Prelude conversion project - some questions

Technical discussion on converting internal combustion to electric
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jonescg
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Re: Prelude conversion project - some questions

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All I know is it used a nickel sulfamate solution, so electrolysis was involved I think.
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Re: Prelude conversion project - some questions

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thermal epoxy going on.jpg
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A shot of the thermal epoxy before the FR4 goes on.

I have had to contend with some passivated sections of busbar which will not take a spot weld. I can't even solder it. But as they might only impact half a dozen cells per busplate, I can't really justify making a new one. SO I learned this neat trick thanks to Youtube:



I'm sure it's not great, but better than nothing.
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Re: Prelude conversion project - some questions

Post by SPanna »

Chris you mentioned using a nickel sulfamate solution, this is not electroless plating. I did some research because I was going to plate my alum bus-plates 43x40x3mm electro-plating $1.85ea, electroless $4.35 for 5 micron, $8.25 for 25micron. Big difference in surface adhesion & uniform coating. The electroplating guy said there would be high spots around holes & not bond to Alum as well as electroless. Needless to say at those prices I'm sticking with bare Alum with Alminox paste.
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Re: Prelude conversion project - some questions

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You may be better off using a thinner copper sheet instead.
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Re: Prelude conversion project - some questions

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Can only get 40 x 4mm C11000 Cu here this is way too thick, sheet Cu is C12200 which is only 85% IACS compared to 101% for C11000. 6060 Al is 54% and is lighter & less than 25% price of Cu. The other benefit is it can be laser cut.
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Re: Prelude conversion project - some questions

Post by nuggetgalore »

SPanna wrote: Sun, 07 Feb 2021, 06:21 Can only get 40 x 4mm C11000 Cu here this is way too thick, sheet Cu is C12200 which is only 85% IACS compared to 101% for C11000. 6060 Al is 54% and is lighter & less than 25% price of Cu. The other benefit is it can be laser cut.
Get a piece of 2mm or 1.5mm C110000 copper plate and cut your 43x 40 bits with a guillotine or hacksaw. Non ferrous metal dealers here in Melbourne have it in stock.
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Re: Prelude conversion project - some questions

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I was thinking more from the perspective of joining to the busbar.
I have been able to buy 1.2mm copper sheet (I had to use it for a project) and I have some 0.25mm and we used to have 0.5mm from when we used to make PCBs.
The laser cutting is an issue. I am just thinking it is much easier to plate to and solder than Al.
I did get the parts made out of 1.2mm cut folded and plated (tin plated). I had to get tin plating because the brackets were a busbar and also a heatsing for transistors that were soldered to it. I never really gave any thought to how they cut them. I just asked the supplier if they could make them out of copper and it didn't seem to be a problem. I had to get a few hundred so I guess it is not a problem when you have enough.
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Re: Prelude conversion project - some questions

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The battery pack is looking really good.
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Re: Prelude conversion project - some questions

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Thanks, I just finished module #2. We had the remains of a tropical low come south to visit Perth, so while the cooler weather is very welcome, the humidity isn't quite so popular. I'm watching the busbars of the remaining two modules start to get progressively more and more passivated. Some of them are almost entirely dark grey in colour, meaning they will not take a tab no matter how hard I work the welder. These will need to be soldered, the slow and hard way with oil and a hot iron.

I don't know if nickel plated copper is any easier or harder to spot-weld, but I will say that spot welding is substantially faster than soldering!
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Re: Prelude conversion project - some questions

Post by francisco.shi »

I think you are thinking of soldering the wrong way. The way to do it fast is to use some solder paste, locate the strips in the right place (some capton tape will probably do the trick) and heat up the whole bus bar. The solder melts and all tabs are done at once. Then you take the whole busbar with the strips already soldered and you spot weld the tabs to the cells.
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Re: Prelude conversion project - some questions

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Ah yes true there is that approach for sure.
I see a guy on Endless Sphere has bought a pulse arc welder for welding 0.4 mm thick copper to cells directly. Does a good job, and 0.4 mm thick copper is about equal in conductivity to 1 mm aluminium, with none of the intermediate resistance of a nickel tab.
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Re: Prelude conversion project - some questions

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Finally, about 5 weeks after starting, I have spot-welded the last tab to the busbars. Last thing to do now is solder the 6 or 7 recalcitrant tabs which can't be welded. You can see them where I've ground back the passivated nickel surface. Then do the cell top welding (about 2 hours there) before putting the final thermal epoxy layer on. Then I can maybe get back to some of my course work I always threaten to do on the weekend...

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Re: Prelude conversion project - some questions

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Last weekend I welded every last cell and glued the top and bottom covers on.

Today was supposed to be the day I filled them with potting compound - EPL-9 which is a polyurethane elastomer with a hardness ideal for keeping batteries snug. My plan was to drill out the missing cell and use this as a filling point for the potting compound.

Best laid plans and all that :( I used a funnel with a 10 mm diameter and made up a batch of resin. It has a working life of 9 minutes. Bullshit. It's got a pot life of about 90 seconds. After that it starts to flow like treacle and sets hard in about 1 hour. I managed to get about 100 ml into the hole before the funnel blocked and I'd wasted a whole batch of resin.

So this time I cut two holes in the front panel big enough to get a decent pour in.
filling with PU elastomer.jpg
filling with PU elastomer.jpg (153.99 KiB) Viewed 129 times
This worked better, but there was no way this was going to infiltrate all the vacancies between each cell. At least it held the wiring in place so having that fret will be far less likely.

It's better than nothing, and there's about 2 kg of resin in each one. It probably needed at least 3 kg each, but this will have to do. I'm pretty confident they are waterproof now.

The sheet metal brackets for securing the modules inside the battery pack are being laser cut next week, and might be ready for folding soon after. If they are ready before Friday there is a remote chance the car will be at Electrikhana. Provided no silliness happens in installation. Like the BMS wiring being wrong :roll:

I test-fitted module one and plugged the first BMS unit in. As I was working on something at the rear I heard a pop and a crackle :shock: The BMS module was getting very hot, so I unplugged it and removed the module (giving myself a hernia in the process). The battery seemed fine and the wiring was OK, but the 12-cell unit was cooking. Pppped the cover off and sure enough every second balance resistor was fried. I've clearly wired this up wrong. Cell 1: 87 volts. Cell 2: 7 volts. Cell 3: 78 volts...

I think I must have got confused as I flipped the module over half way through assembly and wired these up backwards. It's easily fixed with an hour's work, but man what a fright. That all-too-familiar sinking feeling where I rack my bran for ways to find enough money to simply buy Francess a new car cause this one is already way over budget and not exactly problem-free :(

I will also wire up the new EVSE widget tomorrow so if I do get the battery clamps I can at least assemble it and charge the car.
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Re: Prelude conversion project - some questions

Post by brendon_m »

It's all fun and games until a poor balance resistor gets 80V smashed across it...

On the plus side you must be learning a lot in preparation of the crx.
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Re: Prelude conversion project - some questions

Post by nuggetgalore »

"Best laid plans and all that :( I used a funnel with a 10 mm diameter and made up a batch of resin. It has a working life of 9 minutes. Bullshit. It's got a pot life of about 90 seconds. After that it starts to flow like treacle and sets hard in about 1 hour. I managed to get about 100 ml into the hole before the funnel blocked and I'd wasted a whole batch of resin.

One way to increase the pot life is cool all the gear down to a temperature just above where the resin starts to get sluggish. The next best thing is to rig up a vacuum cleaner at the opposite end of where you fill the module (have two holes only, diagonally opposed).* To actually make a proper vacuum chamber would be a big job, but that is how we did fill difficult to pour jobs. Later we imported an automatic resin mixer that pumped the resin into the moulds, some where filled with expanded clay balls where all cavities between the balls had to be filled.
* Edit: the resin needs to be bottom fed from the container so it is pulled in without air being sucked in.
Or the funnel(sealed to the inlet port) being filled faster than the resin gets pulled into the array.
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Re: Prelude conversion project - some questions

Post by T1 Terry »

jonescg wrote: Sat, 27 Feb 2021, 20:53 Last weekend I welded every last cell and glued the top and bottom covers on.

Today was supposed to be the day I filled them with potting compound - EPL-9 which is a polyurethane elastomer with a hardness ideal for keeping batteries snug. My plan was to drill out the missing cell and use this as a filling point for the potting compound.

Best laid plans and all that :( I used a funnel with a 10 mm diameter and made up a batch of resin. It has a working life of 9 minutes. Bullshit. It's got a pot life of about 90 seconds. After that it starts to flow like treacle and sets hard in about 1 hour. I managed to get about 100 ml into the hole before the funnel blocked and I'd wasted a whole batch of resin.

