Let’s talk about Batteries

Back in 2008 I started my journey into the feasibility of building an electric car. At the time it wasn’t going to save any money as the component costs were simply too high. In 2009 I looked at it again, but with the perspective of what kind of performance car could I build for a reasonable budget. This changed the game and led me on the path that brought me where I am today. My 944 went from a 2.5L 4 cyl with 150hp to a 300hp monster with the big DC motor. This was unbelievably fun but proved unreliable and I couldn’t afford to keep fixing it so that’s where the 150hp Siemens electric motor came from. It was smooth, quiet, efficient and most importantly reliable. Here we sit 11 years after that initial change in direction of the 944 project turning from a humble commuter to an electric sports car and the 944 is going to become something I never could have imagined all those years ago.

The battery that made my car roll was LiFePO4 from A123, these were gray market cells, and worked alright. The power was there, but the reliability proved subpar, the pack was never fully built out before the next chapter began. Next came the CALB CA60’s which are still in the car as I write this, to say they’ve proved themselves is an understatement. The pack was 16kwh when it first went in the car, it was expanded upon a couple of times increasing marginally, and has also degraded over time, I currently have about 15kwh of usable capacity or just over 100km of conservative driving. In my search for new batteries I stumbled across BatteryHookup, these guys were mentioned in the last post, and will probably come up time and time again. Use code Robin to get 5% off your order and help support my future endeavors. They were selling what they called 5.94Kwh battery modules made by LG. The part that got me excited was the fact they were selling for $594 US, that’s the magical $100/kwh that the OEM’s are trying to achieve. So was this for batteries that only had 50% capacity remaining? No, this was for modules that were new and had NEVER been cycled. A capacity test came in at 180Ah of a rated 180Ah, or 100%!!!!!! The best part is battery hookup often has promo codes, and I was able to get 10% off plus discounted shipping making the deal even sweeter. I’ve since bought some BMW modules that test at 104% of original capacity (yep, also new) as well as Tesla Model 3 21700 cells that I’ve been building from fantastic small vehicle batteries out of. I have my first gamble arriving this Wednesday which is a lot of 1900 Sony VTC6’s that have discharged in the modules they were assembled into. I’ve recovered a number of these cells that came from another source and they are pretty resilient cells with only a handful not being recoverable. The icing on the cake is they come out to 77 cents Canadian after exchange/shipping/duty/tax per cell!!! Now assuming they aren’t all recoverable, the cost per cell goes up but I’m optimistic at being able to recover 80-100% of them.

There’s another player in this game, sadly they don’t have the friendly shipping to Canada that Battery Hookup has. However, the product offerings are considerably greater!! BigBattery often seems to have the same or similar products provided you live in the USA.

What’s the moral of the story you might ask? Back in 2012 my CALB CA60 pack (16kwh) cost more than the Chevy Bolt LG battery (66Kwh as new) that I just bought. If you look back in my posts throughout the years I make mention many times is that the reason I eventually upgrade the battery won’t be because the existing one is no longer usable, it’s because there is something much bigger and better that I can’t resist. The LG/Chevy pack is everything I knew the future would bring, though I didn’t actually expect the modules to be new.

The most exciting update for my 944 HV

After I blew up my Netgain Warp 11HV and Evnetics Soliton 1 controller I opted for a “safe and reliable” system in the Siemens/DMOC645 combination that were leftovers of the bankrupt Azure Dynamics transit connect project. I’ve had this in my car for years, and while it has been flawless, it’s not quite as powerful and exciting as the DC motor system that preceded it. The battery system is also a carryover, the CALB CA60’s have been fantastic however they are heavy and capacity is limited.

