Replacing a broken motor controller

On a typical lunch break me my four collegues had just started driving back to work when all torque stopped without any warning. The Kelly Controller PM72401B motor controller flashed for "internal voltage fault", so we pushed the Corolla to a nearby parking space and took a walk back to work.

After towing the car back to my garage I figured out that some mosfets from the controllers other half bridge had failed. The PM72401B main circuit seems to have 7 IRFB4110 mosfets in each leg. As tough as the IRFB4110 is, it's still only a 100V mosfet. The PM72401B operates at up to 90V battery voltage which leaves very little margin for overvoltage spikes. Corolla's ME1003 is a high current motor specified to have a low inductance of only 93uH @ 120Hz which leads to a high current ripple and switching high currents lead to high voltage spikes which the mosfets have to deal with. 100V mosfets are not enough with Corolla's 76,8V battery pack and ME1003 motor in my opinion. I am actually positively suprised for how long the PM72401B managed to survive; 3,5 years and 28000km of driving.

As also the current handling capability of the electrolytics inside PM72401B seemed too low for my application I was determined to replace the controller with a controller having at least 150V mosfets and higher current capability.

Sadly there is not much to choose from when it comes to suitable permanent magnet motor controllers and there are even less alternatives if regenerative braking is wanted. I ended up making a decision between a larger Kelly Controller and Paul & Sabrina's 144v 500amp DC EV Motor Controller Kit. It was a difficult decision between a well tried open source controller and a commercial black box. Should there have been used P&S controllers on sale I would have gone that way, but as there weren't, I decided to go with the shorter lead time solution to get the Corolla back on road faster.

I purchased a Kelly Controller KDH12801E for the job. Its advatages over the P&S were the ability to regenerate and its shorter lead time due to not needing to build the controller. Down sides are that I don't know what's inside the black box and I also have very limited possibilities to configure its behaviour.

The KDH12801E is a 2-quadrant controller being able to motor and regenerate into one rotating direction of the motor. It's rated up to a 120V battery pack nominal voltage and up to 400A continuous current, making it a few times higher power specified than the PM72401B. The controller was delightfully shipped with a USB-to-RS232 converter, a pre-charge resistor and some diodes needed for contactor controlling. The pre wired J2 cable assembly also proved to be very handy.

I had to make a rebuild for my controller assembly box as the dimensions of the new controller varied a few cm. A bigger heatsink was also mounted and machined to fit. After a couple of evenings the Corolla was ready for test drives.

The first test drive impression were a dissappointment. I had limited the motor and battery currents to 50% meaning 400A each. Driving like this was simply slow and the controller gave only around 12kW of power at max throttle meaning around 180A of battery current. I had to increase the motor current up to 87% to achieve the same power levels that I had used daily with the PM72401B. This tells me that the current configuring affects not only to average currents but also to peak currents. Other down sides were that the regen stops at remarkably higher RPMs than the PM72401B did. But the worst thing is that a smooth acceleration is at the moment not possible as the controller gives an uncontrollable current peak when trying to accelerate smoothly from stand still. I hope that I can figure out a configuration that would help it even a little. Anyway I am glad to have the Corolla back on the road again!

New Powerfinn charger installed

 

Corolla eFX got back on track with a new Powerfinn PAC-800 charger feeding its traction battery pack! 

I had noticed that two Finnish companies Powernet and Powerfinn would have suitable chargers to replace my faulty brandless chinese made charger. I made a query for both of them and was quickly replied from Powernet that they cannot sell to private persons. I cannot understand this kind of business approach although it is a very typical one within companies aiming for industrial markets. I was happy and also relieved when Powerfinn was ready to see if we could find a solution for my case:)

Powerfinn did not have a suitable charging curve ready to fit my top balanced 24 series connected LiFePO4 cell's so I made an order for a Powerfinn PAC-800 charger and software work to get a charging curve that I wanted:constant current until 87,6V end voltage with a 2A charge cut off current. The charger it self was nicely priced, but the software work doubled the price. If software work is not needed the PAC-800 is very competetively priced in my opinion. If there would be a simple user configurable version of the PAC-800, it would be a superb product for all EV builders;)

 

 

The charger itself is a very nicely built device. It has an active PFC which keeps the input current so low that I am able to use an indoor heater to heat up my car on winter while charging from a 16A schuko socket.

