Can we create a comparison of PHEV kits?

A great idea actually. I made one awhile back but it probably needs a little tweaking by now. The problem is that every conversion company over-estimates their own conversion thus making comparisons on paper more than a bit difficult and ultimately misleading. Such a list would need to be hosted and updated by a neutral party I would think.

Anyway, I'll put together what I got and write back here with a link when I upload it.

Andrew

 

The other issue is that kits like Enginer's for example, have varying Kwh options,: 2, 4 ,6, 8.

 

I would add BMS+.

 

Mmm, I'll have to post my list later tonight as I've run out of time right now. Anyone have any good ideas where to post it? It's an XLS spreadsheet...

Andrew

 

You could put it on Google docs. You could even make it wiki-like, by letting anyone edit it.

 

Okay guys, here's the scoop. I have uploaded my preliminary conversion comparison spreadsheet to Google. These are my thoughts, ramblings and comparisons.

Here are a few disclaimers before the link:

1) I tried my best to make it fair and unbiased. I have a PICC25M conversion in my car but the rest of the information on the mentioned conversions I have pieced together from information I have gleaned on these forums or the conversion companies respective websites. Additionally I have had the opportunity to actually analyze in depth a few of the batteries used in said conversions (where some of the more technical numbers come from).

2) I do not mean to offend anyone--so please, do not be offended.

3) I only included commercially available finished systems that come with a warranty of some variety. This list does not include DIY kits or systems because there are simply too many variables in how you do them to make a fair or realistic comparison.

4) I chose to make it un-editable to the public not because I believe I am 100% impartial but because I did legitimately try to make it a fair comparison in the first place. If you see something you believe to be grievously wrong, let me know and I'll look it over.

5) To the best of my knowledge, the information in this comparison is accurate--but please don't bite my head off if I made a mistake.

6) Yes, I know some systems like Enginer offer different larger configurations now--I chose to only include the 2kwhr and 4kwhr because it is my understanding that larger configurations require somewhat...unique...mounting methods that may or may not be universally acceptable. Just do the math if you want to see how a larger system would compare--most of the values scale linearly.

7) Right now, this list only includes currently available conversion systems for the Gen2 Prius. Promised or future prototype systems are not included at this time. This is designed to be a "What I can buy today right now" sort of list.

8) Note that there are three separate sections to the spreadsheet covering different aspects of each conversion system--each section has its own set of foot notes.

9) Please read the foot notes before complaining or reporting an error--chances are there is a good reason why something is the way it is.

10) I deliberately left off estimated MPG expectations since we all know your mileage will vary heavily based on how far you drive and how often you plug in. There really is no magic formula for determining what mileage you'll get (unless you always use EV mode ).

LINK TO CONVERSION COMPARISON SPREADSHEET:

http://spreadsheets.google.com/ccc?...WJsai1IYm5WbVhXQ01tZ3c&hl=en&authkey=CLOBueEN


Andrew

 

I think the DOD on the Hymotion system is 98%. Thats what I think I remember being told but you can keep it at 90% since I'm not 100% sure.

The Nominal pack voltage for the Hymotion system is 188v according to the sticker on the side of the unit.

Usable capacity for the Hymotion system I think is closer to 5kWh than 4kWh. Since the pack size is something like 4.9kWh I would say its close to 4.5kWh usable. I could be wrong since the only way I can calculate this is from the wall and not from the battery.

I guess I only gave you one piece of useful information.

 

Wow. 98% DOD is extremely high DOD% for LiFEPO4. 90% is pushing it as is for cycle life...hmmm. According to the datasheet, 100% DOD yields only 1000 cycles. That'd be only 25000 miles for battery lifespan yeah?

Thanks for the tip though--I'll run some more numbers and see if I can get a better figure for what DOD% it's configured for.

About how many EV-only miles would you say you can get on the Hymotion pack at low speeds (under 34 MPH)?

EDIT: Mmmm, I should clarify: How many miles of low speed EV on a full charge do you get /without/ crazy hypermiler tricks? =)

Andrew

 

Yeah 98% is what I remember being told. If I remember correctly the guy told me they found that a DOD of 98% was just fine and the batteries would still last a very long time. or something like that. I dont remember exactly. Plus even if it was 1000 cycles thats still 80% capacity after that many cycles. You dont have to get a new battery when it drops to 80%. Its still very good in my opinion.

I can get an easy 25 miles in stop and go city type driving. 30 miles if I really try to work at it. I would say even 35 miles non stop on flat land is possible.

Oh and the weight according to the sticker is 207lbs

 

Hmm, this seems skewed.

What data are you referencing on the Plug-In Supply conversion?

Real world data shows roughly ~44 miles in EV on a 10.2kWh conversion with ~95 miles on blended mode.