This is all about to change! I’ve been battery hunting for quite a while, seeing what’s available, what’s new etc. I found a deal on LG/Chevy Bolt modules from Battery Hookup: https://www.batteryhookup.com Use code Robin to get 5% off your order and help support my future endeavors. These are 10S3P modules comprised of LG 60Ah pouch cells. This is 180Ah and 36v per module or roughly 6.6kwh each. I have 10 of these modules on order to create a 100S pack or 360v nominal 66kwh total battery pack. Let me remind you that the CALB pack is currently about 15kwh. Now this is fairly large, fairly heavy, and simply won’t fit in my existing battery box. The solution? To remove virtually everything in the car, motor/inverter, adapter/coupler, torque tube and transmission. Split the pack up to 6 modules front and 4 rear, plus a small Tesla drive unit in the rear. This pack is just adequate to power a small Tesla drive unit from a power perspective, but it should work pretty well with some liquid cooling on the battery modules. The overall weight of the car won’t change significantly but going from 100km to over 400km of range will be incredibly exciting.

Each module is around 70lbs, making the total pack over 700lbs. Currently I have about 450lbs of LiFePO4. This makes it seem like the car will balloon by over 250lbs, however because of the change from the Siemens/DMOC to a small Tesla drive unit, the car will lose roughly 250lbs keeping things roughly the way they are.

I have the space to use either the small front, or small rear drive unit in the 944. I technically have the space for the large rear drive unit, however the battery system isn’t capable of putting out that much power. The small drive units are capable of 220kw which is nearly 300hp and should be a welcome change to the Siemens/DMOC coming in around half of that power output.

An Overdue Update

First I’ll say, the car is fantastic, full stop.

The drive system has been flawless, the Siemens AC motor is smooth and powerful. The Azure Dynamics DMOC645 has been great, I had the water pump feeding the DMOC fail and instead of stranding me on the side of the road, it simply throttled down the power to keep itself in a safe temperature range. I was able to gently drive home without incident.

The stock heater core in the 944 (which could very well have been the original making it 33 years old) failed, leaking coolant all over the interior. There is a plan shortly to remove the heater core and switch to PTC heaters in place of the stock heater core.

With various changes over the years more items have ended up in the rear of the car than originally planned. The front battery box was removed when I switched over to the Siemens motor, the 12v car battery ended up in the rear in the form of a 4S LiFePO4 battery pack. The DC-DC converter has always been in the rear but there was always a plan to move it to the front. The Brusa charger also lives in the rear. This wasn’t the original plan for weight distribution where I wanted 50-55% of the weight in the rear.

For this reason I’ve already started the shift forward, the 12v battery, DC-DC converter and the Brusa charger are migrating to the front.

  • 12v battery = 18 Lbs
  • DC-DC converter = 8.5 Lbs
  • Brusa charger = 14 Lbs

Now this only totals 40.5 Lbs, however it has an 80 Lb shift in weight distribution moving back to front. Or almost a 1.5% improvement right there.

The weights are in on the Porsche 914

The Porsche 914 ended up about 150lbs over the estimated weight, but that’s likely due to not considering the weight of the coolant and the use of steel battery racks instead of the planned aluminium ones.  The (almost) final weight is 1230kg or just over 2700lbs, although it’s a bit higher than your average 914 it also has quite a bit of power and the battery capacity to provide a lot of range.

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On the plus side the front/rear weight distribution came out perfectly which is probably why the car feels so good.  The front came out to 49.6% with the rear at 50.4%

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The car is an absolute joy to drive, it handles well, has plenty of power and cruises very nicely.  The 12kw EMW charger is finally up and running, it’s been tested at 5kw which is about the limit of my power source at the moment, I’ll do further testing on a 40 and 50A breaker when the charger is complete and mounted in the car.  A quick test drive to and from the scales yielded decent energy use results, however due to a cable issue regen wasn’t working.  A 92km round trip used 41.6Ah out of the 90Ah total capacity at speeds ranging from 80-125km/h.  That works out to about 250wh/mile which is pretty good for mostly higher speed driving and no regen.  If average energy use with regen comes in around 220-225wh/mile the car will meet it’s range target.  With some hypermiling and getting use to the car it shouldn’t be difficult to get the energy use down below 200wh/mile for 60-80km/h drives.



The old, the new, and what’s going on in 2015

Again it’s been so long I’m not sure where to start.  First the car is not complete, but it is nicely drive able (and a joy to drive at that).  Parts, ideas and plans come and go, today, and for the past year or two really there is one goal.  I want a reliable daily driver.  I’m pretty close to being there, I will get to the point that the car just isn’t going to need me anymore, it will just work.  I both can’t wait and dread that day.  It would be nice to just get in and drive, without thinking about the Ah counter, is everything working, how do the temps look today, I wonder if the battery is warm.  The flip side is that when I get there the car is “done”, and I think I’m ready for that.

