JD's VW Bus Conversion EV project (2 of 2)

[dnmun]

4-40 is for jewelers, can you drill out the slot to take the zip screw? you can buy them at the home depot in 100 packs, just easy to use and tapping aluminum is the pits, especially so tiny. if you need some 4-40 1/2 then you can use these and drill it out.

[lawsonuw]

Instead of tapping 60 holes how about just ordering some thread cutting screws? (like McM #98273A115) When I've used 'em in plastic it helped to do some testing to find out what hole size worked best. (with the right size hole, sheet metal screws should also work)

The above McMaster part number is for a box of 4-40 self tapping screws. (I hate that you can't link directly into McMaster's web catalog) Alternatively look up your local Fastenal in the yellow pages. Fastenal's whole business is supplying odd screws and fasteners, they're likely to have what you want in stock or ready for pickup the next day. (there hours usually suck though)

I'd love it if could find the thread forming screws that PC cases use. The threads are three lobbed and they have a tapered point just like a thread-forming tap.

Lawson

P.S. a little poking around Fastenal's web site brought me to THIS search page. Looks like Fastenal has the nifty PC case thread forming screws in catalog.

[oatnet]

Thanks for the advice, everyone - and thanks to dnmun who offered to send me the screws in the above picture.

Using that advice, I stopped by Lowes today and picked up some 1/2" #4 machine screws with a pointy tip. I drilled out all the holes I had marked, and with a little 3-in-1 oil I was able screw them in. It took some trial and error, and the right bit, but once I mastered getting them in with a power screw driver it went pretty quickly. I was really pleased to see the holes I drilled were precise, I had no problem mounting the converters, I was concerned that I would only be able to fit a few screws on each one.

My initial plan was to put three rows of these converters in, 30x48vx2a = 2400 watts, too much for a single Vicor PSU until I get a 220 line installed. This is just for balancing anyhow, so 10 of these will balance a whole 10-supercell row, I'll just need to move it to cover all three rows. Maybe I'll mount a Vicor PSU right on the aluminum plate!

I elected not to use any thermal paste - merely resting on the aluminum plate was cooled the onetested very well, and thermal paste can run and make a mess.

-JD

EDIT 12/14/12: replaced pictures lost when the forum crashed a few years ago.

Test fitting a few converters

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Mounted permanently.

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[oatnet]

I got a call from Fed-Ex yesterday, reporting that my batteries should have been delivered yesterday, but that customs (in Anchorage AL) held them up 'looking for a better description of the product.' I guess these looked like little explosives on the x-ray , but at 8:30am today they cleared, and I hope they will be here tomorrow.

Since the weekend I have been making the copper strips that I use for charging, as well as holding the pack together. This is the second time I have made these strips, I thought I would document their construction...

-JD

I cut (20) 0.5" x 12.5" copper strips, and on one of them measured holes that are 39.5mm apart. This leaves a mere .8mm between each cell - just enough to pass air, and provide some room for expansion, while fitting into the 12.5" space available in my battery tray. Then using a nail I tapped a pilot mark to line up the drill bit.

I stacked the strips and taped them together with electrical tape. Then I remembered that the last time I did this, the tape didn't hold very well, so I wrapped some fiberglass tape around that. Finally, I used a small metal bit to drill out the pilot holes.

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In addition to the pilot holes, I drilled a small hole to slip a few strands for the charging wire through. When the copper strap flexes, I have seen some of the charging wires and solder come off the strap. By getting strands of copper on both sides of the strap, and solder through the hole, I form a mechanical bond that seems pretty strong.

Also note (more on this below) that the entire body of the cell is connected to the positive side. The Negative side of the battery can easliy be shorted to the case, so I put the bulk of the charging wire on the side of the copper strip where the batteries go, and feed just the few strands on the side where the negative end of the cell is at risk, so there is more clearance.

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Here I have drilled 1/4" holes through all 20 strips, which is slightly larger than the M6 set-screws the Headway uses, just right for my needs. Unfortunately my 1/4" cobalt bit was dull, I think drilling the Phenolic plastic did that, so some of the strips on the bottom did not turn out well. Fortunatly, I made spares just in case.

