Lithium Upgrade

2009-12-31

I recieved my ThunderSky batteries. I placed the order on 9/14/09, so it took about 3.5 months to arrive. I bought the cells from EVComponents, who imports the cells in bulk from China. Unfortunately I could not find an American company selling cells this size. The batteries were packaged very well and arrived undamaged. The shipping weight was 900 lbs.





2009-12-31

The group on the left go under the hood, the middle group go behind the seat and where the gas tank used to be. The right side group fit in the spare tire well.





I am using ThunderSky 100Ah Lithium cells, this new chemistry is LiFeYPO4.

This upgrade will increase my range from 30 miles to 100 miles, and lighten the car about 300 lbs. The cells are sold individually, I am using 99 cells. I had them banded by the factory in groups of 4, 5, 6, 7, 8, and 10. Banding is required because the batteries swell when fully charged.

Here is a drawing of the current battery layout, and possible layout with the new cells






The lithium batteries are taller than the Optima batteries I was using. To make the lithium batteries fit, I needed to lower the front battery rack otherwise the hood would not close. I rotated the rear housing of the motor, this puts the junction box on the side freeing up 2" of clearance.





I spent about 3 days getting to this point, the rack is done. I also decided to add a full size radiator.













I put 3/4" aluminum blocks between my battery rack and the frame, this serves two functions. If I need to raise, lower or level the rack, I can add or remove material without rewelding my rack. The frame rails are also slightly sloped, and non-parallel, I machined the blocks with a complimentary taper so the battery rack can mount to a level surface.





I relocated my vacuum pump to use space which was previously unused, allowing me to fit more batteries in the old pump location. Each side of the battery rack is bolted to the frame using 4 bolts.







The ratchet straps I used with my lead acid pack worked out well, so I designed a mount to integrate them into the rack. The ratchet shown in foreground, and the hook on the strap shown in the background.





I was able to re-use parts of my gas tank mounted battery rack. I'll ratchet strap the batteries to the rack so they don't move around. I made the rack so it can be lifted with my floor jack into place.









Spare tire well battery rack. I welded in mounts and hooks for ratchet straps.











Since the cells mounted under the car (where the gas tank used to be) and behind the seat were impossible to access, I mounted some din-rail mounted fuse holders in an easy to access location so I can monitor and balance the cells.


My ThunderSky cells came with a notice that says the cells must be charged to 4.2 volts before being used. They suggest a charge rate of 10-50 amps. When the charge current tapers down to 1% of the original charge rate (100mA), charging can be considered complete.

I am connecting 7 cells in parallel and using a variable voltage, variable current power supply. The no load voltage on the supply is 4.2 volts, so I don't have to worry about over charging. Once the current drops below 700mA I'll consider the group of 7 cells fully charged. This is a slow process... it took about 3 days.

I charged the remaining 92 cells in series till one cell hit 4.2v. I parallel charged in groups of 7, it took about 8 days to get them all to 4.2v.





Sweet crimper



This crimper has 6 Tons of crimping force.



Battery Cable



I used 4/0 gauge wire and crimp lugs. This should have a continuous rating of 380 amps, well above my 300 amp max motor rating. I'm glad I oversized my wires, especially when testing my prototype controller, there were a few instances my motor cables were warm.