The parts have been ever changing, here’s what’s in the Porsche  944 today, and what’s planned for the near future.
-Siemens 1PV5135 – Great motor, liquid cooled.
-DMOC645 Inverter – Also great, but needs a “GEVCU”
-GEVCU – Seems to work great, not quite as feature rich on the traditional IO side as the Wolftronix, but more capability on the CAN side
-CALB CA60FI x83 (the volt pack and range extender, are no longer viable options I may look at more CALB’s)
-Azure Transit Connect DC/DC converter, sorry the name has failed me, I’ll update the part number – Liquid cooled, works great
-Mes Dea vacuum pump – A bit noisy, to be replaced by the Transit Connect pump-Cheap Chinese temp meter to turn on/off the battery heating
-Cheap Chinese temp sensor to turn on/off the battery heating system automatically
-JLD style volt meter, measures the charging voltage (120/240v) and selects series or parallel for the battery heating so regardless of what I plug in to I get full power to the heaters
-Heated seat pads (drivers seat only for the moment, wonderful on chilly days when you don’t necessarily need to turn on the main heater)
-Brusa NLG513 Charger – Bought two, installed one, one is enough for the small pack.
-JLD404 – Not much to say, it works and hides in the glove box, to be replaced/augmented by the EV Display

Items to be installed:
-The Vacuum pump mentioned above
-EV Display main display to be installed where the factory clock was located
-Joying Android car stereo
-Various suspension and normal car tweaks.

The Joying Quad core Android car stereo has a radio, bluetooth, GPS and 7″ screen and some physical buttons so it should give a better car experience than the Samsung tablet.  I could never keep the tablet charged (android battery life sucks even when it’s sleeping) and in it’s happy temperature range, the Joying is controlled by the ignition and operates like a traditional car stereo (with the extended Android boot up time of course).  It comes with the Torque Pro app installed and was designed to work with it, apparently there are two bluetooth radio’s, one for connecting to the Torque device and the other to connect your phone.  It has all sorts of functionality related to phone display and screen mirroring that should provide a nice experience and lots of features when desired.  It has a volume KNOB, I’m a fan of controlling the volume on devices with a knob. It has built in functionality for a backup camera and/or dash cam.  The backup camera add on was $20 so why not, I got use to it in the Infiniti and although the Porsche is much smaller the visibility is also much worse.  And I find pedestrians don’t tend to notice I’m backing up because of the silence, so if I can keep a better lookout for them there’s less chance of an accident.



I’ll give a full review and comparison of the Joying stereo vs the Samsung tablet as well as the Nexus tablet that’s in the Porsche 914.

This update was supposed to come out before the posts about the 914, but I never got it finished so this is much less of a surprise.  The price of oil has dropped significantly, the company I worked for (note the past tense) made control and automation systems for the oil industry.  When I first started we made SOFC test stands (Hydrogen fuel cell test stands), that was interesting stuff, oil rig  stuff, not so much but the job was stable with good benefits.  I and a large portion of the company were recently let go, we got a decent severance to make us just go away.  A friend and fellow EV conversion owner (he actually has 3) has been trying to get me to start something with him in the EV conversion space to augment his existing automotive repair business.  What is a freshly unemployed EV  fanatic supposed to do?  Take that offer and run with it.  I am now a full time EV Converter at Cardinal Automotive, (Go check it out, follow us on Facebook) this is what I’ve wanted to do for many years, but it’s still a bit scary to think this IS what I’m doing.  It’s an iffy time for EV conversions, on one hand there are OEM EV’s to get people familiar with EV’s and what they can do.  On the other hand there are OEM EV’s for a customer to run out and buy TODAY.