Mounting the PAC-800 was easy thanks to the well designed mounting plate. I like the chargers behaviour with slow turn on ramps, controlled fan and high accuracy. All the things that I have measured from it so far have been nicely in its specification so I am very pleased!

Corolla eFX's weakest link

Having installed the new brush set and an air filter to the motor made me think that brush problems would have disappeared. I got about 9 maintenance free months of driving and then without any warning the brush set was destroyed again. We were driving to a grocery store nearby with my daughter when the motor stopped responding to throttle normally. A nasty plastic smell surrounded us as we pulled over. It was a -19 degrees cold winter evening so we were happy that my brother was close by and he gave the Corolla it's second towing back home.

At home I inspected the damage and came into a conclusion that I would again need to buy a new brush set. I purchased one again from Evdrives eBay listing. Everything went smoothly again with the shipping and the customs, thanks Evdrives!

This time I was not able to determine any clear root cause for the brush set failure. I noticed that one brush spring had broken into pieces but I have no way of knowing if it was the cause for the breakdown or not.

Anyway I'm getting more experienced in changing the brush set into a ME1003 than I would like to be.. The new brushes were quickly in their place and ready for burn in. I spent a total of 72h of burn in driving for the new brushes with my 3.3V 10A charger connected directly to the ME1003 terminals.

Now all was set to get back on track with the Corolla. I had planned to get to work with the Corolla on the next morning. But in the morning I chose not to go as I noticed that my 72V 10A battery charger was acting strange.. Later I noticed that the charger had broken down not charging at all, just blinking it's led. So now I'll have to find a new charger, and I'll also think again about replacing the motor with something that doesn't have brushes in it ;)

10000km passed

The new brush set and air filter have worked nicely and Corolla has been in more use than ever! First electric driven 10000 km is now behind and the car is working great.

From Cycle Analyst statistics, I have learned that my average regeneration precentage is around 2,5%. This means that I have gained 250 km worth of energy with regenerative braking while saving the mechanical brakes at the same time.

On our winter holidays we washed our "Red car", as we use to call it, togheter with my kids. The paintwork looks ok when it's wet;)

I have not been able to drive totally without brakedowns. One day when plugging in the car to be charged as usual, the residual-current device opened from my garage's electric cabin. I was suprised as charging had just before worked ok at work, but then again, at work we do not have RCD's on all sockets..

After some testing I found out that the Defa Classic inlet cable was causing the earth fault. It had been in use in this car since late 80's and now water had penetrated through the armoured cable causing the brakedown. The broken inlet cable was replaced with a Defa Mini inlet cable, which is a delight to use compared to the old one:)

Air filter mounted on the ME1003

To prevent brush set breakdown due to dirt I purchased an air filter to be mounted on the ME1003 brush set cover. After finding nothing suitable from local auto parts stores I found a solution from eBay.

 I ordered a HKS super power flow air filter which is a dry type mushroom shaped free air filter. Its diameter is 200mm so it fits the ME1003 brush set cover very well. I removed some unnecessary parts from the HKS filter and mounted its frame on the brush set cover with four M4 bolts and nuts. I think that this air filter is a great match for ME1003, highly recommended!

Having the air filter and brush set ready it was time for running in the new brushes. Mounting the brush set with all of its 16 brushes has not been easy so this time I tied them with cable ties as shown in the above photo. After pushing the brush set into the motor I cut and pulled off the cable ties. This method was easy and fast but it costs 8 cable ties:)

 For running in the new brushes I used a single cell 10A lifepo4 charger as I did not have any other suitable power supply available. The charger supplied only about 3V so the motor ran at around 120rpm. The picture above shows the result after 36h of running in with 120rpm. The brush on the left had only about 60% contact and the other brush was around 75% contact so I decided to keep running in for 24 more hours.

After a total of 60h of running in with 120rpm I decided that the contact surfaces are good enough. I guess having used a 12V power source for about 12h would have given the same result.

 Installing the brush set cover was as easy as before as the HKS filter frame does not block the mounting screws at all. The filter itself is mounted on the filter frame by a single hand tightened screw and the Corolla is ready to hit the streets again!