Those numbers are totally off! I own this conversion kit..

 

Okay, okay calm down. According to your own post here, you have a custom conversion system with Mottcell batteries which are different from the stock Sky-Energy module that come with the system from Plugin Supply:

http://priuschat.com/forums/prius-p...hybrid-error-codes-any-ideas.html#post1148081

The Mottcell batteries actually have a lower capacity I might add--39 amp-hours versus 40 amp-hours--that comes out to 9.4 kWhr instead of 10.2 kWhr for your custom pack (unless of course you have /two/ cars converted ).

Anyway, I'm not trying to be a stickler here, I just find it difficult to believe that any system can yield 44 miles on 10.2 kWhr of energy.

If you do the math, 1 mile roughly equates to 250 watt hours /before/ you subtract energy losses due to heat, internal resistance, contactor transfer medium and OEM battery ineffieciencies (which there are many).

NOTE: Yes /of course/ 250 watt hours is an average (though generally agreed upon to be fair for the average terrain) and yes if you drive really really slow and roll through stop signs and the likes you can get 210 watt hours per mile or better which changes the math slightly. But my goal for this is to provide expected data for what I (and hopefully others) would consider relatively normal driving patterns without doing fancy tricks or avoiding the speed limits.

Math: 10.2 kWhr / .250 kWhr per mile => 40.2 miles.
Now, that is with 100% DOD which is unreasonable and impossible with a contactor based system because of the inability to enforce current limits. I would expect the system is configured for 80% DOD, but even at 90% DOD that's still only 36 miles

((10.2 kWhr * .90 DOD) / .250 kWhr per mile) = ~36 miles

Next, you subtract energy losses due to inefficiencies in the batteries (they are designed for energy storage, not power storage thus they have a high internal resistance). That loss is somewhere between 15 and 20% depending on how much load the batteries are under.

(1.377 kWhr lost at 15% and 2.04 kWhr lost at 20%).

Using 1.5 as the average kWhr lost due to internal resistance:

(((10.2 kWhr * .90 DOD) - 1.5 kWhr) / .250 kWhr per mile) => 30 miles on the nose

Now you add in OEM battery energy loss (total OEM pack has an internal resistance of around 0.280 ohm @25C--twice that if your pack is aged or been abused or cold)...Since the OEM battery efficiency varies widely with temperature and SOC I chose not to include this step, but you can't ignore it. That's 30 miles before subtracting OEM battery efficiency loss (@25C typical losses on the OEM battery can be easily above 10% at full load).

EDIT: The 250 watt-hours-per mile already includes most OEM battery efficiency losses. I should have phrased it such that you now have to subtract any /additional/ efficiency losses beyond what the stock battery would ordinarily produce (say if your battery is below 25C/75F temperature or is relatively old or has been abused--say exposed to abnormal temperature ranges for extended periods of time). The stock battery starts at around 0.280 ohm resistance at room temperature, but I've seen batteries go as high as 0.550 ohm just simply from aging / prolonged use.

To get 44 /low speed/ EV miles on 10.2 kWhr Sky-Energy pack from Plugin Supply you would need 110% DOD with absolutely 0 energy loss due to heat or any inefficiencies in the system or batteries. I had a chance to analyze the batteries in question and I assure you--they do have significant energy losses under load. By my estimates and calculations energy losses add up to around 20% under full load.

With mott-cell batteries, according to my calculations you would need roughly 120% DOD again with no energy loss.

110% DOD would kill the cells after one or two cycles.

I realize that some battery manufacturers are not exactly honest or accurate with their battery listings, but if by some magic you are somehow able to get that kind of range out of the pack I can't imagine the pack will last very long...Often times manufacturers will significantly oversize their batteries to account for capacity degradation over the life of the batteries (that's why the rated capacity is referred to as /nominal/ capacity). That means that while you may be able to squeeze some extra juice out of them at the beginning, it will significantly reduce lifespan capacity down the road so it would be unreasonable to cite that range as normal or even expected.

If I was able to push my NiMH system to 100% DOD I could get near 30 miles of range but that is neither reasonable nor feasible for longevity purposes.

Again, I'm not trying to offend, I'm simply trying to get a fair representation of the various systems around. I'm afraid the numbers you provided just don't add up...30 miles is still a respectable low-speed EV range and according to my calculations is still a bit generous...

Andrew

 

Hello Andrew,
Thanks for this chart. You did a great job.

A couple of comments on the Enginer system.

On EPA testing the Enginer systems have been tested and passed the test. The data has been submitted and certification is pending.

On EV mode distance. The Enginer system(both 2k &4k) actually gives ~5 miles with the note that this starts with the Prius HV battery at 65% SOC and is terminated when the Prius SOC drops because the Enginer converter is not designed to keep up with EV usage.

