Wheel, Tire and Suspension Upgrades
Now that the 320i has passed inspection and is drivable it is time to customize the car a bit. The first thing I did was buy 15" Alpina knock-off wheels. They are 15"x7" spoke rims and look very similar to the original wheels on the car. The knock-off meant that they cost less than $200 a wheel. Real Alpina wheels cost $1000 a wheel! The 13" wheels that came on the 320i really limited the number and type of tires available today because of the diameter and width. The new 15" wheels make many more tires available. I got tires for the 15" wheels that were the exact same circumference as the 13" wheels and tires. That was done so the speedometer would still be accurate. I found a website that calculates things like offset and circumference called Rims and Tires. I also got the 15" wheels to help the clearance issue with the rear disk brakes. When I did the upgrade to disk brakes in the rear the upgrade kit warned that the calipers might interfere with 13" wheels. I had ground down the contact points on the calipers but they still dragged a little bit. Now with 15" wheels there is plenty of room. Of course getting the new wheels on the car would not be so easy. The issue is the offset of the wheel. That determines how far in or out of the wheel well the wheel will sit once it is mounted on the hub. It is important that the offset is correct so the wheel does not interfere with the fender or the shock mounts. The offset for the 320i rear wheels is 13mm. Unfortunately the wheels I got came with 18mm offset. That meant I had to get 5mm wheel spacers to make up the difference. Many wheel spacers are available for the 320i from many manufactures, in the correct diameter, thickness and bolt pattern. However, installing the wheel spacers was not that easy. I found that the rear hubs on the 320i had a 2mm area that was not machined down to the 57.1mm hub diameter. That meant the spacer would interfere on that edge and not make flush contact with the rotor. I had to take the spacers to my local machine shop High Tech Machine and have them cut clearance for that larger diameter offset. I found after installing the wheels a few times that I needed to install threaded studs into the rear hubs. That made alighment of the spacer disk and mounting the wheel much easier.
The next upgrade was to get a new suspension setup with coil-over shocks. A company called Ground Control makes a set of coil-overs for the 320i. I wanted to change the suspension so I could adjust the ride height and make it even in all the corners. With the added weight of the batteries over the rear axel, the rear of the car squat a bit with the old springs and shocks. Unfortunately installing the coil-over system was not that simple. For the front wheels the Ground Control system uses a larger diameter strut tube than what came standard on the 320i. That meant the old strut tube had to be cut off the wheel spindles and a new one welded on. I could not do that work, but I found a company near me that specializes in restoring old BMWs and does that kind of shock work all the time. The company Vintage Sport and Restoration (VSR) has quite an operation going. Not only do they have a multiple bay area with car lifts, they also have a full machine shop, weld shop, a body shop and paint room. They took the wheel struts off, cut the strut tubes off and sent the wheel spindles to Ground Control. For some reason it took Ground Control a long time to turn the struts around. I thought the whole process would take a couple of weeks but the 320i was there for over a month. Even though VSR measured the weight of the car (same weight I measured) and measured the corner to ground heights, Ground Control sent the wrong springs for the rear setup. Too short and too low of spring rate. VSR had to order longer and stiffer springs to get the right ride height. The ride height is adjustable with the Ground Control system and I had them set the height lowered to about 1".
When I was driving the 320i to VSR I noticed that I had a vibration in the front end at 40 -50 mph. Even from the beginning first drives there never has been any vibration of any kind while driving at any speed. The only difference was the new wheels and tires. I doubted it was the wheels and thought maybe the car needed a wheel alignment. When I told the guys at VSR about that, they noticed the new Dunlop Direzza tires I got were mounted backwards on the wheels. High performance tires like that have a rotation direction, so the vibration was caused by the improper mounting. Of course the tires had to be remounted and spun balanced. The new tires really make the ride feel great, very positive tracking. But they do have a downside. Because they stick much better to the payment they really cut the battery mileage down - nearly 20% compared to the old wheels and tires. Even with that mileage reduction I will have plenty of range to use the car as a daily driver. While the 320i was at VSR they also corrected a problem with the driveshaft alignment and an issue with the calipers on the rear brakes. The driveshft issue required the front engine mounts to be lowered more than an inch. That mean the left side mount spacer block was removed and the right side replaced with a bushing. While at VSRt they thought I should refer to the car as the 320e for electric drive. The "I" at the end of the model number for BMW always meant fuel injection. No gas being injected in this car, although you could say electrons are being injected into the electric motor, but that might be a little too much for some people to understand. So I think from now on I will refer to the car as the 320e. Thank you VSR!
