Thanks to the fine folks at KTA-EV, I have a new Elithion main board. I still need to add some more EMI shielding (for the faults that occur during regen), but for the most part, it is working well.
Now I need to figure out why the GFCI is tripping when charging. (Hint: probably had to do something with switching the house over to the underground power). Will keep you posted.
While adding EMI shielding to some of the comm wires, I accidentally dropped one of the wires with exposed shielding onto the battery pack. Nice little spark, but now all but 1 of the banks are not reporting. *sigh*
So now I’m talking to the Elithion support person to see what I should do next (other than pull my hair out).
During a test drive I found that I am still getting bank communication faults with the BMS. Specifically banks 3,6, and 7. In order to help solve this, I’ve found some wrap-around EMI insulation in McMaster-Carr. We’ll see if that solves the communication issue.
Well, I was warned, and I forgot. I was reminded again, and lo and behold – there were loose battery posts. 3 of them.
So, I tightened them up, and charged the batteries, and sure enough – the BMS fault during charging is now gone.
Next step is to take Sparky driving and see if the acceleration also causes faults – I sure hope not.
On the drive home, the BMS decided it was a) too hot, b) over voltage, c) under voltage and d) really confused as to the state of charge. Sparky is hereby grounded until further notice. 🙁
So, what I need to do is figure out the following:
a) why are banks of communication failing during acceleration?
b) why are banks of communication failing during charging (different banks mind you)?
c) why is the BMS not remembering the state of charge?
d) why is the BMS not presenting the correct state of charge via the 0-5v output?
Lots of work ahead for me.
I’ve gotten the computer installed and working. It does some very simple processing, that (to be honest) should have been handled by the motor controller.
The embedded computer measures the outside temperature of the motor, and then turns the motor fan on or off, and changes the power level of the motor controller.
Simple stuff, really. I’m sure *someone* could have done it entirely in hardware, but being a computer programmer from years back, this was a better way for me to go.
I’ve been playing with the Parallax Stamp computer and have come to this conclusion: it is fun. 🙂
My main process is going to have these steps:
main:
read motor temp
if (temp < 130C) use high power, fan is off
else if (temp < 145C) use medium power, fan is off
else if (temp > 150C) use medium power, fan is on
goto main
This loop will only use 2 relays (one for fan, one for power control). If I were to use low power setting, I’d need another relay.
I’m hoping to install the computer this weekend, but the weather may delay that (getting REALLY hot here in San Diego). At the very least, I hope to replace the power supply for the BMS with something much smaller.
I’ve gone and purchased a small embedded computer to read the motor temperature and enable/disable the fan for the motor (www.parallax.com). Nice stuff, very easy to work with.
However, since I now have this computing capability, why not use it to set the power settings for the controller as well? The idea is that when the motor is cold, allow more power to flow into the motor, and when it is warm, turn down the power. Azure Dynamics has 3 power settings available (max, norm, economy), and that is selectable by resistance into a line into the controller.
Hmmm. This is gonna be fun. 🙂
After getting email from Azure and some really nice folks on the 914 conversion list, I have set the power limit for the motor to 30kw. I’ve also installed some custom-made airscoops.
Net result: no overtemp on the drive home. Yay! We’ll see how this works out for the summertime, but this means I can drive home now without a long stop somewhere. (FTW == For The Win, if you aren’t into the geek slang).
Here’s a picture of the custom airscoop:
Well, I added a 10 inch fan to cool the motor, and while it did to *some* good, it didn’t do enough. I’ve sent data to Azure Dynamics to see if they have a clue what’s up. If I can’t find a way to stop the motor from overheating, I’ll have to find a new motor and controller combo.
On the drive home it went into overheat mode at the 7 mile mark (out of 17 mile drive). Obviously, the removal of the rear air dam and the addition of the engine compartment air dam did not help.
Next stop – air scoops and fans.
After some struggle, I got the new air dam in place, and took a video of the airflow. Attached are the three videos (in time order): before_mods, after_rear_valence, and after_air_dam. The videos show the yarn on the motor while driving. The yarn seems much more lively in the last video.
In order to figure out where the airflow is and is not, my mechanic suggested we use a really old technique – tape yarn to the car and see where the wind blows it. Well, we did that. We taped a whole bunch of yarn, courtesy of my charming wife, to the motor, transmission and engine compartment. Then we video taped the yarn whilst driving. We discovered that with the big battery box above the motor, there wasn’t very good airflow from the top to the bottom. Then we removed the rear valence (an air dam just below the rear bumper – used for the now non-existent bumper) and video’d again. Much better airflow. So now, I get to replace the air dam in front of the engine compartment with something bigger, and video again. If this doesn’t improve the airflow, then it will be time for air scoops.
