Hilltop Mode or Partial Fill Mode

[brogult]

My suggestion is that Ford add two settings to allow charging to less-then-full for two separate reasons:

1) I live uphill from where I generally go. I'd like the option to charge to 90% so I have regen braking first thing. If I start from my house at 90% and go downhill to the freeway, I'll have near 100% when I get there. If I start at 100%, I get the jerky braking and end up wasting the energy.

2) If I charge away from home at a Chargepoint (or Blink if I'm desperate and I find a working one) station that charges by the kWh, I may need to leave the car at the station for several hours, but only wish to purchase enough juice to get home. My home power is practically free. So what I need is to plug in and set the car to only accept a certain amount of power, in kWh. There are several charge stations in my normal driving area that would permit this -- and not have any issues with my car sitting there for three hours but only charging for one.

 

[sefs]

This could be done pretty easily with an Arduino.

The two Tyco connectors under the hood that mate the chargeport harness to the charger harness could be opened, get the same two connectors again for a man in the middle approach.

Feed the L1, L2, and ground straight through, no need for modification. Take the pilot signal and feed it through a relay. Take the proximity signal through a relay with a 330 ohm relay wrapping the relay.

Read the CAN bus with the Arduino. When the SOC reaches the desired level, drop out the proximity relay. This will cause the 300 ohm relay to be in series now, and mimic a person pushing the proximity button on the J1772 handle. After a second, now drop the relay that is passing the pilot signal. The car will now act like it isn't plugged in anymore.

You've now successfully stopped a certain SOC.

You could also do this without the CAN bus interface, but that would only be through a timer. Probably would work pretty well, but you wouldn't get exactly the SOC you wanted.

 

[michael]

My suggestion is that Ford add two settings to allow charging to less-then-full for two separate reasons:

1) I live uphill from where I generally go. I'd like the option to charge to 90% so I have regen braking first thing. If I start from my house at 90% and go downhill to the freeway, I'll have near 100% when I get there. If I start at 100%, I get the jerky braking and end up wasting the energy.

2) If I charge away from home at a Chargepoint (or Blink if I'm desperate and I find a working one) station that charges by the kWh, I may need to leave the car at the station for several hours, but only wish to purchase enough juice to get home. My home power is practically free. So what I need is to plug in and set the car to only accept a certain amount of power, in kWh. There are several charge stations in my normal driving area that would permit this -- and not have any issues with my car sitting there for three hours but only charging for one.

I've been asking for the same thing since the beginning for another reason: to limit the SOC and preserve the battery life.

I end up doing this one of two ways: either by walking outside and unplugging the car (how dumb is this...the car is one big computer) or by setting a charging time window at some other time and commanding the car from charge now to value charge.

Either way is cumbersome...the car should provide this option.

 

[Olagon]

Does an EVSE have the option to know state of charge? If so I wonder when EVSEs with this feature will be sold. I'd buy one.

 

[WattsUp]

Does an EVSE have the option to know state of charge?

Not to my knowledge.

The "communication" between the car and EVSE is fairly limited. Basically, the level of current is described/controlled, but the EVSE doesn't really know anything "about" the car.

 

[michael]

While it is comforting to believe that the 90% SOC charging target in the FFE avoids battery degradation, this flies in the face of published articles by the NREL and others.

See for example

https://www.academia.edu/6880216/Maximizing_lithium_ion_vehicle_battery_life_through_optimized_partial_charging

Figure 4 shows anticipated battery life increases from 5 years to 12 years by optimizing charge...basically by charging only to the extent necessary for the next trip and just in time for departure.

Tesla is generally regarded as the leader in the EV field, and they provide continuously adjustable charging level targets. Mercedes and Toyota use the Tesla drivetrain and they provide the option for standard and extended range charges. In the case of Toyota, a standard charge is approximately 35 kWh and extended is approximately 42 kWh. Mercedes charges $500 extra for the ability to access the extended range charge.

Volt uses only about 65% of the usable battery capacity so they by default have a very low target SOC. They also provide a very agressive thermal management system compared to Ford.

Nissan is not the paradigm of good battery management procedures. I think they were rather whorish in taking away the 80% option to get another few miles on the window sticker.

