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Nice to hear, I abandoned the forum/this thread for a while as there didn't seem to be much interest in it. I do have some battery health best charging practices numbers I've been kicking around; but, I am still not sure of the most useful way to present it.
Keep in mind, that 80% is the actual SoC not the App SoC... and the max internal charge rate is actually 50 kW !!! So, even at high SoC the battery can easily accept the full 6.6 kW of the onboard charger (*up to ~87% actual SoC, or ~99% App SoC at ~3 kW... see Note below). Also, that was with the stock EVSE at 240V; so, I believe that technically counts as L2. I will probably log a 6.6 kW charging session at some point; but, any posts with new info here will likely be several weeks from now.
[Note: That tail at the end of the charging session probably shouldn't be like that. I continued my interpolation/extrapolation formulas there when I should have done something different. It seems that is the point where the charge controller switches from constant current to constant voltage charging (or something close to that). It's hard to tell exactly what is going on there as the voltage resolution is relatively poor.]
I was considering taking on the challenge of explaining how they arrive at the total system power; but, this would first require an explanation of how the engine and "eCVT" actually work together/against each other to fully appreciate, so... it's no small task.
Anyone interested?
Yes, interested.
I assume you are getting the calculated SoC from a voltage/SoC table. I assume with no load (other than normal car parasitic drain)? IF yes, could you provide a link to it?
I have a 350h, but have been thinking about seeing is the "normal" SoC is as widely reported 20-80% max of total capacity. It does seem the 450h+ is a little higher than I would have initially thought for max battery life- i.e. max 80-85%. But, of course, on the PHEV, range is very important both for a practical even day driver and a marketing standpoint.
WeberAuto has an amazing video that explains it pretty well...
The video doesn't explain total system power though.
Indeed. An excellent video that reveals the elegance/simplicity of the "transmission"/"starter"/"alternator". A firm understanding of this video is necessary (but not sufficient) to appreciating the total system power... and other characteristics of Toyota's hybrids.
I assume you are getting the calculated SoC from a voltage/SoC table. I assume with no load (other than normal car parasitic drain)? IF yes, could you provide a link to it?
I have a 350h, but have been thinking about seeing is the "normal" SoC is as widely reported 20-80% max of total capacity. It does seem the 450h+ is a little higher than I would have initially thought for max battery life- i.e. max 80-85%. But, of course, on the PHEV, range is very important both for a practical even day driver and a marketing standpoint.
The SoC numbers and voltage come directly from the car while charging. Since the voltage and SoC has such poor resolution, I interpolated between points by Ah counting to make it pretty (and extrapolated the voltage when it switched from constant current charging to maybe constant voltage charging when I probably shouldn't have... you know, the kink on the end? It should maybe be flat). You can read SoC with various OBD devices. As I mentioned above...
Originally Posted by CdO
Some details... Of course, the open cell voltage will be lower... at least 30 to... 50+ mV? I massaged the raw data a bit... apparently the car isn't too accurate at calculating the SoC... charge cycles end from ~88% - ~91; then, the SoC resets to ~90.6%. The SoC is output with an 8 bit number the software truncates (e.g. 231/255=90.588%; Techstream reports 90.58%; some OBDII devices will read 90.5%); but, it is clear the car has finer resolution internally as some events occur between these values.
Some may be interested to know: the car does not report an internal measure of the battery capacity... and Toyota does not warrantee any specific capacity retention as many other automakers do (usually ~70% at end of warrantee period). Toyota says capacity loss is a natural characteristic of lithium batteries. If you go to your dealer and say your battery has lost XX capacity, they can't just connect their computer and verify it. They can see the voltage and internal resistance of each cell; but, unless there are some bad apples there is nothing to see.
Indeed. An excellent video that reveals the elegance/simplicity of the "transmission"/"starter"/"alternator". A firm understanding of this video is necessary (but not sufficient) to appreciating the total system power... and other characteristics of Toyota's hybrids.
Well, I would love to learn how to appreciate the total system power. It doesn't make sense to me that in a parallel hybrid system, where each of the ICE and electric motors (MG2 and MGR) can independently apply some max power, the sum of total power doesn't add up.
