3D Reality

It turns out my Cell Frame was a little too big to fit in the 3D Printer.  I tried a variety of configurations, and some were very functional but I wasn't happy with the look.  So I ended up chopping a little material on the outer edges and decided that I could add a Lexan cover if needed.  I think the effect with the cells in place will be pretty cool.

 A little hard to see in this picture, but the print head looks like it came from an InkJet printer.

The process is time intensive as the display shows:  69.29 hours to do two copies.

 

Visions of Battery Holders

I've been spending a lot of time lately thinking about how to hold my Headway batteries in place.  The lego style holders I purchased with the batteries are fine for testing various configurations, but not super sturdy for long term use.  Additionally they are a little ugly and yellow does not match my color scheme.

My first though was to machine a thick plate of Plexiglass.  Unfortunately, with each additional feature I machine, the odds of botching it go up exponentionally.  50 holes, 50 counterbores, multiple slots.... do the math.  Not great odds of success.

Enter in Fused Deposition Modeling (FDM), more commonly referred to as "3D Printing".  Essentially slicing a model into very thin layers and printing the plastic one layer at a time.  The great thing about FDM is that the part is very functional, yielding almost full strength compared to a molded part.  The downside to the process is that surface finish can be a little rough, but that is not critical for my application.  The other stumbling block is that you need to have access to a fairly expensive FDM machine, or know somebody who does.

The design phase of this model is almost complete.  The front side has the counter-bores for the battery diameter, but the back side is the tricky part.  I've made it thick enough to give some protection from accidental contact with terminal plates and electrically live fasteners.  The horizontal bars almost give the visual effect of a radiator, which I kinda like.  The real thing will be black PC-ABS, so should look like sweet pieces of hardware.

Headway Pack 2.0

Upon receipt of my second set of 25 Headway 40160s cells,  I immediately began to conjure up way to configure them in the bike.  My first plan was for two sub-blocks of cells (5x5) and have the batteries sit length-wise across the width of the tray.  In theory the cells would fit, but I failed to account for the screws & washers on the ends of the batteries.  The two sub-packs would be 1/2" too wide.  Oops, back to the drawing board.

After a some playing around I came up with this arrangement.  It's not ideal,  but it's unique looking, fits the alloted space and there are some advantages to the layout.

 

There is just enough room on front/back of the pack to allow my hand in for taking voltage readings.  I also have enough room to add a cover/shield to prevent curious fingers from getting shocked.  This is probably not the final pack hardware, but will definitely work for the short term.

Holiday Inn

Time seems to be a rare commodity lately.  I had to cover up El Gixxer for the winter to keep the other garage projects from contaminating the old boy.  A sad state of affairs.  Prior to my Winter break I had the 25 Headway cells installed and did a series of test rides to see how they faired.  To say I'm impressed is a gross understatement.  25 of these 16AH batteries are 50 lbs. lighter than the 17AH lead units they replaced, but put out  way more juice. 

Not wanting to damage the cells, I needed to keep my current draw under 10C (160 Amps).  I borrowed a clamp meter and did some riding to calibrate my wrist.  Turns out 150 Amps accelerates the bike pretty well, and maintaining the top speed of 48mph only takes about 50-60 Amps.  I started out at 5.0 miles, and worked my way up 10.2 miles on the last trip, which happens to be 0.2 miles longer than my round trip commute.  With the average voltage of the cells starting at 3.40 I finished at at average voltage of 3.24.  Plenty of juice to get to work and back.  But having spent all funding on batteries, I was out of cash to finish up the 12V wiring. 

Bummed I couldn't be legally on the road, I turned my attention to charging and monitoring voltages.  My plan was to use the Headway 72V charger (which charges to 86V) on the 25 cells without BMS.  By using 25 cells instead of the usual 24 cells, they are less likely to be overcharged. With 25 cells in the pack, the average charged cell is 3.42V, which is just about right, since there is very little capacity above 3.45V.  Some of the cells were noticeably higher, between 3.50 and 3.8V, and some were lower at 3.32 to 3.34.  I made some attempt to top balance, by draining a few of the highest ones with a small light bulb.  But every time I ran them through a discharge/charge cycle, they were out of balance again.  I kinda see the need for a BMS, but still think the safest route is to under-charge and under-discharge.

