After mentioning the motor controller temperature faults to Ives (the designer) at Synkromotive, he suggested we swap it out for a newer one. I went into the shop this evening and swapped out the controller. Ives looked at the old one and basically told me that I had beta test unit #2 with tiny heatsinks, bad ventilation and very little filtering on the temperature fault circuitry. Apparently other customers have had the same issues and the new controller should be far better.
One other thing the folks at Synkromotive showed me was a newer vacuum assist pump for the braking system that's very quiet from EVComponents. It's a bit expensive, but the pump produced very little noise, even with the hood open and my hear near it. Also, to enhance the power steering, they use the electric power steering pump from a Toyota MR2 so that parallel parking isn't as hard. More info here.
So far, the new controller is doing just fine. It also got bumped up to 700 motor amps from 600 when starting from a stop. The tires do a wonderful little "chirp" when I floor it from a stop in first gear before the batteries current maxes out at 300 amps. I could kick both of those up, but choose not to so I can save breaking my transmission and batteries.
I'll try and keep y'all posted on the progress. I'm a bit tired of working through issues right now, so if the car drives well, you might not hear from me for a few weeks.
One other complaint I received was that the open-source Civic plans were not complete on the Civic-EV Google Group. The complaint is valid and I plan on finishing things when the summer is over and I'm past my burn-out stage on this project. I hope to just enjoy driving the car for awhile. The modified charging circuit seems to be doing its job well and I'm happy that problem is over.
In the meantime, I'll be attending the Wayland Invitational at PIR to rub shoulders with the bigwigs in the EV industry at the end of July.
Tuesday, July 14, 2009
Sunday, July 12, 2009
EV Awareness Day, Synkro faults
Yesterday was our local EV organization's big annual event called EV Awareness Day. We held it at Pioneer Courthouse Square in downtown Portland. I gave a press event with the Mayor Sam Adams and two VPs from local power companies (PGE and Pacific Power).
Probably one of the coolest things about the show is that a Tesla Roadster showed up unexpectedly!
Here I am with the Tesla Roadster.
After talking about electric vehicles to people all day in the sun, I was rather fried at the end of the day.
On the way home the Sykromotive controller faulted three times during initial acceleration up a hill in the summer heat. I suspect these are temperature glitch faults that Synkromotive has been having issues with for awhile. Being fried from the show and caught in heavy traffic on a hill with lines of people behind me, you can imagine this wasn't much fun. Fortunately, I've learned that I just need to toggle to ignition key and wait five seconds to try again.
After clearing the third fault on this hill, I was able to very slowly accelerate up the hill until the motor turned enough to not cause noise issues with the temperature sensors in the controller. I'll be uploading all the fault logs soon and contacting Synkromotive for further advice. Other than the temperature faults, the controller has been excellent. This is still a "beta" unit, so perhaps they've resolved the issues. Let's hope so...
Probably one of the coolest things about the show is that a Tesla Roadster showed up unexpectedly!
Here I am with the Tesla Roadster.
After talking about electric vehicles to people all day in the sun, I was rather fried at the end of the day.
On the way home the Sykromotive controller faulted three times during initial acceleration up a hill in the summer heat. I suspect these are temperature glitch faults that Synkromotive has been having issues with for awhile. Being fried from the show and caught in heavy traffic on a hill with lines of people behind me, you can imagine this wasn't much fun. Fortunately, I've learned that I just need to toggle to ignition key and wait five seconds to try again.
After clearing the third fault on this hill, I was able to very slowly accelerate up the hill until the motor turned enough to not cause noise issues with the temperature sensors in the controller. I'll be uploading all the fault logs soon and contacting Synkromotive for further advice. Other than the temperature faults, the controller has been excellent. This is still a "beta" unit, so perhaps they've resolved the issues. Let's hope so...
Thursday, July 9, 2009
Super FET working Comments on Sykro Controller
Last week I was mostly on vacation, so I didn't get a chance to really charge the car at full amperage many times. This week was back to work, so I was able to give the charge detector a more reasonable test.
In short, the three huge FETs with heat-sinks seem to work just fine (I should hope so...). I've charged the car seven times in the summer heat and the charger can dump a full 8 amps into the batteries every time without heating up the charge detector box.
