Tuesday, September 14, 2010

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.
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.