Well, it is the motor that is being overheated. Not surprising, considering there is a huge battery pack just above the motor, blocking airflow upward. I’m now looking into how to install a fan or installing some ducting or both.
Argh. Now that I’m driving the car more, the bugs are starting to come out. On the drive home today and yesterday, the controller has gone into over-temp protection. I need to figure out what is going on. 🙁
I’ve replaced all but the headlights with LEDs and seen a dramatic decrease in current during their usage. What was interesting is that I did not have to replace the blinker relay (apparently you need to on newer cars). I got the LEDs from www.superbrightleds.com.
I’ve also made regen a normal part of driving, so I’ll need to put back the circuit that lights up the brake lights when regen is active. The reason for this is to make shifting easier – when regen is active the motor quickly drops from high RPMs to almost zero within a second or two.
So I’ve done another set of calculations, and I’m getting 350wh/mile driving to and from work. Most of this is freeway driving with some stop-n-go.
Interesting drive. Naturally I was unable to gather stats on the drive in, as the RS232 connector came loose. *shrug* Time for duct tape. 🙂 The drive home was successful, in that I was able to gather data. It also showed that I have some transaxle noise that needs looking at before I drive much more (Calling Dr. 914!)
So for those who are statistics fiends:
Current: min=-48a, max=123a
Voltage: min=330v, max=368.5v
Torque: min=68.6nm, max=120nm
I’ve attached the spreadsheet with all the data, so you can analyze it to your hearts content: InitialDriveHome
Oh – the current at freeway cruise was between 75 and 80 amps at 350v.
I returned from my business trip to Bangkok (long story in itself) to find two boxes waiting for me – the replacement DC-DC converter and new cables for the BMS. It took me about 4 hours to replace the DC-DC converter and the 4 cables, but well worth the effort. The DC-DC converter works as advertised, providing 13.5 volts. The new cables eliminated the intermittent communications problems during charging.
Proof is that the batteries are now fully charged. I can see the car quivering with excitement in the driveway, begging to be driven. I think I’ll do that today. 🙂
BTW, EV Components has been great during all of this – providing excellent customer support and fast shipping of new parts.
Ok, so some tweaks on the pedal parameters make a HUGE difference. I was able to get the accelerator to behave “normally”, and was able to get the regen to work with the brakes. Acceleration is good – better than the 1.8 liter engine. Braking is GREAT! Dang, I sure don’t need those high-priced brake upgrades now. 🙂
So now I get to do some fine tuning on the pedal, and it will be driving like a REAL car. 😀 I was able to pull only 90 amps, so I know there is more to push through.
Seriously, though, I was able to get up to 30 mph in first gear with no trouble, although there is a lot of vibration at 5k rpm, so I will have to pull the motor and balance the flywheel. *sigh*
So now I am waiting for the replacement DC-DC converter (previous one sadly fried due to operator error) and some cable components so I can rewire the BMS circuits.
The BMS works fine except for banks 5, 6 and 8. Oddly bank 7 is fine, but I will rewire it also, as it uses the Cheap Cabling. Hopefully this will take care of the communications errors with the BMS.
Ok, so in the process of trying to “optimize” the driving experience, I made a few mistakes. Fortunately, I’ve been able to fix almost all of them. The regen circuit now is activated by the brake lights, so the car now drives just like a car. Very cool.
While I was fussing around in the controller compartment, I tried to get the DC-DC converter to work. However, this resulted in me frying my DC-DC converter (fortunately, this is an relatively inexpensive mistake). The good thing is that EV Components has more of them.
I’m hoping to get the tachometer working tomorrow. I spent about 3 hours getting a neat circuit put together that will drive some indicator lights. One is the “ready” signal and the other is the “fault” signal – both from the motor controller. Since I know I’ll want to see these lights while driving and while testing, I set it up so there are two of each lights – one set in the dash and one set near the motor controller.
Radio Shack was my friend, as was Tim Kutscha for his diagram. Naturally, I didn’t do it exactly his way, but that is the fun of all of this. This version uses 2 resisters – one for each input and 4 transisters – one for each light. The box has 12v ready LEDs, the other lights are the more usual incandescent lights.
The circuit is inside this box:
