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Converted Plug-In Hybrid Debuts in Colorado; V2G Analysis Part of the Project

The traction battery pack for a Hybrids-Plus PHEV15 in place.

The Colorado Governor’s Office of Energy Management and Conservation (OEMC) is working with several partners on a plug-in hybrid (PHEV) demonstration project. The PHEV is appearing at a Clean Energy Partnerships event in Fort Collins, Colorado today as part of Colorado Tech Week.

Boulder, Colorado-based Hybrids-Plus, Inc. has converted a 2006 Toyota Prius into a plug-in hybrid electric vehicle (PHEV) with a 9 kWh lithium-ion battery pack built with A123Systems cells. The US Department of Energy’s National Renewable Energy Laboratory (NREL) and Xcel Energy will perform a benefit analysis of the project.

A123Systems’ improvements in lithium-ion battery technology will enable much greater yields in conventional transportation for vehicle mileage in a safe and reliable manner. A123Systems is involved in this PHEV demonstration in order to demonstrate the advantages of this technology and make it available on a wider scale to the public.

—Roger Lin, A123Systems
Hybrids-Plus assembled its battery pack from A123Systems cells. This is a shot of the welder.

The OEMC plug-in is a PHEV30—it offers about 30 miles of all-electric range at speeds lower than 34 mph from the traction battery pack, which is built with A123Systems’s 26650 cells (the same cells as in the DeWalt 36V battery packs for power tools).

Hybrids-Plus replaces the OEM NiMH battery pack with the plug-in pack (which adds 81 kg to the car’s weight.) In addition to the estimated 30 miles AER, Hybrids-Plus estimates that the PHEV30 model will deliver 50 miles of blended driving on a full charge, for a total fuel economy of about 125 mpg.

Block diagrams of original Prius battery (left) and of converted system (right). Click to enlarge.

Time for a full charge on the battery is about 9 hours.

List price for the PHEV30 conversion from Hybrids-Plus is $32,500. A PHEV15 conversion using a 4.5 kWh A123Systems battery pack costs $24,000. Hybrids-Plus will also supply just the kit, with the PHEV30 gear priced at $19,200, and the PHEV15 kit priced at $12,800.

This OEMC PHEV Prius will also soon have Vehicle to Grid (V2G) capability. Xcel Energy and NREL will assess the collective effects of thousands of PHEVs providing power back to the grid in such a manner. Further, the study will determine the emissions profile of the car, as well as those from the greater simulated number, to make recommendations how best to incorporate these new-generation vehicles into the electrical grid.

Xcel Energy is committed to supporting the widespread deployment of plug-in hybrid vehicle technologies and preparing to meet future customer needs related to alternative fuel transportation. We expect our joint study with NREL will uncover the potential for PHEVs to ultimately increase the overall reliability and sustainability of our existing electricity grid infrastructure.

—Michael Lamb, executive director of Utility Innovations at Xcel Energy



EnergyCS if they ever start doing this commerically, which they were supposed to start last spring is pricing there retrofit plug-in Prius that I believe has a 50 mile range using Valence Batteries at around 12,000. So that would be cheaper and have better range.
If they ever get rolling.

Greg Woulf

Those are just ugly numbers. 30 miles for range and lower than 35 miles an hour make this a golf cart, probably worse than a golf cart.

I was hoping for more from A123, I'll have to go back to hoping for the next best thing.

Ric Fulop

Greg, just to clarify, the speed rating for this initial convertion is a function of the electric drive OEM motor that comes with the Prius. The OEM motor was not replaced by Hybrids-Plus under this project. The actual A123 battery performance is an order of magnitude greater power than what the original OEM motor can handle.

fyi CO2

While 30 mile range under 34mph is not great, this is no golf cart. Would be nice to know what the range is at 55mph, too.


30 miles and 34mph gets you up to most highways on all electric power and then again from the highway to your destination...of course with highways around here if you are travelling at more than 34mph you aren't driving to or from work during rush hour - that traffic flows at closer to around 30mph averaged over the entire 3 county area on 3 different interstates (I-90, I-5, and I-405).


9 hours charge time with a123 batts ?? what kind of a lame charger are they using ?