The last upgrade was not really and upgrade as much as a reconfiguration. I took the rear seat to an upholstery shop and had them take the leather seating material off and mount it on a piece of plywood, with a 1-inch dense foam pad underneath. The plywood I cut from a cardboard template I made of the rear seat area with the battery box tops. It did not cost much for the upholstery work and the rear seat now fits much better over the battery boxes in the rear seat area. It still will not be possible for someone to sit there, but it looks much better and should support small weight like groceries. Related to the rear seat area I installed sound damping material in the side cavities, behind the lateral trim panels, in the back seat. The new tires make a lot more sound on the road so the sound damping is necessary. In fact the first time I drove the car with the new tires I though there was problem with the tires because with the electric drive, the car is very quite. Of course a lot of the noise was from the tires being mounting the wrong way. After VSR remounted the tires the noise was reduced, but still louder on the highway than the other tires. The Direzza tire formulation is only for summer driving. They are not recommended for winter driving - probably get too hard in the cold. I might get a set of Michelin Energy Saver tires like I have on my Chevy Volt for winter use. I might also have to get another set of cheap wheels. Not that I am going to drive in the snow much, but when there is a nice clear day I would like to drive the car. In the winter around here they put a lot of salt on the roads and I don't want to ruin my new Alpina knock-offs.
The way the 320e drives with the new stiff suspension and new tires is very different than the way it drove before. Because of the heavy weight on the rear suspension the car would pitch a lot in turns and understeer. It also took bumps hard because most of the suspension was compressed with the heavy weight of the batteries. With the new setup the ride is a little bumpy on side streets but on the highway very smooth and very positive control. The car also corners really well now. Very happy with the upgrades!
A video will be coming shortly.Add a comment
Vehicle Inspection, Finally
A lot has happened in the year since my last post. To make room for all the cars at the house, I had a new two car garage built last fall. I also had a car lift installed in the new garage to make working on the 320i and others easier and the lift can be used to store a car during the winter months. I also got married and went on a honeymoon to Hawaii. So the 320i has not been worked on very much. To get the 320i ready to be a daily driver I did have to do some major work on the brakes. I could never get the power brakes to work and finally traced that to the vacuum boost cylinder. I had very difficult time finding a replacement. All of the units I could find were used and in very bad shape - worse than the one I had. The vacuum boost cylinder is not available from BMW or any part seller. Fortunately was very lucky to find a new unit on eBay. Someone must have been holding on to that for 35 years. They sold it for the same price RealOEM listed as the price when the part was available from BMW. Of course, replacing that vacuum booster required removing the master cylinder and then bleeding the brake lines. I have gotten really good at bleeding the brake lines with the pressure bleeder. After completing the work and running the vacuum pump I was able to get power assisted braking. Getting good working brakes was a major requirement for getting the car inspected. As I have said many times in several past blogs the 320i has to pass Massachusetts vehicle inspection before it can be a daily driver. What they really look at closely on an old car like this is all the mechanical aspects like body, tires, lights and brakes. They really have no inspection for the electrical drive so that should be no issue. It has taken nearly a year to get everything on the 320i fixed to the level needed to pass inspection. The last few things have taken months to complete, mostly because I only work on the car on the weekends. The windshield washers are a good example. Part of the engine compartment renovation I did was to replace the windshield washer reservoir. The old one was yellow with age and blue stained from the washer fluid. I could not find the exact part from RealOEM to replace it but found the 1985 320i washer reservoir was available and I ordered it. The problem is that BMW changed the pump motor design that year. The reservoir was roughly the same shape and mounted to the car the same way but the pump mounted differently. On my old reservoir the pump actually was inserted into the reservoir through a sealing gland on the side of the reservoir to pick up the fluid. The newer pump is outside and connects to the reservoir with a hose connection. The problem with the hit and miss part availability from BMW on the part list on RealOEM is that the older style pump was available, but the newer version was not. So I had to figure out how to adapt the old style pump to the newer reservoir. I ended up having to make a small angle aluminum bracket to hold the pump and connected to the reservoir with a hose. Just working weekends this little project took me over a month to complete. I also replaced all the water lines in the process so now the windshield washer system looks brand new. But, the washers work too good. The pressure is so high from the new pump that most of the washer fluid goes over the windshield and lands on the roof of the car. Either a resitor on the pump circuit or a flow restrictor on the water lines will fix that.
