Saturday, October 3, 2009

Rear Batteries In

Today was a busy day. The goal this weekend is to get the car moving again. Failing that, I at least want to get all the boxes and batteries in place. However, before I can do *that*, I need to do a few mods to the car. First, due to the larger size of the PFC-20 charger, and due to the need to have the Rudman Regulators on top of the front battery box, I need to move the charger to the rear trunk. Also, I've been frustrated with voltage drops in the 12V system - the ElectroAuto kit pushes everything from the front via a 10 gauge cable, which has proven inadequate. Finally, I want to make provision for some sort of heating system for the batteries - a water bed heater is likely for each box, but I have not finished thinking about this. Regardless, I'll need a 120V power line for the front and rear to handle this (I want the battery heaters on a separate circuit from the charger).

So, I need to drag a lot of cable from the front (where the 12V aux battery and power inlets are) to the rear (where the charger and original 12V battery was). I procured 20 feet of 4 gauge cable for the 12V system, and 25 feet of 16 gauge 120V extension cord, as well as 50 feet (overkill) of 10 gauge 240V extension cord. I laid them next to each other and taped the mess together, thus:

The red cable is the 4 gauge power cable; the thick orange cable is the 10 gauge 240VAC cable (longer because it goes all the way to the rear trunk) and the thinner orange cable is the 16 gauge 120VAC cable.

And now the fun begins. I need to route all this through the passenger's side heater tube. The driver's side, if you recall, has the DC cables from front to back as well as a variety of control signals. Up until now, the passenger's side only had the PakTrakr cable from back to front. So, it was natural to use it for this harness. I taped my trusty plumber's snake to the harness and fed the snake through the heater duct:

Here it is fed all the way through, with feeding into the front compartment just starting:

And here it is fed all the way into the front compartment:

I routed it under the middle battery rack and through the hole left where the fuel pump used to be mounted. I then zip-tied it to the middle rack:

The Porsche 914 12V battery was originally in the engine compartment. The original kit just had you tie all the 10- and 12-gauge wires together and tape the whole mess up. After unwrapping the tape, I decided the ring ends of the original battery cables were in poor shape. So I cut them off and crimped them all into a 4 gauge lug. I then crimped another 4 gauge lug on the 4 gauge cable. I also crimped a ring terminal on a 10 gauge cable which was fed through from the trunk - this will power cooling fans in the trunk (for a future project). It all got bolted together:

Not shown - I taped that up and then put red heat-shrink tubing over the entire assembly.

Next, I assembled a Weather Pack 2-way connector on the end of the 120VAC cable. Weather Pack connectors are water-tight and lock, a close relative to the Metri Pack connectors from the previous post. Very handy for preventing short circuits and corrosion. This will eventually plug into the rear battery heating solution:

One more thing needed to be done before putting the rear box in. I needed keyed +12V to switch the relay for the rear fans. So I attached it to the lower terminal block on the rear wiring assembly - it's the yellow wire in the lower right hand of the photo. I also assembled a red and black 10 gauge cord with ring terminals and split loom. This was then attached to the most negative power pole (black) and shunt (red). The other end will plug in to the charger. This is actually nicer than the original - I'll be able to look at the actual amps pushed by the charger:

I drilled a new hole and put a grommet in it to feed this assembly through to the trunk. On the passenger's side, I also drilled an identical hole to feed the 240VAC cord and 10 gauge fan power wire and 16 gauge keyed +12v control signal wire. But you'll have to imagine it from this picture of the driver's side:

Finally - I drilled holes in the battery box where the assemblies from Thursday night feed through. I installed the battery box, put a generous dollop of silicone sealer along the edges, and bolted it together. And, finally, I dropped the batteries in place. Note that the AGM-1280T batteries are 0.55 inches narrower than the US 8VGC, so I cut some 3/4 inch and 1/2 inch plywood shims to put between the batteries to keep them from shifting:

You can see one of the regulator connectors fed through - I was testing to make sure it would fit (it does).

Tomorrow - installing the middle and front racks and batteries. And redoing the front relay assembly. And then building and attaching battery interconnects. And (maybe) taking the car for a spin if I'm lucky.


Joe said...

I noticed you used a Weather Pack connector for a 120VAC connection.

I've been looking for a similar connector for a completely unrelated project and saw that the Weather Pack connectors were rated for 0.05–16.0 VDC, 0-20A.

Have you run into any problems?

Ross Cunniff said...

I have not noticed any problems. The 120VAC side draws about 5A. The connectors do not get hot. The issue *might* be with breaking a live connection, but I have no particular need to do that, since I'd unplug the front AC connection instead.


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