While writing this I have done one successful round trip to work without problems. I hope not to face any more brush problems for a good time:)

New vesion ME1013 brush set received!

 I ordered a new brush set, this time from evdrives ebay shop. It was a very nice suprise that the received brush set was the newer version! There were no indication about the version of ME1013 on the item description, but I am glad to finally have this new version after having received one older version from www.electricmotorsports.com.

I wish Motenergy would have made a clear version number for these two different versions of ME1013. While being fully compatible back and forth, the newer version uses welded bus bar connections where the older uses bolt and nut connections which failed on Corolla's first motor breakdown. The newer brush set has also bigger cross section bus bars lowering conduction losses.

 On the photos above the new version of ME1013 is on the left. It can most easily be identified from its bottom side where it has a plastic cover on top of the bus bars shown on the right side photo.

This photo shows the new version of ME1013 with its plastic cover removed. Removing the cover exposes the nice welded bigger size bus bars. No more bolts getting loose and getting burned!

Broken brush set by excessive amount of dirt

Replacing the drive axle rubber boot was a quite labor intesive task. I had not done it previously to any car so there were many new things to learn on the way. After a few late evenings both outer and inner rubber boots were replaced and Corolla was ready to hit the dirty winter streets again!

One day while driving my usual trip to work I suddenly noticed a clear lack of power. I was just getting on top of an uphill about 1km away from my workplace and tried to figure out what could have caused the power loss. As soon as I turned down the volume from the car's stereos I heard some loud whining. Luckily I was just beside a parking area where I rolled the car and walked to work. While rolling the car without the motor spinning the whining noise disappeared so it was pretty obvious that the motor was damaged.

After the workday the Corolla was towed to its garage to get repaired. All electrics were working nicely so I could concentrate on finding the problem from the motor.

 After removing the brush set cover it was easy to confirm that the motor was hurt. The commutator looked very bad and the smell of burned brushes was strong.

 Inspecting the removed brush set made it clear that the brush set was destroyed and it would not be able to be repaired. Brush springs had been cracked, conductors had detached from brushes and some brushes had been welded on their housings.

I crawled back under the car to see if the rest of the ME1003 motor could be rescued. Cleaning the motor and sanding the commutator strengthened my conclusion that this failure was probably due to excessive amount of dirt on the commutator and brushes. Possibly a small stone was the final cause of the sudden breakdown since the commutator had a deep groove that did not look to have been originated from any of the brushes.

My repairing plan is to purchase a new brush set and to sand the commutator back to its original shine. Also not to let this happen again I will build some air filtering on the back of the ME1003 motor.

While waiting for the spare parts to be imported I've been driving our gasoline Mondeo again. I miss driving the Corolla, hope to get it back on the road soon :)

First annual inspection passed

Corolla eFX has been in service for a full year now and it was time for the annual inspection. I knew the car was in good shape so I was not worried to have it inspected.

Time flew quickly as we discussed about electric driving with the inspector while the car was being checked. Everything safety related was ok so Corolla passed the inspection. A bleeding drive shaft rubber boot shown in the picture below was found though, it will be replaced soon.

It was the most pleasant inspection visit that I can remember, thank you Lempäälän Autokatsastus!

The car is now working very well and I'm using it every day. Daily driving is now a lot easier as the range of about 75km gives more freedom and I don't have to charge it everywhere I go:) I do not have much plans for upgrading it now, although I have to admit that I have though of different ways of increasing its power..

But in the meantime I will concentrate more on my open source motor controller: motocone.blogspot.com. Also during winter I am going to get more experiences by electrifying a small Stiga Garden lawn tractor using Motocone motor controllers and a couple of automotive alternators as its motors. This low cost project will be shared in: the-electric-machine.blogspot.com

Finishing touch for trunk interiors

The doubled battery capacity has made driving a lot nicer by keeping the battery voltages higher under load on these coldening autumn days. Increased driving range also gives new possibilities, such as visiting Tampere city (24 km away from home) without having to find a charging place ;) The functionality of the battery update has now been flawless so I am ready to cover the pack to regain a nice and clean trunk. 

First a simple cover was made from 12mm plywood. It is mounted to the battery pack housing with 4 30mm M8 bolts.