I had a little bit of a scare today at work. The Synkromotive controller would instantly fault every time I touched the accelerator. It seems that I had a loose connection between the potbox and the controller. When I wiggled the connector on the TPS (throttle-position-sensor), the controller ceased to go into a fault condition and I drove home. I put anti-corrosion compound on the TPS contacts to help prevent a similar fault in the future. I'll bet that the Sykromotive controller was faulting due to an incorrect input on the potbox wires.
I really like the simplicity of the system. If it fails, it usually fails big and the failure is usually a loose wire somewhere. Get out your Fluke-meter and start debugging.
On my last post, someone left a comment asking about how well the Synkromotive controller was working. In short, it's great. It gives a lot of power when requested and is quite easy to tune various internal parameters through the user-interface over the USB port. Embedded logging makes it really nice as well.
A few nitpicky items I would improve about the controller: The large bus bars that attach to the battery cables are mounted vertically, requiring the use of right-angle lugs or fancy routing of wires. Also, the power given to the motor instantly reflects whatever is specified on the potbox.
If you have a quirky potbox or press the accelerator too quickly, the car seems to lurch a bit. This is especially true if there is slack in the drivetrain from having the motor coast to a complete stop. The lurch instantly takes up the slack in the drivetrain and you can get a jerk that might cause oscillations.
As I've mentioned before, the big solution to this is to use the factory TPS instead of a cheap forklift potbox (like a Curtis PB-5 or PB-6). The factory one is much smoother and more reliable. The downside of the factory potbox is that it never goes to zero ohms which means you can't use it for simpler controllers like a Curtis. The Synkromotive controller has many potbox tuning adjustments so you can set the zero point and the acceleration ramp depending on the travel distance of your throttle cable.
The Synkromotive controller on hot days sometimes gets a temperature noise fault. More recent firmware tends to fix this issue, but I've still stalled once with the latest firmware. Fortunately, you simply need to toggle the ignition switch and wait four seconds for the precharge circuit to run to re-engage the contactor before driving again.
This weekend is the biggest day of the year for our local EV club. We're showing off 30 electric vehicles in Downtown Portland and Mayor Adams is also showing up at our press event to endorse our group. I'm excited but will be happy when it's all over.
In short, the three huge FETs with heat-sinks seem to work just fine (I should hope so...). I've charged the car seven times in the summer heat and the charger can dump a full 8 amps into the batteries every time without heating up the charge detector box.
I had a little bit of a scare today at work. The Synkromotive controller would instantly fault every time I touched the accelerator. It seems that I had a loose connection between the potbox and the controller. When I wiggled the connector on the TPS (throttle-position-sensor), the controller ceased to go into a fault condition and I drove home. I put anti-corrosion compound on the TPS contacts to help prevent a similar fault in the future. I'll bet that the Sykromotive controller was faulting due to an incorrect input on the potbox wires.
I really like the simplicity of the system. If it fails, it usually fails big and the failure is usually a loose wire somewhere. Get out your Fluke-meter and start debugging.
On my last post, someone left a comment asking about how well the Synkromotive controller was working. In short, it's great. It gives a lot of power when requested and is quite easy to tune various internal parameters through the user-interface over the USB port. Embedded logging makes it really nice as well.
A few nitpicky items I would improve about the controller: The large bus bars that attach to the battery cables are mounted vertically, requiring the use of right-angle lugs or fancy routing of wires. Also, the power given to the motor instantly reflects whatever is specified on the potbox.
If you have a quirky potbox or press the accelerator too quickly, the car seems to lurch a bit. This is especially true if there is slack in the drivetrain from having the motor coast to a complete stop. The lurch instantly takes up the slack in the drivetrain and you can get a jerk that might cause oscillations.
As I've mentioned before, the big solution to this is to use the factory TPS instead of a cheap forklift potbox (like a Curtis PB-5 or PB-6). The factory one is much smoother and more reliable. The downside of the factory potbox is that it never goes to zero ohms which means you can't use it for simpler controllers like a Curtis. The Synkromotive controller has many potbox tuning adjustments so you can set the zero point and the acceleration ramp depending on the travel distance of your throttle cable.
