PHEV Recuperation Calculator

@cproaudio

it may be true with add on kit but not so sure with factory PHEV. There are 3 additional considerations which may tip the scale in other direction:
- Tax rebates
- Increased MPG in hybrid mode due to higher battery charge/discharge rate and firmware tweaks
- gas price increase

 

At the amount of miles I drive and with the expectation that gas will go up in cost, I will pay mine back in 4 years

 

I am having enginer 4k kit installed next week for 2895 from authorized dealer. So from what I have been reading this is a good price.I am a salesman at the moment and drive 700+ miles a week for work with company paying me .26 cents a mile of commute have calculated that this kit will be paid by my boss in less than a year !! This kit will make me a whole lot of cash over the years!

 

We currently average about 45mpg. Our trips are generally shortish (10-20 mi) and involve up and down some big hills. I haven't been able to find metrics on how a PHEV performs in this situation. Does anyone have the 4kw kit installed that lives in hilly terrain? If so, how has your mileage changed?

 

Hi!
I've also made a recuperation calculator for my country, Portugal. (it's all in metric and portuguese) It also calculates CO2 savings by inputing information from the electricity company CO2 usage.

I must say that in my calculations no kit is ever going to save you money, only CO2.

One thing I have in my calculator is the number of 100% DOD cycles that the batteries are expected to last.
So I have 2 inputs wich are the number of 100% DOD cycles from the batteries specs and the DOD wich will be used in the kit.
DOD used in the kit will affect usable capacity, then I use a curve of number of cycles vs %DOD to figure out how many cycles batteries will last if DOD in the kit is not 100%.

That really affects the payback time!
Just imagine your batteries only last 500 cycles...

Maybe you should try to add that to your calculator.

Best Regards

 

OK.

The formulas I use are:

For the calculation of the life expectancy (in number of cycles) of the batteries I get the 100% Depth of Discharge cycles from the specs.

Then I use this formula
Number of expected cycles at a given [used DOD] = (78264*([used DOD]^-1,1404)-60)/350*[100% DOD cycles]

Note: this formula is kind of an average for different battery chemistries, you can adjust the values to match the curve to a specific kind of chemistry.

For example, a battery with 1500 100% DOD cycles will make 2009 cycles @ 80% DOD and 3616 cycles @ 50% DOD.

With this formula you can calculate the life expectancy of the batteries taking into account 2 things:

1. If in your daily commute you don't use the full capacity of the batteries they will last longer

2. If you limit your maximum Depth of Discharge you can have the batteries last longer


In my calculator I weight the available battery capacity with the [used DOD].
Then I calculate how many miles of EV mode will the batteries last at that DOD.


If your daily commute is more than the calculated EV mode range then your batteries will be used till the max DOD you specified, lasting that number of cycles.

If your daily commute is less than the EV mode range then I calculate how much % of batteries are used, and recalculate the number of cycles giving you more life expectancy.

Examples:

I have 4kWh of batteries that are good at 100% DOD for 1500 cycles.
I limit the DOD to 50% getting 3616 cycles of life expectancy.

Usable capacity will be 4kWh * 50% = 2kWh

Those 2kWh can get you 8 miles of EV.

If I drive more than 8 miles between recharging I will be using 50% DOD and my batteries will last 3616 cycles.

If I drive 4 miles between recharging I will be using 25% DOD and my batteries will last 8281 cycles.


Be aware that reducing DOD from 100% to 50% more than doubles the number of cycles, so using smaller DOD's will shorten EV range but will enlarge battery life wich benefits long term recuperation of your investment.

Example:

30 miles daily commute with 1 recharge per day
Mileage without PHEV: 50 MPG
4kWh of batteries that are good at 100% DOD for 1500 cycles.

Batteries used at 50% DOD, will last 3616 cycles
EV mode 8 miles
Blended mode: 22 miles
Mileage: 68 MPG
Battery life expectancy: 9.9 years = 72320 miles
Gasoline used: 1063 Gallons


Batteries used at 100% DOD, will last 1500 cycles
EV mode: 16 miles
Blended mode: 14 miles
Mileage: 107 MPG
Battery life expectancy: 4.1 years = 30000 miles
Gasoline used: 280 Gallons for the first 30000 miles
After batteries die:
Gasoline used: 846 Gallons for the rest 42320 miles
Total gasoline: 1126 Gallons

Hope this makes sense, if not please tell me

Regards
Alex

 

Appreciate the spreadsheet. Surprised recoup yrs (C45) doesn't change when changing PHEV Battery Capacity (C37) (ie. 4kW to 8kW), ....even w/o changing Final PHEV $ cost (C30). I did see where it will change playing with the PHEV MPG (C34) and/or Estimated EV wh used/mile (C36).

I'm just a visitor to your forum, as I don't own a prius, but I am interested in PHEV add-on for my kia hybrid. Other than DIY, I think my only option is Enginer kit?? Jack will give me discount if I'm 1st kia customer, and I take pics to share for other future kia installers.

