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.

Finally Some Electrical Bits!

Now that I've got my remaining electrical parts, I can get started.  I can't do the whole job yet because I'm searching for some "affordable" plastic boxes to hold the contactor, potbox and terminal blocks.  I'm not leaving those out to the elements as the EA manual says.

Anyway, I was able do get started.  This is the supplied DC high-voltage, high-current cable.  It's called welding cable or locomotive cable, and is made up of hundreds of hair-sized wires, so it's very flexible.

EA is supposed to supply a cable lug crimper, but it hasn't shown up yet...  I checked around at work with the electricians I know and found that Kelly Minton has a great hydraulic crimper.  You can see the steps to make a solid crimp below.

You can see the crimper crimps from 4 sides for an extremely good connection.  The final step is to put some shrinkwrap tubing and shrink it down.

I mounted the controller to the backing plate.  This was heavy and messy due to the white heatsink compound.  I built cables and mounted to the controller and the motor.  The rest will come in when I mount the contactor in the box.

The First Electric Part Installation

So I gathered up my courage and jumped into the first step of the installation instructions. 

I cut out the paper template for the motor controller mount and taped it into place.

I got to install my first rivnut.  It's a decent solution to install a blind nut when you can't get access to the back side of the panel.  Since I'm so paranoid about rust, I decided to paint each hole I drill with rust reformer paint.

I then bolted the standoff bracket into place.

Finally I temporarily bolted the motor controller plate with the current-sensing shunt into place.  I don't have the controller yet so I'll have to remove the plate, bolt on the controller and re-mount when it arrives.

Then I decided to move on to the Potbox mount.  I'm a little concerned about leaving the potbox out in the open, where it can get dirt, mud and water inside it, so I plan to make an alternative mounting scenario, placed in a plastic enclosure.  Lucky I thought of this, because my car doesn't match the instructions for mounting the potbox.  The manual shows quite a large "brake equalizer", but mine just has a simple T-junction for the hydraulic brake lines.  I'll have to do some investigation to find out if mine is a post-factory hack or just a different style than ElectroAuto is expecting.  That's the T-junction, right at the top of the paper mounting template, with the line from the master cylinder coming in from the south-east.  It just ain't gonna fit.

Then I decided to review the steps for installing the transmission and motor, and found about half of the needed hardware was not supplied in my parts pickup.  I left a voice mail for Shari and asked her to let me know what's going on with the rest of my order, because I've had no email or phone contact since my visit to them a couple of weeks ago.  We'll see...