Mounting battery boxes

It has been a long pause again in my blog - again. The main reason is that blog update stands not on the top of my priorities list among family, main job, and actually working on HR-EV. I reckon if I would have worked normal working hours it would have taken me around 4 months. But now we are approaching 2nd anniversary of the project. Anyway, it's good that it is moving.

This time I want to show the mounting of battery boxes. Apologies for bad quality photos taken from my mobile because camera died when I needed it and I've been to busy to look for another camera.
The battery boxes are mounted on two 20x20x3 stainless steel angles: one in front bottom and one in rear top.

I used most of the car's stock bolt places on the chassis to fasten front rail using just one additional which was welded in. Rear rail was fastened to bottom sheet of the car where the spare tire is placed.
Here is the picture of one box mounted on the rails.

As you may possibly see the front rail is basically hanging on 4 20x3mm stainless steel bars bolted on top to chassis and bent around the angle bar at the bottom and welded to it. This construction allows the angle to swing a bit which is good as you don't have to be dead precise when making these rails. Being very precise in garage conditions is quite difficult. Lateral stability of this bar is achieved by the fact that boxes are bolted to it and boxes themselves are fastened at rear. The other stability element is the 0.8mm steel cover which is bolted to car and to small legs which were formed from the 20x3 bars bent around the angle ( you can see these three legs on the photo above).
Here is the picture showing the rear of the box and I hope you can see the angle bar in dark top left corner of the photo.

Here is the view from inside the car's trunk where the spare wheel is placed.

You can see 4 bolts caps in a row. That's how the rear bar is attached. Simple, isn't it? Well there are 2 additional long bolts on both sides securing the very ends of the rear rail angle. These are not visible on this photo.
On the above photo there are 4 cut opening providing access to boxes terminals to interconnect them together. You can see couple of LEDs lit up on the left which were shot when BCMS was scanning the cells.

Below are couple of very crappy photos which taken with the same mobile camera. The sad fact for the hobby project is that it is rarely possible to work in daylight as in winter night is starting early and job is usually done after main work. I will re-take with proper camera and place here. I promise :)
Here is the view from front left with all battery boxes in place. You can see the thick cable running prepared to be connected.

Here is dark view from the back bottom view of the batteries (that's how you define darkness :)

Here is the dark view of the batteries on the front rail when viewed from the car front.

Here should be photo of the boxes with protective steel sheet installed but I was too tired to remember to take a picture with it. Next time, when I bring the car on the lift again.

Kelly KDH14651B post-mortem

There were quite a few things happening since last time and I was so busy working on them that I could not spare time to update the blog timely. My excuse finishes here :)

OK, the main thing was that my Kelly controller KDH14651B blew up in smoke. The good thing about it that after all reading all comments from around the net I was kind of expecting it. In a way I felt a relief that I don't have a doubt about its reliability.
Actually it happened at the end of September when I was drive-testing my HR-EV. I was driving it around for a day to test the power consumption and battery capacity. After fresh charge it scored 53km and 203Wh/km consumption in Vilnius city-like driving profile (quite a few ups and downs) which was quite good comparing to standard 250Wh/km as a benchmark. The main parameters during this event were following: speed ~70km/h, slight up-slope driving for around 2-4 previous minutes, battery voltage ~124V, battery current ~180A, controller heatsink temperature ~+29C. So it blew up while continuously delivering around 22kW power for last few minutes. Just to note that the highest power possible I recorded with Kelly was 43kW.
Kelly were not willing to provide me some money compensation. Only offer was a notable discount on new controller which would be basically the same one as just blew up. This was not an acceptable option. Here I'll put some photos what I found investigating its failure.

Disclaimer: Of course it is not proper engineering failure analysis so I reserve my right to be wrong at some of my conclusions. I am basing my findings on my own electronics knowledge and experience.

First I took out my control box from the car. Looking closely you may see the Kelly's cover is slightly popped open from inside explosion.

And here is the photo to see it closer. The cover was just glued to aluminum chassis.

When taken the controller out of my control box I could open the cover more widely. A lot of black ash inside.

Some ash left on inside of control box where the controller was sitting:

Of course the controller like many products of China was built in such way that it would not be possible to disassemble normally for repair. That is a reason that I have not heard of any repaired Kelly Controller. You just scrap the old one and pay Kelly for the new one. That did not stop me :). I sawed off the two sides of aluminum chassis to split top and bottom parts apart to have access to the whole board. And below is the photo how it looks with the top off.