The only thing I can think of is that the high voltage system isn't able to send max power to all three electrical motors since the high voltage system is shared by both. So when MG1 requires max power to create an underdrive gear ratio for the ICE then MG2 and MGR cannot receive full power. No idea if I am hot or cold here...
Well, I would love to learn how to appreciate the total system power. It doesn't make sense to me that in a parallel hybrid system, where each of the ICE and electric motors (MG2 and MGR) can independently apply some max power, the sum of total power doesn't add up.
This article talks about the power from the 3 electric motors. See if that helps.
...It doesn't make sense to me that in a parallel hybrid system...
It has characteristics of both parallel and series hybrids; so, many call it a series-parallel hybrid. (It cannot operate entirely in parallel or entirely in series... I hope this will become clear later. I'll try to remember to circle back to this distinction.)
Some of the marketing material says it uses the best features of each type. My immediate reaction was to disagree with that; but, the more I think about it... I guess it actually does.
This article talks about the power from the 3 electric motors. See if that helps.
I have some problems with that article...
"There are three electric motors in total. The pair at the front axle work together to deliver 179 hp"
The pair at the front do not work together. One front motor by itself is rated 179 hp (i.e. MG2). The other provides the CVT functionality and starts the engine.
"As usual, the total combined output of the hybrid powertrain is not as simple as just adding up all the numbers..."
True.
"The gasoline engine and electric motors won't reach peak output at the same time..."
This is the explanation most people give; but, at this point I don't think it comes into play in a major way. (I need to generate/extract more data before I can say for sure... but, that won't happen for at least a couple of weeks.)
"For instance... there's a limit to the amount of power the 18.1 kWh lithium-ion traction battery can supply."
Also true.
Sorry to be a tease; but, I don't like to put stuff out there until I'm ~100%.
"There are three electric motors in total. The pair at the front axle work together to deliver 179 hp"
The pair at the front do not work together. One front motor by itself is rated 179 hp (i.e. MG2). The other provides the CVT functionality and starts the engine.
This is a matter of perspective. MG2 may be rated at 179hp but can't produce it without the electrical energy generated from MG1 (and some from battery too where appropriate to top it up), so they do work together, it's just not a case of the power ratings of the two motors being additive as you say.
This is a matter of perspective. MG2 may be rated at 179hp but can't produce it without the electrical energy generated from MG1 (and some from battery too where appropriate to top it up), so they do work together, it's just not a case of the power ratings of the two motors being additive as you say.
I believe this thread is about the NX450h+ which can produce that power from battery power alone.
Also, note CdO's post here which shows power output going down with the state of charge decreasing. When the state of charge in the NX450h+ is low, it can produce 80% of power out. What is interesting is the NX450h+ has 302 combined HP and the NX350h has 240horsepower, which is 80% of the NX450h+.
@Droid13 is correct that MG1 and MG2 working together is a matter of perspective. (MG1 does generate electricity that can be used for MG2 in high load and low to medium eCVT "gear" conditions.)
For me, working together is like you and I lifting something together.
From the perspective of the article, they would have to mean that while you lift something I feed you some gummie bears or something to give you more power. We're working together, in a way.
I read a new Prius Prime review where the author said something like "the engineers claim" the power of everything doesn't just sum up... but, we may just be a software tweak away from a 300+ hp Prius (instead of the rated 220.) After that, I'm not in a charitable mood.
...When the state of charge in the NX450h+ is low, it can produce 80% of power out. What is interesting is the NX450h+ has 302 combined HP and the NX350h has 240horsepower, which is 80% of the NX450h+.
I'd say that's a coincidence. I wasn't able to immediately find the battery capacity of the 350h. I did find that it is 70 cells / 259 V. They can't possibly be the same as the 450h+ cells. If they were like the outgoing Prius Prime that used 96 cells that totaled 8.8 kWh, it would be 6.4 kWh. Those are much older cells; but, I believe they are NCM/LMO. (The addition of LMO chemistry would give higher power than NCM alone.) Highly unlikely the battery is that big... some sources say the 350h battery is only 1.8 or 1.6 kWh? I guess that's plausible, the 450h+ is quite a bit heavier.
