Saturday, April 16, 2016

Battery Pack and Related Electrics Version 2.0

I spent the afternoon of my birthday playing around with a new Lithium ion battery pack design for the 914, if I ever return to civilization.

To save money and complexity, I'll keep the existing Curtis 1231C-8601 controller which is rated for a maximum 144V pack and 500 amps.  This is still sufficient for me driving through town.

Based on years of experience at EVTV with the China Aviation Lithium Battery Company (CALB) 180AH CA-series cells, I know how to bottom-balance them, charge them and discharge them safely.  This is in deference to the many YouTube guys building up Tesla-like 18650 packs from dodgy laptop battery packs.  I did the math to determine I need 42 of the CALB cells at a nominal 3.4V each.

I brought up an old SketchUp model I made a couple of years ago and worked out how to place these batteries and other components.  I'll fill up the rear battery box where the gas engine used to be and put the rest in the battery box where the gas tank used to be, with a good amount of space left over.

This means I can remove the 2 single-battery-sized boxes from the trunk and weld some steel plates into place, prime and paint and turn it back into a fully usable trunk.

I also gain all of the capacity of the battery box where the spare tire used to be right in the front.  I created shapes matching the sizes of the rest of the components I need and fitted them all into place.  This means the new TCCH 4KW or 5KW charger I'm looking at and its controller, the new GEVCU controller, the existing relay board and the existing DC-DC converter all fit inside the front box.  The TCCH is air cooled but the box already has an exhaust fan that switches on during charging, so it looks like it will be a perfect setup.

Cleverly I'm moving the 12V auxiliary battery from it's ugly, nasty, breaking-off-prone mounting bracket on the front of the front battery box to inside the gas tank battery box due to some newly available space.  I'll run the 12V wires down the passenger side of the frunk to the DC-DC controller and leave the high voltage battery pack wiring where it runs now down the driver's side.  There's even still a bit of empty space so I'll play with the position of the batteries to maintain side-to-side weight balance and fill the gaps with some stiff foam.

So, here's the layout.  I've also built up a list of to-do items, some must be done concurrently with this major upgrade, while the rest can be done at my leisure.  I'll bling up the installation by replacing the white plastic battery pack lids with transparent lids.