Hmmm, first impression is bad. Not just because of black ash all over. The layout of components is really bad if you are dealing with multi-hundred A currents switching. The electrolytic capacitors sit on one side and power connectors on the other with many switching transistors in between. This layout is a recipe for uneven current and voltage spikes, temperature distribution and stress on the components. There are 42 IRFB4227 transistors in this controller connected in a half-bridge configuration: 21 on lower arm and 21 on upper. The basic rule of paralleling is to keep the conditions as equal as possible for every paralleled part. This rule was clearly taken carelessly.
In addition to that there is really "interesting" solution to increase the power of the controller taken closely in the picture below.

As you can see there are two 10x1.5mm copper bars connecting the bigger and longer row of power transistors on the left to smaller row on the right. This gives me a clear hint that originally the controller was designed to handle maximum currents of up to "400A" and needing a more powerful model they added this section to extended the current by ~200A-ish to total "650A". That would be OK if design approach was taken properly and wide connector plates were used to ensure small inductance and, again, even distribution. Having a long bar with 15mm2 cross-section would certainly not help to achieve that. In hundreds Amp currents every 0.1uH counts.

Closer look at possible failure cause indicated that the epicenter of explosion was first transistor which was closest to bar connectors. Based on previous observations this surely looked like a most probable place to fail: closest to the load and furthest to filter circuits.

It was clear that this transistor was producing majority of bang and smoke.

 The PCB track beneath it was also severely damaged. I reckon that after it's failure all other transistors failed in avalanche fashion which is quite normal for paralleled designs. Out of 42 I found possibly 3 that were showing good initial parameters.

Another point is that it is very important to place good filter capacitors on power lines of such switching devices which could help to reduce voltage spikes and even the conditions for paralleled designs. For that you would need good film capacitors. I didn't find them. I only found ceramic SMD capacitors stacked in several places. These usually not good enough for high current spikes filtering.

The next thing was looking at the attachments of these transistor for heat transfer. For that I was taking off bus bars from the transistors. The bus bars are 3x16mm giving 48mm2 cross-section. This is usually good enough for transferring currents from A to B of 600A from which could potentially be drawn from battery. But on controller itself this should be by a margin bigger to allow more even conditions distribution (again) due to smaller resistance and inductance. Anyway I found that each 7 H-lower arm transistors were attached on L shape 3mm thick aluminum plate which is in turn bolted to the chassis base through PCB. Notice anything wrong? Yes, the PCB was used as a heatsink transfer element! OK, the PCB has perforation with metallisation to build many heat transfer channels but still it is not sufficient to drain the excessive heat from transistors down to the base plate at good rate. Below is the photo of PCB what I found under plate and bus bar.

This makes the excess temperature be the main contributor to failure. Remember, I was driving for few minutes in slight uphill. This allowed the transistor temperature to rise but transfer to baseplate and heatsink was not sufficient to keep transistor in normal operating temperature range.

Here is how the PCB looks from below.

Taking into account MOSFET's increased heat dissipation at increasing temperatures this heat transfer certainly does not look enough to me.

Here is how the aluminum case base plate from below PCB looks.

After these findings I certainly would not buy another one from Kelly even at half the cost because I know it would blow up again. It might work well in golf-kart or similar but it is not suited for high currents.

After that I left without controller. As there are no acceptable options (reliable, not overpriced, flexible, powerful enough, with easy integration, available within 1-2 week lead time, etc) I decided to build my own which would be based on IGBTs. But that is the topic for different post...

Motor RPM Sensor

I have built motor RPM sensor from Melexis MLX90217 chip and door magnet. The Melexis chip was ordered from DigiKey a while ago and cylindrical magnet has taken from door magnet and reed switch pair which is used in house alarm systems.
I made an enclosure of the sensor from 30x30x2 square steel tube of approx 60mm length. I welded on the 2 mm sheet cover on one end and two holder arms with holes on other end. Then made a 14mm hole on one side and welded in a piece of steel tube. Then I glued in the magnet with MLX sensor on its end directed to the inside of the box with three short wires running out to the outside. These wires are connected to shielded microphone cable which is running from the sensor to control box. I've painted the sensor with hammered black Hammerite, let it dry for a day and attached to motor on accessory axis side. Here are couple of photos of finished sensor. Sorry - didn't have time to capture whole manufacturing process.