If one expects the 450h+ AWD battery to fully power the electric motors in EV mode, the battery would have to be capable of a 9.6 C-rate discharge without affecting its longevity. (A 1 C-rate discharge/charge rate means a battery would fully discharge/charge in one hour.) That is an unrealistic expectation for an automotive battery. One should then have a much lower expectation for the 350h battery power.
I do suspect the new Prius Prime uses the same cells as the 450h+. I see it uses 72 cells and has a capacity of 13.6 kWh; so, exactly 25% less cells (and capacity... and EV power?).
Anyone have any definitive info?
Last edited by CdO; Apr 14, 2023 at 02:39 AM.
Reason: OCD
Just sharing some frustration here. This is like the charge curve above; but, total pack voltage instead of cell voltage. These are two charging sessions (one starting from higher SoC) with the stock EVSE at 120V. It illustrates how poorly the SoC% is estimated. The orange curve is pretty close to where it should be; but, the blue session thought it was about 2% lower SoC. (I also had one that would be to the right of the orange one.) You can see they both (automatically) stopped at ~391V; but, with seemingly different SoC. As I mentioned above, the SoC apparently resets to ~90.6% after each complete session.
This is why it was necessary to scale and interpolate the values in the earlier graph to get a more precise view of the curve. (I updated the original with an extension of where I believe the curve would end if there was no funny business or charge rate taper.) It is important to know this final voltage in order to get an idea of how charging to various levels will affect the degradation of the pack. That's what I was going to discuss next; but, since I updated the earlier graph... I'll have to recalculate some things. Anyway, I'm pretty well fed up with it at this point; so, it'll be another day or two or...
Just sharing some frustration here. This is like the charge curve above; but, total pack voltage instead of cell voltage. These are two charging sessions (one starting from higher SoC) with the stock EVSE at 120V. It illustrates how poorly the SoC% is estimated. The orange curve is pretty close to where it should be; but, the blue session thought it was about 2% lower SoC. (I also had one that would be to the right of the orange one.) You can see they both (automatically) stopped at ~391V; but, with seemingly different SoC. As I mentioned above, the SoC apparently resets to ~90.6% after each complete session.... Anyway, I'm pretty well fed up with it at this point; so, it'll be another day or two or...
@CdO , don't despair
Your posts are very informative and highly appreciated. Take your time, and we'll enjoy your analysis whenever you get to it.
Perhaps some Toyota engineers are lurking around, and will consider your findings for future improvements.
TL;DR - Your 450h+ battery could retain its capacity a lot longer if you only charge it as much as you need each day / trip.
Battery (cell) manufacturers rate the capacity of their batteries and their cycle life. What is cycle life? Usually how many charge cycles before the cell loses 20% of its capacity. What constitutes a charge cycle? It seems to be: charging from 3.2 volts to 4.2 volts. Notice:
- The midpoint of this range is 3.7 volts
- Lithium cells are often rated at 3.7 volts (nominal)
- The 450h+ pack is rated 355.2 volts... 3.7 x 96 = 355.2
Lexus does not allow the batteries to charge to 100% or discharge to 0%... more like 10 to 90%. Is that 0.8 cycles? Why not 20-100%? That's also 0.8. What if you charge from 50 to 90 twice? Or 20 to 60 twice? They are all 0.8 cycles; but, not all cycles degrade the battery at the same rate. Extreme temperatures play a role, charge/discharge rate, calendar days/months passing by, etc. Let's just look at the voltage / SoC.
It seems to be a good rule of thumb that a cell charged to 4.2 volts will lose capacity at twice the rate of a cell charged to 4.1 volts. (I looked at some crowd sourced phone battery numbers that follow this rule of thumb very closely... so let's go with it.) What voltage does the 450h+ stop charging? Well, for this exercise... I'm going to use ~4.1 (it's maybe 4.07; but, 4.1 is the number we need for this). How many cycles are these cells rated for? Who knows? We just want to know how charging to different levels affects our degradation relative to a 'full' charge.
Let's say you want your battery to last twice as long before it loses some arbitrary amount of capacity... stop the charger just after your app says 94%. This may double the life of your battery; but, you only lose 12% of your range. (A full charge is really ~102.2 App% since it keeps charging after it first says 100%.)
My car just fully charged while I was distracted with this! (I don't need a full charge now.) Good news is that after 12k miles (~50% EV?), it is showing 52 miles of EV range!