Driving the Porsche 914

ElectraFest 2015 was a great show, lots of interesting people and nice cars.  The majority of vehicles were OEM’s but there was a handful of conversions at the show.  The single most attractive feature that most people found with the 914 was the 200+km range.  This seems to be a mental threshold where all but a few people said “That would work for me.”  My 944 with 100+km range doesn’t get the same response with probably 50% of people saying that’s not quite enough.



The lead up to the show was hectic and we actually left at the last minute not giving us much extra time.  The 914 is an old car and as I found out not all of the grounds are good.  I had reused a factory ground point for the inverter wiring and this turned out to be an issue.  I wasn’t getting a good enough ground for the inverter to call it “ground”, it was close but not close enough.  This caused the inverter to boot up, but the signal inputs (mostly grounded/floating) weren’t registering correctly meaning the inverter wouldn’t fully turn on.  This took hours of troubleshooting and wondering if something in the inverter itself had failed.  In the end I ran dedicated ground wires and all the problems went away.  The car runs great and after some software tuning the regen/shifting and throttle feel pretty good.  The potentiometer on the brake pedal gives a nice feeling of power brakes with the adjustable regen on the completely mechanical brake system of the 914.  The regen disable signal runs through both the clutch pedal microswitch and the center console regen disable switch.  There is a small amount of regen dialed into the throttle pedal when fully released to mimic engine braking.  When the clutch pedal is pressed it disables regen from the off throttle position and/or regen based on the brake pedal.  This makes shifting easy and the car is quite fun to run through the gears.  Starting in 2nd it feels really good with plenty of torque and is easy to shift to 3rd and beyond.  1st and reverse aren’t really needed, which is okay as they are somewhat segregated in the transmission requiring a firm push to the left against a spring plate to engage them.  2nd gear is good for forward or reverse using the electric forward/reverse switch in the center console.

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The cooling system is installed and being evaluated for both size and effectiveness, the Siemens Inverter seems to produce more heat than my DMOC645, but it does have a built in DC/DC converter as well.  The overkill cooling system in my 944 has a temperature rise of 3 degrees C over a 30-40 minute drive, depending on ambient temperature 10-20C is perfectly acceptable in the 914, however driving at highway speeds for more than an hour will have to stay within the thermal limits of the Inverter.  The pump and a single low speed fan run all the time, there are two higher speed and higher power fans that will be controlled by the Inverters fan output to assist in cooling when required.


The stereo has been updated with a Bluetooth capable media player that can connect either to the tablet in the center console or a smart phone to easily accept phone calls and stream music.  The front factory speakers are in the kick panels which is close to the ideal location in most vehicles as far as imaging goes.  The aiming isn’t perfect but it’s not bad and works better than most door locations.  The problems came in the speaker mounting, the aftermarket coaxial speakers have a protruding tweeter that doesn’t allow the speaker to sit flush with the housing and mount the way the factory speaker would have.  Because of this the front and rear wave weren’t isolated so there was ZERO bass.  The solution to this was to design and 3D print speaker spacers that allowed the speaker to be sealed to the front of the enclosure as they were meant to be.  The sound is much better, but only as good as a 4×6″ speaker can be, I’ll do some testing with a small and lightweight subwoofer to augment the low end.

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The 3D printed spacer is visible through the grill and surrounding the speaker, printing in black ABS blends the part with the existing plastic housing.

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The Tachometer is connected and working properly, the existing set up was for the Porsche 928 which had a V8, the 914 was a 4 cylinder car so the output pulse count had to be adjusted.  This wasn’t too difficult to find in the software, F_out_Factor lets you change the pulses per revolution which was set to 4 for the V8 and needed to be changed to 2 for the 4 cylinder (2 pulses per revolution).  Although not completely intuitive the Siemens software is quite flexible and allows most important parameters to be adjusted easily.

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The dash and door panels had a few cracks from age (what car from the 70’s or 80’s doesn’t have a cracked dash?)  This is now a thing of the past and now looks quite exceptional thanks to a vinyl repair shop, they did some amazing work, recovering the tops of the door panels and fixing up the dash.  The car looks so good now I’m probably going to get a quote from them to fix my 944 dash, it has a couple of similar small cracks.  Between that and a new windshield my 944 can have a similar facelift.