Another activity to get the car ready for inspection that took weeks to complete was gluing down all the last bits of carpeting. I had installed and glued most of the carpet, but did not finish the rocker panels or the rear seat or some areas around the accelerator pedal and transmission tunnel. Of course gluing up the last of the carpeting took much longer than the main part of the carpet and I ran into problems. When I was manipulating the accelerator pedal to get it through the hole I had cut in the carpet to my horror it broke off the mount on the floor of the car. I guess 35 years of acceleration was too much for the old rubber. Fortunately a replacement accelerator pedal was available on RealOEM and I was able to install the new pedal and get that part of the carpeting glued. Another problem I had to take care of before inspection was the gear shift. Ever since I installed the motor and transmission a couple of years ago, the gear shift was not in the correct position. It shifts okay but is not centered and my hand would hit the dashboard when I shifted into reverse or 5th gear. It has a bracket inside the transmission tunnel that mounts on top of the transmission that was really hard to manipulate on my back under the car to mount correctly. Now that I have a car lift in my garage I was able to remove the driveshaft and then remove the gearshift mechanism. The 320i has a short shift setup and my original mistake was to reversed the gear shift lever. The lever has a 30-degree bend in it and needs to be oriented correctly for the gear shift to be centered. Once I installed that correctly I installed a new drive shaft and universal guibo.
Trying to save space and weight I had originally installed a small 10 A-h 12V battery in the engine compartment to power the contactor relays when the car is started. Once started the DC-DC converter would provide all the 12V DC power needed to operate the car. Unfortunately the small milliamp leakage in the 12V circuit when the car is off drains the 12V battery below 12V in only a few days. I was having to connect my battery charger to the 12V battery to get the car to start. To eliminate this problem I decided to make the 320i like modern BMWs and put the battery in the trunk. I could use a much larger battery, the only problem is I needed to run a battery cable from the trunk to the engine compartment. That required pulling up some of the carpeting that I had recently glued down. I got a 12V dry cell from Summit Racing for the replacement battery. It is a 44 A-h battery and being a dry cell it can be mounted in any position. That solved the battery draining issue. For long term storage I put a manual disconnect switch on the battery.
The final issue to fix before inspection was the horn. The horn had always worked and I had removed the fuse just so I would not blow the horn accidentally while I was working on the car (working with high voltage it is better not to be startled). I had removed the steering wheel several times to make working on the interior easier and had replaced it to do my first two drives. Sometime during all the steering wheel manipulation I manage to shear off the electrical pickup for the horn. The horn circuit still worked, but pressing the horn button on the steering wheel did not. Again fortunately the replacement part was shown to be available on RealOEM, and was available from several BMW part sellers. That is one cool things about RealOEM. Through the diagram view of all the parts of the car it is possible to get the exact number of the part sought. A Google search can then be done on the part number and if its available it will show up as new from several parts dealers and BMW dealers, or if not links to ads for used parts on EBay. Of course replacing the horn pickup was not that simple. The old one was riveted to the steering column end plate, so those rivets had to be drilled out and replaced with nuts and bolts.
Finally everything was ready on the car for inspection. All my preparation paid off and the inspection went through without an issue. The inspector really did not check a lot of things, seems like they checked more on my new cars I have taken there but they did test that the windshield washers worked. I have been going to the same inspection station for the past 3 years and have been telling the guy there about my project. He was really happy to see the car and very impressed with the work. Now the car has an inspection sticker. The last thing I did was to get the Massachusetts EV plate. Massachusetts is one of the few states to offer EV plates. They are a cool way to indicate you have an electric vehicle and helpful for first responders if you get into an accident. They will know its and electrical powered car and know not to cut any orange cables! Now with everything compete I started driving the 320i as my daily commuting driver.
A video of this fun can be found here.Add a comment
2nd Test Drive, the drive between houses
Working on the 320i unfortunately has taken a back seat to a lot of things going on in my life. The biggest of which is I sold the house I have lived in for the past 15 years and bought a new house. We started the house hunting process last fall and it seemed like every weekend until the snow started we were out looking at houses. Once the snow started I started my usual winter activity, skiing. We finally found the house we wanted and purchased it earlier this year. We had some renovations we wanted to make before we moved in and those took until May to be completed so we just moved into the new house last month. The garage still needs a lot of organization. I had to breakdown 3 years of all the systems, components and tools I had put together and have them moved to the new house. I am in the process of setting everything up. The only problem is the new house has a smaller basement, but larger bedrooms. I will have to setup part of my operation in one of the bedrooms that I will also use as an home office. The 320i is still in the garage at the old house and will have to be moved soon. I would love to drive it to the new house but the car has not been inspected. Massachusetts requires autos to be inspected every year. The 320i has not been inspected in three years so the inspection sticker is expired. For an old car like the 320i even if it had the ICE still in it they would not do an emission test. They mostly focus on the mechanical aspects of the car and for an old car they really look at everything. That is reason why the 320i does not have an current inspection sticker. Although it drives just fine there are still a couple of little things that need to be finished before it would pass inspection. All of those things could each take a weekend to complete. The vacuum power brakes are the biggest issue to resolve and were my biggest concern driving the car. I planned to drive the car early on a weekend day, so there would be less traffic.
First I had to charge the battery pack. For all the time since the first drive I was letting the pack sit at half charge. Every week or so I would turn the car on and spin the wheels for a couple of miles. That did not really take much out of the battery. I still was showing 35 amp hours out of 60. But before driving it on the road again I wanted to fully charge the pack. Even though the drive to the new house is only 16 miles, 4 of those miles are on the interstate and I wanted to get a good measure of the battery use. To start the charging I checked all the connections on the car and I turned it on to charge the 12V battery (from the DC/DC converter) to make sure all the relays would latch. I then plugged the Siemens EVSE into the 320i. I had a lot of problems with this EVSE - the first one I received would not even charge my Volt. The one now installed has been working for over a year charging my Volt every day and it worked the last time I charged the batteries on the 320i. But when I plugged it into the 320i, it initially came on but then shut off with an error. I repeated the connection an noticed the Brusa charger was also coming up with an error. Who was erroring out first? To find out I used the J1772 cable that I had connected a NEMA plug on the end so I could bypass the EVSE and directly connect the Brusa to the 240V source. When I did that the Brusa came right up so the Siemens must be the problem. I have one of those AVC2 modules installed for controlling the J1772 interface but the Siemens does not seem to work with that. I used the serial interface on the Brusa to monitor the charge and checked individual battery voltages. Everything appeared ok and I charged for three hours to put another 10KW into the battery pack. I checked every battery voltage and none deviated by more than 25mv so the batteries are still looking good. I took the car out for a spin around the neighborhood. The vacuum brakes still are not working and the vacuum pump runs a lot. Not as much as before, but after each brake application it runs for several minutes. I tested it and the reservoir starts to lose vacuum with just a small amount of pedal travel. The pedal has to move half way to the floor to get the car to stop so it completely depletes the reservoir. It might be possible the vacuum brake cylinder is not working or has a leak. That would be a pain to replace, the master cylinder would need to be removed, which means disconnecting the brake lines so the brake lines would require pressure bleeding again. The other problem is just finding a replacement vacuum brake cylinder. That part is not available from BMW or any auto parts online store. On eBay I found there are vacuum brake cylinders available for other early model BMWs so I ordered one to see if it would fit. It has to fit the master cylinder perfectly to work. The mounting bolts to the firewall could be modified it there is some discrepancy.
The day for the drive from Methuen to Andover could not have been better. Sunny and nice cool temperature for July. The drive went very well, even went on the interstate for a few miles. Very smooth and no vibrations. Just had to get use to the manual brakes, that will stop the car, but require some leg strength. I think on these old cars the brakes never worked like they do now. They did not stop on a dime and you had the anticipate stopping and giving enough room to brake. I started out driving in 3rd gear which gave really good pickup, but the motor/transmission really screamed a lot when the rpm got to above 3000. I will have to determine what is going on there. In forth gear the car drove very smooth, even on the highway at 65mph and 3500 rpm. When I finished the drive I checked the power usage. For the 14.5 mile drive the car used 4384W so that comes to 302W/mile which is a really good number and right on with the rule of thumb that the energy usage is the car weight divided by ten. The car weighs just over 2860 lbs and with me and a tool box another 185 lb for a total of 3045 lbs. With the full battery pack capacity of 27KW that would be 90 miles. But the full capacity would not be used often. Usually the 80% capacity of 21KW would give used which should give 70 miles range. That is a bit lower than my design goal of 100 miles. To get to that goal I would need over 30KW of battery capacity and that could only be achieved with the new CALIB CAM72 cells that are smaller and have more capacity. I cannot add more batteries as I am at the 400V limit of the inverter so I would have to replace the whole battery pack. That is not going to happen.
A video of this drive can be found here.Add a comment
1st Test Drive!
The last item on the punch list for the first drive was calibrate the brake pressure sensor. I had spent a lot of time and effort in getting that sensor mounted near the rear brakes that I detailed in an blog from last year named Almost Rolling. The pressure sensor is used to indicate braking which will signal to the GEVCU to command the DMOC/Siemens into regen to slow the car. Because the regen torque can be set to a very high level almost no brakes are required. But the transducer has to signal the brakes are being applied and the brake lights come on. The calibration procedure is very simple, just take a reading with the brakes off and then with the brake pedal pressed. Unfortunately when I press the brake pedal the pedal went to the floor with no resistance. Somehow air had gotten into the brake line and the brakes would need to be pressure bled again. Previously I had a real problem pressure bleeding the rear brakes. I could not get a good flow of brake fluid to remove all the air in the line. Something was preventing the flow. Besides the master cylinder the only other component in the brake line is the proportionating valve that is used the regulate the pressure in the rear brakes so they don't lock up. These types of valves were used before ABS was developed. I was concerned I might have to replace that valve because of the rear disk brakes I had installed. They would brake stronger than the drum brakes that the car came with and might lock-up with hard braking. But I also increased the braking strength of the front brakes too with new rotors and pads. I thought I could just see how the brakes would work without changing it. With the brake bleeding problem it became necessary to replace the valve. I installed an adjustable valve from Wilwood brakes. That solved the brake bleeding problem but I still could not get a good brake pedal. The only thing left to check were the rear brake calipers. I had read online that some new calipers need to be bench bled. Before going to that effort I unbolted the caliper from the hub, with the flexible brake line still attached, I rotated the caliper so the bleed nipple was straight up. Using the pressure bleeder I found both calipers had a lot of air in them, especially the right rear. By moving and rotating the caliper I was able to get all the air out. Once I was able to do that and bleed the rest of the brake system once more I got a good stiff brake pedal and I was able to calibrate the brake sensor.
Just when I was in the process of getting the car ready for the first test drive I discovered the GEVCU was not sequencing the high voltage contactors correctly and the DMOC would not spin the motor. It seems the GEVCU lost some of its configuration data. When I was trying to figure out what was going on I discovered the contactors were fused because I could measure high voltage at the buss bar when the car was off. That means they do not switch the high voltage and are permanently shorted. They can be damaged when a high current pulse happens. The DMOC has a large capacitor bank and when not charged looks like a dead short and will take a large current pulse from the battery pack if not controlled. In my design I use a precharge resistor to limit the current inrush. But that only works if the contactors sequence correctly. With the GECVU loosing configuration data it must have caused the contactors to fail because I had bench tested the contactor box many, many times. I even found a problem with the GEVCU MOSFETS that would have lead to this problem. But I fixed that circuit issue on the GEVCU I am using and had tested it extensively. Unfortunately the contactors are not easily replaced in my build. They will have to be replaced but since they are fused they should conduct enough current to move the car. To get my first test drive I built another precharge/contactor circuit that runs off an Arduino Uno processor and relay shield. Once I installed that and verified it was working I was ready for the test drive.
Finally I was able to get the car off the jack stands and back it out of the garage under EV power. That is the first time the car has been out of the garage since January 2014 when I pushed the car out of the garage and pressure washed the engine compartment after the internal combustion engine (ICE) was removed. I drove the car out of the garage this time to finish painting inside the engine bay and the area where the hood is mounted. After the painting was completed I had to drive the car back into the garage and wait for the paint to dry a couple of days so I could mount hood. I mounted up several GoPro cameras around the inside and outside of the car. After that I went on the first test drive. The car drove great! Very smooth and responsive! I did not drive it further than around the block a couple of times because of the fused contactors. Before going on the test drive I weighed the car. On this website in my design section I showed after all the ICE components were removed the car weight was just 1776 lbs. Now with all the electric vehicle components the car weight is 2860 lbs and the weight is nearly 50/50 front to rear (48/52). If the rule of thumb for energy use holds then the 320i should use no more than 286W/mile. My Leaf used to do better than that and the Leaf was a heavier car. The Chevy Volt I have now is a much heavier car but because it has such low coefficient of drag I have seen energy use as low as 250 W/mile. Obviously the lower the number the further the car will go on a given battery capacity. So with my total capacity at 3.5V charge being 26.6KW the 320i should be able to go 97 miles - almost the full 100 mile design goal! Of course how far the car will drive on a charge is dependent on so many factors, the most of which are how aggressive I drive the car and how fast I drive on the interstate. The Volt does so well because of its aerodynamic shape, but the 320i is a bit of a brick so it will consume a lot more energy at highway speeds.
I still have to finish the carpet installation and install the passenger seat. I still don't know what I am going to do with the rear seat. There really is not much room in that car for the rear seat so maybe just a platform that protects the battery boxes would be good. Something will have to be done with the contactor box. I might just jumper over the failed contactors and continue to use the new contactor box in the trunk. I also need to fix the BMS board and find out why the instrument cluster is not working. I tested that before I mounted it in the dash so all the cabling should be correct. For the test drive I used my Samsung tablet to display the embedded website so I could monitor all the drive functions. Once all these issues are resolved I plan to fully charge the battery pack and take the car for a long drive to see what the energy use will be.
But there still is a lot to do before the car can become a daily driver. I have some BMW badges that need mounting along with the "Electric" badges I got. Have to make sure all the lights are working and then the car needs to be inspected. I need to have the registration changed to show it is electric drive now, although on old cars like this they do not do an emissions test. Mostly just mechanical and lights but that will put the car in the registry database and I will be able to get an EV license plate, if I want.
A video of the first drive and some of these other fun issues can be found here.