 

[Olagon]

https://www.academia.edu/6880216/Maximizing_lithium_ion_vehicle_battery_life_through_optimized_partial_charging

Figure 4 shows anticipated battery life increases from 5 years to 12 years by optimizing charge...basically by charging only to the extent necessary for the next trip and just in time for departure.

Fascinating! But who would want to only have enough juice for the predicted next day usage other than commercial applications?

One day it would be cool if we could have packs that have some set of modular batteries of about 25 pounds each in the trunk. That way, we can remove capacity/weight when not needed, or have extra sets that can swap out charged units for empty units to get quick though partial charge back in a hurry. Then...a few batteries being charged in your garage would be enough to go a little further and these smart charging algorithms may make more sense.

 

[michael]

https://www.academia.edu/6880216/Maximizing_lithium_ion_vehicle_battery_life_through_optimized_partial_charging

Figure 4 shows anticipated battery life increases from 5 years to 12 years by optimizing charge...basically by charging only to the extent necessary for the next trip and just in time for departure.

Fascinating! But who would want to only have enough juice for the predicted next day usage other than commercial applications?

Obviously you would also want to have a comfortable reserve as well. The article I cited assumed a 10 mile reserve and a 1 hour safety factor for the just-in-time charging.

But the answer to your question is: Anyone who wants to minimize needless battery degradation. I drive straight to work every morning....I charge up to 70-80% at home and arrive with 20%-30% remaining. It's predictable, no benefit in punishing the battery. I charge up at work in the afternoon (not morning) the car doesn't sit in the heat all charged up for 6 needless hours.

In aviation, this is a standard practice: carry only the fuel required plus an acceptable reserve. An airplane is a very poor way to transport un-needed fuel from one location to another considering the weight penalty. Similarly, the battery of an EV is a very poor way to transport un-needed electricity from one location to another considering the battery life penalty.

 

[WattsUp]

Similarly, the battery of an EV is a very poor way to transport un-needed electricity from one location to another considering the battery life penalty.

Not quite a complete analogy. The reason in aviation you carry only the fuel necessary is both for the transport cost savings of moving unnecessary fuel (airplane fuel is heavy) and to avoid a larger-than-necessary fireball if you crash.

But, with an EV, you will always eventually use all the "fuel" in the battery and the "transport cost" difference between a partially-filled and completely-filled battery is exactly zero. So it doesn't really matter that you carry extra fuel around "unnecessarily".

For me, my car spends most its time partially-charged (since I usually just drove from somewhere) and parked in relatively cool garages. So, I don't worry about overly "managing" the battery health. Plus, the car is doing the most healthy thing that can be done for the battery by automatically keeping it from going into temperature extremes too often.

 

[michael]

The transport cost in an EV is a needlessly degraded battery. If you are not worried about that or believe it's not true then definitely keep your battery topped off

That high levels of charge degrade batteries is not my opinion. It is the conclusion drawn at NREL and pretty much universally by experts in the field. I have never seen a paper say that to keep a battery highly charged is beneficial or even harmless.

While it is true that carrying electricity does not add weight as does fuel, I think it has a real cost.

Going back to the original posters point, all I'm asking is that Ford make partial charging easy as does Tesla. I'm not saying anyone needs to make use of that feature if they think it worthless.

 

[brogult]

It is the conclusion drawn at NREL and pretty much universally by experts in the field.

I would be a bit careful with those assertions for a couple of reasons. I read the NREL paper you cited and I have a couple of issues with it and the whole topic generally.

1. These batteries have not existed long enough for actual long-term testing. The NREL "model" may be good, but is is based on a blend of theory and experience with NCA chemistry batteries. It looks at specific types and modes of degradation--there may be others that haven't been discovered or explored yet.

2. We don't know for sure what the FFE battery is, but my guess is that it is an NMC-spinel blend, like the Volt. The SOC and temperature effects on these batteries may be similar, like other Li-Ion technologies, or may be vastly different, like LiFePo4.