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We’ve had the car out to a few shows now and the response is overwhelmingly positive, and the more I drive the car the more I love it.  It’s still a bit quirky, it is of course still a 1972 Porsche 914, but the driving experience is tough to beat!  Remove the top and cruise around on a sunny day and the EV grin multiplies.  The Siemens power system is perfect for a car this size and weight, there is plenty of torque and it accelerates very nicely, it cruises smooth and quiet and is simply a joy to drive once you get the hang of that 1972 gear box.  Yes it does take a little bit to get use to, it’s not quite the same as a modern manual transmission however it does work very well and shifts smoothly when you get the hang of it and where the gears are located.

The Porsche 914 next to it’s modern equivalent the 2010 Tesla Roadster!

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The to do list is getting shorter and shorter and the car is driving better and better every day.  It won’t be long till it’s ready for someone else to enjoy this beauty every day.



ElectraFest 2015

For those of you in the Vancouver area you may have already heard about ElectraFest 2015.


We will be bringing the 914 to the show, come down, say hello and check out the car.

914 Progress, LED’s all around

The Porsche 914 trunk area had been abused for decades, a hole for this, a new hole for that. All of those holes are filled and finally painted.  The remaining holes are for the Siemens Inverter, the main power input, motor output, cooling hoses and DC/DC output all required routing outside the trunk area.  The repair process went fairly smoothly however it was much more time consuming than I would have expected.



Repaired and painted:

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The trunk carpet from 914 Rubber fits nicely (sorry for the varying white balance, the car didn’t change colors!)

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Although the inverter barely has any miles in it, the conversion that this piece came out of is a number of years old now and it’s showing it’s age.  The casing was stripped down and repainted as well to match the the fresh install, can’t have the center piece of the trunk looking old and ratty.

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The trunk with new gasket, new light, new roof holders all installed and the cooling lines connected to the inverter.

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There is still enough trunk space for a few bags or other small cargo including the hard top that can be removed and stored in the trunk above the inverter.


New LED headlights, new LED turn signals, new gaskets, new boots.  The 914 Rubber kit included boots and gaskets for all of the turn signal related requirements, everything fits nicely.  The new front trunk gasket is also in and fits very well compared to the old multi piece version that was falling apart.

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New gasket for the tail light housing to car, and more LED bulbs.  Although the inverter has a very good built in DC/DC converter there’s no need to waste power, this should help keep the load on the 12v system to a minimum as well as brighten up what were otherwise dim lights all around.  The new tail light and front turn signal lenses are in transit and should complete the transformation nicely.

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With the re-arranged Volt modules in the front of the car, the stock plastic covers didn’t fit properly.  Now modified slightly they fit nicely and continue the clean appearance through the front of the car.  I have some terminal covers designed that will go over the positive and negative terminals to make the front area touch safe.  These will be 3D printed and tweaked as required to fit the various requirements and cable terminals used.  A fuse cover is also in the works that will be 3D printed and will complete the process of making the front trunk area touch safe.  There isn’t a lot of space left, but some small items or a tool kit could easily be stored up front.

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Excellent progress on the Porsche 914 and going up for sale

The Porsche 914 has one major thing that my Porsche 944 didn’t have, RUST!!


This provides a time consuming challenge that I simply didn’t have to deal with before, but it will all be properly repaired and give the car many more decades of service.  Another problem is along with being 43 years old, the car was a previous EV conversion, so instead of dealing with stock parts and pieces there was already one level of modification, odd wiring and changes that made it difficult to figure out what parts are stock, what parts are missing and what parts I don’t even know are missing.  The car will be put back as close to stock operation as is practical in an EV conversion, and be a great example of a 914 regardless of the drive system.  Any pieces reused from the original EV system have been cleaned up and restored/repainted where required to make the car look as good as it performs.


The front trunk area is complete, this area holds two liquid heated/cooled Chevy Volt modules in parallel reconfigured for 133v nominal and 90Ah.  Two of the temperature controllers are mounted to the front of the Volt module on a 3D printed bracket.  One controller monitors the center front battery, the other monitors the lower rear battery in the back of the car, either one will trigger the Volt heater to turn on if the temperature is below the preset threshold.  Gone are the plans of incorporating the gas heater, mainly because there is a nice included Chevy Volt electric heater that came with the battery pack, and with the doubling of the battery pack space is at a premium.  This car also likely won’t be driven in extremely cold weather, so a heater that works down to -5° or -10° should be plenty.