The sensor serves second purpose too - it covers the shaft from dirt and moisture to prevent its corrosion.

Intermediate Shaft Holder

HR-V's ICE engine had a fastening place where the front left driveshaft's intermediate shaft was attached to with three bolts making sure that intermediate shaft sits firmly in it's place in gearbox and is in steady position at the junction with front left driveshaft.

As the ICE is gone this intermediate shaft did not have its attachments position so it had to be manufactured. I took 2mm steel sheet and welded a sort of box with on side concave following Warp 9's contour and the other side flat with three M10 bolts welded in for intermediate shaft bracket attachment.

On concave side there is one hole. This hole is used to firmly attach the holder to the Warp's 5/8" lift eye-hole with one bolt

 I painted the part with hammered-black Hammerite, let it dry for a day and attached to the motor and intermediate shaft.

Now this intermediate shaft is not going anywhere.

Rack for Control Box and Charger

Behind the scenes  I was doing occasional test drives of my HR-EV for last few weeks. I don't have video of myself but I have video of my wife's EV-grin when she was first driving it which I'll edit and post it at some near time.
Testing was involving a lot of wiring and parameter tweaking to make more and more features of BCMS and car working. For temporary drives I placed control box on two wooden blocks across longerons of the car which worked quite ok but I don't have the photo of them - sorry :) Then I got to the point when I needed to have control box and charger fixed under the hood firmly for longer drives.
To fix control box and charger firmly I designed and built the rack from stainless steel square tubes. I didn't prepare any drawings or sketches for it since it seemed to be quite trivial task from design point of view.
The rack is basically two 30x20x2 stainless steel tubes across car's longerons connected with two bars and fastening loops for bolts at the end to fix it to the longerons. I used 3 stock bolt places on the car's body for fastening the rack and I had to weld in the fourth nut place where no other suitable option was possible. I drilled and welded in 8 bolts for places where Control box and charger will be fixed
The rack came out quite nice. Here are some photos of it.

The control box is almost finished. Next I'll need to make a cover for it. As you can see at the bottom on the sides are two bars with bolt holes for fastening control box to the rack.

The end of the box has all the connectors and cables. I can disconnect all the cables and take the box out for maintenance of itself or the motor underneath.

Here is the picture of rack placed with charger on it.

And here is the rack with control box on it. Of course control box and charger will normally sit together.

The whole construction came out sturdy but at the same time easily dismantable if maintenance would be needed. The intervention into chassis structure is minimum.

Building Electric Heater

Hello folks! It's been a while I didn't post any updates. But that does not mean I wasn't doing anything. There are many things that you need to take care of and building a heater for coming winter is one of them.
The heater cores are taken from cheap household ceramic heater-blower.

I've dismantled two heaters to get two ceramic heater elements as I learned from other EV builders that one element is not enough. Here is the picture of them side by side.

I needed to get the HR-V's stock heater radiator out of the car to measure it's dimensions and to build an adequate substitute. It seemed to be a fairly easy task but I found out that I have to completely dismantle cabin dashboard to access the ventilation box, take it off and get the heating radiator out.
Here is how the car cabin looked when I finally took the ventilation box.

Once I opened the ventilation box I got access to liquid heater radiator.

I placed 2 ceramic heater elements on liquid radiator where the best airflow is expected and marked the dimensions outline of them so I would know their location when building heater elements box.

Next I took 0.8mm stainless steel sheet and built the heater box by marking, cutting, bending and riveting it to resemble the dimensions of stock liquid heater radiator. To hold the elements I used the plastic holders that were originally in electric heater. I sawed them off to take the shape and fit side by side. It fastened them to the box using two bent steel sheet retainers which are riveted to the bottom plane of the box. I connected the heater elements through over-temperature protection switches that were in stock electric heaters. I run a 2.5mm2 wires cable through plastic cable-through holder in the same place where one of water pipes is going out on stock liquid heater. This way the heater cable goes out into the engine bay where the liquid heating pipe used to come in. Here is box view from top.

Must admit that initially box came a bit over-dimensioned because stock radiator had round corners while mine had square ones. So to fit it in I had to grind corners a bit and adjust bends.  After that it lost a bit of it's tidy look. Here is the view from bottom.

I then placed the newly made electric heater box into ventilation box. Had to make a bit wider openings in ventilation box plastic where white cable holder goes out.

