My Audience

Last week was a bit of a cliffhanger, so I think I need to finish (or at least update) that story.  You may remember I had a nicely charred connector going into the back of my fuse/relay box.  After a staring at it for a while I finally concluded that this wire was the 12v supply for my headlights.  Makes sense since the headlights don't seem to be working.  I clipped that wire off and plugged the connector back in and everything's working identically to how it worked before.  All I need now is the right bullet connector to put that wire back in and hopefully my headlights will work again.

In other news, the blog recently passed 10,000 views!  I had no idea it would turn out to be so popular.  The pace is getting ever faster too because in the last month alone I've had nearly 1,000 views.  It's also interesting to see where people are who are checking it out.  Some of the top hitters are United States, UK, and Germany, which all make sense since I know people in all those locations.  However, there are tons of people checking in from places I don't know people from like Latvia, Russia, Sweden, Australia, Ukraine, and the list goes on.  Even more fun than that, I get occasional emails from people with questions or comments, like my new penpal from the Ukraine who is converting his own Porsche 924!  If you've ever thought about it, please feel free to send me a message.  I love talking about my project, just ask my wife!  On to the latest progress...

This is a good time to check what's left to do (not that it'll ever be 100% done).
- I still have not finished installing and programming the BMS
- I need to install the DC-DC converter
- The charger could use some more optimization to boost output and efficiency
- There are a number of cosmetic things that would be nice to fix

For some reason I've been ignoring the BMS for a while.  Probably this is because it would be nice to have a solid day or two to install, debug, and calibrate the whole thing.  Even though it really shouldn't affect things, I feel like anything hooked up to the HV system shouldn't be in a state of debugging for an extended period of time.

Not having the DC-DC converter in has been inconvenient for a few reasons.  First, that would have avoided that first breakdown, and second, it's a pain to have to charge the 12v battery every night.  I actually started installing this just the other day.  I've got all the wires attached to the converter and mounted it, I just need to make the connections to the HV and 12v batteries now.  This is a Meanwell HRP-600 12v power supply.  It can put out up to 53 amps, and costs only $130, which is a steal compared to the DC-DC converters you see on EV websites that are "designed for EVs" that cost hundreds of dollars more.  Here it is with the wires hooked up and before I put it in the car.

The two little wires go to the HV battery +/- terminals, and the 10 gauge wires go to the battery terminals and the body.

Speaking of breakdowns, I also mentioned a while back that after the 12v battery died on me I still had problems after charging that battery.  I believe if figured out that problem.  In the process of troubleshooting, I wiggled the connector that plugs into the control board in the motor controller.  I'm pretty sure that either the 12v or ground pin on there was loose.  The wires are probably a little too short and were pulling on the connector.  "Soon" I will replace those wires with longer ones and recrimp the pins.  If the problem comes back I'll just solder them directly to the board.  For now it seems to be working after going back to the old wire.  I've had no problems in the last 50 or so miles.

The charger probably will get another look when I install the BMS because I'll have to reprogram it to accept a BMS input.  Until then I'll settle for 4.3 amp charging rate out of a standard outlet that doesn't seem to trip the breaker (unless I'm also trying to use my electric lawn mower).

As far as cosmetic work on the car, I replaced all the hardware for the sunroof.  Now when I take it off, the wind dam doesn't want to dangle in my face while I drive!  The next thing to do is get a new interior light that's dangling in front of the rear view mirror from its wires.  That and the lack of a driver's side sun visor and window crank knob are really annoying!

Well, I've taken up enough of your time for one post, plus I need to put the kids to bed!  Next time I'll tell you about all the problems I'm having with my cycle analyst.

Good News, Bad News Part 2

Good news everybody, the Porsche is finally registered!

The other good news is I can finally charge the car without having to open the hatch and the hood.  I installed this spiffy outlet where the gas tank fill spout used to be.  I also got a nice 12 gauge cable so I don't have to worry about overheating the wires anymore.

Now for the bad.  I also had my first breakdown!  I was driving to work and I suddenly lost power.  Luckily I had enough momentum to easily coast into a parking lot.  I realized the voltage on the battery was way low and quickly remembered that I haven't charged the auxiliary battery in about 80 miles!  I conclude that the power to the controller was so low that the brownout feature on the microcontroller shut it down before it started malfunctioning.  My kind and loving wife picked me and the battery up, I hooked it up to the charger, and took the jeep into work.

After work I pick up the battery and my wife drives me back to the Porsche.  I plop the battery in and away I go.  I'm about 7 miles from home and after 5 miles, the car starts shutting down again.  Now I'm not feeling so good because the voltage still reads okay.  I figure out that if I take my foot off the pedal, the controller seems to reset and I am able to limp home.

After thinking for a while, a friend comes over and holds the laptop for me while I drive.  The same problem keeps coming up, and luckily I get a clue from the RTD program.  When I lose power that the controller sends restart info to the RTD program, so it appears that the controller is momentarily losing power.  When it regains power it goes into "high pedal lockout" mode.  The controller will sense if you have your foot on the pedal when it starts up and won't allow the PWM signal to start until you take your foot off.  That explains why I can lift my foot off the pedal and keep going.

So now, what's causing this?  I've got a few theories and I try running a dedicated wire straight from the battery to the controller.  Luckily, this seems to work!  I drive 4 miles and have no problems compared to at least a dozen restarts in the previous 4 miles.

There's a relay I put in to power all the stuff I added (controller, pumps, fans, etc.) and it turns on with the ignition.  I've had problems from the beginning that the instruments seem to have a bad ground or something.  A fresh 12.5 volt battery only reads about 11 volts.  The headlight motor doesn't work either (forums tell me that anything less than 12 volts will cause this to not work) and when the headlights go on, the voltage drops even more.  In fact, it seems like turning on the blinkers would cause the controller to cut out.  I'm thinking the voltage gets low enough that the relay loses power and flips off momentarily.

I've known I need to fix this for a while, and it seems like now is the time.  I checked all the ground connections, and those seem to be good.  I look at the fuse and relay box and find a couple of loose wires!  Unfortunately, it is not obvious at all where these go, but it doesn't appear that they have anything to do with grounding or the headlights.  I snoop around for a while, and suddenly I see this!

Gah!  I'm pretty sure this is one of the 12v power supply lines going into the fuse and relay box.  This must have been loose for a while and the poor conductance built up heat and eventually fried this connection.  I have no idea how long it's been like this, and to my knowledge I've never messed with these connections.  I'm not sure how I'm going to fix this but I'll have to reroute power to the fuse box.  Hopefully this is the problem!

Let's end on some good news.  I've racked up 235 miles so far, so I've almost saved an entire tank of gas!  I can feel the savings rolling in!

Officially Electric

I finally achieved one of the major goals today.  Here's my story!

In order to register your vehicle, you have to have your car emissions tested.  Unfortunately, not having a gas cap or any of the emissions equipment the car was originally equipped with, I can't pass this test even though I'd pass the intent of the test.  So I basically have to have the emissions test waived.  To do that, I have to get an "Alternative Fuel Certificate" issued for my car.  To get that, it must be inspected, and unfortunately, that cannot be done any any old MVD office.  In fact there are only two offices in Arizona, the closest of which is 21 miles from my house.  I guess it could be worse if I had to go to the Tucson office.  My design of the car was for a 50 mile range, so that doesn't leave a lot of room, especially when you consider you can't test much until you get the car registered!

Luckily, there is a 30 day temporary registration option that I got back in mid June.  I've racked up 137 miles of testing since then, the longest trip being about 25 miles.  One thing I learned is my range is theoretically greater than I was planning.  The car is more efficient, ranging from 200-240 Whr/mile depending on how many lights I hit, and I was designing around 275-300.  Another way to look at it is I get a little more than 1 mile per 1 Ah on the batteries, and since they're 60 Ah batteries, I should get 60+ miles.  Of course I haven't really tested this yet, but it makes me feel a little better.  Also lucky, my friend, Joe, lives about 6 miles from the inspection office and he offered to let me charge a couple hours before I made it rest of the way home.

With my 30 temp plate expiring on Sunday, I took the Porsche on the journey this morning.  The most direct way to get there is on the highway, so I decided to add that to my list of new things to do for the day.  The car had no problems speeding up and keeping up with traffic.  I even got up to 70 mph at one point!  I pulled into the inspection area after consuming 19.5 AHr.  Three guys hop out of a little hut and come check out the car.  98% of the questions they ask have nothing to do with the paperwork they needed to do, and one guy even pulled out a camera for a few pictures!  One of them said they hadn't seen an electric conversion in over a year, which surprised me.  I'm guessing the electric vehicle tax incentive that went away 18 months ago has something to do with it.  5 minutes later I'm back on the road with my embossed certificate!

6 more miles to Joe's house and I stop to add about 14 Ah back into the batteries.  Then I'm headed back home.  About 2/3 of the way home a sickening feeling enters my stomach as a terrible melted plastic scent fills the car.  I feel slightly better when I see a truck pulling onto the shoulder with his hazards on, and much better when I pass him and the smell goes away.  10 minutes later I'm safely home with 48 miles under my belt for the day.  I figure I'm about 30 Ah down, so it'll take about 6 hours to top the batteries off again.

Now I just need to make a stop at the MVD (yes another one) to get the registration taken care of.  I'm hoping to get one of those alternative fuel license plates with a custom number.  I'll let you know what I decide on.  18 months, and the car is finally legal!