Well, simple... a 1 kW charger.


They are probably trying to be careful and use 110V charges rated at less than 15amps current draw thus giving the long charge times. If you drive only 10 all electric miles per day (the remainder being gasoline assisted without recharging those initially "spent" miles) and recharge everynight it should require only about 3 hours per night of charging.


All in all, a horrible deal and one not likely to encourage anyone in their right mind to purchase such a system. At these prices, I wait for the Tesla to come down in price.


$25,000 for a new Prius (I believe they are still overloading them with options and forcing you to buy them that way since they are so popular) + $33,000 for this alteration is indeed a very expensive proposition for what you get. Just the kit is $19, typically that would be a $11,520 cost to a retailer with a $19,200 list (most use 60% off of list for dealer costs) and then if you figure they would have 25 points over FOB costs to the dealer that gives a real FOB cost of around $8640 for the company [assuming they would use a dealer distribution network model and direct sales would not undercut the dealer's profits so they keep list prices the same]. That $8640 figure already takes into account that the suppliers of components (batteries, electronics, etc) are getting a profit as well.





That low all-electric speed is not a function of the Prius' electric motor, it's a function of the transmission and maximum speed ratings of the generator. The car will cancel EV mode above that speed, but it's still possible to use just the electric motor to move the car at any speed, especially when the battery is full (or it's been tricked into thinking it's full) but the gasoline motor has to spin as well, using some energy. The gasoline motor also come on to supplement the battery when more than 20kW is requested. The lithium ion battery should be able to deliver much more power, but wiring and power control software would have to be changed as well.


Sanyo in couple of weeks begin to sell so called Eneloop Ni-Mh batteries (you can Google Eneloop). In AA format it has 2 A*h, versus 2.7 A*h of best regular Ni-Mh batteries. But it has revolutionary feature: extremely low self-discharge. Sanyo claims that after 1 year storage at 20C battery retains about 80% of initial charge.

Such batteries with well established Ni-Mh chemistry could be directly used on production Prius with minor software alterations and very cheap charging interface. Such modified Prius will have decent PHEV capabilities, comparable with described in this news post, but virtually with zero price premium.

Roger Pham

Absolutely, Erick,
The thing is, if you have got that size of battery, you don't need Toyota's Hybrid Synergy Drive anymore. You simply need an electric motor directly driving the rear wheel, and a tiny IC-engine coupled to a starter/generator driving the front wheel via a tiny CVT unit. With this setup, you can drive the PHEV at any speed until your battery is nearly exhausted with great acceleration from a 60kw motor and a battery capable of easily over 60kw (minimum of 10C power burst for any Li-ion battery). Long-range cruise with battery near exhaustion can be done with the IC-engine via CVT alone at 70% throttle for maximum efficiency while charging the battery as well via the starter/generator.

To all who are disappointed with the Prius' numbers:

You don't need a Prius for this modification. A Civic Hybrid would be a better choice for higher performance in the electric-only mode, though you will need to add an electric motor of about 30kw power to the rear wheels, or hey, how about a pair of Siemen VDO in-wheel motors, eh? Plus, of course, power inverter to control that motor. You'll get excellent regen braking with both the rear motor(s) and the front starter/generator, far better than the Civic Hybrid can ever dream of. Acceleration ain't bad, either, when the front starter/generator of 20kw power can contribute to the 30kw rear motor(s). And, to satisfy your occasion need for drag-racing at the red light, rev up that 1.3liter IC-engine while sending the juices to all motors, and I'll bet your 0-60 time can easily hit the 6-7 sec mark, and you can easily out-run the Camry Hybrid.

Can't afford the 20,000 USD price for a Civic Hybrid? Well, get a Honda Fit, or Toyota Yaris, instead at ~12,000USD for a base model, and add your rear-wheel 30kw motor and power inverter. You'll have a more leisure electric-only mode, and may have to change your starter more often if you turn off your engine at every red-light in the gas mode, but, hey, with a 40 mi electric-only range (given a much lighter Yaris). Or to save money on the battery pack, get a re-trofit kit of 4.5kwh battery pack for 20mi electric range, and save a total of 8,000 for using the Yaris, and ~12-15,000 for choosing a kit with a smaller battery pack. Let's see, 12,000 for the Yaris, plus 12,800 for the 4.5kwh battery kit, and let's say 8,000 for the 30kw motor plus inverter, and your total is ~just above 32,000USD. Pricey? Just compare that to the Tesla at $100,000USD with battery much less durable than the A123 battery capable of thousands of charging cycles.