3. Although the simulation in the NREL paper matched the FFE in some ways (6.6 kW, 18 kWh), it was based on the NREL theoretical model, NCA chemistry, a primitive charging algorithm and entirely imaginary temperature spikes during charging. I don't know how precisely the FFE controls charging, but I think we can assume that there is at least some optimization beyond the basic taper. We do know the the FFE has an active TMS, and thus the battery should never see the temperatures supposed in this simulation. This is important, because the paper itself notes the significant life gained by allowing the battery to cool after charging and before driving. Imagine if the battery were never allowed to get warm in the first place?

4. The NREL paper assumed some type of charging EVERY DAY, even though the car's usage was fairly light. In practice, many people who drive significantly less than the maximum range only charge when they need to--perhaps every two or three days. I routinely skip days on charging, even though we put on 1000 miles a month. So if you have far fewer max SOC events, coupled with controlled temperatures, I think your results look much different even (incorrectly) assuming NCA chemistry.

5. There is no information about low SOC states or the beneficial effects of routine cell balancing. My experience with other Li-Ion systems is that while continuous overcharging, as in early MacBooks, will eventually kill a battery, many more failures are due to low SOC. I suspect (but have no proof) that high rates of discharge at low SOC are problematic with some systems. There may turn out to be some real benefits to keeping the batteries out of the lower ranges of SOC.

I think the real story is that we FFE drivers are actually beta-testers. This is new technology that LG Chem and Ford are interested in testing out. We're doing that for them!

I don't expect Ford to ever sanction a reduced charge/range for the purpose of extending battery life. It would just cause them other problems and reduce confidence in their product. Besides, I don't think anyone actually knows what the actual benefits would be. My idea was to give them viable alternative reasons for implementing a reduced-charge function.

 

[michael]

Well, I agree one needs to be careful, but I prefer to go with what appears to be the most credible information available.

You have stated that you can routinely go without daily charging, so you will be little impacted by reduced battery capacity. I on the other hand drive nearly 100 miles daily and need to charge twice daily. So I need to decide whether to operate between (roughly) 100% to 40%, 80% to 20%, or 60% to 0%.

Obviously the last choice is unacceptable, so I go with the 80/20 option. And I need to trust the published, peer-reviewed results from recognized researchers, not the opinions expressed on internet message boards. An electric car is a $20,000 battery on wheels, you don't get a second chance.

As an example, you have expressed the opinion that many more failures are caused by low SOC operation than by high SOC operation. This is directly contradicted by an Army CERCOM paper

http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA527711

which states in part:

During analysis of the data a series of trends stood out. The
first being, whenever the cell was held at an elevated
temperature both the capacity and power capability of the cell
decreased significantly (Figures 3-5). The one notable
exception is when the cell was maintained at 0% to 50% state of-
charge (Figure 6).

The second is when the cell was maintained at a high state of
charge (Figures 3 and 4). The capacity of these cells faded at
an increased rate. This is especially true for the cells
maintained at a state-of-charge of 50% to 100%.


The paper also provide a graphic (Figure 1) which showed that cells cycled between 0% and 50% lasted better than those cycled between 50% and 100%, or even 25% and 50%. The paper does say that at low temperatures, batteries kept at the lowest SOC didn't do well, but for my location this doesn't seem to apply.

Now, you may say that these are different batteries than those in the FFE and the situation is different, and you are quite possibly correct. But the the best available reports (to my knowledge) state the same thing....keep the battery at a low level of charge.

Show me evidence or reports to the contrary if you can...I truly want to find the best strategy since I depend on the health of my battery. But if I need to weigh an opinion against a published scientific paper, I need to go with the paper.

I wish we could have a series of drive-offs comparing FFEs maintained using different charging strategies, but this isn't practical. It would seem the effects of the different strategies are subtle, but as you point out there are few cars with lots of history. But I'm going with what I consider the best available information.

 

[jmueller065]

You guys are leaving out a data point (sort of): Ford (e.g. LG--LG designed the battery). Presumably they picked the range of the battery after some experimentation. Granted this is speculation but I would guess they cycled a few prototype batteries under a range of conditions and then picked the operating characteristics that lead to the longest lasting battery (at least that would be the logical approach).

The FFE was announced in 2009 but the first one went on sale in early 2012: three years is a long time to be experimenting with batteries (likewise I'm sure GM did a similar thing with the Volt--or GM/Ford did the experimentation together (or LG just shared their knowledge with both)).