The Synkromotive controller on hot days sometimes gets a temperature noise fault. More recent firmware tends to fix this issue, but I've still stalled once with the latest firmware. Fortunately, you simply need to toggle the ignition switch and wait four seconds for the precharge circuit to run to re-engage the contactor before driving again.
This weekend is the biggest day of the year for our local EV club. We're showing off 30 electric vehicles in Downtown Portland and Mayor Adams is also showing up at our press event to endorse our group. I'm excited but will be happy when it's all over.
Thursday, June 25, 2009
Time to Get a Larger Hammer
After two days of running perfectly, I found yesterday morning that the amps were down and the FET had blown again. This really stumped me because I thought I had done everything to keep it cool and out of the switching region.
After showing the system to the power supply EEs at work, they told me that any FET in a TO-220 case like the one I had would not handle a constant 8-amps for a long time. The heat dissipation comes from the bond wires going to the silicon inside, not the actual silicon itself. They suggested that I put multiple FETs in parallel to lower the resistance and spread the heat over multiple sets of FET bond wires. If you can lower the resistance by half, the power dissipation goes down by a factor of four.
As you might imagine, I'm getting really tired of blown FETs, so I rummaged through our lab stock and got the biggest FET I could find.
Here's a comparison of the FET's I'm using. Instead of one TO-220 case FET on the left, I'm installing THREE of the TO-247 case FETs on the right in parallel with heatsinks. I'll be taking the "on" resistance from 30 milliohms down to 3 milliohms. By dropping the resistance by a factor of 10, I can theoretically lower the power dissipation by 100 (I^2*R from ohms law).
Here are the three high-power FETs installed inside the charge detector box. Note the burnt spot in the lower right corner of the printed circuit board from the smaller, individual FET that burned up yesterday morning.
I just started charging with this new circuit about an hour ago. The charge detector box is COLD. I can barely feel a slight temperature difference between the top of the box and the vehicle chassis.
Some might think this is overkill. Those folks would be right. It probably is, but I'm sick of wasting my own time and the time of all the folks at work who are graciously helping me out. I would rather nuke this one with an overdesigned system instead of having to revisit it several times.
Here's a third schematic (click to enlarge) including the changes to Q1, Q2 and Q3 FETs on the right side.
I sure hope this issue is dead. I've got a few EV shows coming up and I'm done with dealing with this issue. Let's see what happens. Hail Mary.
After showing the system to the power supply EEs at work, they told me that any FET in a TO-220 case like the one I had would not handle a constant 8-amps for a long time. The heat dissipation comes from the bond wires going to the silicon inside, not the actual silicon itself. They suggested that I put multiple FETs in parallel to lower the resistance and spread the heat over multiple sets of FET bond wires. If you can lower the resistance by half, the power dissipation goes down by a factor of four.
As you might imagine, I'm getting really tired of blown FETs, so I rummaged through our lab stock and got the biggest FET I could find.
Here's a comparison of the FET's I'm using. Instead of one TO-220 case FET on the left, I'm installing THREE of the TO-247 case FETs on the right in parallel with heatsinks. I'll be taking the "on" resistance from 30 milliohms down to 3 milliohms. By dropping the resistance by a factor of 10, I can theoretically lower the power dissipation by 100 (I^2*R from ohms law).
Here are the three high-power FETs installed inside the charge detector box. Note the burnt spot in the lower right corner of the printed circuit board from the smaller, individual FET that burned up yesterday morning.
I just started charging with this new circuit about an hour ago. The charge detector box is COLD. I can barely feel a slight temperature difference between the top of the box and the vehicle chassis.
Some might think this is overkill. Those folks would be right. It probably is, but I'm sick of wasting my own time and the time of all the folks at work who are graciously helping me out. I would rather nuke this one with an overdesigned system instead of having to revisit it several times.
Here's a third schematic (click to enlarge) including the changes to Q1, Q2 and Q3 FETs on the right side.
I sure hope this issue is dead. I've got a few EV shows coming up and I'm done with dealing with this issue. Let's see what happens. Hail Mary.