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Strips stacked on top of the vicor chargers. The fuses have been soldered on the ends for the charging wires. It is VITAL that charging wires have fuses immediately where they leave the battery, because if you short charging wires, your pack will go up in flames - I learned this, first hand, on an ebike pack.

I connect the charging wire to opposite sides of the supercell to make all the individual cells the same electrical distance from each other. I eventually will stack rows of batteries in box full of trays, so I want all of the fuses to be accessable from one end. Hence, some of the straps have a long wire. This wire runs along the length of the copper strap, and if it shorts out to the same strap it is soldered to, no fire. Still, I double-heat-shrink the connection between 10ga extension wire and 10ga fuse wire.

The unused straps at the top will be cut up to make the 4s4p 12v40ah battery that will power the bus's lights/turn signals/radio etc.

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I cut a piece of cardboard to the same dimensions as the contact patch of negative end of the cell, which is slightly larger than the positive side. I used an M6 screw to line it up, and drew the contact patch on the side of the copper strap where the negative ends of the batteries will go. This helps me line up the heat shrink.

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I found this GREAT adhesive-lined heatshrink at a local electronics swap meet for $1 per 4' tube. I didn't even realized it was adhesive until I used it on the last battery strips, I just bought it for diameter, but it is perfect for this job, this heatshrink won't slip, and it is extra thick.


I measured the length I needed, cut up two tubes, and had the exact number of pieces I needed to do this job. Spooky. Here you see pieces laid out ready for the heat gun.

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Heatshrink shrunk into place. It is vital to have this heatshrink here. If one of the cells twisted 90 degrees, exposed copper could cut through the battery's plastic wrap and short the negative terminal to the case. Between the heatshrink and the adhesive, that's not gonna happen now.

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The copper past the terminal carries no current, but it too could short against the negative terminal and casing. It was simple to trim off with metal shears. I left some excess strap on both ends, in case I made a mistake drilling the fuse wire hole, or the other end came out too short; its all about the fallback positions!

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Here is the copper strip against the negative end of the battery. The silver ring is the end of the case, carrying the positive charge. It is covered in some protective plastic, but you see how easy it would be for the strap to short between the silver ring and the negative terminal. The heatshrink covers the entire area where contact could occur, and you can see the adhesive oozing out which holds it firmly in place and makes a hard, thick coating. I like adhesive shrinkwrap!

Note that the set screw is put into the negative side of the battery. Once can put the set screw, hard against the bare metal of this side. The positive side is not a solid chunk of metal, and it seems like you could cut into the cell if you bolted the screw down on that end. With it bolted into the negative end, there is plenty of room to tighten against the positive end.

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The Fuse end of the charger strip needs to be protected from shorting against the case. Because of the charging wire and the short length of the space, this is difficult and never comes out neatly. I found that cutting the heatshrink on an angle helped.

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EDIT 12/14/12: replaced pictures lost when the forum crashed a few years ago.

[oatnet]

Heatshrink shrunk, and pushed into place as best I can. It also helps secure the charging wire.

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Finally, complete battery connector strips, waiting for cells.

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Hope that wasn't too boring!

-JD

[pwbset]

Very cool! I may have missed it, but where do you get that copper strapping? All I've been able to find locally is plumbers "copper plated" strapping, which I'll use, but wonder about conductivity losses or whatever.

I also saw last weekend a "new" auto shop in the neighboring town that carries old Type II Westys! They are beautiful! Now all I need is a lot of money.

[oatnet]

Very cool! I may have missed it, but where do you get that copper strapping? All I've been able to find locally is plumbers "copper plated" strapping, which I'll use, but wonder about conductivity losses or whatever.

I also saw last weekend a "new" auto shop in the neighboring town that carries old Type II Westys! They are beautiful! Now all I need is a lot of money.

Thanks pwbset! I went through the same painful search, but I finally found the ebay seller "metallectric" who sells 1/2", 1", and 2" thick rolls. I just went to look him up, but his ebay store says he is 'away' so ebay won't let you even look at his completed auctions. Hopefully he will be back soon, I have wiped out my stock of 1/2" and 1" (see below). I hope you find the Westy of your dreams! I think a splitty would be a very cool conversion, but I think the 72 up versions are the most practical and servicable.