With the gas heater out of the equation it became necessary to incorporate a heat exchanger into the stock fan box that will transfer heat from the coolant heated by the Volt battery heater into the cabin.  This makes for a smaller and fully electric solution that will have a small impact on range but keep both the batteries and passengers warm on those cold days.


The area formerly occupied by the fuel tank is now home to another Volt module in a stock configuration of 111v nominal 45Ah, it’s parallel partner is located in the rear of the car beside the motor & transmission.  The pump and stock Chevy Volt heater are located below the Volt module, a repurposed Subaru overflow tank serves as a reservoir and fill tank for the coolant.  It fits nicely with the contour of the space and almost looks like it belongs there.


The instrumentation for the car has all arrived and been configured, this consists of an EV Display 450v version with bluetooth dongle that allows it to talk to the Torque Pro app installed on a Nexus 7 tablet that will reside in the center console in a 3D printed mount.  I finally installed this same system in my 944 as well, and for daily instrumentation it’s simply amazing not to mention so much more intuitive to read than the JLD404.  It may seem like such a simple thing, but with the JLD404 you must know the pack capacity since it starts at zero and counts up.  It wouldn’t be difficult for anyone unfamiliar with the car to just drive it till it stops because there is no indication of when the battery is “empty”.  The EV Display and Torque app let you program in the battery capacity as well as provides a fuel gauge that can have a programed empty buffer.  IE when the fuel gauge reads zero the State of Charge may be 10% which would allow the car to limp to a charging station.  The Ah counter itself starts at the battery capacity and counts down, IE the 90Ah pack in the 914 will start with a 90Ah reading and decrease towards zero as energy is used.  The Torque app also allows programmable warnings for each gauge.  Once the pack drops to 10Ah for example the that gauge will start flashing to alert the driver that it’s time to recharge.  The same can be done with temperatures, voltages, or any of the other parameters incorporated into the display.



Above you can see the 3D printed Nexus mount, the 3D printed temperature controller mount and the machined bracket for the Bosch throttle.

The new rubber parts have arrived from 914rubber.com, they have an excellent selection of just about every rubber piece that was originally on the car.  These parts aren’t exactly cheap, mainly because you need to replace every rubber part on the car because after 43 years very few of them have survived.  The rubber kit that they provide is excellent, and included parts that I didn’t even know I needed as they were missing from this car.


Due to recent changes in situation, this car will be for sale at the end of the conversion and restoration.  Not only is this going to be a 200km+ electric car, it will be a restored 1972 Porsche 914.  The interest and attention that these cars gather at car shows is amazing, my 944 drew a lot of attention, interest and questions at last weeks local car show.  Not only will you have the coolest (and greenest) car on the block it will gather a bigger crowd and get more attention than a $120,000 Tesla and you don’t have to spend anywhere near $120,000 to get it.

The car has been outfitted with the 4 piston big brake kit on the front along with the 911 suspension upgrades and 5 bolt conversion from Renegade Hybrids.  The rear retains the stock suspension and calipers, however has the same 5 bolt conversion as the front that allows the use of more modern Porsche wheels.  This car stops just as well as it goes!


The car is currently outfitted with lightweight 16″ Fuch wheels and Falken 205/45-16 tires which have a good balance of performance and efficiency.  The wheels will be cleaned up and the centers will be refinished to return them to the period correct black center.


The headlights have been converted to LED’s, using the same exceptional 7″ round Trucklight headlights that I installed in my 944, they give HID type performance with even lower energy use.  They are one of the few DOT approved LED headlights available at the moment and well worth the high price tag.




The front and rear of the car gets similar treatment with LED’s all round, parking lights, turn signals, brake lights, backup lights all LED!



The licence plate lights, trunk light and dome light also get LED treatment, this is more important than it sounds, these older VW style interior lights don’t provide much light with the stock bulbs, switching over to LED provides a much brighter and more usable light inside the cabin and trunk.



