Ah, so my original assumption was correct. I'll be interested to read how well that worked. 4KWH is not really that much battery, and the HSD is not optimized to run on EV.
A few details:
The unit was originally conceived for the Prius, and by far the greatest number of installations were in Prii, but installations were successfully made in a number of other hybrid vehicles including Highlanders, Lexi and Ford Escapes,
The unit consists of a bank of lithium ion batteries (parallelled and seriesed to 48 volts), a 110 VAC to 48 VDC plug-in charger, a DC-to-DC converter (48 VDC up to whatever DC voltage matches the car's hybrid battery bank), a battery control, monitoring and balancing module, a control switch and wires and cables,
The basic unit is 4 KWH, but there was also a 2 KWH version. A number of enthusiasts made 6 KWH and even 8 KWH
I first tried 2 KWH and then upped it to 4 KWH. The Camry Hybrid has a 1.6 KWH HV battery; so the total for me became 5.6,
The list price of the 4 KWH unit was about $4000, but I obtained the unit at a big discount because I was the first pilot tester for a Camry Hybrid installation.
I did the installation myself, and I had to work out all of the Camry-specific installation details, mechanical and electrical. There were some Camry-specific settings that the manufacturer needed to make to the DC-to-DC converter.
The unit mounted in the trunk. It took up about as much space as is lost in the C-max Energi vs. the Hybrid.
The system worked very well. At street speeds, I could do about 20 miles before the kit battery was depleted and I could get 75 or 80 mpg.
In the end, I discovered that a Plug-in hybrid was exactly what I wanted - plug-in efficiency and outstanding fuel economy with zero range anxiety.
Maintenance and reliability, however were serious problems. I wound up wanting a factory PHEV rather than a DIY aftermarket solution.
I have been completely satisfied with the C-max Energi. The car has never been back to the dealer coming up on 3 years. I've lost a little HV battery capacity, but I still get about 20 miles of EV range, I get a couple thousand miles out of a tank's worth of gas, and my lifetime average is about 150 mpg, and the impact on my electric bill has been minimal. In fact, I often say that plugging in my Energi actually caused my electric bill to go down. That happened because the chore of trying to calculate the impact caused me to discover that I was paying over 16 cents a KWH; so I shopped around and got that down to 9 cents.
Given my experience with the Camry conversion and the experience of others with Ford Escape Hybrid conversions, I would think that one of the "Prius" units - as the OP put it - should work out ok either to convert a C-max Hybrid to a Plug-in Hybrid or even to add more EV range to an Energi.
But, considering the maintenance and reliability, if I had a C-max Hybrid, I would trade it in on an Energi rather than do a PHEV kit conversion.
Edited by Smiling Jack, 16 April 2016 - 09:19 AM.