First off though, LiFePO4 Porn - Headway Heaven - (120) new cells arrived today via FedEx. The last batch of cells got here 3 business days after I wired payment, these cells took 5 days, but only because Customs interrupted the shipment in Alaska and SAT on them for two days, I guess maybe they looked like little bombs or something on the x-ray - the last batch sailed right through.

They are lined up like this, out of their white 2-cell shipping boxes, because I tested every cell; most arrived at 3.37v, 3-4 were at 3.38v.

THANKS Victoria, for a great product at a great price point and EXCELLENT customer service. It is always a pleasure to deal with you!

-JD

2 boxes of cells, ignore the reflection.

Headway Heaven 6112.JPG (77.09 KiB) Viewed 3086 times

Here is the last of my 50' roll of 1" copper strap, getting cut into strips that I will laminate together to form the ends of the third row of cells. Note the one strip that has already been marked up, top center, and drill points punched.

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The individual straps are hammered flat between two pieces of iron, one piece marked, and all of the strips are taped together for drilling. That will have to wait for tomorrow, I am beat from checking all the cells!

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EDIT 12/14/12: replaced pictures lost when the forum crashed a few years ago, plus deleted (1) smilie since apparently an 8-smilie limit was implemented after I added this post.

[markcycle]

Wow that sure is alot of cells those pictures are almost NSFW because its not good to endlessly stare into the monitor smiling with envy at some point your going to have to explain what your looking at.

I can see that bus burning rubber any day now

Mark

[oatnet]

I can see that bus burning rubber any day now

Now THERE's a thought. I wonder if I can get to that point? That would make a heck of a video... Even if I end up not needing the full 180v the controller can handle, I oughta do it to see if I can do a burnout. Wow.

-JD

[Doctorbass]

Oatnet.. I really like your project!!..

wow all these cells at your home!! I would love having that!!!..

I just think... 100+ hours of intense test!! lol

Be carefull with 180VDC !!.. we want to keep you alive just 100VDC on my arm kick me strong!!!

Alot of Wh!... eee.. may i should replace with kWh !!!

Doc

[Lapwing]

Be carefull with 180VDC !!.. we want to keep you alive just 100VDC on my arm kick me strong!!!

Alot of Wh!... eee.. may i should replace with kWh !!!

Doc

Yep, anything over 48V needs careful attention. Rubber linemans gloves are not overkill.

If you haven't already, this is a "must read"

http://www.evdl.org/pages/plasmaboy.html
http://www.evdl.org/docs/plasmaboy.pdf long version

Perspective is everything, and it helps to learn from others experiences.

I run a 72V system of 220Ah lead acid GC in my boat, and decided to isolate the batteries in 24V blocks. When the 3 contactors are off I have 3 x 24V banks. (easy and safe to work with and charge). Only when the contactors energise is it a 72V system.

[dogman]

Those isolated blocks of 24v are a damn good idea! While 48v might be pretty safe, you still get that tendency to vaporise a fitting when you screw up. I love good common sense ideas like that.

Now if I can just find a clean shirt to wear after looking at the pile of headways, dooling copiously. I can't stop thinking about that same pile of lithium in a geo metro or bug. As they say in Waynes World, someday,,,, it will be mine!

[Fishmasterdan]

Great project, somehow I missed this thread.

Keep up the good work. This looks like a really fun project.

[oatnet]

Yep, anything over 48V needs careful attention. Rubber linemans gloves are not overkill.

I hear you Lapwing!

In the picture below, note the linesmans gloves on the right. Each of the rows of batteries is 10 cells, 30.00v/33.75v/36.50v (nominal/resting/fresh charged). Note the red 2/0 cable connecting rows 1 and 2, with 400a Silicon fuses on BOTH sides. Rows 2 and 3 are connected by a solid bus bar for 60.00v/67.50v/73.00v, which I am thinking about cutting so I can fuse between them. The wire for each single-cell charger is fused right at the battery terminus, and although the unterrminated ends are just floating around right now, there are no fuses in them.

I also have contactors on both the negative side and positive side, energized by discrete circuits.

I spent a LOT of time thinking about every exposed surface, and have taken great pains to cover every potential contact point possible. I don't have exposed terminals like an SLA battery, and I am pretty sure i could drop a wrench anywhere and not conduct current - but I don't want to test it out either. When I put a sheet of plywood on top, this pack should be pretty well enclosed and maintenance free.

For the final mounting of the 180v pack, I am thinking of putting it between the front seats, 5 supercells per row, stacked 9 rows high (13.5"). Each row will rest in a tray that slides into a big steel box, each tray will be lined on all 6 sides with phenolic plastic, and each row will be connected by a silicon fuse. Cooling will become an issue at that point, and I have a lot of other vehicle-mechanical things to sort out first, so it will be a while before I go there.

ANYHOW, I busted my hump last night, and got all of the new batteries installed. I finished about 8:30pm and thought I would take it for a quick test. Clicked on the main contactor, clicked on the control contactor, pressed the pedal... and nothing happened.

So I tried to sort it out in the dark. I thought maybe I had popped a silicon fuse, but everything tested fine. Frustrated, I gave up for the night. I tested it again this morning, found continuity between the contactors, just no power! I ran a wire to test continuity of the negative 4/0 cable, which I had just been moving all over the place, and yep it was OK. Moved the wire to the positive 4/0 cable, which hasn't moved much - no continuity! I wiggled the battery side of the negative cable, and to my horror it came off in my hands, pulled right out of the lug.

So, power off, jammed the cable back into the lug, and viola! 108v. I could not resist taking it around the block to see how it rides. At 108v the bus now has at LEAST as much power as it did with the old ICE - plus with electric torque it is a little faster off the line.

This means I have met one of my design goals; I have successfully converted this bus to match ICE speed/accelleration, and because I used LIFEPO4, it is LIGHTER than when it started. There was no need to use 10c cells because the 80ah supercells will only be running around 2c continious, 40% of Headway's continous rating.

The Cycleanalyst, which is only rated to 100v, was flickering under load, and I could smell something burning, so I unhooked it. Until I can figure out how to get it working over 100v, or buy a new Custom version from Justin, I am not gonna have performance data The cells were ice-cold immediately after the "ride."

Next, I need to fix/replace the 4/0 cable, wire the Vicor DC-DC single-cell charger system, and start dealing with mechanicals like the motor mount, brakes, fluids etc.

Then I am gonna try to soup it up - it will be a real screamer when I bump to 180v, even with the extra 80 or so lbs over stock that will take me to (I have hauled 1500lbs of slate in this bus, 80lbs is cake ).

-JD <----- Sporting the EV Permasmile!

108v finished_6119.JPG

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Cable on the right, lug on the left.

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[Lapwing]

Awesome project. Glad you are taking the safety thing seriously.

Quick recommendation on crimpers. For a couple of years I used a cheap set of chinese made, box-crimpers up to 4/0 for my marine battery installs (what my employer provided). I was never happy with consitancy of crimps, even when I got really good at judging just how much "extra" to adjust the size nut. Had a several slip out in what seemed a good crimp.

When I quit the boatyard to go out on my own, I e-Bayed a set of THOMAS & BETTS - TBM5. What a difference. Heavy buggers but for $50 - perfection. I use only Ancor and T&B lugs, because these two brands fit the tool and have good dipped plating that holds up.

I did a bit of dangle-load testing on 2/0 cable and ran out of weights at 330#.

There is a set on e-Bay now item - 170311308703 http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=170311308703

[oatnet]

[quote="Lapwing"]When I quit the boatyard to go out on my own, I e-Bayed a set of THOMAS & BETTS - TBM5. What a difference. Heavy buggers but for $50 - perfection. I use only Ancor and T&B lugs, because these two brands fit the tool and have good dipped plating that holds up.
quote]

Great recommendation - I'm gonna buy them, I need to go spend time with my wife RIGHT NOW, she has been incredibly patient with me being EV absent!

[oatnet]

I've been a little hung up on a technical detail, and worried that it was a design flaw.

