Batteries Interconnected

A few things have come together over the past few days. First, I mounted the DC-DC converter, the relay box, and the AC-DC 12V power supply on the board where the old Zivan charger had previously been mounted:


Next, I reinstalled it in the front compartment:


Next up was attaching the interconnects. But I discovered that my BMS wiring was not quite the right length - so I modified several of them. I made one side longer by about 4", and shortened the other side by a similar amount. Here are a few of them, rebuilt:


And here is the front compartment with interconnects and BMS wiring installed:


Middle compartment:


Rear compartment:


It is getting so close to done I can almost taste it. I predict a late-night final push some time this week...

Revised Front Wiring

This weekend ended up cold and snowy, so mostly I worked on finishing up the front wiring. Photos will come later, for now, here is the revised circuit diagram. This includes the details of which connectors go to what - this will make it much easier to attach things when in the car:


You can find the PDF here. It is sized to print on legal 8.5 x 14 paper.

Battery Interconnects

After procrastinating for quite some time (not to mention healing my injured arm...) it was time to figure out battery interconnects. I had originally been planning on using 3/4" wide 1/16" copper bar stock, stacked two high, as the interconnects. But putting the bend in it was a pain. And I hate drilling through thin copper. I got some hole punches, but the 1/16" copper laughed at them.

So, on to Plan B. The local metal supply store had sheet copper 0.020" thick. This turned out to be perfect - I can cut some of the weird shapes right out of the sheet. Cutting straps 3/4" wide, 7 of them would stack up to form the same cross-sectional area as 2/0 cable (0.105 in^2). After much careful measuring (and a first failed prototype - good thing I tried cutting the paper out and fitting it first!) I created a layout that fit on a 8.5" by 14" legal piece of paper:


You can find the PDF here. I printed out 7 of them, and then cut out around the outside edge and used spray adhesive to stick them to the copper sheet:


I cut around each one to make for easier handling:


Next up - the holes. This hydraulic punch did not do much with 0.0625" copper, but it sails through 0.020" copper like butter. I call it Mr. Punchy:


Here are the holes punched in one section. To reach the interior holes, I cut each piece in half. Mr. Punchy can reach pretty far in, though. It is *much* easier to line up the hole punch than it is to drill through thin sheet:


My assistant, Naiche, came by and together we used aircraft shears to cut out all 105 pieces:


Now for the tricky part. To make sure that the straps don't pry the battery posts out of the batteries, I designed a bend in each one - basically, a 3/8" by 3/8" triangle. I tried just using pliers to bend it, but it was very difficult to get a precise bend. So, time to design a tool. This is the bending jig. It is basically just a piece of plywood with holes drilled to align with each different piece. A 1/8" deep inset is routed into the surface, and a welded metal piece is screwed to the base. This piece has a small angle welded to it, on top of which a welded stamp fits:


You can find the sketchup file here. I extracted a PDF of the base and rotated it so the holes would fit on 8.5" by 11" paper (did not want to make another trip to the copy shop):


This PDF can be found here. After a pleasant afternoon of metal cutting and welding, plus wood routing and drilling, I had my bend jig:

You can see the stamp on the upper right. To bend a strap, all you do is put screws through its end holes into the holes on the jig. This keeps it aligned. Then you place the stamp over the ridge in the metal base and pound it down with a hammer:


Remove it all, and you have a nice bent piece of copper strap:


And, finally, after bending all of the pieces and stacking them up, I put heat-shrink tubing over all of them. All done:


Next up, attaching the straps, hooking up the PakTrakr and the regulator harnesses, and then finishing the wiring. So close I can almost taste it...

Warmers Installed

EDIT - DO NOT ATTEMPT THIS TECHNIQUE - IT DOES NOT WORK. See this post for why.