I'm not so sure how the Enginer 5kW DC/DC convertor will adequately feed my 40.2hp EV motor for my mainly hwy driving habits?? Kia system allows EV mode @ 65+MPH.

Also, not sure how to determine appropriate C36 or C34 field parameters. I'm thinking I need 8kW system for my upto 150miles/day trips (to neighboring city & back), where I might be able to 40-50% partially recharge during the day. Anyone care to comment??

Note: Kia stock Li-Ion battery is rated 30kW (Pout), 270V, 5.3Ahr

 

To make the numbers easier, suppose that, at 60 MPH, the energy consumption is 250 Watt hours per mile. That means a power requirement is 15 kW. I don't know the allowed SoC range of the Kia, but suppose it is 70%. 0.7*270V*5.3Ah = 1 kWhr.

So, with the assumption of the Enginer kit supplying 5 kW, the car must supply 10 kW, and can maintain this for at most 1 kWhr/10kW = 1/10 hr = 6 minutes. If you have the 8 kWh system with two converters, then you could potentially double the highway EV range to 12 minutes (miles).

Thus, you need to be thinking about how to best make it work in blended mode. If the Enginer kit is contributing 1/3 of your power requirement, then your highway MPG will go up by a factor of 1.5. If it is 2/3 (2x 5 kW converters), then you get into serious hypermiling territory, as MPG goes up by a factor of 3.

But there are too many caveats here to list. I suggest you start a thread at the enginer.us forum with your ideas and concerns. The two main assumption here are that the converters will output 5kW, when 3-4kW continuous is more typical, and that the car will even allow extra power to be added.

 

You have a 1.4KWh battery, with probably a 0.56KWh usable capacity. You won't be doing 150/mi day in EV mode with 8KWh. Did you want 150mi of pure EV? That will fill your trunk with batteries.

 

My goal (like I believe all PHEV add-on users) is best MPG/$. Yes, kia stock battery is not large and their system charges it 3 ways (regen braking, while coasting to spin EV motor, and with generator being turned by IC eng). I'm guessing prius does same??

On my long trip days (not everyday), I can probably partial recharge PHEV battery during day - after 70mile one way trip to neighboring city.

Not sure how the Enginer converter will work suppling enough current at the highway speeds to suppliment the stock battery??

 

Thanks for reply...makes sense. I am thinking the 5kW dc/dc output current limitation (ie. ~18A) will then only assist my generator to recharge the stock battery a little bit faster on hwy??

My other crazy idea is to hard mount a 4kWh Enginer system, and also buy additional removable battery case kit(s) to place in parallel when needed. For instance, Codd power (search via ebay) will sell case kit (48V/60Ah w/5kWBMS & 15A charger) & claim the batteries are rated upto 10C discharge rate.

I would mount recepticle connector(s) to interconnect 1 (or 2 per your recommendation) of these case kits when needed on my 150mile days. This allows me to plug in the seperate case kit(s) to recharge & leave it charging while I travel in the neighboring city doing my outside sales work calls.

Any more comments/concern/recommendations much appreciated, thnx

 

I think your 150 mile requirement is a deal breaker. In terms of energy requirement, you need ~38 kWh. If you just want to get to 80 MPG (2x epa), you'd need to figure out some way to get 19 kWh net into your drivetrain. That's likely at least 20 kWh gross due to efficiency losses if using an upconverter, plus you have to account for the fact that you cannot to 100% depth of discharge, so you somehow have to juggle 24 kWh of energy storage, whether it is removable packs, charging remotely, etc. The calculator does not account for the endless hours that you would spend fiddling with your system, trying to make it work. I don't know if the calculator factors in battery lifespan, but better figure on it being 4 years, considering that the Hymotion guys are having problems at 3 years.

These things work best, and here I am talking about any PHEV, not just Enginer, if you travel less than 40 miles, particularly at lower speeds, and then park for 4-8 hours to recharge.

 

bummer...but, appreciate the discussion, wisdom beats expensive experiments

 

2895 installed sounds like a very good price.... If someone near me offered it I would do it to my 2011 for that price.

Shane

 

Yes. $2,895 would be an unrealistically good price, considering the 4kwh system itself now costs $3,495 on the Enginer site, plus an additional $250 to ship it. So a total of $3,745.

And if you wanted to actually pay someone for the time of installing it, that should add $500 - $750 more.

 

Wow! Very detailed analysis.

I took a much simpler approach and got roughly the same answer:

Not worth it for most people. Link below:

http://priuschat.com/forums/gen-iii...ions/102131-conversion-plug-in-not-worth.html

 

The Easy Way !!!

My rule of thumb is easier to calculate.

Do NOTHING until either is reached AFTER car is paid for :
a) 8 years
b) 200,000 miles

Pay for 5 years, have a great 3 years of no-hassles driving with no payments, then think about a plug, instead of getting a newer car.

:welcome: