Talk:EAA-PHEV PRIUS Documentation - Revision history

Rjf: cleared.

2006-01-22T12:50:06Z

cleared.

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Rjf: EAA-PHEV-PRIUS+_060122rdg.doc

2006-01-22T08:57:59Z

EAA-PHEV-PRIUS+_060122rdg.doc

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Rjf: Felix comments(2nd)

2006-01-22T07:23:50Z

Felix comments(2nd)

Rjf: Original Document

2006-01-22T07:23:12Z

Original Document

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Rjf: changes Felix made.

2006-01-22T07:16:05Z

changes Felix made.

Rjf: discovering changes by felix

2006-01-22T07:15:21Z

discovering changes by felix

New page

History. I was the technical lead for CalCars 2004 PRIUS+ modification of
my 2004 Prius into a pluggable hybrid (PHEV). Felix Kramer, CalCars
founder, enlisted me in mid-2004, shortly after I first contacted him. The
project had a lot of internet collaboration as well as physical volunteer
help, largely from Electric Automobile Association (EAA) members (thanks to
everyone). You can view much of the history of the project at
http://autos.groups.yahoo.com/group/priusplus/messages.

Greg Hanson offered EnergyCS help at low cost. They had a CAN bus
controller that they turned into a battery management computer to replace
Toyotas Battery ECU by emulating that OEM computers CAN messages to the
rest of the hybrid system. This system, though proprietary, got our PRIUS+
working quickly; first smoke-tested in late September, it was working well
by early November 2004.

Greg and others at EnergyCS then got excited, built their own Prius
conversion using Valence Li-ion batteries, and with CleanTech, a company
to which Felix introduced them started EDrive Systems to commercialize
Prius PHEV conversions. This is an exciting development, which may provide,
for most people, the first opportunity to own a PHEV.

However, there is also a community of experimenters, schools, and others
interested in doing such modifications themselves, and the EnergyCS
controller is not available for this purpose. Fortunately, Dan Kroushl
discovered and shared the information that a higher-voltage battery is
capable of fooling Toyotas Battery ECU into giving a higher SOC reading. I
started experimenting with higher voltages of PbA batteries and came up with
an algorithm for fooling the Battery ECU in an organized way. It has so far
been tried only with PbA batteries, and only with manual control, but I hope
and expect it to work more generally. It will be described in detail below.

Battery pack. I specified a BB Battery PbA battery pack (18 EVP20-12B1
modules from http://www.electricrider.com/batteries.htm) for our first
conversion attempt, in order to go through our learning curve with
inexpensive, fairly indestructible batteries. This turned out to be an
excellent decision, as, though it required replacement after 200 cycles and
just under a year, this pack has sustained our PRIUS+ through over a year of
work on finding a more advanced battery pack. The BB electric bicycle
batteries, though very marginal for this application, are actually quite
remarkable among PbA batteries. When fully charged, these 20Ah (12Ah @ ½
hour rate) batteries have a lower internal resistance (~250 milliohms) than
the OEM battery (300-350 milliohms) and are capable of supplying the Priuss
maximum draw of 200A a 10C or 17C rate, depending on which capacity you
calculate it against. At low SOC, however, the internal resistance is >500
milliohms, too high for full hybrid functionality. My PRIUS+s performance
has been documented in CalCars PRIUS+ Fact Sheet, available at
http://www.CalCars.org. In short, the BB Batteries weigh about 260 lb and
provide for approximately double the normal Prius gasoline mileage for
around 20 miles of mixed (town and highway) driving on each charge.

Next, we planned on installing a NiMH pack, largely to prove that the
chemistry that is already in all of todays mass produced hybrids is also
capable of powering electrically and economically effective PHEVs; thereby
removing one more auto company excuse for not building them. After that, we
would move on to Li-ion, which we expect to require additional engineering
work to ensure proper cell-by-cell charge and discharge control as well as
to engineer out any likelihood of thermal runaway problems, to which this
chemistry is prone.

I also looked at many Li-ion possibilities. The least expensive option is
currently 18650 cells, produced in huge volumes for laptop computers.
However, these, like the sub-C NiMH cells, are very small (2-2.8Ah). Also,
they are typically designed for 2-5 hour discharge rates and lack high power
capabilities. One pays more for high power, low susceptibility to thermal
runaway, and long cycle life and you still have to parallel many cells to
reach the necessary capacity. A typical PRIUS+ pack would use at least 1200
cells, providing plenty of failure points. While looking only at
technologies that are in production, if only in the early stages, CalCars
has begun discussions with more than one specialty Li-ion manufacturer with
lines of high-power-capable Li-ion cells.

CalCars and Electro Energy, Inc, in Danbury, Connecticut, are now in the
late stages of a joint project to adapt their unique form of NiMH packs to
the PRIUS+. As part of the project, I have designed control circuitry that
is specific to the characteristics of this battery as well as Toyotas BMS.
When complete (expected yet this first quarter of 2006), the pack should
weigh about the same as the BB Battery pack but last for 40-50 miles of
mixed driving. Internal resistance figures we have seen so far are in the
200 milliohms range. It is possible that Electro Energy will elect to sell
this pack to experimenters, so stay tuned.

@@ Line 4: / Line 4: @@
 Permission granted for private use as long as the following is recognized:
 This circuitry is experimental.  Its use may void Toyota warranties,  It could possibly damage the vehicle or make it drive erratically.  Due to lethal high voltages involved, all due safety precautions must be taken to protect oneself and anyone who comes near the vehicle.  You MUST have experience with high voltage safety precautions!
-History.  I was the technical lead for CalCars’ 2004 PRIUS+ modification of my 2004 Prius into a pluggable hybrid (PHEV).  Felix Kramer, CalCars’ founder, enlisted me in mid-2004, shortly after I first contacted him.  The project had a lot of internet collaboration as well as physical volunteer help, largely from Electric Automobile Association (EAA) members (thanks to everyone).  You can view much of the history of the project at http://autos.groups.yahoo.com/group/priusplus/messages.
+History.  I was the technical lead for CalCars’ 2004 PRIUS+ modification of my 2004 Prius into a pluggable hybrid (PHEV). (I remain CalCars' technical lead.)  Felix Kramer, CalCars’ founder, enlisted me in mid-2004, shortly after I first contacted him.  The project had a lot of internet collaboration as well as physical volunteer help, largely from Electric Automobile Association http://www.eaaev.org (EAA) members (thanks to everyone).  You can view much of the history of the project at http://autos.groups.yahoo.com/group/priusplus/messages, especially the summary at http://autos.groups.yahoo.com/group/priusplus/message/421. (This group is currently closed to new members, but postings are viewable by non-members.).
 Our first attempt to interface more battery capacity to Toyota’s hybrid system (not unexpectedly) didn’t work.  We discovered that Toyota’s (Battery ECU) battery management computer uses Amp-hour integration as its major way of determining battery state-of-charge (SOC).  Therefore, just as with the OEM battery, after a mile or so, it would pop the vehicle out of EV-only mode due to a very low SOC indication (in spite of the new battery’s much larger capacity and high actual SOC).
-Greg Hanson offered EnergyCS’ help at low cost.  They had a CAN bus controller that they turned into a battery management computer to replace Toyota’s Battery ECU by emulating that OEM computer’s CAN messages to the rest of the hybrid system.  This system, though proprietary, got our PRIUS+ working quickly; first smoke-tested in late September, it was working well by early November 2004.
+Greg Hanssen offered EnergyCS’ help at low cost.  They had a CAN bus controller that they turned into a battery management computer to replace Toyota’s Battery ECU by emulating that OEM computer’s CAN messages to the rest of the hybrid system.  This system, though proprietary, got our PRIUS+ working quickly; first smoke-tested in late September, it was working well by early November 2004.
-Greg and others at EnergyCS then got excited, built their own Prius conversion using Valence Li-ion batteries, and – with CleanTech, a company to which Felix introduced them – started EDrive Systems to commercialize Prius PHEV conversions.  This is an exciting development, which may provide, for most people, the first opportunity to own a PHEV.
+Greg and others at EnergyCS then got excited, built their own Prius conversion using Valence Li-ion batteries, and – with CleanTech, a company to which Felix introduced them – started EDrive Systems http://www.edrivesystems.com to commercialize Prius PHEV conversions.  This is an exciting development, which may provide, for most people, the first opportunity to own a PHEV.
-However, there is also a community of experimenters, schools, and others interested in doing such modifications themselves, and the EnergyCS controller is not available for this purpose.  Fortunately, Dan Kroushl discovered and shared the information that a higher-voltage battery is capable of fooling Toyota’s Battery ECU into giving a higher SOC reading.  I started experimenting with higher voltages of PbA batteries and came up with an algorithm for fooling the Battery ECU in an organized way.  It has so far been tried only with PbA batteries, and only with manual control, but I hope and expect it to work more generally.  It will be described in detail below.
+However, there is also a community of experimenters, schools, and others interested in doing such modifications themselves, and the EnergyCS controller is not available for this purpose.  Fortunately, Dan Kroushl discovered and shared the information that a higher-voltage battery is capable of fooling Toyota’s Battery ECU into giving a higher SOC reading.  I started experimenting with higher voltages of PbA batteries and came up with an algorithm for fooling the Battery ECU in an organized way.  I tried it first with PbA batteries, and only with manual control, but I expected it to work more generally.  It will be described in detail below.
 I have now completed (3) schematic diagrams for a PRIUS+ conversion using this technique, and am working on software to automate the control as well as display and record relevant vehicle information.  This is intended to run first on a laptop computer, then on a PocketPC PDA that can be semi-permanently mounted (and left running) in the car.
-Battery pack.  I specified a BB Battery PbA battery pack (18 EVP20-12B1 modules from http://www.electricrider.com/batteries.htm) for our first conversion attempt, in order to go through our learning curve with inexpensive, fairly indestructible batteries.  This turned out to be an excellent decision, as, though it required replacement after 200 cycles and just under a year, this pack has sustained our PRIUS+ through over a year of work on finding a more advanced battery pack.  The BB electric bicycle batteries, though very marginal for this application, are actually quite remarkable among PbA batteries.  When fully charged, these 20Ah (12Ah @ ½ hour rate) batteries have a lower internal resistance (~250 milliohms) than the OEM battery (300-350 milliohms) and are capable of supplying the Prius’s maximum draw of 200A – a 10C or 17C rate, depending on which capacity you calculate it against.  At low SOC, however, the internal resistance is >500 milliohms, too high for full hybrid functionality.  My PRIUS+’s performance has been documented in CalCars’ PRIUS+ Fact Sheet, available at http://www.CalCars.org.  In short, the BB Batteries weigh about 260 lb and provide for approximately double the normal Prius’ gasoline mileage for around 20 miles of mixed (town and highway) driving on each charge.
+Battery pack.  I specified a BB Battery PbA battery pack (18 EVP20-12B1 modules from http://www.electricrider.com/batteries.htm) for our first conversion attempt, in order to go through our learning curve with inexpensive, fairly indestructible batteries.  This turned out to be an excellent decision, as, though it required replacement after 200 cycles and just under a year, this pack has sustained our PRIUS+ through over a year of work on finding a more advanced battery pack.  The BB electric bicycle batteries, though very marginal for this application, are actually quite remarkable among PbA batteries.  When fully charged, these 20Ah (12Ah @ ½ hour rate) batteries have a lower internal resistance (~250 milliohms) than the OEM battery (300-350 milliohms) and are capable of supplying the Prius’s maximum draw of 200A – a 10C or 17C rate, depending on which capacity you calculate it against.  At low SOC, however, the internal resistance is >500 milliohms, too high for full hybrid functionality.  My PRIUS+’s performance has been documented in CalCars’ PRIUS+ Fact Sheet, the latest version of which is always available at http://www.calcars.org/priusplus.html In short, the BB Batteries weigh about 260 lb and provide for approximately double the normal Prius’ gasoline mileage for around 20 miles of mixed (town and highway) driving on each charge.
-Next, we planned on installing a NiMH pack, largely to prove that the chemistry that is already in all of today’s mass produced hybrids is also capable of powering electrically and economically effective PHEVs; thereby removing one more auto company excuse for not building them.  After that, we would move on to Li-ion, which we expect to require additional engineering work to ensure proper cell-by-cell charge and discharge control as well as to engineer out any likelihood of thermal runaway problems, to which this chemistry is prone.
+Next, we planned on installing a NiMH pack, largely to prove that the chemistry that is already in all of today’s mass produced hybrids is also capable of powering electrically and economically effective PHEVs; thereby removing one more auto company excuse for not building them.  As soon as we have the people-resources, we will move on to work with one or more of th newer high-performance Li-ion suppliers, which we expect to require additional engineering work to ensure proper cell-by-cell charge and discharge control as well as to engineer out any likelihood of thermal runaway problems, to which this chemistry is prone.
 I spent the first nine months of 2005 looking for NiMH and/or Li-ion batteries that fit the PRIUS+ requirements.  In the process, I learned a lot about the characteristics of these advanced battery chemistries.  For example, special problems are encountered when NiMH cells or strings are put in parallel.  This should only be done with full strings, and with special control electronics such as that designed for the Electro Energy pack (below).  Wayne Brown and Dan Kroushl are using many parallel strings of NiMH sub-C cells in their enhanced (but not PHEV) Prii.  These small (3-3.6Ah) cells have good high power capabilities, and the parallel strings work well in their application where the cells do not get fully charged.  I figured that D cells, also quite available, would require few enough parallel strings that the electronics might not be overwhelming.  However, though many looked good on paper, all D cells I tested had at least double the expected internal resistance.  Fortunately, Electro Energy came along with their specialized and capable NiMH batteries (below).
-I also looked at many Li-ion possibilities.  The least expensive option is currently 18650 cells, produced in huge volumes for laptop computers.  However, these, like the sub-C NiMH cells, are very small (2-2.8Ah).  Also, they are typically designed for 2-5 hour discharge rates and lack high power capabilities.  One pays more for high power, low susceptibility to thermal runaway, and long cycle life – and you still have to parallel many cells to reach the necessary capacity.  A typical PRIUS+ pack would use at least 1200 cells, providing plenty of failure points.  While looking only at technologies that are in production, if only in the early stages, CalCars has begun discussions with more than one specialty Li-ion manufacturer with lines of high-power-capable Li-ion cells.
+I also looked at many Li-ion possibilities.  The least expensive option is currently 18650 cells, produced in huge volumes for laptop computers.  However, these, like the sub-C NiMH cells, are very small (2-2.8Ah).  Also, they are typically designed for 2-5 hour discharge rates and lack high power capabilities.  One pays more for high power, low susceptibility to thermal runaway, and long cycle life – and you still have to parallel many cells to reach the necessary capacity.  A typical PRIUS+ pack would use at least 1200 cells, providing plenty of failure points.  While looking only at technologies that are in production, if only in the early stages, CalCars has begun discussions with specialty Li-ion manufacturers with lines of high-power-capable Li-ion cells.
-CalCars and Electro Energy, Inc, in Danbury, Connecticut, are now in the late stages of a joint project to adapt their unique form of NiMH packs to the PRIUS+.  As part of the project, I have designed control circuitry that is specific to the characteristics of this battery as well as Toyota’s BMS.  When complete (expected yet this first quarter of 2006), the pack should weigh about the same as the BB Battery pack but last for 40-50 miles of mixed driving.  Internal resistance figures we have seen so far are in the 200 milliohms range.  It is possible that Electro Energy will elect to sell this pack to experimenters, so stay tuned.
+CalCars and Electro Energy, Inc http://www.electroenergyinc.com/, in Danbury, Connecticut, are now in the late stages of a joint project to adapt their unique form of NiMH packs to the PRIUS+.  As part of the project, I have designed control circuitry that is specific to the characteristics of this battery as well as Toyota’s BMS.  When complete (expected yet this first quarter of 2006), the pack should weigh about the same as the BB Battery pack but last for 40-50 miles of mixed driving.  Internal resistance figures we have seen so far are in the 200 milliohms range.  It is possible that Electro Energy will elect to sell this pack to experimenters, so stay tuned.
 Several EAA members have recommended Hawker PbA batteries which don’t appear to exist any more under that moniker.  However, I believe I just tracked down their descendents:  Odyssey batteries by EnerSys Inc. (http://www.enersysreservepower.com/documents/ODY_BR_101R_0503.pdf).  They have a model PC625 that may be less marginal than the EVP20 and thereby useful for experimenters’ PRIUS+ conversions.  I don’t yet know price of availability.  Though rated at 16Ah, they have the same rated ½ hour capacity as the EVP20, are 1 lb lighter, and have a claimed 1800A short circuit current at full charge, requiring an internal resistance of less than 7 milliohms (126 milliohms for a full pack of 18).  Also, they claim an 80% DOD cycle life of 500 and the ability to withstand long periods of discharge with little damage.
 Several PRIUS+ battery pack specifications are provided in appendix A.