So this time I cut two holes in the front panel big enough to get a decent pour in.
filling with PU elastomer.jpg

This worked better, but there was no way this was going to infiltrate all the vacancies between each cell. At least it held the wiring in place so having that fret will be far less likely.

It's better than nothing, and there's about 2 kg of resin in each one. It probably needed at least 3 kg each, but this will have to do. I'm pretty confident they are waterproof now.

The sheet metal brackets for securing the modules inside the battery pack are being laser cut next week, and might be ready for folding soon after. If they are ready before Friday there is a remote chance the car will be at Electrikhana. Provided no silliness happens in installation. Like the BMS wiring being wrong :roll:

I test-fitted module one and plugged the first BMS unit in. As I was working on something at the rear I heard a pop and a crackle :shock: The BMS module was getting very hot, so I unplugged it and removed the module (giving myself a hernia in the process). The battery seemed fine and the wiring was OK, but the 12-cell unit was cooking. Pppped the cover off and sure enough every second balance resistor was fried. I've clearly wired this up wrong. Cell 1: 87 volts. Cell 2: 7 volts. Cell 3: 78 volts...

I think I must have got confused as I flipped the module over half way through assembly and wired these up backwards. It's easily fixed with an hour's work, but man what a fright. That all-too-familiar sinking feeling where I rack my bran for ways to find enough money to simply buy Francess a new car cause this one is already way over budget and not exactly problem-free :(

I will also wire up the new EVSE widget tomorrow so if I do get the battery clamps I can at least assemble it and charge the car.
There are videos on how to resin fill a large area using plastic sheets and a vacuum pump through a catch can so resin doesn't accidentally end up in the vacuum pump.

As for the cell BMS wiring, I got to the point I measured the voltage at the end of each cable so I got the order correct, then put them into a plug, and I was only doing a 48v push bike battery :lol: I had enough problems not ending up with the same voltage on two cables and a two cell jump to the next cable voltage meaning I'd somehow soldered to the negative on one group and the positive on the next group instead of the negative on that group. Now I write in black marker the colour of the wire that goes on that negative connection, then mark all the positive red so I double check I've got all the polarities correct, this getting old and over worked really sucks :oops:

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Re: Prelude conversion project - some questions

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All I need now is the sheet metal clamps.
almost reassembled.jpg
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almost reassembled2.jpg
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It's T I G H T... I think I'll be doing some fibreglassing on the enclosure to make it fit.
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Re: Prelude conversion project - some questions

Post by brendon_m »

Looking good.
Hope to see it at electrikhana
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Re: Prelude conversion project - some questions

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brendon_m wrote: Sun, 28 Feb 2021, 18:01 Looking good.
Hope to see it at electrikhana
Everything will need to go right, but we'll see how we get on.
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Re: Prelude conversion project - some questions

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The front busbars are going to be fairly easy to put together, but it does mean that the battery clamps will need to be as tight as practical, and as close to the modules as I can get them. There's barely a 1.6 mm gap there, so I'll have to ensure a sheet of FR4 sits in front of the busbars to prevent them from ever touching the sheetmetal clamp.
I also don't know the exact locations likely to fret against the fiberglass cover, so I think I'll be doing some grinding and glassing of an evening too.
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Re: Prelude conversion project - some questions

Post by brendon_m »

Did you end up looking at that water proofing membrane?
Or did you come up with a different solution?
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Re: Prelude conversion project - some questions

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I will need some of that stuff yes. It's used on bathroom tiles right? I will need to hack and modify bits of the cover to make everything fit regardless, so once that's done I'll get busy with the sealant.
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Re: Prelude conversion project - some questions

Post by brendon_m »

Yeah, the stuff I was talking about is used under tiles.
https://www.bunnings.com.au/our-range/b ... ng-sealing

I specifically used this stuff
https://www.bunnings.com.au/sika-4l-sik ... l_p0191692
Screenshot_20210301-210642.png
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And there is material matting stuff for reinforcing corners, bit like fibreglass mat
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Re: Prelude conversion project - some questions

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It's still going to be a rush to get things ready for Saturday... The battery cover certainly won't be waterproof in time, but I might be able to get the internals finished.
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