Designing a PHEV system for the Civics, Insight 1 and 2 ------------Micro V-Buck PHEV
starting point
My V-boost system showed the possibilities, Peter Perkins Lithium PHEV Insight confirmed it, adding a booster battery that allows a MIMA equipped Insight to use increased assist in the hybrid mix can push the Insight's MPG to well over 100MPG.
The development of a safe inexpensive booster battery system for the Insight owners with MIMA. a Booster battery system using lithium batteries,would be the best for long range PHEV range and light weight, but is a big financial outlay. Because of the good availability and low price of surplus Prius battery packs,I feel they will provide a suitable booster pack for those with a shorter commute. The fact that they are at a higher voltage than the 144V nominal voltage of the Insight packs makes a perfect combination for a Buck converter design to control current and final boost voltage. A dual stage grid charger would charge the boost pack. The final piece of the system will be a microcontroller board that will interrogate the prius BCM, and control the buck controller, as well as communicate with MIMA. After proving the design, I will be offering it to all Insight owners with MIMA.
This blog will share the development process, and share all the Insights gained so others may boost the amazing Insights remaining on the planet to there maximum potential, and show how simply allowing the driver to drive the electric gas mix that we can push MPG by 50% or more.
A prius joins the stable of hybrids
A Prius joins my Fleet
Sue had the 1996 Dodge Caravans brakes fail on her, and luckily She made it home safely. After seeing the rust and deterioration under there, I made the decision that it was time to retire the 17MPG monster vehicle, and get something bigger than the Insight, and of course the Prius came to mind. Thanks to some guidance from a friend, I located a 2006 with 152K for a good price, and picked it up today. Already looking at a plug in pack to bump things up a notch. Time to dig out the V-Buck? Why can't I just leave things the way they are???
(Posted 8/7/2012 by mikey)
Micro V-Buck prototype is in my hands
Micro V-Buck prototype
I meet Doug and his family at Solarfest last weekend, and we swaped components so we can continue development of the system. I gave Doug a full Prius pack, and he gave me my first prototype of the Micro V-Buck system. Still lots to do, but now we both have the same hardware to work with. Stay tuned for further developments.
(Posted 7/20/2010 by mikey)
Full power test run
getting the output in the zone
Doug built a test panel so he could better monitor the performance of the V-Buck converter. The photo shows the system bucking down the 220VDC battery pack voltage to 144V, and the 24A output with only 16A in. test run was for 20 minutes. All is looking very promising.Doug, be careful with all the batteries and chargers, we don't want you to burn your place down.
(Posted 2/23/2010 by mikey)
V-Buck converter
Prototype under bench test
Doug Hartley has been bench testing the prototype buck Converter by gradually raising the voltage and load while monitoring the internal voltages. He is nearly at the required input and output voltages, and hopes to have run the prototype at full voltage and load in the next week or two.He is still very busy at his full time+ job, so the project will have to wait for him to steal time to work on it. A Custom PC board will be designed for the project once the system components have been firmed up. The components are designed to allow the device to operate over a wide range of input and output voltages, and retain full adjustable current control. The plan is to be able to use the system with Civic,Insight1, and Insight2 systems.
(Posted 1/18/2010 by mikey)
Engineer system PHEV compared to a prius pack based PHEV
Lets compare the systems
The engineer system has 40AH Lithium batteries in a 48V pack. Thundersky shows a 5000 cycle life if cycled 70%, so the 40AH becomes 28 useable ah There boost converter is probably running at 80% efficiency so it will reduce the useable AH to ~22AH The engineer system has to boost the ~48V PHEV battery voltage to ~144 which is ~ a 3 X boost, so the current will be 3 X what is delivered to the stock battery. The effective capacity when converted to 144V will be 22AH/3 = ~ 7.3 Ah of PHEV capacity at 144V
Buck Inverters work like a step down transformer. As they step down the voltage they increase the current by the same factor. They increase effective AH since they boost current while dropping voltage. A disadvantage: The PHEV pack must be 10 or more volts higher than the battery it is charging, so we need lots of cells.
The stock second generation Prius HV battery is 209V which is a perfect voltage for charging an Insight 144V pack with a buck converter. With the Insight pack full at ~170V, and the Prius pack depleted at ~ 180V, we always will have that voltage differential which is important for Buck converters operation. My first approach is going to be to start with stock surplus Prius battery packs, which come with precharge and main contactors, current sensor , temperature sensors, and a built in prewired BCM, for~ $500 They would be tested rebalanced and repaired if necessary. I will effectively recycle prius packs into Insight PHEV packs. A simple inexpensive CAN battery controller interface would take full advantage of the Prius BCM, for safe reliable battery care during charging and discharging.
This Prius pack while only 6.5AH, is at 209V nominal.
Buck converter: 209/144 = ~1.4 boost in current, effectively making the 209V 6.5 Ah pack look like a 9.4AH 144V pack. Assuming we want long cycle life from the Prius pack, and we limit the discharge of the prius pack to 60%, we would get an effective 5.4AH boost in useable storage capacity at 144V
The buck system using prius cells will deliver 5.4 Ah peak output up to 25A The engineer system delivers 7.3Ah . peak output less than10A.
The ultimate PHEV pack. 40AH 209V lithium pack, 70% DOD = 28AH useable for max cycle life. deduct Buck converter efficiency losses 90%+ = ~25AH Buck current magnification 25 * 1.4 = 35 effective AH at 144V A 40 AH lithium pack would deliver 35 effective AH at 144V Over 10 times the stock capacity You would be able to drive for hundreds of miles with MIMA while in PHEV mode, cruising in the 100mpg club.
Battery life factors: Buck battery current @ 10 A to stock pack
7.5A from a 40ah Lithium pack is a mild load negligible heating 7.5A from a Prius NIMH pack is a very mild load negligible heating
Boost Battery current @ 10 A to stock pack Drawing ~35 amps from a 40AH lithium is a heavy load will heat up
The V-Boost system has worked well with the donated Vicor power blocks performing trouble free at all temperatures. thanks Vicor. The problem with the concept is that the Vicor power blocks cost over $2K and thats just for the components. What did I learn: MIMA manual control of the electric side of the hybrid drive is essential for getting the most out of any PHEV system. I want to drive with the flow, and tend to use MIMA rather aggressively. I can draw 16.5A of charge for my HV battery by drawing 65A from my lead booster monsters in the back. I found that for my type of driving, 16.5A was not quite enough to keep up. Other driving conditions and speeds may be happy with much less. Having the ability to tune the charge rate on the fly will be a feature of the Buck converter design. As discussed any boost or reduction in voltage between the PHEV battery and the stock battery will come with an equivalent increase or decrease on their input current. Input watts = output watts - efficiency losses. Boost The biggest disadvantage of a low voltage to HV boost system like my V-boost and the Engineer system is the high currents required from the LV battery for reasonable currents in the output.High currents means lower efficiencies,less reliability and higher operating temperatures, and shorter battery life.
As a firm believer in recycling as the best way to save energy, so recycling the many prius packs into Insights for PHEV service seems like a way to kill two birds with one stone. I want to recycle the Prius drive components as well: EV Insight Time will tell