Thanks,
Dan

 

Hi Dan,

Thanks for your input.

Do you have more information about the testing done on the Enginer systems (specifically where the tests where conducted, when and how the systems ranked)? EPA testing is actually different than CARB (EPA checks for general fuel economy whereas CARB checks for actual tailpipe emissions and is the necessary portion for certification in California / New York as far as I know). Typically tests are performed on the standard UDDS driving cycle.

One really important thing to know from any federal testing done on the systems is if EV mode was enabled for any of the tests as that determines whether or not they are able to sell the system with said EV mode enabled for emissions compliance.

Andrew

 

Hi Adric,

Glad you like it. I think you can get it in a standard HTML format by using the "download as" feature through Google Docs (if not, I think you can get it as a PDF at least).

I left the 4 kWhr Plugin Supply system on the list though I heard a few rumors from a couple Plugin-Supply dealers that that particular system is no longer available for purchase so you may have trouble tracking it down (again, just something that came up in a casual conversation and not necessarily true). You might want to inquire with them directly before you make up your mind.

Plugin Supply used to offer a lead acid version of their 4 kWhr system but I left that off because that one has officially been (to the best of my knowledge) discontinued in favor of the lighter and longer lasting LiFEPO4 batteries.

As for sustained EV with Enginer--yes I realize that it is possible to sustain EV mode with the Enginer system if you are careful. By "Extended" EV range I was more referring to 5+ miles of constant EV driving without necessarily stopping or letting the pack recharge. Since sustained EV range with Enginer heavily depends on your route / comfort of acceleration I decided to leave it as N/A rather than "0" or "NO" or something like that. I might put a footnote in basically to the effect of what you said however.

Andrew

 

Thanks for the clarification on how you're generating your numbers.

Anyway, I'm just one of the users of the Plug-In Supply kit. I'm testing the system using Mottcells(Seems to work fine). I've seen FIRST HAND that a Thundersky/Sky Energy(CALB) will average around 50 miles in pure EV and 100 blended.

In my vehicle using Mottcells, I had one cell that was replaced due to my own fault(BMS didn't work..). This one cell was supposedly charged to 100% SOC. Instead, it was roughly 50% SOC.

I made three trips from my home in West Covina to San Diego and averaged 130 MPG for roughly 50 miles. Having a cell that was improperly balanced explains this issue.

I'll be driving from my home again to San Diego with all of my cells balanced later this evening.

Every single Plug-In Supply vehicle that I've seen running the latest 4.0 firmware release can easily average over 140 MPG at highway speeds (70 MPH).

 

Thanks for your response. It seems like your kit is brand new which may be why you are able to see such a high EV range. I suspect that the EV range will drop quite quickly over a few charge cycles with that high of a DOD%. Lots of people who use the thunder-sky batteries online report a significant and predictable drop in capacity as the batteries age (a drop that is directly proportional to DOD%).

Can you try actually clocking pure EV range with the odometer (TRIPA/TRIPB )? 40 miles on less than 10 kWhr is hard enough for me to believe with the numbers provided, 50 miles seems a bit beyond impossible unless those cells are being / have already been murdered (have you had more than just 1 cell die so far? You may want to check the rest)...

What was your average speed and acceleration profile for your EV range test? Very slow speeds (< 20 MPH) might require closer to 200 watt-hours per mile (not the 250 watt-hours-per mile @ ~34 MPH used in the calculations) thus that would throw off the calculations entirely. For point of comparison, I can get 25 miles in EV if I drive under 20 MPH with my PICC-25M system (even more if I get out and push )--I get just shy of 20 miles in EV if I drive around 34 MPH. Road speed, air resistance and increased current draw all play in to how much energy is required to move the vehicle.

One other thing to consider is that Mottcell batteries do have a higher efficiency rating than Thunder-sky / Sky Energy because they are built up of multiple smaller batteries--thus less energy is wasted as heat with your setup versus what is officially available from Plugin Supply. Have you driven a Thunder-sky or Sky Energy equipped PS conversion systems?

Andrew

 

Actually, the kit is not brand new. I had 64 cells in my Enginer kit for about 2 months. I added in an additional 12 cells to equal up to 76 cells. I forgot to manually balance the 12 cells to the 64 cells. That's the main reason why I had one cell go out(Problem was compounded by a malfunctioning BMS that I developed).

I finally got the entire kit working last night. I went out for a pure EV test drive averaging 32 MPH for 34 miles. Unfortunately, I didn't have a need to go out for 40 miles.

The car is currently charging. I'll be driving to San Diego later this evening using blended PHEV mode.

I'll report the numbers once I'm back in SD.