Electric Porsche 944

I finally got around to test fitting the 7″ tablet in the center console of the Porsche and this is one of those times where luck turns out better than good planning.  The tablet fits perfectly and requires no cutting and no special trim panel to make it look nice.  The one issue that I knew I would have right from the start is lack of space to run the audio output jack as well as dock connector out the left and right sides of the tablet.  The solution is to remove the back cover and relocate the jacks for easy use.  I also need access to the power switch and possibly the volume controls that are normally on the “top” in the orientation that I will be mounting the tablet, this means soldering extension wires to some very tiny buttons inside the tablet and routing them to an external switch.  I may be able to use the ignition switch as a trigger to turn the tablet on and off when the car is turned on and off.  Otherwise I will use one of the vacant switch openings to install a momentary switch that will be re purposed as the on/off switch to the tablet, this may also be handy to turn on the tablet while the car is off for testing, internet or watching movies.  The tablet comes with a good size lithium battery that I will use to power the tablet while driving, it will charge along with the main pack when the car is plugged in.

Above:  Tablet test fitted in the center console to evaluate “glare”, looks good right now but might be an issue with the sunroof off.

Above:  Back cover removed, battery and guts visible.

Above:  Close up dock connector removed and rotated 180 to face inwards.

Above:  Close up of the new switch wires, 30awg soldered directly to the surface mount switch terminals, VERY TINY!

I still have some work to do to the tablet before it gets mounted to the center console for good.  I need to secure the wiring and new positions of the dock connector, and switch wires along with add RCA jacks to the tablet for easy integration into the car stereo.

The module assembly is coming along nicely, now that all of the details are worked out everything is going together nicely.  I have 5 finished modules, two of which I’m using to power the chargers for further cell testing.  Once the battery box is finished and I can start installing things permanently I need 8+ modules to start driving the car again.  12 modules should give me decent performance and all 24 modules will give me excellent performance and the full designed range.

In the early days (a year ago) when I bought my cells there wasn’t much available, I jumped on some tabless cells that work perfectly but had been de-tabbed by the factory.  These cells are simply a pain to work with, they require uncovering the tab under the plastic/aluminium casing to make the connections.  This works well, but is simply time consuming and messy work and doubles or triples the cost of the cells with the added labour.  I just bought a new batch of cells to finish the car and they have short but more normal tabs.  There is still an issue with what I ordered and what I received, those in China aren’t the best vendors, I made it very clear the type of cell tabs that I wanted and we agree’d on pricing etc.  They came back with a higher cost due to a “mistake” in the quote, I think this is poor business practice as I had already sent the payment but before shipping they demanded more money.  So buyer beware when buying directly from China.  The cells are still a good deal with potentially useable tabs, not the tabs that I wanted though so we will have to see if they give me some of my money back or not due to their quite significant error.  I will have to test a module made from these cells and see if they can handle the current, most likely they will only be good for electric bike packs.  They also aren’t made in the country that I was told, my existing cells were made in Korea so I was happy when I was told the “short tab” cells were also made in Korea, but I received cells marked “made in USA”.  These cells don’t have the same discharge curve to the Korean cells, they are still good, but different, so if I am able to use them half of my pack will behave slightly different than the other half.  If they don’t back their product I may have to warn against doing business with this company and stop recommending these cells on this blog and all forums that I visit (diyelectriccar.com, endlesssphere.com etc).  To date I’ve been one of the biggest supporters of these cells, but if you can’t buy them from a fair company that isn’t out there to rip you off and send you what you order it’s just not worth it.  I won’t mention the company yet, I’ll give them a reasonable amount of time to respond and fix the error.  I only have 70 of 152 cells because of DHL’s wonderful shipping but that’s another story and I’m sure the rest will arrive soon.  It’s still pretty early to tell as I’ve only tested 36 cells, but the average capacity is down slightly and the IR is up slightly on these made in the USA cells vs the Korean cells that I’ve been using.

You also may have noticed I’ve gone back to my Nikon SLR for photo’s, the in car shot is with my Iphone 3GS, but the remainder are obviously much better quality from the Nikon.  I had gotten lazy and simply used the Iphone or tablet camera because they were handy, I will try to use the Nikon again as the images are drastically better quality.

My first A123 pack design used a large number of aluminium spacer blocks to connect the tabs.  Shown below is the first module design in the form of a 4S3P (12v) battery that I’ve been using for a few months now.  Initially I had built a pair of 16S3P modules that I used to drive the car to work but found flaws in their functionality.

In general the battery works very well, however it is very fiddly to assemble and requires a lot of custom parts.   There are 29 aluminium blocks consisting of 6 different types, the final pack would require 24 of these modules (696 blocks….) I also had some small issues at high current, there was more voltage drop than I was expecting and I had a few loose connections when I disassembled the very first large 48cell test packs.  The solution to the voltage drop is reduce the number of aluminium spacer blocks and join the 3 parallel cell tabs directly together and clamp them (tightly!)  This reduces the block count in the current path from 5 to 1, that should help with the voltage drop.  The solution to the loose connections is a complete redesign of the hard ware used as well as the clamping method for the tabs.  Luckily this aligned with the reduction in block count and allowed me to use the required hardware.  I’m now using a pair of M5 cap screws with a 4mm allen drive vs an M4 flat head (countersunk) screw with a 2.5mm allen drive.  This allows for a much higher tightening torque to be applied to the fasteners, and they are larger and stronger in general.  The use of a traditional cap screw means there is a proper surface to use a Nord-lock washer!  Jack R of EVTV has been recommending them for years and although I’ve been aware of this for a very long time, they just didn’t fit with my module design.  It was time to change the design so that they did work!  Below is the revised module design using 13 blocks consisting of 4 types (312 total for the car).  The end terminals are different in this test pack but will be the same in the final design, the most positive and negative terminals will be slightly different but there are only two in the entire pack so it’s worthy of extra attention.

The Nord-locks are amazing and do exactly what they say they do!  (Thanks Jack R.)  I still have some very minor things to revise and tweak with this design, but I will be making the final test blocks today and if all is well I will be making all of the blocks required for the pack.  The other part I’ve been struggling with are the holes in the tabs, drilling doesn’t work, a metal punch is better but not perfect, a hole punch (for paper!) actually works very well but is hard to use and align.  This led me to find a hole punch that WILL work for me and hopefully I’ve found it!  It’s on order so I haven’t tried it yet but it’s a heavy duty paper hole punch with adjustable center to center distance for the holes.  This will allow me to set it for the 1.25″ spacing of my blocks and punch each tab in one motion with hopefully consistent spacing and alignment.

Most of the cells have been prepared and tested, leaving lots of punching and assembly work to make the final battery modules, once I have the final details worked out this will be quite fast and easy (I hope!)

The DC/DC converter/charger that I’ve been talking about forever is finally done.  The board is designed to hold a raised bracket with a 120mm low profile 12v fan.

I started by milling a copper clad PCB to the desired shape and size to hold the fan.  (this is the strongest thinnest material that I had on hand).

Mounted the fan to the PCB with the included fan hardware.

Finally mounted the milled PCB to my DC/DC charging board PCB using suitable stand offs.

I used a low speed (very quiet) low profile computer case fan to keep the height in the desired range.  I still need to find a grill or filter to keep fingers and other things out of the fan blades.  I have an extra set of 12v terminals on the input side of the PCB, so initially I will be running the fan off of the 12v signal that turns on the board itself.

By day I work for a company that designs and builds control and monitoring systems for service rig and frac equipment.  The shop guys do some amazing work making what would otherwise be a rats nest of wires and connectors into beautifully neat and organized works of art.  I will be doing my best to duplicate their efforts in my car.  I bought a variety of ferrules and fork/ring terminals to eliminate any loose or frayed wiring as well as make things tidy and professional.  They also use shrink tube labels and wire wrap labels on every wire at every connection.  I’m trying to get a reasonably priced label printer to duplicate those techniques as well, the Kroy K4100 looks like it would work very well for what I want to do, I just need to find a good used one at the right price.

Below is an example of a wire wrap label:

Below is an example of a shrink tube label (from a different brand):

The one thing I’ve learned recently is that if I wasn’t so picky the car would have been done a long time ago!  I believe everything will work very well when it’s done though so it’s worth the wait.

I’m living up to my high C personality for those familiar with DiSC profiling/assessment.

The battery box is coming along nicely, I haven’t welded anything substantial in almost 2 decades however I’m starting to get use to the welder and develop some basic skills that are making the process easier and better as I go along.  I started by cutting all of the steel angle to length along with any 45deg angles on the ends and cleaned up the pieces ready to weld.  I used my cut sheet and sketchup drawing to fairly quickly assemble those parts into the fairly complex “box” shown below.  I’m still cleaning up the welds but it will be ready to paint shortly to protect it from the elements.  After painting I will rivet on the aluminium skin that will form the remainder of the box followed by a generous coat (or two) of rubberised undercoating to protect and insulate the box.  Finally the rigid foam insulation will go inside the box and I will be ready to install the box semi permanently in the car.  It will be removable or at least ”lift able” to give clearance for transmission work.

To speed up the Cell Measurement process I picked up a 2nd PowerLab 6 that ties into the first and lets me control both with a single software interface and only a few mouse clicks.  I’ve decided to leave the cells empty at the end of my cycle testing instead of charging them back up.  The cells arrive at 30-50% SOC so I’m putting in a fair amount of energy before the discharge cycle, this lets the charger measure/calculate the IR of each cell.  Then it automatically discharges the cell and I can record the capacities.  Once assembled into my 12v packs I will use my new dc/dc converter boards in a 50 or 100A configuration to charge/balance the cells (or without the balance taps hooked up to simply charge the cells as a group).  The charging process with the PL6 isn’t 100% efficient and although I’m using regenerative discharge which puts energy from the test cell back into the 12v pack I still have to put energy back into the 12v battery on a regular basis.  By eliminating the recharge process where I top the cells back up and leave them full I now find it almost unnecessary to recharge the 12v battery as it is using the energy in the cells when they arrive to make up for the energy wasted in the charge/discharge process.

Some people have had issues getting their PL6 to charge/discharge above 10A, this is because some of the presets are limited to 10A if you pick one of the “high power” presets you can set it up to 40A.  The custom preset for the PL6 I’m using can be downloaded here.  A123 19000 mAh High Power

I’m using my “defective” A123 cells (anything with low capacity, questionable IR, or soft casing) as a 50.75Ah 12v battery, I’ve been using this pack for a few months to power my charger (now chargers) for testing the remaining cells.  I also use this pack to drive the car (yes as the traction pack, not the 12v system battery) when I need to move it in and out of the garage as well as jump start both my Infiniti G35 and Ford F150 when I had battery issues and very cold weather.  Basically for a pack of defective cells it is working flawlessly, I keep it above 10v and below 14.4v and beyond that it just works.  I have a few hundred shallow cycles on this pack along with some 100% discharge cycles and it works well beyond my expectations.  I believe the main pack in the car once complete will operate simply and reliably for many years.

This is just an update to share a quick demo of the electricporsche.ca Cell Log 8 Breakout Module.

This is a very simple but highly effective breakout board to allow safe and easy connection and use of the Cell Log 8 (CL8), it has provisions for 32 series cells using 4 CL8′s.  The alarm’s of each CL8 are isolated from each other and powered by the first 4 cells in a group.  It is important to note that there must be at least 4 cells connected to a CL8 for the alarm’s to function properly.

There are three methods of interfacing with the breakout module to make use of the CL8 alarm signal.  The first and simplest is an NC (normally closed) loop, when there is an alarm condition on any breakout module the NC loop is opened indicating a fault.  This system requires the use of additional hardware to make use of the NC loop.  A simple and existing solution would be the Head End board sold by Dimitri at Clean Power Auto LLC.

The 2nd and most inexpensive method is to use the RJ45 connector on board with a Cat5/6 cable and 4 resistors/LEDs.  The 8 wires in the Cat5/6 cable are connected to the Com and NO terminals of the 4 alarm relays.  By connecting pins 1,3,5,7 to the respective negative terminals of 4 LED’s and connecting pins 2,4,6,8 to the cars ground, then connecting 12v through appropriate current limiting resistors to the positive side of each LED you have a simple display that will indicate an alarm condition along with which CL8 triggered the alarm.  Use a suitable length Cat5/6 cable to mount your LED’s in a suitable location so it will be noticed while driving.

The 3rd and most customizable method of interfacing with the alarms is to use the NC/Com/NO terminals on the bottom of the Breakout Module and create your own interface.  This could be anything you imagine, for example it could be connected to digital input pins on an Arduino microcontroller connected to an Android tablet that displays an on screen warning of the alarm condition as well as the battery group that triggered the alarm.

All of the alarm related connections are completely isolated from battery system it’s monitoring, making it safe to run the alarm wiring into the vehicle cabin to a convenient location.

I will add the CL8 Breakout Module to the store shortly, I won’t be selling the Cell Log 8′s though.  If you are buying Cell Log 8′s from Hobbyking.com I would highly recommend you also purchase the Turnigy 3mm flat screwdriver similar to what I used in the video.  This screw driver fits the terminal block screws on the Breakout Module perfectly, it’s good quality and very inexpensive.

I’ve been working on the idea of a DC-DC charger for a long time now, however I could never settle on a feature set to design the PCB around.  As the project gets closer to actual completion I decided to just keep it simple.  The PCB is more of a breakout board for the Synqor DC/DC converter modules and allows them to be securely mounted with nice terminals and simple connections.