The dashboard gauges are also being outfitted with LED’s to improve visibility of what are otherwise dim and tired looking gauges.  A replacement multi gauge is on route that will complete the stock trio of instruments and connect to the EV Display to drive the fuel gauge portion along with the low fuel indicator.  Other indicators including a green light to show ECO mode is on and other functions/warnings as appropriate.



The front and rear bumpers are out for repair and rechroming.  The mounting brackets were, you guessed it, RUSTY.  This will all be taken care of and clean, solid and beautiful bumpers will go back on the car.  The remainder of the trim is polished aluminium, it appears Porsche saved weight wherever possible and instead of using chromed steel parts they used polished aluminium.  These parts will be cleaned and buffed to restore their appearance as well.

The ultimate EV question, AC or DC

In the world of DIY EV’s there are many choices to be made, type of donor vehicle, automatic or standard, clutch or  clutchless, battery size, high voltage or low voltage, but one of the biggest ones is AC or DC motor & controller/inverter.  I have the benefit of having used both in my 944, same car, same battery, same transmission set up.

Water cooling3


I’ll list the main points first and go over them in more detail individually.

– Cost

– Performance

– Reliability

– Driveability

– Maintenance

– Heat

– Efficiency


Almost all EV Conversions have a budget.  Paying retail the DC system is almost always cheaper.  On paper this gets even more one sided if you consider a used forklift motor and performing some modifications to make it “more” suitable for EV use.  On the other hand with more OEM EV’s on the market and the availability of surplus and salvage pieces the prices can drop significantly below “retail”.  On the other hand if one of the HPEVS systems fits your performance needs they are priced quite fair.  My DC system was purchased new and used some of the higher end pieces available.  The Warp 11HV was not a cheap motor, the Soliton1 was also a fairly pricey piece.  Due to the demise of Azure Dynamics my AC system was less than half the cost of my DC system.

If you simply look at 0-60 times and HP/Torque numbers the DC system was in a different league, with almost 300ft-lbs of torque and 270HP the car was fast and powerful, 0-60 in 4.8 seconds with traction problems, with the right suspension set up I’m sure the car would have gotten into the mid to low 4’s.  The AC system while still fun, simply doesn’t come close, 220ft-lbs but less than 150hp.  It’s more than enough for a daily driver in a vehicle of this size, but it’s no longer faster off the line than almost anything I could pull up against.

On the surface it’s no question, the AC system has no brushes or wear items with the exception of bearings.  Many of the AC motors are sealed including the Siemens motor I purchased.  This virtually removes the possibility of contamination, either dust/dirt/rocks/snow/rain/fluids from damaging the motor.  The electronics are actually more complicated than the DC system, so long term reliability of the electronics will depend on the design and ruggedness.

A very minor pet peeve of the DC system was how well the car coasted, normally that would be a good thing, however if the traffic in front of me let off the gas the engine would slow them down slightly, when I let off the throttle the car coasted really really well, so I had to use the brakes a lot to avoid getting too close to the vehicles in front of me.  Same with going down a hill, the car just coasted too well and I was always catching the vehicles in front of me.  I was always on the brakes with the DC motor, being on the brakes means wasted energy and momentum.  The AC system is about as opposite as a vehicle can get.  I almost never have to touch the brakes now, regen is set up on the throttle pedal and I can drive the car 90% of the time without removing my foot from the throttle.  I capture quite a bit of energy that would otherwise be wasted as heat and traffic jams are really not that bad anymore.  I can speed up and slow down using the throttle pedal and cruise at any speed, there is no minimum speed like a manual and I’m not riding the brakes like an automatic.  I couldn’t be happier with the driveability of the car.

For the first time in my EV I’m working on new things and tidying up loose ends that I never got to before.  The car just works, I’m not worried about brushes or heat, I look at the pack temperature if it’s chilly to make sure I’m ok to use regen (charging batteries below zero is bad, that includes regen charging) and just drive.