More Driving Stats

I've had the car registered for almost 2 weeks now and have racked up 90 miles of driving. I had some clients from Boeing in for a review at work this week and I got to impress them with the car.

Efficiency tends to be in the range of 210-240 Wh/mile depending on how many times I have to stop. I've got RTD explorer working and tracked the temperature of the controller. On a 103 °F day it got up to a peak of 129 °F at the end of an acceleration from 0-50 mph and quickly drops down to 124 °F. If I coast to a stop at a light, it's down to 117-120 °F within a few seconds and seems to stabilize there. So I'm guessing the temperature of the coolant in the system stabilizes to around 117 °F or less (<15 above ambient?) since it's no different after 11 miles of driving.

I've been experimenting with charging. I don't have a heavy duty extension cord yet, so I have to string two regular (probably 16 awg) extension cords together. Originally I had an old computer cable pigtailed to the inlet wires in the loop too. That was bad because that wire was 18 awg and it got hot! All the internal wiring is 10 AWG in anticipation of wanting to charge at 20 amps or higher. If I charge the car at 5.0 amps, the clamp meter reads 14.5 or so Amps rms in from the house 120v line, and a 15 amp circuit breaker would eventually trip. So I've either had to drop down to 4.0 amps or run a third extension cord through my garage door and plug into the 20 amp outlet in the laundry room. Not great for charging when it's 118 °F outside. At 4 amps it takes about 5.5 hours to charge 22 miles (around 21 Ah). At 5.3 amps it's down to around 3 hrs 50 min. When I get a 240v 30 amp outlet installed and am brave enough to try it, I should be able to charge it in about an hour if the charger doesn't get too hot.

In the meantime I've been working on the BMS. The head board is complete and one of the slaves is complete. I've been modifying the code Joe sent me and think it's about ready to test. Unfortunately I completely missed a bunch of connectors in my order and have to wait until July 2nd for Mouser to get them here, so I can't do any testing until then.

So with no car work that needs to be done, I'm focusing on a few things I've been neglecting around the house. My wife is really happy that I cleaned out the garage and she can park in there again! I also tried my hand at cleaning the air conditioner to try and make it more efficient. The bozos who installed the unit in my attic put it in backwards so the access panel faces into a wall! I've had problems with it not draining properly because there's a bunch of sludge built up in the drain pan that I've never been able to clean out. Well, we've got a ton of family coming over on Sunday and it's supposed to be around 118 °F out so it needs all the help it can get so I bite the bullet, got up at 5:30 this morning and head up in the attic. After nailing down some boards I can lay down on and an hour and a half of cursing I managed to get the access panel off. Another hour and I've vacuumed all the sludge out and sprayed down the evaporator coils with some cleaner. Hopefully it was worth the effort. It's currently 115 °F outside and 76 °F inside. So far so good but the forecast is for 122 today.

I've only got two more weeks on my temporary permit to test out the car. I'd love to have the BMS functioning by the end of that before I take the 40 mile trip to the MVD, so hopefully I'll have enough time over the 4th of July weekend to make that happen.

Stay cool!

Free Parking

Today was a momentous occasion for me, I finally drove all the way in to work and back!  My employer has  a solar array in the parking lot and they lease shaded parking spaces under there.  But there are a few fortunate people who get free spots for 100% alternative fuel vehicles, carpooling, and hybrid vehicles (in that priority).  I pulled into my spot this morning even though I didn't have a permit yet (they've had one set aside for me for about two months now, but wouldn't give me the permit until I started driving the car) and within 3 hours I already had my first parking ticket!  Luckily there's no substance to the ticket, and I now have my permit so I can park legally from now on.

Here are the stats from today's drive.
According to Google it's 11.2 miles each way, so 22.4 miles total.
Total energy consumed: 4792 Wh
Energy per mile: 214 Wh/mile
Theoretical max capacity of the battery pack = 3.3x70x60 = 13.68 kW-hr
% Battery consumed: 35%
Max battery amps: 162 A
Minimum battery voltage: 216 V

Unfortunately, RTD explorer apparently experienced a user error and I didn't get any data from the trip other than when it first started up.  Mostly I was wondering how hot the controller would get.  It started out at 104 °F and finished hot to the touch, but not so hot you couldn't keep your hand on it.  So maybe 120 °F at least on the outside?  Not too bad.  Now I get to sweat through 4 hours of charging.  Speaking of sweating, pretty soon I'm gonna need to get the AC working!

On the road

Happy Father's Day to all you fathers out there.  Today I celebrated by driving the car to church!  At 5 miles each way, this is my longest drive to date.  I got a  30 day temporary registration on Friday, so I've got a nice amount of time to test things out before taking the 20 mile (each way) drive into Phoenix to get all the registration stuff sorted out.

