Sunday, September 11, 2011

Unusual problems found with "normal" use patterns.

Here's what I've found so far as the BugE is used for it's intended use - a pure electric commuter vehicle that operates in cool rainy conditions while keeping the occupant free of windchill and rain.

First, in terms of BugE specific issues, I've noticed more tire wear with the front two tires with little wear on the drive tire. This suggests my 'toe' is out of adjustment. I'm guessing too much toe-in. So, an adjustment of the steering rods will be needed. Fortunately, this is a simple task. Visit the express links on the right to see how this is done.

Another unusual incident happened. It has to do with the BMS system. This type of BMS is no longer sold and has been replaced with a more reliable system. Unfortunately, I have the older setup. So, I came home to find the meter showing my batteries were rather low . I knew this, only due to noticing the BMS indicator lights were completely off. What apparently happened was that the DC-DC converter was doing a steady draw down of the batteries to power the BMS. However, the BMS wasn't triggering the AC charger to replenish the main pack. Finally, the DC-DC converter had the sense to cut off. However, the lead-acid battery discharged completely (turning off the BMS and it's indicator lights.) I'm sure the lead-acid battery took some damage but it's duty is normally rather light. So, it may have survived well enough to remain in service.

Fortunately, the main pack was not completely drawn down, just low. The cause was apparently due to a faulty LIN HUB. It failed such that it would only work if I bent the connector. When bent, all components seemed to work. When not, nothing worked. Unfortunately, when I tried solving the connector problem by trying to solder on a more robust replacement connector, I managed to loose what little function that circuit board still had. Unfortunately, it's a multi-layered board so it's beyond my ability to repair.

So, I removed the board, did an unbalanced charge of the pack to 50V and eliminated all parasite loads. Although 50V was not a full charge, it hopefully kept the lithium batteries in a safe state. Meanwhile, my vendor shipped me a replacement hub. Once replaced, the BMS returned to normal operation. Hopefully, the batteries are OK. We'll see if this is true in the next range test.

The last failure was severe enough to get my BugE trucked home. At times, if I accelerated even slightly, the vehicle stopped. After powering the vehicle on/off several times, the problem would go away. When I first noticed this, I thought the fault might be in the spade connectors I used for the throttle cable. So, I soldered the throttle wires to the speed controller inputs. This helped for a while, then the failure returned more often. So, this caused me to think the throttle potentiometer was at fault since it seemed to have similar symptoms to my previous throttle failure.

But no, these electric cars can be sneaky. Testing out the various components with a multimeter showed what the real cause was. After putting the rear tire up on blocks, I measured various voltages along the system. I found the potentiometer in the throttle was working just fine. However, the contactor (also known as the solenoid) was giving a voltage difference across it's terminals when engaged. This was not good since it's supposed to simply act as a hunk of wire between it's terminals when active. In fact, that's how I tested my hypothesis that the solenoid was at fault. I put a hunk of wire across the terminals. Sure enough, the motor driven by the speed controller worked just fine. So, I've ordered a new solenoid, at nearly $100 bucks. Hopefully, after installing the new one, I can take apart the old one to salvage it for a spare. It did cause me to question why these solenoid's are needed at all. For an explanation, look HERE.

Sunday, September 4, 2011

September 30, 2011 - My first commute!

At last. It was time for my first real commute from Auburn NY to Wells College in Aurora NY. Russel Watson's "Faith of the Heart" song came to mind when I took off on this historic journey.

Although the BugE will do 50MPH on flat ground, this test wasn't a speed trial. Rather, it was to figure out the speeds that will be fast enough to be useful yet be slow enough to not loose too much energy to wind resistance.

Distance was just over 20 miles. Morning temperature was 60 degrees and sunny. Canopy practically eliminated windchill. Speed was kept at a minimum of 30mph, up the gentile slope to the ridge line. Along the top, maintained 35mph. The journey was so pleasant that I overshot my planned turn. Fortunately, I had an excess of charge so I could take the next turnoff which made the journey slightly longer than planned. The last 2 miles downhill were done at 45. Arrived with 40% of charge still left. Commute time was 45 minutes which was two minutes longer than I had planned.

The BugE recharged at the Stratton Science Building where it was put on exhibit for the day. Charging was done before noon. At the end of the day it was time for the return journey. Rolling the BugE out of the building, the outside temperature was 80 degrees & humid. This caused a temporary fog on the canopy that quickly dissipated in the sun. I did the long climb up to the ridge at 25mph to see if a lower speed would help conserve the battery. It did. Once half way up the hill, I maintained speeds of 30-35mph. Since I had more charge than expected, I took the last 2 miles home at 45mph. Pulling into my driveway, I still had 1/3 charge left.

The trip had one noteworthy incident.
The throttle didn't work! So, I exercised the interlock relay several times. Then, the throttle worked. When I returned home, I tried some contact cleaner compound on the throttle spade connectors. That seemed to fix the immediate symptom. However, this likely isn't the real cause. I suspect the interlock arrangement I have may be at fault. So, I'll be doing a wiring change to test this hypothisis.