Monday, August 29, 2011

BugE Q & A

This blog posting is a partial response to some questions fermi_of_borg had in his BugE build.

The first photo shows how I oriented my direction switch. I found it was easiest if I had the forward direction pointing backward. However, this is probably opposite of what people normally would think when it comes to direction. I had to remove quite a bit of material with a Dremil tool to get a sufficient sized notch for the switch to go into. I decided to go with a notch instead of a hole since I open and close the battery compartment quite often for small adjustments. Now, no need to remove the handle!

The second photo shows the switch orientation without the cover. The direction switch is held in place with a couple of "L" brackets attached to a platform I made from a cutting board I bought at Wal-Mart. It's cheap, easy to cut, non conductive and needs no painting. Anyway, In the lower left is a little photo of a wiring change I did. In the original 48V wire diagram two wires were to be attached to a contactor terminal. Problem is, it's quite a tight space. So, I decided to attach the two wires together instead at the top terminal of the reversing switch. Electrons don't care which end of a wire they are on. To them, one terminal of a wire is identical to the other terminal of the same wire.

When it comes to connecting the lug rings, the type of nuts should connect very TIGHT! Using Nylock nuts will help. Also, double check the little screws on the lithium battery pack. They should be tight too. One way I happened to find a couple of a loose screws that I had forgotten to fully tighten was when my BMS said it had a "volt diff" error when I accelerated. Inspecting the pack, then tightening the loose terminal screws got rid of that error.

Last is a photo of my BMS wiring harness which is an example of perfection being given up for progress. It's ugly, but it works. Making a better harness will be a winter project. Meanwhile, this mess seems to work for me right now.

Sunday, August 28, 2011

Another range test

This range test was a 22 mile test to simulate a commute in terms of distance and hill climbing. This would be to the half way point, then do a return on one charge. First part of journey was at going to half-way point on relatively flat ground, then downhill from 860ft to 420 ft. Speed as before was kept between 30-35mph. At bottom of hill, I briefly tested battery recovery. Unlike a lead-acid pack, parking for 5 minutes showed no significant battery voltage recovery from the batteries in the main pack. Then back up the long slope at 15-25mph. The remainder leg home was done at 40-45 over the flat and downhill sections of road.

However, as I feared, my charge controller could not charge the accessory battery fast enough to keep up with usage. So, near the last mile of the journey, the 12V battery became weak enough to make the headlight interlock relay de-energize. So, the main pack still had 25% charge left but I couldn't go! No problem. I pushed the BugE to the side of the road. Turned off all navigation lights. Then waited 5 minutes for the charge controller to catch up. Then quickly proceeded home. Still had 20% left.

What this says is either that I'll either need to increase the accessory battery size, reduce loads or use a faster method using the DC-DC converter to re-charge the accessory battery while under-way. Too bad I can't find a reasonably priced DOT approved LED headlight for a motorcycle! Hopefully, lower cost LED headlights will appear soon.

Sunday, August 14, 2011

Lithium charger mounting

When using a lead-acid pack, I found an external lead-acid charger arrangement worked for me. However, the new lithium battery charger is larger, more expensive and has a really wimpy data cable that would quickly be destroyed through repeated connects and disconnects. So, I've decided to find a way to mount the charger so it does not need to be removed for each journey. To the left, you can see the end result. The charger has sufficient ventilation to keep cool. It also allows inspection of it's indicator LEDs on the end of it.

To the right is an image of how the holder just before it was installed. To mount, it's bolted in with nylocks and washers to the fiberglass battery pan structure. If assembled correctly, the charger should just "snap" into place. The only cable modification I needed to do was to lengthen the battery charger data cable so it could reach the "LIN hub". I suspect a "new" BMS system would only provide connectors & cable without being assembled, providing an opportunity to make cable lengths correct the first time.

Parts & tools required:
6ft piece of angle iron (you'll have some left over)
an angle iron bender (or use a vise & hammer)
scratch awl
tape measure or ruler
(10) 6-32 flat head screws with matching Nylock nuts
(4) washers - used for mounting to the Plexiglas battery tray
spray paint and primer
zipties (to run data and power cable to battery tray)

Sunday, August 7, 2011

Range tests

One of the most frequent questions I get asked usually includes the phrases, "How far and at what speed?" Due to these factors being dependent on conditions of the day, It's an impossible question to accurately answer. However, I can say this.

I did my first extended range test today. My route to work is 20.3 miles. I decided to go to the halfway point on the route I plan to take to work. According to the GPS, I start out going to work at 620ft above sea level. Then took several small hills for an average climb height to 860ft. I figured if I had 75% of the pack left at that point, it's likely I could make it to work with a comfortable reserve since the remaining part of the journey is either flat or down hill. Once at work, the plan would be to charge up during the workday for the return trip.

For this test, temperature was around 80 degrees, overcast, with occasional sprinkles of rain. Travel through town was stop and go which limited speed to around 25mph. Once out of town, roadway turned to tar & stone. The roadway outside town had enough bumpy areas that I limited my speed to between 30 and 35mph. Visibility was very good. I was followed briefly by one car. Otherwise, I saw only three cars going in the other direction. For the return part of the journey, I decided to take a faster route home. Speed was kept to about 40mph for most of the journey. However, once I encountered the smooth road of the arterial highway, I decided to speed up to 50mph for about a mile. No problem. I returned home with 60% of charge left.

Tuesday, August 2, 2011

First test drive on the lithium pack

Woha! The new battery pack makes this BugE perform much better! I decided my performance test would be at night. I drove in a mix of conditions with stop-and-go traffic along with hills. Total mileage was just over 10miles. I tried to keep speeds at least 30mph and go 40mph where I could. Passing cars was fun and I could even do so going up hills! At the end of the test, I decided to do a speed test on flat straight road. For the speed test, I sustained a speed of 50mph over 2 miles! At the end of the journey, pack still showed 60% of capacity left.

I decided to keep the retro analog meter to see how acceleration affected the pack. I noticed that the pack was either in white (full) or upper green at all times even during acceleration. I was worried that the 12V accessory battery would be depleted but it apparently has enough capacity to keep the lights relatively bright. Although I didn't have a digital meter, I did observe that headlight brightness seemed to be unchanged through the journey. The lithium pack also seems to have other benefits too. For example, braking and acceleration seem to both be better. Also, the BugE seems to deal with bumps better too.

The drive was not problem free. The BMS electronics have problems. For example, the LED readout has two LEDs that have already failed. Fortunately, I have the larger readout I can use instead. Also, the wiring seems to be of all the wrong lengths. I'm guessing this is because in it's original installation, the LIN HUB and all instrumentation was probably installed in the dashboard rather than in the battery compartment.

Still to do. The BMS system works but shows an error when the battery charger isn't present. So, next step is to mount the battery charger in the cargo area.