A new removable floor was made from 18mm plywood. A handle was cut in the middle of the plywood so that it can easily be lifted off to gain access to the spare tire space.

The battery pack cover was finished using black felt that was glued on top of the plywood and secured with staples from its sides.

Same felt was used to cover the spare tire space floor.

The spare tire space now works as a place for all the necessary items that I want to keep in the car but hopefully never have to use :)

The new plywood floor covers up the spare tire space with its items.

The original trunk floor felt was cut to fit on its place with the battery pack installed. It was glued to the new floor plywood for easier handling. Now the trunk looks usable again, with still quite a good space left for shopping bags.

 

Corolla eFX's first annual inspection will need to be done soon. I think the car is ready for that now!

Rear battery pack ready for work

Installing the rear battery pack is finally done and it is connected parallel to the front battery pack as shown in the circuit diagram posted earlier. The rear battery pack is electrically a copy of the front battery pack, but mounting it in the trunk is a lot easier environment than the engine room. In the trunk no waterproof encolures were used for the electronics.

This picture shows how the rear pack cable feed through looks from inside the trunk.

The first attempts to make a full charge resulted in a state where the Signalab PCM board blinked two leds next to each other and on the same time it switched its charge protection fets on and off with a frequency of approximately 1Hz. In this state the PCM kept its discharge protection fets off not allowing me to drive. The only way I could find out how this state could be resetted was by disconnecting the PCM from the battery pack. At first I had no clue what was happening and if I could rely on the PCM or not. I could not find a manual or functional description of this Signalab PCM so I did not know if it was some error state or if the PCM was broken.

I decided to double check the wiring if I had done some mistake that would have caused this problem. While checking I noticed that I had missed to install one blade fuse which resulted in a situation that the PCM did not have a connection to one of the cells in the battery pack. To make sure that the problem was linked to this forgotten fuse I charged the battery pack to get the fault state back again. Once the fault was active I installed the missing fuse and the fault disappeared. What a relieve!

Looking back I realized that the fuse was missing between the two cells whose balancing leds were blinking on the PCM. Without any proper manual or schematic I do not know if this was a designed feature of the Signalab PCM or not, but its a good indicator in such cases where connection is lost between a cell and the PCM.

After assembling the missing fuse the Signalab PCM has worked just like the one in the front battery pack. This regained my trust in it and I am hoping for a lot more careless kilometers just like with front battery pack alone.

The rear battery pack cells were not balanced manually in any way before use. The cells had a very consistent 3,3V reading so I decided to give the balancing task to the Signalab PCM board and see if it could handle it without having to help it manually. In the picture above the lit leds tell which of the cells are being bleeded by the balancing circuity at the time when the charger decided that the battery is fully charged and stopped charging. At this same moment the highest cell voltage I measured with my multimeter was 3,8V. I think a few more full charge cycles will be enough to make a good top balancing for the rear battery pack, just like with the front pack where nearly all balancing leds are lit just before the charger ends charging.

Things seem to be working as they are planned and I can enjoy driving with increased power output and efficiency due to lower voltage sag of the cars doubled battery capacity! Next step will be to cover up the rear battery pack nicely.

Installing the second battery pack

The second battery pack installation has been done in very small steps not disturbing the every day driving needs for the car. The pack takes about 1/3 of the space in the trunk which still leaves me with a good enough space for a few shopping bags.

 

The pack is mounted in a housing made from plywood. Each cell is attached to the housing bottom using threaded rods.

 This photo shows how much 24pcs of Winston LYP60AHA takes space from a -87 corolla hatchback.

Using this type of PCM causes a lot of wiring inside the batterypack. In here the cells are connected in series and the PCM's cell voltage monitoring wires are connected.

A 50mm diameter PVC tube was mounted under the car to the place where the exhaust pipe and gas tank used to be. The tube acts as a conduit for the rear battery pack cables.

Power and control cables to the rear pack are fed to the spare tire space under the rear battery pack enclosure. Now all the hard work is done for the second battery pack installation. A few more late evenings will be needed to finish up the connections and to prepare for functional tests!

Circuit diagram update 8.8.2014

Adding a second 76,8V 60Ah battery pack to the trunk means changes also to the circuit diagram. The low cost LiFePo4 PCM (Protection Circuit Module) that I am using is not designed for parallel connected battery packs, so I got to design how they could be used in this case.