The PCB is designed to hold 8 converters in two groups.  This allows them to be put in series or parallel depending on the intended use.  Putting them in series makes an 8 cell 25A LiFePO4 charger that is adjustable from 3.3-3.65v. Putting them in parallel makes a 50A 12-15V dc/dc converter with an input range of 36-75 OR 72-150v.  Using 1 1/2 boards (12 converters) makes a 75A dc/dc converter with a 108-225v input range.  I will be using this configuration for my first battery pack in the car (56 series LiFePO4 cells)  I will also be using a 50 or 100A version of this module to charge the 12v modules that will go in to the main battery pack.

I still wanted to be able to plug in a Cell Log 8 for quick testing or monitoring so the plug is included, but does not take up the same kind of board space as the old design.

There is a trim pot and test points to set the voltage on each channel.  For less accurate results the Cell Log 8 can be referenced to set the voltage of each channel very quickly.  These Synqor modules don’t have a heat sink, but the still need cooling, I will be designing a fan mount for a 120mm fan to be directly mounted to the PCB, the fan will be powered by the same 12v signal that turns on the board.

The main reason the Cell Log 8′s were removed from permanent mounting on the PCB is because of a 2nd PCB I had in the works.  This is simply a Cell Log 8 Breakout Module that allows up to 4 cell logs to be mounted to a PCB with real terminals for connecting wires, as well as the required relays and connections for using the alarms and turning the Cell Logs on and off.

The design is simple and all traces were routed by hand for direct routing and minimum use of vias.

The stock alarm wire that comes with the Cell Logs is shortened and plugged into a connector on the bottom of the PCB.

The PCB layout is simple and compact, with sturdy terminals for all connections.

I’m in the process of testing both boards right now, but as you see below everything is working as it should, the charger boards are adjusted to ~3.5v and the cell logs are reading all channels.

For testing since I don’t have a 32S battery pack assembled yet I simply used 32 channels worth of the DC/DC charger (4 compact boards).

This is actually better than using a battery pack for testing since I can vary the voltage of each cell to test the various alarms and make sure everything is working as it should.

Once I get the warning lights or buzzer hooked up to the alarms I’ll do a short video showing the 3 different alarm states that can be used with the cell logs and how that can be useful on your dashboard to see what cell group is tripping the alarm.  With this type of set up you could use one Logging Cell Log 8 and the remaining can be the less expensive Monitoring only Cell Log 8′s.  If an alarm was triggered you will be able to tell what group the alarm came from and move the Logger to that location.

Once I’m finished testing both of these boards will be available for sale in the store.  The Cell Log 8 will be available in a populated form with all connectors and relays, but without the Cell Log 8′s. The DC/DC converter board will be available with the relay, pots and connectors but without the DC/DC converter modules.  I will be supplying a list of compatible dc/dc converters that would work with this board.

I’ve decided to go a different direction with regard to the gauges in the center console below the stereo.  The “old” plan shown below was a pair of blue digital gauges that would show battery voltage and current.

BUT out with the old and in with the new!!

EMW (emotorwerks.com) is working on an android app and hardware to collect useful EV data and send it via bluetooth to any android tablet or phone.  I picked up a 7″ Samsung tablet that will be permanently installed in place of the stereo to act as Stereo/Navigation/Gauges as well as all the normal stuff you can do on a tablet.

Below is a screen shot from the basic version of the app (set up with my personal idea of a useful layout).

They are working on an “EV Control System” that will provide all of the existing functionality plus control and interface to other hardware in the EV.  I’m looking forward to making the tablet a center piece in the car, I kind of wish I could fit in a 10″ tablet.  I will still have existing hardware gauges that will show battery voltage/current, state of charge etc.  So while using the tablet as a navigation system for example I won’t loose all access to critical information.  The tablet will however provide much more information in an attractive single location.

They are still in development so I asked about including touch screen switches that would allow custom use of unused arduino pins to turn things on and off.  They like the idea, so hopefully it makes it in the final software version!  I think this would be great for the heated seats that I would like to add to the car.  All of the kits that I’ve found use round switches, and I must be too picky because round switches just won’t match the rectangular switches (shown above) that are located below the stereo.  Having touch screen switches would solve this problem.  Other features could be set up in a similar manner to turn on the main heater etc.  I’m also going to talk to the developers about having some on screen “LED’s” that could be used as indicators tied to arduino inputs to show an alarm event on screen.

I’m an Iphone user, but I’m really starting to enjoy this Android tablet.   It’s only running Honeycomb (3.2), but there is talk that samsung will be making an upgrade to Ice Cream Sandwich (4.0) for this and their other dual core tablets that came out recently.  Apparently ICS streamlines the interface making the tablet faster and giving some new features.

After some reading and reviews I’ve decided to try Sygic as my navigation app.  I don’t have the car up and running yet, however just playing with the app it seems to work very well and looks great too.  It was around 12 Euros for the Canadian map version and has free app and map upgrades.  (this was important to me because the Nav system in my ’07 InfinitI is locked in late 2006 map data and cost a small fortune to update).  Although I don’t really need a Nav system for my day to day driving, simply being able to calculate the distance to a destination will let me venture closer to my range limits with confidence.

I’m testing apps to use as the main music player, I like winamp however the “default” app has the mini tray app that can be used over top of either the Nav or Gauges without requiring you to switch apps to change music etc.  I’m not sure about the size and usability yet though, that’s something that will probably have to be played with after I get the car running.

I have a system worth of stereo components that I put together for use in my F150, however since we don’t drive the truck very much I decided not to go that big with the stereo.  A slightly smaller/lighter version of that sound quality system may end up in the EV.

There are also browsers and movie players that would let me entertain myself or passengers while not driving.  The tablet connects nicely with my Iphone to provide 3G internet while on the go, however the gauges, music and Nav systems won’t require any internet access for normal operation.

Battery testing is coming along slow and steady.  Once I had 76 cells tested I decided it was a large enough sample group to let me calculate the average capacity and start grouping the cells.

The final ideal 3P group size is 55.451Ah so I played some Battery Sudoku and with some help from Excel grouped 72 of the cells into 24 groups each totalling either 55.45 or 55.46Ah.  Although this is a pain and time consuming it gives me the ideal battery modules that should all perform virtually the same.  Internal resistance was also measured and any high cells were weeded out of the groupings.  I’ve got some friends and co-workers playing with a software solution that would group the cells automatically however it seems that mental number crunching provides the best results.

I picked up a second PowerLab 6 to help me speed up the process so that I can test 2 cells at a time, which should cut the testing time in half.  I have to catch up on preparing the cell terminals though so progress has slowed at the moment.

I’m also in the process of welding the battery box.  I decided to switch from bolted aluminium to a welded steel frame that will have aluminium panels riveted in to complete the box.  Below is the outline of the box, there will be some triangulated cross braces added to stiffen up the finished box.  The basic frame is shown below, the odd shape is due to the location of the transmission and transmission mount in the rear of the car.

This should make a fairly lightweight but strong battery box.  The total weight of the pack will be in the range of 300lbs plus dc/dc converters and chargers so the box should be plenty strong enough.  The finished box will be bolted to the car for future serviceability.  The box will be insulated with 1/2″ foam and have heaters installed in the bottom.  I’ve gone back to the original design of 96 series cells partly because the new layout should fill the battery box evenly and completely.

I have completed the design on two PCB’s which are currently being manufactured.  The first is a cell log 8 breakout board which will allow easy connection and monitoring for up to 32 cells per board using 4 Cell Log 8′s.  There are relays and alarm outputs to allow easier use and mounting of the popular and inexpensive Cell Log 8S and 8M.  The PCB’s should ship to me any day now and once I get to test them out I will make them available to anyone who wants a simple and inexpensive cell level monitoring system.

The 2nd PCB is a much simplified version of the DC/DC converter charging PCB that can also be used as a platform for a pack voltage to 12v dc/dc converter with the correct configuration.

The simplification allows for multiple uses and I will probably use it for both cell preparation (charging and balancing) as well as act as a dc/dc converter that will keep the 12v system battery charged and balanced all at the same time.  This requires more wiring both at the HV pack level as well as the 12v output, however the extra protection that it provides is easily worthwhile.  Each module can run off of either a range of 36-75V OR 72-150v.  Using 1 1/2 boards would allow 108-225v input range which would cover many of the common builds and put out 12-15V @ 75A.  I haven’t decided on final packaging yet but an integrated fan will be required.  The on board mounting for the Cell Log 8 has been removed, however there is a location where a JST-HX style connector can be soldered to the PCB to allow the use of a Cell Log 8 with this board.

It’s been awhile since I’ve made an update but I have been plugging away on small and time consuming projects.

I’ve found that Murphy’s Law trumps the Law of Averages.  In the two 16S3P packs (96 cells) that I built I managed to have a single group with 3 of the smallest capacity cells that I’ve found so far.  This means that my total pack was limited in capacity to the total of those 3 small cells.  These A123 pouches are already smaller on average than their rated capacity so I’m not really getting 20Ah per cell, it’s more like an average of 17.8 – 18Ah on the cells that I have tested.  I’m counting on 53+Ah total to give me the range I’m expecting.  The solution?  Pull apart the existing packs and measure the capacity of every cell, along with testing the capacity of all the remaining cells so that I can throw them in a spreadsheet and find the average capacity and then try and group them in sets of three that total measured average capacity x3.  This will mean grouping the larger cells with the smaller to make sure that all of my cell groups are within a very tight range of average capacity.  It takes about an hour to test each cell giving it a complete charge/discharge cycle while measuring the capacity.  Both the charge and discharge are automated so although each cell takes an hour I only have to be there to load fresh cells in the charger and discharger and record the results.

Another small project I put together was a modification to give me a two stage charging voltage on my dc/dc converter.  When the car is “on” I want between 14.4 and 15v to run the lights and wipers and other stock automotive systems.  Since I will have a 12v lithium battery I still want to be able to charge it to an appropriate peak voltage, but I don’t want to hold the voltage there indefinitely and overcharge the cells so when the car is “off” I want the dc/dc output voltage to be roughly equal to the no load open circuit voltage of the cells.  The dc/dc converter will remain on to keep any parasitic loads on the 12v system from draining that battery as well as avoid the requirement to switch pack voltage to the dc/dc converter which would require another EV200 contactor.

The starting point is a Mean Well SP-320-15 power supply.

I completely disassembled the power supply to look at the board traces and figure out how the trim voltage works and how I can tie into it from the top side.

There are two wires soldered to the power supply PCB, I used orange because I had some and polarity isn’t important for the resistor. One wire is soldered to the LED lead “K” on the PCB and the other wire is soldered to the lead of R73 closest to the terminal strip. These two points happen to be parallel to the trim pot, so adding any resistance here puts it in parallel with the pot.

The relay is a simple SPDT 12v relay I had laying around, I picked this one because I wasn’t sure if I would need the NC or NO terminal to adjust the voltage in the correct direction when “off”. It turns out I used the NO (normally open) contact so any standard SPST 12v NO relay will work just fine. There happens to be an open area just a hair larger than the relay on the PCB so I stuck it in place with a small dab of epoxy.

A 2k resistor (I used a pot for testing, but settled on 2k) is connected to the NO terminal of the relay and one of the orange wires. The other orange wire connects to the com terminal of the relay.

I don’t plan on using all 3 V+ or V- terminals so I cut one of the V- terminals (beside the AC ground terminal) so that I could use it as the input signal to trigger the relay, I will simply connect this to the switched 12v from the ignition. I cut the terminal strip lead close to the PCB and bent it up leaving plenty of room to solder on my relay wire. I also need a ground connection but that just happens to be right next to it as one of the remaining V- terminals since they will be connected to the cars chassis ground anyways.

When 12v is applied to the new terminal (I labeled mine “T” for trim) the relay closes and the 2k resistor is now in parallel with the pot. This raises the voltage from 13.6v to 14.6xv.

Some of you may have noticed I decided to go with A123′s in my 944 conversion. I don’t need a lot of range, but I am hoping for quite a bit of power so these cells meet both criteria. It’s also hard not to borrow some of Crodrivers findings and he likes these cells so why not. Especially since it appears that he’s using them in his Concept_One electric supercar.

I’m sure one of his battery modules cost as much or more than my entire conversion including the car, but it is an elegant package and will put my foam insulated boxes to shame.

Visit Rimac Automobili for more info on his amazing creation.

These aren’t “new with warranty / cost a small fortune cells” I took a gamble on some grey market cells and these appear to be cells that were rejected and destined for recycling. All of the ones I’ve tested have good IR (1 – 1.5mohm), but only come in at 18 – 18.25Ah. Because of this the cells were castrated… well had their tabs removed. There is plenty of tab material still covered by the plastic casing, it’s just a pain in the ass to uncover and make useful without going to far and puncturing the cell. Below is a cell that is “half” done, the casing material has been removed but the remaining adhesive needs to be scraped off to reveal the aluminium and copper tabs.

With some of Yabert’s help on connection method ideas I settled on a simple sandwich type connection with block – tab – block – repeat. There are 4 aluminium blocks for each end terminal and 7 blocks for all of the main series connections. The battery shown below is only 2S3P for testing, I will be assembling them into 16S3P modules for the car.

As you can see from Yabert’s rendering above that there will be a lot of different blocks to connect these cells. Initially he had a line on a company that would laser cut the green parts for a decent price, but I would still have to make all of the red and blue blocks, then due to limitations on available material thickness to be laser cut it just makes more sense to make ALL of the pieces myself. Below are a few pieces from the first batch of parts used for assembly.

Each block goes through many steps before it’s done, first the material is cut to length, then marker holes are drilled using the CNC router, then the marker holes are fully drilled on the drill press, along with some parts that get a countersink, some threaded etc. Each 16S3P module has 65 of the “green” blocks above, 15 “blue” blocks, 16 “red” blocks and 2 large terminals shown below.

That’s a total of 98 blocks per module or 588 blocks for the 6 modules in the final design. The pink foam spacer in the center of the pack is just what I had on hand, I have 0.06″ plastic sheet that will be cut to size for the actual pack assembly. During assembly each side of each cell tab is cleaned with a stainless steel wire brush, along with the aluminium blocks and treated with No-Alox, this is another time consuming process but the initial results are worth it.

Above charging with my dc/dc converter charger, it’s simple and reliable but 3 parallel cells are too much for this method without some current limiting. During the charging process the dc/dc converters overheated and shut down, they do turn back on automatically when they cool off though, but I’m sure doing this too often would shorten their life span. The cells charged up perfectly to 3.5v per cell though. (Please ignore the lack of proper terminals, I have terminals for the high current connections, but I neglected to buy small terminals for this purpose)

The cell tabs first need to be uncovered, this is time consuming surgery and must be done carefully or risk damaging the cell. Then two holes are drilled in each tab to allow the screws to pass through that hold the blocks together. I created a jig on the CNC router out of MDF that allows me to align and clamp each cell and drill the 4 holes with a built in guides.

The jig is simple and effective allowing me to quickly and precisely drill the 4 holes I need. If I were to do it again I would probably find/make metal sleeves to line the pilot holes to keep the holes tight with repeated drilling.

I wanted to do some high current discharge testing to make sure that the connections are sound and don’t heat up at high currents. I was only able to test this pack to about 700A but all of the terminals and the cells themselves were cold and the pack only sagged to about 3.1xV per cell (measured ~6.25V under load). I can’t say the same for the load, I wasn’t exactly setup for 700A discharges and melted the insulation off some 4 awg wire and made my resistor bank hotter than I ever have before. OOOPS! The cells perform exceptionally well though in all tests I’ve done to date.

My final comment is it’s a good thing these cells perform otherwise all of this work to prepare and connect them just wouldn’t be worth it. I can’t wait for the day that a large prismatic has the same or better performance to these A123 pouches but already has 2 big screw terminals at the top.

The car has been progressing slowly, work has been busy so I haven’t had the time or energy to do all the things I had hoped to have complete by now. There is no drop dead completion date, so I will just keep plugging away and make sure things are done right. Just like everything else in this build decisions are made, then changed, then changed again! I finally have the batteries on hand. It’s not the Thundersky that I chose early on, it’s not the Headways that I switched to later. The winner is A123 and the 20ah pouch cells. They aren’t easy to get, and for a product that’s made in AMERICA (or Korea) the easiest way to get your hands on them is from China. The cells test incredibly well though, so I think it’s just the right cell for my car and my goals. From the cells I have on hand I will be building a 15.8kwh pack to get me started this should give me 60-100km of range if I drive nicely, or a lot of fun on my 17km commute to work. I’m still working on the details of the connection method but I will be using aluminum blocks/spacers to create the series/parallel connections that I need.

I have been putting off removing the transmission for months since I knew it would be a lot of cramped under the car work to get it out. Finally I bit the bullet and went ahead with the removal, and it turned out to be exactly as expected, not horribly difficult just time consuming and uncomfortable under the car with limited working space. I took this opportunity to strengthen the transmission mount at the same time, a seemingly common fix is to use a two part urethane to encase the stock rubber transmission mount to remove unwanted movement but unlike a steel or aluminum mount it won’t transmit all the gear noise to the cabin.

With the transmission out the gas tank removal was very simple and straight forward. With the gas tank out the hatch floor removal was also simple and straight forward. And finally with no hatch floor the transmission installation could not have been easier. I will get the remaining bolts torqued down and the new Stage 8 locking CV bolts installed then the drive train is virtually complete and should hold up to the extra torque from the electric motor.

I did a quick test fit of the locking 3 prong socket that I may use for my charging port, it fits well in the stock filler opening.

Battery boxes to come!! I also have the coupler back from Charlie of evcouplerconnection.com so I will have to slide the motor forward and reinstall the coupler. This time I will photograph the process a bit better along with the mounting of the A/C, controller, vacuum pump and throttle.

This update was in Draft form so long that many things had changed.  As it turns out there is a completion date (or dates)!!!  I have agreed to do a small informal presentation at work about the electric car project so it would be really nice if I could BRING THE CAR.  Completion date #1 Oct. 12th, the car really only needs to drive there and back.

With the exposure the car has received there is interest in showing it at the Global Clean Energy Congress, completion date #2 Nov. 1st.

To conclude this update is a scan of a small article on my electric Porsche in the Calgary Herald.

Or you can just click on the link below for an easier to read version online.

The Calgary Herald.

Since the coupler is on it’s way back for some rework with Charlie at evcouplerconnection the car is stationary, but I’ve been doing some testing with the Soliton1 off a ~50v battery pack.  I have the tach sensor hooked up and working (including rev limiter), I even tried the idle function in the Soliton, and it works very well, makes A/C testing a breeze (no pun intended).  After a few trips back and forth to the auto parts store I have my new A/C belt, it’s a goodyear gatorback “the quiet belt”.  Hopefully it lives up to it’s name.  The A/C compressor is mounted and working very well, and if my measurements are correct I should be able to leave the A/C compressor connected to the motor when I move it ahead to reinstall the coupler, making for fairly easy serviceability. I tested the vacuum pump, and although it’s pretty quiet it still makes some noise, I may or  may not put it in some sort of enclosure to reduce the noise a bit more.

Machining the A/C bracket:

As I test fit the Soliton1 mounting location I’ve decided to use more of the Bosch Rexroth extrusion because it’s so easy to work with, and also easy to mount accessories to.  A couple of years ago I built my CNC router almost entirely out of Bosch extrusion with very good results and very good reliability in a high vibration environment.

This happens to be the machine that I used to mill/engrave the motor mounting plate, A/C bracket, and the recently completed frame rail brackets to finish the motor mount setup.

The beauty of the t-slots and t-nuts that go in them is you can adjust and move the mounting location of something without leaving ugly holes behind.  So items are easily adjustable and movable/removable all with what amounts to built in lock washers everywhere.  There is a slight taper on the extrusion in the t-slot area so when a t-nut is tightened the extrusion acts like a spring (lock) washer.  Also being extruded aluminum it’s lightweight and very strong.   Pictures to follow next update.

I haven’t done any video on my blog because there simply wasn’t anything that a picture couldn’t capture.  Well the Warp11HV powering the stock Porsche A/C compressor is one of the first things that actually moves so it gets my first very lame video.

I did some testing on power usage of the A/C system vs the power to idle the motor.  With the A/C off, it takes about 250watts to idle the motor at 1000rpm, with the A/C on it took about 1300watts to run the motor, so all things being equal the A/C requires about 1050watts at 1000rpm (1.4hp plus a bit extra for the power used on the 12v side)  Not unreasonable for a car that will peak at about 270,000watts (362 electrical hp).   Sometimes it’s the smallest parts that take the most time.  Ever since my Evnetics hall effect throttle arrived, I’ve been wondering how I was going to attach my Porsche throttle cable to it.  I contemplated trying to find a way to attach the stock throttle cam onto the Evnetics throttle, but that didn’t seem appealing.  I thought of cutting off the stopper on the end of the cable and crimping on some sort of ring terminal that would attach to the Evnetics throttle arm.  I just wasn’t happy with any of these ideas, I simply wanted the stock throttle cable to attach to the throttle arm and be done with it.  Well it turns out that is easier said than done.

There is no question the Evnetics throttle is a nice unit, but the end user is left to come up with a solution on how to make it work with their vehicle.

This is one of those times that the CNC router shines.  I spent a couple of hours coming up with a simple design and making up the CAD/CAM files that would turn that idea into a real part (two parts actually, almost identical top and bottom).

The scrap piece of aluminum I was using was big enough to make three pieces, I did this just in case I messed one up, and sure enough I did mess one up, but still had two good ones that got used.

The final result is simple, and the machined aluminum matches the Evnetics throttle nicely.  Although it took 3-4 hours to simply hook the throttle cable up it’s something that I should never have to deal with again.

Since the car is stationary it’s a good time to do one of the last big jobs that I’ve been putting off.  Drop the transmission, remove the fuel tank, upgrade the transmission mount and install a set of locking CV bolts from Stage 8.  With a hoist and transmission jack this would be an easy task, however with a single garage and jack stands it takes a bit more work.  The transmission is out, but I’m too tired to take pictures, more updates to follow.