Monday, June 22, 2009
Cautious Optimism
After talking with the power supply EEs at work, I came home and tried a few experiments to see if I could fix the alternative charge detector circuit.
First, I used an external 12V UPS battery instead of the AUX power output on the Belktronix charger to see if noise on the power supply was causing my problem. Nope: The circuit still behaved as if the opto-coupler latched closed.
Next step was to pull out my oscilloscope and start probing around the system. Fortunately, most of the battery pack and components are floating, so I can attach the ground of the scope to several different high-voltage points to serve as a reference.
Yowzers! There's a hell of a lot of noise in this system. Whenever the Belktronix charger starts up, I get 50V spikes at ~200Khz on the oscilloscope by just holding the tip of the input probe with my finger. Keep this thing away from your pacemaker! I'm guessing that these high voltage noise spikes are causing problems with the opto-coupler.
Here's a modified schematic. The EE folks at work suggested adding C4 (.01uf cap across the opto-coupler input) to help cut down on the noise. I also reduced C3 down to 10uf from 47uf. This reduction increases the maximum switching frequency for the FET (due to the hysteresis in the 555) from 1Hz up to about 5 Hz. While the FET switches at a slightly higher frequency, it's still so slow that the FET stays out of the linear switching region for long periods of time.
I plugged in the system and (gasp), the FET stayed on like I intended it to. After suspiciously pondering the circuit thinking that I had messed something up, I shorted out the OVP signal and the FET quickly turned off and the LED came on. The link-10 meter shows a full 8 amps going into the batteries. In a few hours, the BatMon boards should start lighting up and I'll see if the circuit responds correctly. The charge detector box is a bit warm to the touch, but definitely not hot.
I'm very excited that adding a .01uf capacitor to the opto-coupler input cleared up much of the noise. Someone over in the UK had their Belktronix charge detector blow up too with a lithium ion battery pack, so I hope this circuit can help them too.
After my heated rant last night, I received several supportive e-mails and comments from people. Thanks to all who responded for your ideas and well wishes. I feel good when I hear from folks because I don't know how many people are actually keeping track of this blog, especially since things have quieted down recently.
Let's keep our fingers crossed with cautious optimism. Cheers.
First, I used an external 12V UPS battery instead of the AUX power output on the Belktronix charger to see if noise on the power supply was causing my problem. Nope: The circuit still behaved as if the opto-coupler latched closed.
Next step was to pull out my oscilloscope and start probing around the system. Fortunately, most of the battery pack and components are floating, so I can attach the ground of the scope to several different high-voltage points to serve as a reference.
Yowzers! There's a hell of a lot of noise in this system. Whenever the Belktronix charger starts up, I get 50V spikes at ~200Khz on the oscilloscope by just holding the tip of the input probe with my finger. Keep this thing away from your pacemaker! I'm guessing that these high voltage noise spikes are causing problems with the opto-coupler.
Here's a modified schematic. The EE folks at work suggested adding C4 (.01uf cap across the opto-coupler input) to help cut down on the noise. I also reduced C3 down to 10uf from 47uf. This reduction increases the maximum switching frequency for the FET (due to the hysteresis in the 555) from 1Hz up to about 5 Hz. While the FET switches at a slightly higher frequency, it's still so slow that the FET stays out of the linear switching region for long periods of time.
I plugged in the system and (gasp), the FET stayed on like I intended it to. After suspiciously pondering the circuit thinking that I had messed something up, I shorted out the OVP signal and the FET quickly turned off and the LED came on. The link-10 meter shows a full 8 amps going into the batteries. In a few hours, the BatMon boards should start lighting up and I'll see if the circuit responds correctly. The charge detector box is a bit warm to the touch, but definitely not hot.
I'm very excited that adding a .01uf capacitor to the opto-coupler input cleared up much of the noise. Someone over in the UK had their Belktronix charge detector blow up too with a lithium ion battery pack, so I hope this circuit can help them too.
After my heated rant last night, I received several supportive e-mails and comments from people. Thanks to all who responded for your ideas and well wishes. I feel good when I hear from folks because I don't know how many people are actually keeping track of this blog, especially since things have quieted down recently.
