Can we create a comparison of PHEV kits?

Andrew,

Since we have not seen these LI packs out in the field for an extended time, I am wondering how much your constant rant of high DOD's leading to lowered pack life is based in fact?

I should have some time in the coming week to test and post a review of my 10-12KWh pack in pure EV mode.

Scott

 

Here is some good information about cycle life. You have to scroll down a bit to see the charts.

EVTV.ME: Life in LiFePo4 - Cycle Life and Attenuation Data

500 cycles its pretty much draws a straight line down the graph. So you could estimate cycle life from these graphs.

 

Thanks for the post Jay. To add to this, LiFEPO4 battery health also declines faster at higher discharge rates (say for example, in an application such as a contactor-based PHEV conversion where you can't limit the current output). The test mentioned above is done on a 100Ah cell at 30A discharge (0.3C) whereas in an application such as a conversion system you'd be seeing closer to 100A (2.5C) discharge peaks (with a 40Ahr module of course).

@Scott/Kiettttty: I'm not saying anyone is lying or anything here, what I'm saying is that if a cell starts off with a significant amount of "extra" energy storage doesn't mean it's fair to say that is the expected range for the life of the system (if that is infact the case here--I don't see any other possible explanation for how one could get significantly more than 30 miles of "normal" EV range out of said conversion system: check my math again if you'd like and feel free to point out any discrepancies). The "nominal" capacity of a battery takes into account amp-hour degradation over the life of the battery which is where the 10.03 KWhr comes in.

Now, one thing that might help figure out what is going on would be if someone has a data log of a trip yielding such EV range (an OBD2 data log to be specific--preferably produced by something like a CANUSB, ELMSCAN or CANdapter). I've worked on CANBUS programs in the past for parsing data from said logfiles and could probably pretty easily come up with a program that calculates how many kWhr are used over a drive by integrating current and voltage over distance. I don't suppose anyone has a data log of such a trip handy?

Andrew

 

If you want data I have data. A whole years worth.

http://priuschat.com/forums/gen-ii-prius-fuel-economy/47849-2006-prius-data-analysis.html


You will have to pars it out if you want to go through it.

Data was captured about every 2 seconds.

Dont know how useful that would be to you but the data is there if you want to play with it.

 

Ooo. I was more interested in a logfile from the magical 50-miles-on-9-kWhr EV trips that people were talking about actually--I'm already convinced that your estimates are correct b/c of what you've been able to do with your system (plus A123 batteries are amazing). Interesting never the less though--thanks for the link .

EDIT:
Hmmm, data every 2 seconds isn't fast enough to do energy tracking unfortunately (need every 8ms or so for accuracy since current changes so quickly) but there may be other interesting things that can be pulled from the data.

Andrew

 

The way a contactor based system works is you have a high voltage contactor that goes between the auxiliary pack and the Toyota OEM pack. Since the two packs are comparable in voltage, when you parallel the two packs together by engaging the contactor high amounts of energy transfer from the auxiliary pack into the OEM pack.

The contactor is turned on and off by a control board since if they were permanently paralleled the OEM pack would explode from over voltage conditions (the auxiliary pack holds more energy thus can over power the OEM pack).

The big difference between a DC/DC converter and a contactor setup is the overall current transfer capabilities. A contactor can allow /huge/ amounts of energy to transfer--but you cannot restrict total current flow which may not be a problem in the summer time when the batteries are under optimal conditions but may be a problem in the winter when the OEM battery / auxiliary battery may not be able to output the maximum current load.

One big associated risk for contactors is should the contactor ever fail closed (that is, fail paralleled) and you don't happen to be ready to quickly pull the emergency disconnect you can easily ruin your OEM battery or worse (contactor failure is rare but has happened--contactors have been known to fail in the "ON" position in the stock Prius for example which is easily mitigated by shutting down the inverter--not so with the auxiliary battery pack since it's a direct connection).

There is also discussion as to whether or not the high energy transfer loads of a contactor based system puts additional strain on the two packs beyond what would normally be there if a high power DC/DC converter was used. I had a contactor system in my car for over a year and noticed significantly decreased performance from my OEM battery once it was removed--but that could have been from other factors such as normal aging (though the pack I had wasn't particularly old). I didn't take enough data to determine if it was degrading due to use of the contactor system or not and such cannot definitively say one way or the other.

On the flip side a DC/DC converter slowly but steadily injects a specific amount of energy into the OEM battery until it runs out. The advantage there is that you have constant current and the ability to restrict the total throughput to prevent damaging either battery pack. Obvious draw back is the significantly reduced energy throughput (unless you bust some serious bucks on a very high power DC/DC converter but those run several thousand dollars).

The codes you are asking about on the Prius computer are from a separate thing called Forced Stealth Mode which is how they get 52 MPH in EV mode (I'm sure you've heard my rants / concerns about said system).

That help?

Andrew

 

Forced stealth works by causing a what's known as a "fatal" fault code in the vehicle by doing something to disable the engine (cutting power to the injectors, disabling the ECU, etc). The car then goes into "fail-safe" mode where it does not use the gasoline engine at all, regardless of how heavily you press the pedal. The dash lights up like a christmas tree for a second until the system clears the codes (and all learned engine efficiency data / emissions related data).

To restart the engine you then have to turn the car off and back on completely. This can be a safety problem if you are stuck in an intersection and require the full power of the car to get out or avoid an accident. Additionally, the engine is required once the auxiliary pack depletes--thus if you are driving along in forced EV mode and the pack depletes (which may not be readily noticeable depending on the setup) you have to restart the car to prevent it from stalling or getting stuck.