With a liquid cooled motor and controller and the fact I went back to the stock radiator and two loops there is no worry about heat.  The inverter typically reaches 5 degrees above ambient temperature at the end of a drive, the motor fluctuates based on load but comes down quickly with the cooling system.   Again I no longer have to worry about heat and how long my motor is going to last.  The stock radiator is overkill but keeps things nice and cool even without the use of a fan.

This is where things start to get interesting.  In theory there isn’t much difference between an AC system and a DC system, perhaps a few percent which could easily be overcome by driving style.  In reality there are a large number of factors that together have significantly increased the efficiency of the car.  First there is power, sure it’s not an apples to apples comparison, the DC system had almost double the power, but with double the power it makes it easier to “waste” energy, accelerating a bit faster than you should, passing or driving a bit faster than ideal.  Many people would choose the DC system over an AC system to get higher peak power, so I’d say this is a fair comparison to leave in.  Next is regen, now this depends on where you live, how you drive and how regen is set up in your vehicle.  For me with regen on the throttle I use it all the time before mechanical brakes.  When I first set up the GEVCU I didn’t have the brake lights connected so I have a very small amount of regen configured, it basically mimicked engine braking and let me slow down when traffic slowed down without riding the brakes.  To come to a complete stop I had to use mechanical brakes almost all the time.  Energy use was already down significantly compared to the DC system.  A conservative drive in the 944 with DC was 300wh/mile, right where the rule of thumb says I should be for a roughly 3000lb car.  I was able to get it down to 275wh/mile with ultra conservative driving, but this took a lot of work and just wasn’t much fun.  On the other hand a few heavy accelerations put energy use up around 350wh/mile and spirited driving resulted in almost 400wh/mile.  From day one and very limited regen the AC system was around 250-275wh/mile with average driving, no attempt to  drive conservatively.  With more aggressive regen enabled that average energy use dropped below 225wh/mile, and conservative driving resulted in 200wh/mile.  This is all mixed driving with some 60km/h, some 80km/h and 100km/h zones.  The comparable numbers are, between  300-350wh/mile for the DC system is around 225wh/mile with the AC system in average driving, and 275wh/mile for the DC system vs 200wh/mile for the AC system with ultra conservative driving.

The range of an EV is just an extrapolation of it’s efficiency but I wanted to point out how significant the difference is with the same car and battery.  The pack is 16kwh, but ideally shouldn’t be discharged past 80%  very often, this gives us 12.8kwh of energy to use on an everyday basis (I don’t use that much but we’re comparing numbers here).  We’ll use 325wh/mile as an average of the normal driving with the DC system, this results in 63km or just shy of 40 miles of range, and conservative driving bring that up to almost 75km or 46miles.  Due to the efficiency increase the AC system is 91km or almost 57 miles with average driving and 102km or 64 miles of range with conservative driving.  Now of course your results will be different, but this is the difference between a 1986 Porsche 944 with a Warp11HV and Soliton1 vs Siemens 1PV5135 and DMOC645.


I’ll start by saying I wish the car had a bit more peak HP, it’s not bad, but I think that a 150-200kw AC system would be amazing in this car, sure it would decrease the range without very careful driving but it would be worth it for day to day use.  Second I’m amazed at the difference in energy use switching from DC to AC* (*in this specific situation/car/components).  I love this car, no question about it, if I were to do it over again I would have kept the clutch in the AC system, first gear is amazing, but like an ICE you need to shift fairly quickly and without a clutch that’s a 2 second event which kind of kills your speedy acceleration.  I have yet to test it but I’m pretty sure my 0-60mph time would be faster in 2nd gear only instead of being quicker off the line but a slow 1-2 shift.  I would probably be happier with the power level of the car if I had kept the clutch.  This issue didn’t exist with the DC system, it had unbelievable power from 0-5500rpm with no obvious decrease in power within that range.  1st gear was unusable and traction was even an issue in 2nd gear at times.  In short I would never build another daily driver with a DC motor, but I would use a  DC motor for a toy, or something that might make it to the track or autocross event if an AC system at the desired power level didn’t exist or was simply too expensive.  (I still have the 11HV, and one day I might repair it and use it in something else with a Zilla 2k, unless of course Tesla drive systems become available and usable with 300kw+)