Let's keep our fingers crossed with cautious optimism. Cheers.
Sunday, June 21, 2009
Failure Again!
I came home this evening after a 20 mile drive with excitement to see the new charge detector circuit work. I plugged in the car and the circuit had an interaction with the optocoupler on the BatMon board and didn't see the correct signal. Nothing is burning up, but the FET is stuck in the off state for now, leaving the system to charge slowly with a really hot 3-ohm resistor.
I'm so angry at this charging system! It's a good thing I just got back from my mindfulness meditation session or I would throw a wrench at the car. God, I'm pissed! It worked so well with the batteries near a full condition, but the circuit fails when the batteries are discharged. I suppose this is a good data point for further analysis, but I'm rapidly running thin on patience.
I'm taking the circuit into a bunch of EE experts tomorrow at work (they always like working on these problems instead of their real jobs) and we're going to get to the bottom of this. I'm running out of energy to get this working. Damn, this sucks.
I'm so angry at this charging system! It's a good thing I just got back from my mindfulness meditation session or I would throw a wrench at the car. God, I'm pissed! It worked so well with the batteries near a full condition, but the circuit fails when the batteries are discharged. I suppose this is a good data point for further analysis, but I'm rapidly running thin on patience.
I'm taking the circuit into a bunch of EE experts tomorrow at work (they always like working on these problems instead of their real jobs) and we're going to get to the bottom of this. I'm running out of energy to get this working. Damn, this sucks.
A New Hope
After the utter failure of the Soneil and the Joule chargers, I did some more research on individual battery chargers. Ideally I was looking for the following:
I decided to go back to the drawing board and see what I could do with the Belktronix charger. In concept, the charging system was great. It's a nice power-factor-corrected series charger that dumps out a solid 8 amps and it's sealed so that bugs and dirt don't get in.
Since I've moved to the Synkromotive motor controller, there aren't any more mid-pack taps off the battery pack, so the batteries tend to drift out of balance more slowly. Arguably, the resistive shunts with the Belktronix charging system should be able to handle this quite well.
The problem in the past has been the charge detector. Without going into all the details of operation, the OVP lines from all the BatMon modules would pulse and cause the FET inside the charge detector to turn on and off. Since this pulsing was frequent, the FET was often in the switching region and easily overheated.
The FET inside the charge detector determines if the large 3-ohm 180-watt series resistor is inserted in the charging circuit. If the FET is on, then the 3-ohm resistor is shorted and the batteries get a full 8 amps, which is great for fast charging. This brings up a problem when the BatMon boards detect a "full" condition on the batteries. The small 3-ohm shunt resistors start to burn up if they have to sustain the 8 amp current flow. Thus, the charge detector needs to turn off the FET to insert the large series 3-ohm resistor to limit the current. If you turn off the FET too early, it takes forever to charge your batteries and the large 3-ohm series resistor gets really hot. Turn off the FET too late and all your shunt resistors burn up, causing massive smoke and potential fires in your EV. (ugh)
Here's a picture of the inside of the blown charge detector. The FET is clearly blown in half with burn marks all the way around it. Note the melted region on the case cover in the lower right.
The FET in the charge detector is a very good one with a very low turn-on resistance. If we can limit the amount of FET switching and turn it on/off hard to keep it out of the linear region, it should stay relatively cool, even with 8 amps flowing through it. So, I put on my EE hat and designed a completely new circuit to put inside the charge detector box.
Here's the charge detector box with the new circuit inside of it. The circuit (shown at the end of this post) uses the comparators and flip-flop inside a 555 timer (Radio Shack special!) to drive the FET with hysteresis on the input to limit switching.
Here's my old Radio Shack 555 timer handbook. It's a crying shame they don't sell these anymore. I guess it doesn't make a profit and people just aren't into dinking around with 555 timers anymore. As you can see (click to enlarge picture), this tiny chip contains two comparators, an RS-flop and an output driver. This is just what we need to observe the pulsing OVP signals from the Batmon boards to determine if we should turn the FET on and off to short the large 3-ohm series charge resistor.
I tend to go overboard with these things. This is my kitchen table with all the soldering/test equipment on it.
