Sunday, February 22, 2009

Maximizing battery performance

To get the absolute most performance out of an Optima lead-acid battery pack, the batteries should be balanced. In the original plan, batteries were arranged in series. They were charged with a single 4A 48V charger. The charger has a regulator that shuts off the charger when the overall pack has sufficient voltage across it. However, as batteries age is possible that some batteries may be lacking charge, while other batteries may be overcharged. If the imbalance becomes too great, it will lead to a shorter pack life or less than optimum performance.

Fortunately, someone else has thought of this problem and has made some electronic modules which dump (or take) excess charge from a neighboring battery. Ordering the parts from EVSource took a while since they apparently had a backlog of orders. I've since learned that Harvey Coachworks also carries these modules. I can't recommend these modules enough. I have operated my pack without these modules and it doesn't take too long before each battery voltage starts to vary by quite a bit. I then need to manually charge some batteries more than others and it's basically a big headache. With these modules installed, charge averaging is all taken care of. I'm convinced my pack would not have lasted as long as it has if I hadn't had these.

Anyway, the battery terminals were bought from Autozone, a local car parts chain in my area. Spades and terminals were mixed since I didn't have enough terminals for all the wires. The color of the wire is important. Each module MUST be connected with Yellow wire (+), then purple (-) on other battery, then white (com) on the common terminal between the batteries. Failing to do this will make the module think there is a massive imbalance in the battery arrangement and it may burn out. So, for wiring reliability, the connectors should be soldered, not just crimped on so there is less possibility of having a wire detach and cause a problem. Also, when connecting the (-) there will usually be a visible spark. Also, it's VERY important to connect and disconnect wires in order according to the instructions since it's possible to damage the modules.

The battery terminals also need some preparation. The nuts holding the bolts can fall out when there was no bolt present. Since nut dropping is not something that should be happening when attaching touchy expensive electronic modules, something needs to be done. One solution is to melt some solder to the underside of each terminal so the nuts stay on even when bolts are out. As you can see, attaching solder to the terminals doesn't look pretty, but it works. It also is something that cannot be seen by the casual observer since this side of the terminal connector faces down.

After connecting all the powercheq modules, they need to be mounted somewhere so they can't rattle around in the battery compartment. So, I made a small mounting tray made out of wood covered in duct tape so the modules can be zip tied to it. The wood could be painted instead. However, covering with duct tape is faster than waiting for paint to dry. To hold the tray, two flat head screws pass through and screw into a battery terminal. The clamp is then attached to an unused battery terminal. The little red terminal cap on the bottom of the tray is there so you can see the battery terminal better.

My first mounting attempt going across looked OK. The powercheq modules blinking on and off when equalizing gave a high-tech look to the battery pack. However, I could no longer stow the stick I use to prop up the fender during maintenance! So, I rotated the tray 90 degrees. To do this, I needed to extend the length of some powercheq wires so they would reach the battery terminals.

3 powercheq modules
6 battery terminals
2 flat head screws
3 zip ties
9 terminals that fit 1/4" battery terminal end screws (avoid using spade connectors since they pull out)
Wood for shelf
Duct tape (or paint) for shelf.
12Ga wire (to extend powercheq wires when tray is mounted sideways).

Jigsaw (to cut wood)
Drill with 1/4" for ziptie holes and countersink bit (for flathead screw holes)
Mini ratchet w/ 2 sockets for securing bolts on battery terminals.
Soldering station (solder pen, helping hands, solder, wire stripper, heat shrink tubing, ect...)

Around 3 hours, to think of and construct solution, not including blog time.


I have run my Optima batteries with and without battery management modules. I definitely think the BMS system was a good purchase. It saved me the trouble of manually rebalancing the cells in the pack. Plus, I later found it also had the benefit of allowing me to use a single inexpensive 12V charger rather than a more expensive 48V charger. To do this, I just attached a cigarette lighter port to one battery. Then, I charge the battery through that port! The BMS then balances out the charge equally with each battery. Charging this way isn't as fast as doing it in series. However, 12V chargers are rather inexpensive, widely available and light enough to just throw in the cargo area just in case field charging is needed.

Saturday, February 21, 2009

First test drive! Feb 22, 2009!

The test can be seen on YouTube.

One of the concerns I had was if the BugE could climb out of my driveway! It's quite steep. As you can see from the video, it's no problem on relatively dry pavement. It has plenty of torque! However, passing over the snow made the tire wet so the tire had some trouble gripping the driveway. However, I found going up slow would solve that problem. Also, there is always the option of adding some roadway grit too. Overall, a very good result!

I have not put on the transparent canopy yet since I have some tweaking I still need to do. However, the major goal of building a working car has been reached! After the canopy has been installed and the BugE registered & insured, I plan to make more performance video tests.

Sunday, February 15, 2009

48V motor test

A frantic rush to the finish continues.

To complete the 48V motor circuit, I had to make a few more cuts. I have found that grouping tasks such as cutting with the Dremil saves time.
I found I had to trim the battery tray lip in the rear to allow the #4 wires to be passed under the vehicle. On the left, wires go from the reversing switch to the controller. Also, the brake line goes through that lip too. Smaller circle shows the brake cable. Larger circle passes 48V lines. On the right, one cable will be passing from under the speed controller, up , to go to the negative battery terminal in the battery tray.