As for over-spinning the motors, it does allow MG1 to spin beyond what Toyota otherwise limits it to but that does not necessarily imply damage--it just means its operating outside Toyota specifications which could cause warranty issues or degraded lifespan.

PS: Contactors are loud, yes. Depending on where they are mounted I suppose the sound could be somewhat muffled though. They click on and off pretty frequently to keep the OEM battery in the SOC sweet spot.

Andrew

 

Pure EV range * PlugINSolutions 10Kwh system

Again, my system as installed by 3ProngPower, Berkeley; consists of 10KWh (Sky Aviation) LiPO4 cells (note is made that on the KillWatt meter it takes 12.2KW to recharge from an empty condition). BMS by elithion.

Today, did my first test run in pure EV mode (ICE-kill). Temps were 75-85F, no AC, stereo blasting. I was on rural roads, estimated average speed was around 38mi. Probably less than 10mi at the maximum (52mph). One 10 min stop otherwise, continuous driving. Terrain mostly flat, slight occasional hills. I ended the test when I noted "blue bars" on the monitor, It has been my experience that this is the time to pull over and reset. Total mileage for a full charge was 48.7!

Otherwise the car has been operating flawlessly, my true mileage (measured at the gas tank) for the last 2000mi is 69.6 mpg....It should be noted that I am not a hyper-miler, that my usual commute involves some hill-climbing, and is mostly at 60mph.

Will be updating my blog soon, see the car at: Scott's Plug-in Pruis Blog

Scott

 

Re: Pure EV range * PlugINSupply 10Kwh system

That's just another name for forced stealth / forced EV.

Andrew

 

Re: Pure EV range * PlugINSupply 10Kwh system

Part of the system, as installed is an ICE-kill switch up on the dash, by the small triangle window. At any point in your operation you are able to go into "ICE-kill", you just need to pull over and reset to return to regular mode. So, in my usual commuting I engage "ICE-kill" when I start, and reset at the Hwy stop sign. and again after my last hill for the last 8mi into my work parking...There is also a "rocker-switch" on the dash that enables/cuts the entire conversion system. This is left on mostly (good for the BMS when recharging), only turned off when I am at a low (large pack) state.

 

Re: Pure EV range * PlugINSolutions 10Kwh system

See Andrew?

Scott is one of the real world cases where you DO get ~50 miles in EV with the older firmware.

Unfortunately, I have a damaged cell in my kit. I have a 36 mile EV range with a 70ish mile blended range. Apparently I replaced the damaged cell with a not so damaged cell a week ago.

Keep in mind that I am using my latest firmware for the Plug-In Supply kit. It should also be noted that in field testing with this firmware, users have seen at least a 35% MPG increase on the highway(the upper limit of this number was 60%). In addition, high way speeds are considered 65 to 70 MPH.

We'll see what my numbers come out to when I replace the cell sometime next weekend.

-Kiet

 

Re: Pure EV range * PlugINSolutions 10Kwh system

Do you have the ability to take CANBUS data logs (surely you must because you work on software for the vehicle)? A full data log of a pure EV trip should help figure out what's going on here. I have a program that can calculate watt-hours-per mile and determine how much energy is actually coming out of the batteries.

Andrew

 

Re: Pure EV range * PlugINSolutions 10Kwh system

You know I can't give you that

 

Re: Pure EV range * PlugINSolutions 10Kwh system

Fair enough then--I think for now we're just going to have to agree to disagree. I'm not convinced that anywhere close to 50 miles is a real-world expectation for a 10 kWhr pack (especially account for pack degradation over the life of the system). Unless you can prove that the system either dramatically reduces watt-hours-per mile or magically has a significant amount of extra capacity that doesn't degrade heavily as the system ages I'm going to have to leave the spreadsheet as it is for now.

Anyone else have an issue with my calculations / spreadsheet or are we in general agreement that it is fair?

Andrew

 

Re: Pure EV range * PlugINSolutions 10Kwh system

Am I not in the real world?....do not know Andrew, I only expect my numbers to be getting better and also my efficiency...Robb P has offered to firmware upgrade my system, and I expect the performance to only improve....

excerpted email:


Plug-In Supply is very close to releasing a new operating system for our Prius systems. The increase in performance is amazing.

In blended mode you get 99.9 mpg all the time on the flat, including gently rolling hills, all the way up to 70+ mph. You need a Scan Gauge II to see the actual mileage and it is typically way north of 100 mpg.

In EV mode we have not quantified the exact improvement but the range is greater.

The software is backwards compatible with our circuit boards and earlier systems.

 

Re: Pure EV range * PlugINSolutions 10Kwh system

Unless someone can explain to me how a firmware upgrade can significantly increase the range of an already over-discharged pack (which, even if its true I'm assuming no one here is going to do) I'm going to have to go with no on that for now...The general rule of thumb is that as mileage increases overall range decreases because you end up using more electricity. My guess is it's done by telling the computers that the SOC is slightly higher than it was before to get more drain.

I'm really not trying to be difficult here, but as I have stated so many times my purpose for this spreadsheet is to create a fair and realistic expectation report for the various systems under normal driving conditions for the normal driver--which is why I used 250 whpm as a basis even though people well experienced with a Prius might be able to do better. I /realize/ you are utterly convinced that this is realistic to expect from the system but the numbers simply don't add up (If you see a problem with my math, by all means please point it out). Unless someone can provide a reasonable explanation (Other than "Firmware upgrade") for how the system gets the extra range (EG: They switched to 50Ah cells and didn't tell anyone or something like that) we're just going to have to agree to disagree for now. If new evidence comes to light as time goes on I will update my information accordingly.

PS: I assume the new firmware update they are talking about is your upgrade Kietty, yes?

Andrew