 30 amp 240 volt portable plug in unit by Clipper Creek at KOA.

mindmachine said:

I agree, I usually only charge up to around 60 to 70% soc myself. My trips are usually short anyway an this method of charging means I am not leaving the car sit a lot with a nearly full battery(which is not good for the batteries). If a longer trip comes up I can just top up the battery in a short time, usually in about 60 to 90 minutes.

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I hope BMW will give us an option soon in the car and the app so we can do something like "charge to 80%", "only charge during these hours" and maybe more than one range of allowed charging times. I like the way you're doing your charging but right now (unless I've missed something) there's no way to have it happen automagically.

wayne325 said:

I hope BMW will give us an option soon in the car and the app so we can do something like "charge to 80%", "only charge during these hours" and maybe more than one range of allowed charging times.

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Yes!! It will get old walking 200 feet and down 2 floors to reach our parking space so that I can begin and end charging manually to avoid full charging unless we're planning to drive a long distance the following day. I know that there are those who say, "What, me worry?" figuring that if repeated full charging and parking for many hours with a full battery pack degrades their battery pack, so what? They would no longer own their i3's by the time their battery pack warranty expires, or that they would be protected by this warranty (but who wants to live with 29% degradation?). For those of us who plan to own our i3's for longer than the battery pack warranty, I don't want my battery pack to degrade due to my non-ideal treatment of my battery pack. I'm appalled that BMW recommends fully charging the battery pack before storing one's i3 for a few months.