Tuesday, April 21, 2009

Batteries Ordered

I've ordered my batteries!

After going back and forth between Lithium and Lead countless times, I've finally decided on Lithium! LiFePO4 to be exact. These are a relatively new battery chemistry that don't have the energy density of other Lithium Ion batteries, but they are significantly cheaper and much safer.

Thundersky TS-LFP100AHA

They'll last 2000-3000 cycles depending on amount of discharge. I've ordered 30 cells, 3.2 nominal @ 100AHr, for a 96V nominal total voltage. Minimum voltage for a cell is 2.6V, which corresponds well with my controller's 80V minimum. Maximum voltage for a cell is 4.2V, which at 126V peak won't overload my motor. The batteries should fit in a single grouping underneath the hood, and the final weight/balance of the car will match very closely to stock. I purchased with a group from diyelectriccar.com - batteries should arrive in 2-3 months.

Sunday, April 12, 2009

Old Tires / Wheels

I got a response from my motor controller manufacturer; it turns out the controller has an 80V cutoff so I won't be able to test it until I get my full pack in. The Spitfire is much happier with my new electrical system though (at least according to the car's voltmeter), and I've cleaned up the wiring a bit...

My wife bought me tires for Christmas, but I haven't had time to install them as I've been busy with other parts of the car. My existing tires weren't looking too pretty...

Unfortunately the picture also shows the sad shape of my wheels. After I pulled off the two rear tires I saw just how bad the wheels were. Lots of dents and rust. So much so I'm surprised one of they still hold air! Looks like I'll have to replace them as well.

The Spitfire has a bolt pattern of 4-95.25 - completely nonstandard so the junkyard is out. http://www.victoriabritish.com has a few styles of wheels, but they start at $660. I tried 3 local tire stores, but they'll have to call their suppliers on Monday to get more information. Apparently they may be able to take an unfinished 13" wheel and drill my bolt pattern into it. I'm also keeping an eye on Craigslist. I don't mind a fresh set of wheels on the car, but I'd like to keep it as inexpensive as possible.

Sunday, April 5, 2009

Fuse Block

As I mentioned last week, the original wiring on the Spitfire was a mess. After my low speed test failed, I decided to take one of the questionable items out of the equation and bypass the car's original electrical system.

I already had the relay, but I went ahead and bought a new fuse block. Rather than attach all the negative connections to random spots on the car's ground, I bought the model that included the negative terminals. I'll use one of the car's original 12V lines that is closed when the car is "on" to trigger the 12V relay closed. To minimize any resistance / uncertainty, the relay + will be wired directly to where the battery's + cable goes. The fuse block - will be wired directly to where the battery's - cable goes. I won't mess with any of the car's original 12V components since they more/less work now.

I also found two excellent locations for my new components. The fuse block will go next to the car's original fuse(?), and the relay will sit nicely next to the pot box.

Components screwed down and wiring started...

Wiring finished. The new fuse block will handle the motor controller and both contactors. If I add anything new to the car it will also use the new block. Over time I may even transfer some of the car's original components to it.

I tried a second low speed/voltage test with the motor controller. I used two 12V batteries in series - here's the "high voltage" side wired up...

The batteries...

Results: Still didn't work! The contactors and key switch should be operating fine now. I sent an e-mail to the motor controller manufacturer asking for some help. Hopefully he can point me in the right direction as to what's wrong.