You are a dreamer. Any DIY modification is 10 times more expensive then OEM offering. It is OK for enthusiasts, but from the point of view of regular buyer “to save money” it is nonsense. I am also fascinating with FWD HEV abilities to offer high performance with addition of pure electric rear wheel drive, but looks like this scheme is not very popular among HEV manufacturers.


you are a dreamer if you think NiMH batteries with even lower energy density than the existing Prius batteries can provide 30 miles EV range at anything like the same mass as lithium-ion that can be discharged 100%. And zero price premium? 9 kWh of NiMH is at least $6,300 weighing 225 kg.

Tony D

I like the idea of rwd for the HEV. I wonder if the diPitro rotary air engine could be substituted for the in wheel motors. One wheel for 0-12/15 mph the other for 15-35 mph. No batteries at all, just a tank for compressed air. Maybe the DYI would be easier.


Hmmm...I think a few people have never looked into converting a vehicle to RWD or AWD. Even with an electric motor driving through a differential (for torque multiplication) or a really powerful motor for direct drive there are very extensive modifications necessary.

You will need to do something with the fuel tank (either find a japanese market version that is AWD and grab that tank or put in a fuel cell which you will modify for evaporative emissions compatibility because racing fuel cells are not designed for emissions friendliness). It is more likely than not that nearly every single US market car will require cutting out the trunk and modifying it by either welding in the rear pan out of an AWD vehicle or custom fabricating some sheet metal for a trunk to give mounting points and clearance for the rear differential and motor(s). You will need to find rear spindles & suspension off an AWD japanese market version or custom fab something that will accept drive shafts and remember the stock suspension in the rear is designed with 36-39% of the stock weight of the vehicle on top of it. Adding 300 to 400lbs of batteries, electronics and driveline components (axles, diff, motor) will make it dangerous to drive (can we say oversteer?) until the suspension is setup properly.

Of course it can be done, and I've often thought about having a go at it but it takes a great amount of money, time, and knowledge (or access to knowledgeable people which requires more money for their time). Fabricating a mount on your stock motor and a controller to do idle start-stop function with limited traction drive would be much easier and more cost effective but the benefits would be very small (it would be a much easier job to complete in incremental steps as the smaller motor could be bench tested, the mount fab'd and everything installed without removing my car from daily use for more than a few hours to mount everything and the system could be disabled dynamically to test the algorithms controlling the motor & engine interface).


Sanyo battery already can store 50% more energy then standard Prius batteries (it never used top of the line batteries). And for entry-level PHEV (15 miles of city travel) 9kW*h battery is way overkill. Regular sized Ni-Mh will do. For everything else – you are right – wait for Li batteries. But for how long?


It seems to me that Li-ion Batteries are over-kill. If we can dismiss their higher cost as a factor that may eventually go down in cost comparable with Ni-Mh, the Li-ion battery's only advantage is reduced weight. However, carefully placed battery weight can lower vehicle center-of-gravity and improve stability and handling, thus offering an invaluable, life-saving safety advantage.

Other important points should be made about a smaller battery pack's limited speed and range. Driving speed need not be above 35mph in many if not most neighborhoods and commercial districts. This limitation is another safety factor. Similarly, limited range (on electricity alone) can afford an economic incentive to drive fewer miles to patronize local businesses, services, entertainments and amenities, etc. In time, more destinations become accessable without having to drive. Thus, walking, bicyling and the ability to structure mass transit, all more energy efficient means of travel than the most efficient car, become practical. Limited range limits car use and makes cars safer where they will be used less.

Yeah Yeah. All you all want to hear about is how fast the future car can go. How quaintly 20th Century.


Wells, the fastest way to go around a corner is to "add lightness" to paraphrase Colin Chapman.