Then I've assembled back the ventilation box and ran a short test by connecting the fan to 12V battery and heater elements to 220V socket. After few brief moments I had around 50 degree Celsius hot air  blowing out - should be ok in a car on a cold day. Of course car's nominal voltage is around 140V so out of two 1500W@220V AC rated each heater elements I should be getting around 1900W. I also placed a small DS18B20 temperatures sensor into the box airflow path to be able to measure the air temperature and regulate the heater element temperature from a control box BCMS. 

Then I put assembled ventilation box back into the car and started assembling the cabin dashboard again.

This dashboard disassembling and assembling served another purpose too - wiring the additional cables. Cabling took quite some time to do as I was only taking out unneeded cables that were going to ICE and leaving the useful ones. I also had to wire some additional cables to be able to control RPM, fuel level and temperature gauges of Honda's stock dashboard instruments from BCMS. The whole process took about a week working on evenings after the work.

Real characteristics of Kelly KP Series 0-5V Throttle

As I made the control box and most of its wiring I started experimenting with it on the the desk with 1kW lights connected as the load instead of the motor. I found that I can control the lights with the throttle quite ok but sometimes they go off and sometimes they don't when I release the throttle. I thought that it might be Kelly controller glitches as I didn't trust it.
But then I looked at the voltage of throttle output signal through oscilloscope. And I didn't like what I saw - at released throttle was sometimes producing rippled voltage of sawtooth shape oscillating between 0.9 and 1.2 V at around 30Hz frequency. Sometimes it was stable at 0.9V. I suspected that 5V supply to the pedal could be noisy causing hall chip to generate this ripple but when analyzed it with oscilloscope I found it pretty normal 5V power supply noise ripple of only around 0.1mV which should not be an issue at all. Anyway I added extra 0.1uF capacitor to measured the 5V supply voltage which didn't change anything - I was still seeing the nasty ripple on released throttle. In addition to that the movement range from low throttle to the moment when the output voltage started rising was quite big - around 6 degrees out of ~35 degree range. I also noticed that full open throttle was giving only around 3.8V. This is certainly not even close to 5V stated by Kelly.
After finding that I contemplated on two options: send the throttle back to Kelly for repair or repair it myself. First option looks logical when you are dealing with respectable company in your country which will provide good customer support to resolve the problem. With Kelly it is different story - I've read many posts about terrible support of Kelly in the forums and it could be likely that I would spend additional money and time for shipments of repair/replacement with likely the same end result - throttle not working in full range. It would also be little use trying to claim the money back as Kelly is in China where business ethics in some companies could be close to jungle and their government does nothing to protect foreign customers. So I decided to look what's inside and correct the throttle box myself.
I opened the box using Dremel-style grinder cutting through black potty on the bottom to get to the bottom cover. Finally I opened the bottom cover. I found crudely hand-made marginal quality mechanics that is typical for Chinese products with magnet rotating against hall sensor. The hall sensor is AH49E which is produced by several manufacturers with similar characteristics. Datasheet could be found on http://www.bcdsemi.com/upload/datasheet/AH49E%20P1.1%2020080619.pdf. Datasheet shows that this device has output operating voltages range from around 0.9V to 4.2V so it can never output the voltages close to 0-5V range. This confirms that trying to send the throttle for repair would be waste of time and money as they would likely be replacing it with another AH49E. Replacement could possibly fix auto-generation sawtooth ripple on the output but not the total range.
I understand that the range of 0.9 to 3.8V could also work by adjusting the throttle lower and upper dead limits but such solution was not appealing to me at all.
So I replaced the AH49E with Melexis MLX90215 programmable hall effect sensor. I calibrated the sensor's gain and offset by programming it's parameters and I got stable voltage in 0.2V-4.8V range for full throttle movement range from moment when throttle switch clicks from idle till the throttle is full open. This is what I would expect from product which states that it's range is 0-5V

Conclusion: Kelly KP Series 0-5V Throttle can only give you voltage ranges from 0.9V to 4.2V in best case if you are lucky getting the one which was somehow adjusted to give these voltages range over full throttle movement. But in reality I would expect the range of usable movement and voltages to be even worse. In addition I am not sure self-generation of ripple would not be seen on other units as well. If I was a manufacturer I would not dare to put such specifications for cheating customers. I wish I read something like that before buying anything from Kelly.