 

[WattsUp]

... an Army CERCOM paper ... states in part:

During analysis of the data a series of trends stood out. The
first being, whenever the cell was held at an elevated
temperature both the capacity and power capability of the cell
decreased significantly (Figures 3-5). The one notable
exception is when the cell was maintained at 0% to 50% state of-
charge (Figure 6).

The second is when the cell was maintained at a high state of
charge (Figures 3 and 4). The capacity of these cells faded at
an increased rate. This is especially true for the cells
maintained at a state-of-charge of 50% to 100%.

Both of those results seem to be qualified with the condition "whenever the cell was held at an elevated temperature". Now, it probably doesn't "hurt" to keep the battery at a mid-level of charge all the time -- and I certainly don't fault anyone for wanting to be more "careful" with their battery -- but since the FFE tries hard not to "hold its cells at an elevated temperature", I personally choose not to fuss too much about the state of charge. I just fill the battery whenever I can and drive the car when I need/want to.

I'm sure the study cited is accurate and credible and draws interesting conclusions in the general field of battery management, but since the results are based on purposely stressing the battery both temperature-wise and capacity-wise (presumably, they mean actual 0% and 100% states of charge) -- none of which the FFE does to any comparable extreme -- I personally consider the information to be of marginal relevance to my FFE at best. We also don't know if the battery chemistry is the same between the cells used in the study and the cells used in the FFE.

 

[michael]

Right...you can correctly argue that this information might not be relevant and you may well be right, but I believe it is the best available information. I'm still waiting (actually...hoping) to see a peer-review published report that says it doesn't matter, go ahead and charge it up all the way, no harm will result. Or better yet a specific test of the FFE showing that regularly charging to the max provided has some defined effect. I haven't seen this in a published report, only in opinions expressed on internet forums like this.

And obviously if you are correct, I will have wasted effort managing my charge levels. But I'm trying to get 60,000 miles out of this thing without significant degradation. I have seen too many Leafs crippled by reduced range to want to risk this.

 

[Josephus]

It's debates like this that make me wish that each EVs published their BMS and regen numbers. Through experimentation many here have come to "believe" that the FFE uses only 19.5 of its 24 kWh battery. At this point I "assume" 100% on my FFE means the smaller of these two numbers. Does this change over its life span? When it runs out, is there still reserve charge in the HVB? How much? When going down hill, does speed or duration benefit more? yadah yadah. It is kinda fun to have a black box that we are trying to reverse engineer. But then again, I wish the manual plainly stated this stuff.

 

[WattsUp]

And obviously if you are correct, I will have wasted effort managing my charge levels. But I'm trying to get 60,000 miles out of this thing without significant degradation. I have seen too many Leafs crippled by reduced range to want to risk this.

And, as I said, I don't fault you for doing so. And you are right that nobody knows (yet). It will be interesting to see how things turn out a few years from now.

However, keep in mind that one big difference between the Leaf and FFE is that the Leaf's battery has virtually non-existent temperature management and, given the examples of what happened to Leafs in Phoenix and other hot climates, this design flaw (IMO) has almost certainly contributed to their marked battery capacity loss problems.

On the other hand, and speaking of anecdotal evidence, virtually nobody with an FFE has reported any significant battery degradation -- and certainly nothing that smacks of a clear trend as in the Leaf's case. Although this is admittedly anecdotal, trends do speak for something. After 2-3 years since the first FFEs hit the road, I would venture to say that there is no clear trend that FFEs have any tendency to suffer significant battery loss (and many, like mine, are actually near the halfway point of your 60,000 mile goal).

 

[Olagon]

Folks on the iMiev forum had a bunch of threads on battery life like this one http://myimiev.com/forum/viewtopic.php?f=23&t=2007.

 

[Rogerschro]

This topic appears to be the electric version of synthetic vs regular oil or premium vs regular gas. Endless speculation on what the mfg intended, what type works best, various studies related or not, methodology, etc....... Interesting to read, but I am going to admit I am too lazy to actually concern myself with it to much. I just plug my car in and unplug it when I am ready to drive. We'll see what happens down the road. I'll be your beta for irresponsible charging! LOL! really, keep up the work, it's interesting stuff to read about.

 

[Steve0512]

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