I would much prefer a 3000lb vehicle than a 3300lb vehicle even if that 300lbs extra were placed at the lowest most centralized point (to reduce Cg and minimize polar moment of inertia). The heavier the vehicle the larger the suspension, brakes, tires, and drive system need to be for comparable performance. Also if all vehicles are lighter they cause less damage to other vehicles (lower liability insurance costs & less chance of injury and/or death to the other occupants). This is easy enough for you to check for yourself: Go to a local SCCA solo II autocross. Bring some large slabs of steel or other heavy & dense weight in flat form (weight plates from a weight lifting set would work well). Now go do a few laps without any weight and then put 300lbs worth of plates on the floor of the vehicle (lowest Cg you will get) and do a few laps. Even though you know the course better now and are more familiar with the way your vehicle handles you still won't overcome the added weight even if it is added at the lowest possible point. You will find the slalom to be more difficult and you can't carry as much speed into the turns without hitting ABS or overheating your brakes (and possibly locking up your tires if you don't have ABS as the first few laps you won't be ready for the effects of the weight). Of course if your vehicle weighs 6000lbs you won't notice the extra 300lbs but in a typical sedan that is around 3000lbs you will notice it.

Roger Pham

Andrey & Patrick,
I may occasionally be a dreamer, but I was not dreaming during my last posting. What I've suggested is very practical way that can be quickly implemented to accelerate PHEV for mass utilization, pending mass production of A123 battery.
If in-wheel motor is not (yet) commercially available, a simpler way to make electric RWD than Patrick suggested would be to machine a helical gear reduction unit right at the wheel hub and install one 15kw motor driving each rear wheel. No differential unit to bother with, and no need to modify the rear fuel tank. The motors would be serially connected such that if one motor burns out, the other would stop running also, to avoid the thrust asymmetry that can impair handling. The gear reduction unit for each wheel and electric motor can be ordered custom built to spec by specialty shops. I don't envision an individual to go about with the modification, but rather, it is a job for a conversion shop like Hybrids-Plus Inc..
Oh, I may have over estimate the $8000 USD cost of the motor(s) and inverter. I think that for the cost of the kit at $12,800 for the 4.5kwh battery pack, the power inverter should already be included in the price of kit, as well as other electronics. The motors should cost no more a few thousand dollars the most, making the Yaris or Honda Fit PHEV version quite cost-effective at $26-28,000 USD complete. This will give you a very fast 5-seat PHEV with sport car performance that can nearly rival with that of the Tesla (speed sells car, just like s*x will sell men's stuff), (or well, may be close enough at 1/4 of the cost) with superior and far more durable nanotech battery. At 20mi electric-only range, it is practical for most daily commute, and with the built-in gas engine, you'll never afraid of being stranded due to running out of electricity. One problem, though, is that you'll have to find a way to run the AC compressor with electric motor for summer comfort, and be willing to drive and brake without power assist in the electric-only mode. So, may be the Civic Hybrid at $8000 cost premium is a better choice for summer comfort and driving comfort. May be a used Civic Hybrid would cost less.


Patrick, your argument is specious. My point was that lowering vehicle center-of-gravity with carefully placed battery arrangements adds a handling safety factor, though it may reduce speed. It's not merely the additional weight, but how it is placed that offers the safety advantage, even on your crass example of SCCA autocross. Speed is not a safety feature. Many vehicles on the road, the SUV in particular, are top-heavy and statistically prone to rollover. Reducing the SUV center-of-gravity will make these cars safer in 2 ways: better handling and less maniacally speedy.

Roger Pham

Oh, a cheaper way to come up with electric Air Conditioning for the PHEV Fit or Yaris is to buy an electrically-powered AC compressor directly from Honda or Toyota designed for their hybrids, and install it into the Fit or Yaris after removal of the factory AC compressor. Electrical power steering and braking may be done similarly by adapting components from established hybrids, if possible, for those weaklings among us who are not man enough to handle steering and braking of a subcompact without power assistance. Some engineering will be required, but I think that it may be cheaper than the $8000-10,000 price premium of the Prius or the Civic Hybrids.


Some time ago I stopped to “invent” hybrid drivetrains. Everything achievable appears to be done at Toyota, like combination of FWD Synergy drive with rear wheel motors on Lexus 450.

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