I also did some cuts on the rear fender. One is for the reversing switch handle so it doesn't need to be taken off every time I need to lift the fender. At this point, I've put on and taken off the fender several times. Since the switch has dragged on the inside of the fender several times, it has managed to mark a path of it's travel inside the fender. So, now I know where and how wide the notch should be. Notch is cut, then switch handle is attached.

Note, switch handle didn't come with a screw. I happened to have one. Size and TPI will be noted later.

Two other Dremil operations are for the battery cutoff switch and the charging port. I put the holes towards the front on either side, but behind the glove box indentation so wires would be in no danger of hitting battery terminals. To trace a circle, I used a coin on the inside to serve as a guide for my Dremil cut. Then, I smoothed the cut while widening it with a Dremil drum sander tool. Nice fit!

Now, I have screwed on the fender for the final time (yea, right). Then, the batteries go in, one by one. Once the switch and port are mounted, their wires are pushed out of the way. They will be attached later.

At first, I wondered about why there was a space left between the battery packs. Once I took off the temporary handles from the batteries, I found out why the extra space around the batteries is important. If not loaded correctly, the batteries are in the perfect position to pinch fingers! After loading the batteries, the space between is a perfect fit for a 2x4 piece of wood. After slipping in the wood, the batteries seem to be rather secure. Nice design!

After the batteries are installed, the remaining 48V cables are constructed. The process is the same as it was when I put the reversing switch on. Sit next to the car, measure a run, cut cable, strip end, crimp end, wrap end in tape, put split tube on outside, wrap split tube. Sounds like a bit of work but it goes quickly. I found wearing nitrol gloves, with cloth gloves on only keeps my hands warm but also keeps my fingers free of little copper metal bits! I am putting wire wrap on all the wires I can in the battery tray. I may be a bit paranoid but I really don't want something shorting against something else.

The wire sections are connected to the battery posts VERY tightly with 5/16" nylock nuts rather than the wing nuts that came with the Optima batteries. I'm not sure if split tubing is really needed around all the cables for protection but I'm putting it on just in case.

The only really difficult wires to attach were the final wires to connect to the battery pack. I needed to drop the controller shelf so I could attach the large #4 wire to be connected to the battery. Fortunately, this is held on by two bolts which are rather easy to get at. Then, attach all wires tightly and lift the shelf back up.

I'm not attaching the positive and negative cables to the 48V motor circuit yet. First, it's time for a final 12V circuit test.
- 48V charge meter works
- battery charge port works
- tail light, signal lights, low beam all work.
- horn didn't - (traced to a lose spade connector).
- brake light spring is just a little bit too tight. This was fixed by stretching spring. I also decided to solder the brake indicator connectors rather than rely on crimps. Since I have attached & detached the brake indicator connector several times, I am really glad I spent an extra $2 to put on a quick-disconnect for that little piece of the wiring!
- lo-hi beam indicator lights on speedometer are reversed (purple colors are very close to each other, so this is understandable and can be fixed later).
- hi-beam is dim. Monitoring the Yahoo group shows more than one person has had this problem. However, since this is not critical for the 48V test, I'm going to press ahead with the 48V test.

  • Block front wheels so they cannot move.
  • lift rear wheel
  • Attach all cables & final 48V battery cable with nylock nuts
  • Test 12V
  • do low speed 48V forward & backward test.
Now, this is a big test, with big wires that can unleash the full power of the battery pack. Safety glasses, no wrist watch or rings and the one-hand rule are used when connecting wires.

First, the contactor and DC-DC converter wires are attached to the battery cutoff switch. The charging wires are attached to the positive and negative posts on the battery. The 48V meter reads that the pack is full.

The negative DC traction motor wire is attached to the pack's terminal along with the DC-DC converter feed wire using a nylock.

The positive DC traction wire (via fuse) is then attached along with the other DC-DC converter feed wire. No spark. This seems good.

Finally, the big moment. Things will either work, not work or smoke. I turned the switch & the contactor clicked. 12V lighting works. Good. Now, gently push on the throttle..... nothing. Tracing out the wires, I found the key switch spade connector was detached when the controller was dropped to attach the large power wire. This was re-connected.

Try the key again. Just touch the thumb throttle ... success! Due to the chain drive, it's not as quiet as I expected, but it's much quieter than a regular motorcycle! Then reverse was tried. Success again!

It's been a big night.

I think a small test drive is really close to happening!

Other tasks done:
- Put in a spacing washer for the parking brake so the handle can lock.
- screwed on the front door. Still need to hot glue a better seal around the door.
- put in a wood stick for propping up rear fender when servicing the BugE. Also need a way to prop up the cowl too.

Still to do:
Tighten steering tube bolt.
Install more padding for cowl on frame to absorb bumps better
Build little shelf in battery area for powercheq modules
Troubleshoot 12V wiring issues. (look at hi-beam light issue - why is it so dim? - found that re-seating the bulb in the headlight solved the problem)
Make cowl wiring neater - give some thought to a dashboard.
Arrange to transport to/from an inspection station.
Arrange transport to/from symposium location
-design and install a dashboard console to include a car radio & rocker switches for accessories.

Unanswered questions
-If storing outside in cycle shelter, would a small heater (such as a light bulb) to eliminate condensation from electronics and bubble be needed?

Installing seat isn't mentioned in the tasks. However, for servicing, then driving, then servicing again, having a seat that easily slides on and off is REALLY NICE.

Also, I put in a better keyswitch in series with the battery cutoff switch. This allows lights to operate when the BugE is exhibited but the motor contactor will not be ON without the secondary switch being ON too.