The only thing I wanted for Christmas was another set of Headway 40160S cells and Santa sure delivered. 

Next step is to build up my 2P25S pack of 50 cells and turn up the Amps.

From the Ashes...

With a bunch of burned out chargers and smoked battery, things were not looking so good.  I contemplated buying replacement chargers or more of the Battery Tenders, but that would mean buying a battery or two.  Unfortunately, I could not justify $2000+ for Thundersky or CALB units, and even if I could, what would I charge them with?

Epiphany:  If I use a cylindrical cells, I can put together a modular pack that will handle my daily commute with a lower initial cost.  I may need to charge at work, and watch my Amps carefully, but at least I will be on the road.  As funds allow, I can add more batteries. Sure, the $/AH will be higher, but if my goal is decent acceleration and a 10.0 mile round trip, this really makes sense.

Big Break #1:  One of the guys on ElMoto.Net was selling a 72V charger made for Headway batteries.  It was a bargain so I jumped at it, thinking it could be used for any LiFePO4, and even temporarily for SLA's, if I stay that route a little longer.

Big Break #2:  Headway comes out with a new bigger cells (40160S).  These 16AH cylindrical cells will do 5C continuously and 10C for 30 seconds.

Big Break #3:  Manzanita Micro starts carrying Headway cells.  A reputable US based supplier is critical.  They are a long time player in the EV industry and have a terrific reputation for service.

So I dropped a small fortune on 25 cells, bus bars and holders.  Only problem now is all the empty space that is left.

Up In Smoke

Last month, after a test run on a fairly hot day, I plugged in my bank of ACI chargers and left them to do their job.  I returned a few hours later and noticed flashing red LEDs.  As I got closer I could see some severe distortion of the charger cases.

Crud!

All of the chargers had blown thier fuses, and three of the six had significant heat damage.  I tried replacing the fuses but the damaged ones still did not function.  A quick disection reveals the transistors smoked themselves - note the burn marks on the heat sink.

I'm no longer a fan of the ACI chargers. In fact I was pretty upset at ACI for building such a crummy product, for a while.  But you get what you pay for and they are cheap. 

The bigger question was what am I supposed to charge my SLA's with?  I proceeded to plug in Ole' Reliable:  my Deltran Battery Tender Plus.  The Battery Tender only charges at 1.25A, so it's slow and I could only charge one battery at a time. 

The other question, is are the batteries still any good?  After two days on the charger, the 17AH batteries seemed to be holdin a charge OK and voltages looked almost normal, but two were slightly lower than the others. Suspect cells were at 12.7V and 12.9V vs. 13.1-13.3V for the others. 

A trip down the street and back, the bike seemed to run fine.  Then I took El Gixxer around the block a few times and the batteries started to feel sluggish - so I gave the throttle a little more wrist. Oops! A high pitched squeal pierced the air - I thought it was a controller alarm, so I let off the throttle and the sound went away.  Then I heard a sound like a pressure cooker belching steam and looked down to see the #5 cell spewing gas only inches from my knee.  The controller went into Limp mode and I barely made it back to the garage.

Double-Crud!!



Back in Black

I've been risking life and limb with every test ride, due the fact that my rear tire is beyond bald. There was  significant amount of cord showing (check out the cross section).  So for Father's day my lovely wife gave me a new rear skin (OK I did the shopping).  In addition to the useless rubber, the rear rim is blessed with fluouresent green and purple showing through the two layers of poorly applied flat black   Might as well pull the tire and clean up the rim.  Check out the edge of the rim for the previous color samples. 

It was a total pain to clean and sand, thanks to massive amounts of chain lube and globs of paint.  I think the last coat of black was rolled on.  I also had to clean up the gouged edges of the rim where somebody had ridden the bike on it's side.  Honestly it's still not that great, but is a whole lot better.

Here it is with the new tire, a sport-touring dual compound that will last a little longer with my mild riding habits.  Nice to have some tread to use.