Here is the simple circuit I put inside the charge detector box to control the FET that shorts out the large 3-ohm series charging resistor. Note that this lacks a few safety features that would prevent a blow-up if the user hooked things up in reverse, so this is not a product-worthy circuit. It's simple enough and you can get most of the parts (except the FET) from Radio Shack. If you click to enlarge the picture, you can see the theory of operation and get more details.
I'm going to try this out for a few days and see if I can charge faster without blowing up the FET. The potentiometer still probably needs adjustment to properly set the duty-cycle detection on the OVP pair, but this is a good start. If this works, I'll have fast charging without setting the small shunt resistors on fire. Here's to hope...
- Power factor corrected
- Weather-proof for mounting under the hood
- Isolated to work with a series pack of batteries
- 6-8 amps charging capacity
- low power enough to put all 12 chargers on one 15 amp circuit (possibly 20 amp circuit)
- somewhat affordable
I decided to go back to the drawing board and see what I could do with the Belktronix charger. In concept, the charging system was great. It's a nice power-factor-corrected series charger that dumps out a solid 8 amps and it's sealed so that bugs and dirt don't get in.
Since I've moved to the Synkromotive motor controller, there aren't any more mid-pack taps off the battery pack, so the batteries tend to drift out of balance more slowly. Arguably, the resistive shunts with the Belktronix charging system should be able to handle this quite well.
The problem in the past has been the charge detector. Without going into all the details of operation, the OVP lines from all the BatMon modules would pulse and cause the FET inside the charge detector to turn on and off. Since this pulsing was frequent, the FET was often in the switching region and easily overheated.
The FET inside the charge detector determines if the large 3-ohm 180-watt series resistor is inserted in the charging circuit. If the FET is on, then the 3-ohm resistor is shorted and the batteries get a full 8 amps, which is great for fast charging. This brings up a problem when the BatMon boards detect a "full" condition on the batteries. The small 3-ohm shunt resistors start to burn up if they have to sustain the 8 amp current flow. Thus, the charge detector needs to turn off the FET to insert the large series 3-ohm resistor to limit the current. If you turn off the FET too early, it takes forever to charge your batteries and the large 3-ohm series resistor gets really hot. Turn off the FET too late and all your shunt resistors burn up, causing massive smoke and potential fires in your EV. (ugh)
Here's a picture of the inside of the blown charge detector. The FET is clearly blown in half with burn marks all the way around it. Note the melted region on the case cover in the lower right.
The FET in the charge detector is a very good one with a very low turn-on resistance. If we can limit the amount of FET switching and turn it on/off hard to keep it out of the linear region, it should stay relatively cool, even with 8 amps flowing through it. So, I put on my EE hat and designed a completely new circuit to put inside the charge detector box.
Here's the charge detector box with the new circuit inside of it. The circuit (shown at the end of this post) uses the comparators and flip-flop inside a 555 timer (Radio Shack special!) to drive the FET with hysteresis on the input to limit switching.
Here's my old Radio Shack 555 timer handbook. It's a crying shame they don't sell these anymore. I guess it doesn't make a profit and people just aren't into dinking around with 555 timers anymore. As you can see (click to enlarge picture), this tiny chip contains two comparators, an RS-flop and an output driver. This is just what we need to observe the pulsing OVP signals from the Batmon boards to determine if we should turn the FET on and off to short the large 3-ohm series charge resistor.
I tend to go overboard with these things. This is my kitchen table with all the soldering/test equipment on it.
Here is the simple circuit I put inside the charge detector box to control the FET that shorts out the large 3-ohm series charging resistor. Note that this lacks a few safety features that would prevent a blow-up if the user hooked things up in reverse, so this is not a product-worthy circuit. It's simple enough and you can get most of the parts (except the FET) from Radio Shack. If you click to enlarge the picture, you can see the theory of operation and get more details.
I'm going to try this out for a few days and see if I can charge faster without blowing up the FET. The potentiometer still probably needs adjustment to properly set the duty-cycle detection on the OVP pair, but this is a good start. If this works, I'll have fast charging without setting the small shunt resistors on fire. Here's to hope...
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