My assistant Naiche came by yesterday and helped me install the warmers. First step is taking most of the batteries out - the warmers fit pretty tightly and it is very difficult to shove them between the batteries. So, out they come, and in goes a warmer:


Here is the rear box, all complete (you can see the pink foam peeking out between the batteries):

I had to drill a new hole and install a grommet in order to get the cord for the middle box to come out in a useful location:


All three warmers are hooked up to this terminal strip, with the input 120V AC line hooking up as well:


Finally, installed an inlet just like the 240V inlet (except with a 120V 15A plug) and wired it up. Here it is, plugged in and warming:


Using a clamp-on AC ammeter, I determined that it is pulling about 5A, which is about 600W, which is about what I expect from the warmer cable I'm using. Not a lot of heat - but hopefully enough to maintain the batteries at a warm temperature. It's very cold out right now, so I'm warming the whole garage with a 4000W electric heater right now. I'll let the batteries stay at this temperature for about 48H and then see if the warmer can maintain them in the cold.

Battery Warmers

EDIT - DO NOT USE THIS TECHNIQUE - IT DOES NOT WORK. See this post for why.

Despite a healing arm, I managed to find time over the past month to do some work on the battery warmers. I started with GroQuick heater cable. The instructions say not to allow the cable to self-intersect, so I designed a foam structure to hold the cable in place:


It goes between the batteries, like this. Fortunately, the AGM-1280T batteries are just smaller enough than the US-8VGC that this all fits in the existing box:


I laid out the pieces so I could make a PDF template for cutting:


Since I'm healing, I enlisted the help of a henchman. This is my daughter KatC's friend Naiche:


He helped me cut the foam and aluminum pieces for the warmers:


I used a Dremel with a 1/4 inch bit to rout nice even grooves for the cable in each piece:


Here is the biggest warmer in progress. First, the cable goes in the grooves, up to the point where it must go *through* the warmer to catch the other pieces:


A loop is pulled through to the back:


And one of the other pieces put in place, with the cable inserted in the groove:


Most of the extra pieces have two sides, a mirror image of each other. The cable goes back up and around:


The last piece on the rear warmer ends like this:


As you can see, the warmer cable is just a little too long. So, I cut it off. To make it work again, I need to crimp the two internal heating elements together to make a circuit. First, I stripped off about an inch or so of the exterior insulation. You can see the copper grounding braid peeled back and about ready to cut off - you don't want to accidentally ground your heating elements:


In this blurry picture, you can see the next step - the red central insulator is split to reveal the two finely wound heating elements:


The two elements are twisted around each other and bent over to create a larger footprint for...


...crimping a closed-end connector on.


Finally, heat-shrink tubing (with built-in glue) is applied - the glue lets you pinch the end shut:


Lastly, the aluminum facing pieces are installed. They are held in place with heavy-duty duct taping - actual duct tape, of course, withstands heat (since it is intended to be used with heating ducts):


In the new year, these will all get installed into their racks. I hope everybody has a safe holiday season and a fantastic 2010!

Been on hiatus

This video shows why:



Arm is getting better, but won't be doing any major work until January at the earliest.

Miscellany

October was a busy month on non-car activities, so not much got done. I did find some time earlier in the month to add an in-line high voltage 400A fuse (Ferraz-Shawmut A50QS400-4). It is in a link with a Cam-lok connector, and is located between the front battery boxes and the rear battery box:


Yesterday was much better, sunny after a blizzard, generally a good day to work. I spent an hour or two cleaning up tools that had been placed in haste during the month, and then got to work. I started with the battery charger mount. I installed 1/4-20 RivNuts in the rear compartment - the orange-handled tool is a RivNut tool that I got for the ElectroJeep project. Much nicer than the allen wrench tool I used before on the Porsche:


Here is the charger snug and happy in its new location. The only concern I have is that the charger gets quite warm. I will rig up an active air circulation system for the rear compartment, both for charging as well as operating (to help keep the DMOC cool).


I also test-installed the battery warmers. I decided to go with Gro-Quick soil heating cables. Since there is space between the batteries (due to them being smaller than the original batteries) I think that will be a fine place to put the warmer cable. This cannot be the final configuration, though - the documentation has fairly dire warnings about crossing the cable or allowing the cable to touch itself. So I will be routing cable channels into the plywood battery spacers to hold the warming cable.

In the meantime, here are a couple of pictures showing how the cable loops back and forth between the batteries. The rear box:


The front box:


I also cut the clear acrylic tops for the regulator boxes. This shot is a test-fit of the tightest spot. Looks like there will be plenty of clearance, even if the regulator boxes are on top of the hold-down straps (which I think they will have to be):