Or you can check out the prequel video to the first drive here.Add a comment
I took part of the summer off, going on vacation and spending time with my family so not much work being done on the 320i for the past three months. I was able finish the dashboard and all the 12V wiring. I installed the AVC2, which is a module for controlling the J1772 connection to the charger. Back at the beginning of June when I was getting ready to go on vacation I had charged the batteries up to 30AH and 375V which is half capacity and a cell voltage of 3.2V. I assumed with nothing connected and even the manual disconnect switches open that the battery pack would just sit there and stay charged and be ready for me to drive it when I got back. Just a couple of weeks ago I wanted to test out the AVC2 connection and turned on the car. I always check the JLD404 to verify the voltage and state of charge. To my horror instead of reading 370V the pack was only reading 77V!!. That meant the batteries had been discharged to less than 1V! Not a good practice for lithium batteries of this type. Over discharge can cause large losses in capacity because the lithium gets tied up in the cathode material. I do not know what caused the discharge. The only thing connected to the batteries was the BMS. The current leakage in the switches used in the BMS is only a few microamps at 800V. At the voltages the BMS switches see the current leakage should be sub-microamp so it would take a long, long time to drain down 30AH ( more than 30,000,000 hours!). Something else must be going on. My biggest concern was the state of the batteries. I measured the voltage of every battery. They were all around 0.6V and the lowest was 0.25V and the highest was 0.85V. No battery was at 0V so the bottom balancing I did earlier might have saved all the batteries. I removed one of the batteries from the front battery box and connected to my lab bench supply and charged it at 1A until the voltage was 2.7V. That did not take very long - about 60 min. I then could put the battery on my Powerlab charger - that charger will not work on batteries discharged to a low level. I charged the battery at 10A to 3.65V and the battery looked just fine. The charge curve was normal and the battery charge capacity was 64AH. As received from CALIB the average capacity of all the batteries was 66AH so a very small loss in capacity. The problem I had was with the Bursa charger for the main pack because it would not work on a low pack voltage so I had to charge groups of batteries up to 2.7V using the Keithley 2420 source meter I have. Earlier this year I had used that power supply for bottom balancing some of the batteries. I have a program I wrote for doing the bottom balancing, which is essentially what I would be doing again. I charged batteries in groups of 10 to 18 up to an average voltage of 2.7V at a 1A charge rate. I carefully checked the voltage of all the batteries during this initial charge. After all the batteries were bottom balanced I could charge at the Level2 rate with the Brusa charger. Once again I charged the pack to 375V and 30AH and carefully monitored all the battery voltages during the charge. Nothing looked out of the ordinary. I then finished fully charging the pack to 60AH and 413V. Everything still looked ok, except one battery went to 3.65V when the average charge voltage as just 3.45V. I stopped the charge because that battery went to full voltage and I did not want to overcharge that battery, even though I will probably replace it. The question now is how did the pack become discharged in just a couple of months. I know earlier from making measurements there is no leakage path to the car ground. I only measure capacitive voltage when I test from the battery peak voltage to car ground. However, recently when I was changing out that battery in the front battery box that went to 3.65V during the charge I got a shock when I brushed against the battery box. The battery box is grounded, but the batteries should have no reference to that ground. When I measured from the last battery in the front box to ground I measured 53V, which should not be there. I started disconnecting things and found the ground reference was in the Delphi DC/DC converter connection. When I removed the high voltage cable the voltage reference to car ground went away. So either the DC/DC converter is the issue or the cable is. It might explain how the pack could be fully discharged in such a short time. Using a 33k ohm resistor I measured the leakage to car ground from the high voltage point of the battery pack. I got a 2.5V drop on the resistor indicating a 0.076mA current flow. That is well inside the spec for the Delphi DC/DC converter. The voltage that appears to car ground is disconcerting and is probably what gave me a shock. But that small amount of current leakage should not have discharged the pack in just a couple of months. Something else must be going on. The BMS was the only other component that was connected. I still need to connect that and measure any current leakage. When I first started testing the BMS I found that the 3.3V DC/DC converter on the board was not working. That explains why the BMS was not sending any CAN messages when the USB was disconnected. I need to repair that board so I can do some more testing.
Other fun I have been having before the first drive is installing the carpeting and front seats. The carpeting I got from a company called Stock Interiors. When I received it I checked it against the old carpeting. It seemed to have the right shape and contours in the right place. Aftermarket new carpets never have any of the holes cut so I had to cut the holes for the gear shift, e-brake, throttle pedal and the seat mounting points. I did not realize at the time that the contours for the seats areas were not quite right. I struggled to get the carpet in the correct position before I started cutting. It seemed like the carpet was too small in some areas and too big in others. The carpet over the transmission tunnel is loose, but under the seats it is tight. The info on the company's website says it should take 3 hours to install the carpet. I don't know what universe that got that number from but it took me two days to install most of it. I still don't have the kick panels or the rear seat section installed. That number is probably for a late model car that does not have as many contours as the 320i. I got the driver's seat installed, the steering wheel and center console. Everything I need to make the first test drive.
A video of all this fun is avialable here.Add a comment