1975 GMC Palm Beach Restomod

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Mike Perez

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Oct 2, 2019
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Have you figured out your discharge and recharge current rates? The only reason i ask, based on how long your proposing recharging and the voltages your planning. Do you have a thermal management plan? (Im not talking fire.....controling battery temps is what i mean)
Yes. I’ll get into more detail on this in the near future.
 

Mike Perez

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So I started working on the house battery setup. What a PITA! Each battery pack contains 4 modules. In order to remove the 4 individual modules from the OEM pack structure and other unnecessary equipment, you have to remove hundreds of fasteners. The rub is that there are at least 5 different sizes of torx, hex, and of course, a proprietary metric half size 12 point. I believe it is 11.5 mm. I got one pack completed and I'll do the other later this week. The pile of metal is what was leftover after disassembly.

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Matt Colie

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Oct 25, 2019
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Mike,
That half size 12-point might well be a ISO-Triple square. I do not know who (other than Snap-off) can supply the correct tool. They were specified as both male and female drives. Too bad you aren't closer, I still have a set that I had to buy about a hundred years ago.
Matt
 

Mike Perez

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Oct 2, 2019
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Mike,
That half size 12-point might well be a ISO-Triple square. I do not know who (other than Snap-off) can supply the correct tool. They were specified as both male and female drives. Too bad you aren't closer, I still have a set that I had to buy about a hundred years ago.
Matt
No worries. A 6 point 5/16 worked. I just had to be very careful so they wouldn't strip. I'll use something more standard when I put the buss bars on.
 

Mike Perez

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So here are all 8 modules and the big junk pile of what is leftover. I managed not to shock myself or burn down the house, so that's good. I think I have a plan more or less of how this is going to go. Per Panasonic, these batteries should not need any real cooling at the slow discharge rate that they will be subjected to vs. running an electric drive motor in a car. Now heating is another story. I'm going to have to build a sealed box that will mount under the coach in the bay in front of where the forward gas tank used to be. In that box, there will be a battery heating pad that will keep the batteries above freezing. It will be controlled by the battery management system (BMS), and turned on when needed. While I'm at it, I'm going to use similar heating pads for the fresh water tank that I'm going to mount in the next bay back.

I'm down to two different BMS units, but I'm leaning toward the Orion Jr. 2 BMS. It is good up to 16 cells (or paralleled cells) in series so that will work for my 14. The original Ford onboard charger charged these batteries at the rate of 3.3 kW. All of the chargers I've been looking at charge at less power than this, so it will be a bit slower than the onboard Ford charger and that's OK.
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JodyPackerfan

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Feb 2, 2020
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Yeah, the bath module is gone. I wish I could have saved it for someone, but I was unfortunately under the gun for time and it wasn't part of my design so it was removed in pieces.

I personally don't like the majority of the floorplans from the original coaches for a few reason. First, I'm not a fan of wet baths. Mine will have a dry bath. Second, I don't need that much seating. 99% of the time it will just be me, the wife, and the dogs. I think my original floorpan had seating for 13 people. 2 in the drivers seats, 3 on the couch, 4 in the dinette, and 4 in the back. That is insane. Mine will seat no more than 6. Also, I'm not a fan of the bed at the rear being across the coach. The problem with that is that if the person in the back has to get up to use the bathroom in the middle of the night, then they have to crawl over the other person. I'm not a fan of that. So for me, I think rear twins with a connected area around the shoulders is the great design. A couple pictures for reference. You get the idea. Rear twins still allows for the generator and propane compartments in the back. Also, since you don't need the area above your feet to be very high and it is forward of the window, you can have a closet cabinet start above your feet if you want.
I hate the wet bath as well and agree on the layouts. I'll enjoy watching what you come up with. Not sure about loosing the rear window. I kind of like that
 

Mike Perez

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Here is what I've been drawing for the C-max cells. Lower plate will mount to the bottom of the two crossmembers. The rest will be welded (outsourced) to the main plate with the exception of one of the longer ends. It will be bolted to the ends of the dividers and the ends. The reason is because the cells need to be under compression when they are installed, and there is a fair amount of force to compress them. I'm hoping I can use some pipe clamps to get every thing tight and then bolt the end on to secure it. I'll have to drill and tap 18 holes.

The inner dividers are shorter by 1.5" because there is 1/2" of insulation with a heating pad recessed and then an aluminum sheet of 1/16" that will be under the batteries. The lower center dividers allow room for the connections between paralleled cells. There will be a sheet metal lid with insulation covering the entire setup and bolt to the flange on the bottom. What could go wrong :oops:
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6cuda6

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Oct 3, 2019
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I see you have addressed possibly heating requirements but what about cooling requirements? With this quantity of cells i would also recommend a fire sensor, in the box, that triggers a light on your dash just in case something goes wrong.....at least youll know before the box vents if it should ever happen.
 

Mike Perez

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I see you have addressed possibly heating requirements but what about cooling requirements? With this quantity of cells i would also recommend a fire sensor, in the box, that triggers a light on your dash just in case something goes wrong.....at least youll know before the box vents if it should ever happen.
I'll probably do a fire loop. Per Panasonic, these cells do not require active cooling other than a fan even in an electric car. In the C-max, they are rated up to a discharge rate of 225 amps, which is almost 10C. In order to discharge at 1C, I'd have to be running nearly 15,000 watts of stuff. Even if I was running two A/C's and the microwave and getting close to the maximum continuous amp draw through the inverter, that would only be about 3500 watts, or around .25C of discharge. I'm guessing at such a slow discharge rate, they'll barely get warm. . I'm hoping a 4 foot by 3 foot aluminum "heatsink" will be enough to keep them at a good temp. The maximum temperature is 176 degrees F. I'll do plenty of testing before they go under the coach.
 

Mike Perez

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Plan B. I decided to scrap the DIY battery cages for a number of reasons. Mainly because I just think the way they were originally contained is better than anything I can design. The cages are extremely rugged and keep the batteries from moving at all. Also, while I'm making changes, I've decided to simplify the busbars and overall setup. What this means is that I'm going to slightly reduce the overall pack size to 12.6 kWh from the original 15.2 kWh. The reason for that is to keep the modules symmetrical. I'm still going to build a 48v system, which requires 14 groups of cells in series, so to keep things simple, I'm going to use 7 cages of batteries. Each cage will contain 20 cells, which will be paralleled in groups of 10. The cages hold 21 each, so I'll have to remove a cell from each cage.

With the help of a buddy of mine, I'm going to mill some HDPE sheet stock and make a "spacer" that is the exact size of one cell to put in the middle between groups of 10. Also, while I'm waiting for my spacers, I had to weld up a jig to put the modules back together. The battery modules need to be compressed back to their original compressed length before they can be put back in the rack. In the meantime, I'm having a local company make busbars which will take a week or so. I'd do it myself, but I don't think I can drill accurate enough to be perfect over the span of 21 holes that have very little tolerance between the hole and battery studs.

When it is all said and done, I'll have 28 cells left over. I'll keep them for the time being until I confirm that I don't screw anything up or strip any threads. After that, I'll probably just sell them. With 7 groups of 4, it would make a nice 24v battery for somebody.

Side note.....whoa copper is expensive.
 
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