The schematic above shows how I am going to connect the batteries. The circuit is designed so that it fills the following simple rules:

1. Stop charging if overvoltage is noticed in any cell of either of the battery packs
2. Stop discharging if undervoltage is noticed in any cell of either of the battery packs

Once I have installed the new batteries to Corolla's trunk, tests will show if the two rules will be filled or if more changes are needed. Once the rules are filled I am expecting many more carefree kilometers just like it has been so far.

Corolla eFX will get double range

I decided to build a similar battery pack into Corolla's trunk as there is under its hood. Due to a temporary www.ev-power.eu stock shortage 24pcs of Winston LYP60AHA were ordered in a format of 6pcs LP12V60AH.

The LP12V60AH contains 4 LYP60AHA batteries, and as I want to have access into each cell I need to dismantle the LP12V60AH pack's. It sure felt weird to start cracking open these brand new finely packed 12V batteries! The picture shows all of the tools I used to open the case.

Here is a picture of the LP12V60AH with its cover removed. I think its a quite nice assembly:

To compensate the weight of the battery pack to be installed, I removed the gas tank (13kg) and spare wheel (14kg). This way the Corolla will gain about 30kg weight after the new battery pack is installed, but it will still weight about 20kg less than original.

Cycle Analyst installed

I found the Cycle Analyst while reading these great finnish EV-builders blogs:

http://kwsaki.blogspot.fi
http://electricfinn.wordpress.com

Thank you guys for sharing!

Having got positive recommendations of the Cycle Analyst, I was expecting for a nice product. However it still managed to exceed my expectations. I had reserved a lot more time to install the than what was really needed, and the useability is excellent.

The biggest reason for replacing my old led panel meters was to get an Ah measurement, but all the other statistics that the Cycle Analyst can give are also very nice to have. It is really fun and enlightening to see the Ah reading run while pedaling. Its even more fun when the reading runs backwards while braking!

Bad contact in ME1003 motor brush holder

One day when I arrived at work I noticed an unfamiliar smell coming under the hood. I thought the smell was originated from some insulation material that was overheated, so I looked through all battery terminal connections which seemed ok and did not smell at all. The smell wanished pretty fast after the car was stopped so it was not easy to find its source.

After one short drive when I once again tried to find the source of the smell I noticed that one of the motor terminals was very hot while the other one was cool. The terminal connections looked tight and identical so I realized that I'll have to search for the problem inside the ME1003 motor.

First thing to do was to remove the brush holder cover:

Quite a lot of sand can be seen on the brush holder. At this point no faults could yet be seen.

Next the brush holder was removed for closer examination. It was far easier than I thought, this motor is clearly made for easy maintainance.

Once I got the brush holder on a table the problem could be seen:

The terminal on the left had blackened due to a bad contact caused by a loose bolt. By smelling it from a close distance it could be confirmed that this is the source of the smell. The terminal on the right looks healthy and its bolt connections were tight.

I also noticed that the brush springs were all not identical. One of them was significantly weaker than the majority:

In the picture above two spring on the left represent healthy springs in my opinion. The one on far right had loosed its form possibly due to overhating due to the loose contact as that spring was located on the brush closest to the overheated terminal. I tried to give back its original form but not with a very good result. As my brushes are still quite new the sping force on their current position is quite good also with the damaged brush spring. But as the brushes get smaller the damaged spring will not be able to deliver the designed amount of force, so I'll have to keep an eye on this.

To get back on the road I replaced the overheated bolt and nut and cleaned the contact surfaces:

The picture above shows the result of the repaired contact. I also checked the tightness of all other current carrying bolts and I would consider that 40% of them were too loose! After tightening all of them I reassembled the motor and I've been driving again with no mysterious smells;)

Knowing that I have a weak brush spring and that the current carrying bolt connections can get loose again I searched the internet for others experiences. I was more that happy to find this link:

http://evmc2.wordpress.com/2012/11/17/motenergy-brush-holder-me0804-rev-a-dept-of-a-closer-look/

I am seriously concidering of ordering that improved brush holder version with those welded connections and larger buss bars. It seems like an excellent solution for my brush holder situation!