I didn't want to get the 30 day tag until I knew I could recharge the batteries, which means I can recharge the batteries now!  Last Wednesday was the first test.  Here you can see the mounting location for the charger.

Of course, mounting the charger means making another bracket.  Man, I've made so many darn brackets.  They look so simple, but to get this charger in took two full evenings of measuring, cutting, and welding.  Thankfully this is the last major fabrication I have to do at least in the foreseeable future.  As you could see in the picture above, I still don't have the charger permanently wired in yet, which is good.  I've had a few minor issues to deal with and reprogrammed it a couple times.  The voltage sensing circuit had to be calibrated, and I keep getting an occasional safety fault that trips and shuts things down.  Here's what it looks like when it's charging.

Set is the current setting.  Out is the actual current going into the battery.  IrmsIN is the RMS current coming in from the wall (not right at the moment). BMS is a signal from the BMS that tells the charger the max current it will let it charge at (currently hard fixed since the BMS isn't finished yet).  Then on the right, the top number is the voltage it will charge to and the one below is the current voltage.  The fourth like is the IGBT temperature, and finally the time it has been charging.

On Thursday night I'd worked out a few bugs and charged all the cells up.  I think 51 °C was the max temp I saw.  Considering it's about 100 degrees F out, that's only a 23 °F rise in temp, which is good.  On Friday, after getting my temp tag I took the Porsche on its first real trip - 1 mile each way to the grocery store.  Then today I put in another 10 miles.

I hooked up some instrumentation that keeps track of the voltage, current, and total energy consumed (among other things), so now it's time for a little post-trip analysis.  For some reason it didn't turn on for the first mile, so I only have data for the proceeding 11 miles or so.  I maxed out at 163 Amps to the batteries.  I have the controller set at 166 Amps max, so that checks out.  The min voltage was 203 volts, so if the nominal voltage was 235 (resting voltage), that's about a 14% sag at 2.7C discharge.  I'm guessing that most of that isn't due to the batteries, and mostly attributed to the 90 or so connections in the string.  If none of the sag were due to the batteries, that's about 2 milliohms per connection.  That's good enough for the aircraft industry, so it's good enough for me.  I consumed 2,345 Watts, so that's 213 W/mile.  Granted 11 miles is only an estimate, but that's really good for an electric car.  Also, I was consuming slightly less than 1 Ah per mile.  The cells are supposed to be 60 Ah, which implies a better range than I was originally expecting.

Soon I'll be hooking up the charger for good, which means I need a fancy plug in place of the gas cap.  I picked one of these up online.  It's a charging port for a boat so it should be fairly weather resistant.  I need a disc of metal to mount it to.  Unfortunately, I don't have 7/8 inch and 3.60 inch hole saws to cut it out with.  Luckily I'm still borrowing my buddy's lathe, so here goes nothing!

I'm making a lot of progress on the BMS.  Hopefully I'll have more to share on that soon...

The Master

I had an evening at home with the kids so I decided to watch a movie with them and put together the BMS master board.  

So, master board, what what's a typical day look like for you?  

Well, I take the battery info and give it to the charger and driver.

So you physically take the battery info and give it to the charger?

Well, no, I have cables that do that for me.

So, what is it that you actually do do?

I've got lots of IO's!  I know how to talk with an LCD!  I've got processing power, can't you understand that?  What the hell is wrong with you people?!

In other news, I finished top charging all the batteries, so now the total pack voltage is around 246 volts.  Time to take it for a spin!

There's a 35 mph zone in the neighborhood, so that's my first stop.  One mile up and back and I've got the need, the need for speed.  Out on the open road (well, Gilbert road at any rate) I do a 2.5 mile loop, max out at 50 mph and return home for a total of around 4 miles!  Now's a good chance to see if any of those connections are a little loose, which you can do by touching each one to see if it's hot (with your other hand in your pocket to avoid a deadly shock of course).  Everything seems in order.  The laptop battery wasn't cooperating, so no data from the controller.

The next day I can't help but boost the current to the motor.  Previously I'd had the motor current set to a value of 3, which corresponds to 3 / 8 x 500 x 5 / 3 = 312.5 amps of course.  This time around I toggle it up to 4, or 416.7 amps max to the motor.  The battery limit is still set to a value of 100, which anyone knows corresponds to 166.7 amps, right?  I take a spin around a 4 mile block and check the stats.  Controller temp has reached 102 °F (39 °C), both the motor and battery currents maxed out, I consumed an approximate 1 kWh, and I've got a huge grin on my face!  The battery current limit is actually limiting me to around 55 Hp, so I'll have to bump that up next time around.  Booya!