I planned on charging each of my 80ah SuperCells with those Vicor 20a DC-DC converterz, and bought a whole mess of 30a ATC fuses to allow 50% headroom. Yesterday it just occured to me that TWO current flows will be going through each wire - Positive for one charger on the 1st cell, and Negative for the next charger for the second cell, etc, so it could be 40a - with headroom, too high for an ATC fuse. More, actually, since I am trimming v down.

I emailed Doc and Gary about it. Doc came up with a clever idea for putting hooking the converters in series, charging the whole string with that, as well as connecting the charging wires to each converter with a resistor in series to hold it to 10a.

Gary reported back that since the two current flows are going in the opposite direction, amperage is not cumulative.

So I guess I am back to my original design!

-JD

[Doctorbass]

I emailed Doc and Gary about it. Doc came up with a clever idea for putting hooking the converters in series, charging the whole string with that, as well as connecting the charging wires to each converter with a resistor in series to hold it to 10a.

Gary reported back that since the two current flows are going in the opposite direction, amperage is not cumulative.

So I guess I am back to my original design!

-JD

JD,

The idea i suggested to you was what you said but you forgot to mention that i said to still use the balancing wire (all next wires betweeen the main NEG and POS) to balance the cell.. but the idea to use a resistor to limit the current. The entire pack will charge via the main neg and pos.. and the balancing wires will still balance the pack with the single charging method.. but their balance current will be reduced.


I think what Gary said is that the two current flows athat re going in the opposite direction in the balancing wires result in no amperage.. but this occur ONLY when you close the current loop.

EX:

- let supose that you have only two cell and two dc-dc. cell1 with dc-dc1 and cell2 with dc-dc2
- if you charge separatly every cells with their own dc-dc at let say 15A,
every wires will have 15A circulating in them.

now if you connect these combo in serie for 2s1p... that will change nothing right..? ok

now if you only use one common wire for the cell1 and the cell 2 to the dc-dc.. what will happen?

yes... it will have twice current..

Doc

[PaulM]

- let supose that you have only two cell and two dc-dc. cell1 with dc-dc1 and cell2 with dc-dc2
- if you charge separatly every cells with their own dc-dc at let say 15A,
every wires will have 15A circulating in them.

now if you connect these combo in serie for 2s1p... that will change nothing right..? ok

now if you only use one common wire for the cell1 and the cell 2 to the dc-dc.. what will happen?

yes... it will have twice current..

Doc

I'm not sure I agree with this; would it not be possible to charge with the two cells hooked in series, the two converters hooked in series, and no common wire at all?? The common wire is only needed if the cells are not balanced.

[oatnet]

I'm not sure I agree with this; would it not be possible to charge with the two cells hooked in series, the two converters hooked in series, and no common wire at all?? The common wire is only needed if the cells are not balanced.

It is safe to assume that they will not remain balanced due to variations between the cells. Frodus's postings showed that his 1p large format T-sky cells went widely out of balance on each discharge because of cell-to-cell differences. I am hoping that by building 8p with smaller cells, they will average out to be similar from supercell to supercell, but I am still doing single-cell charging to keep them in balance. I also have the onboard charger which charges across the whole pack more effeciently, I'll see what method I end up using later but for now I want the pack balanced every charge.

I should note that this is another place where a BMI/PSI/Lifebatt cell allegedly will outperfrom the Headway. They assert that the automated process resultes in less cell-to-cell variation, which (if true, I'd believe it but I have no direct knowledge) would keep the cells in better balance. I couldn't afford to do this conversion with those cells though, so I have to work with the cells I can afford, I am just pleased to find good quality cells that can do the job are in my price range. Maybe I'll luck out and my 'averageing' theory will hold true.

The idea i suggested to you was what you said but you forgot to mention that i said to still use the balancing wire

Doc, I am sorry I butchered the explanation of the suggestion you were so kind to dream up and share with me my ignorance of electronics is showing, I apologize.

It took actually (3) Gurus to get the concept through my thick head, I went to Guru Fechter for clarification, whose explanation made what you and Gary were saying click. Apparently, even though each charger is connected to each cell individually, they effectively act in series so 20a will be going through the wires at each end of the pack and the balance wires will see 0v - if the cells are in perfect balance. Where the cells are out of balance, some current will go through the balancing wires for each cell.

That is, assuming I didn't mangle his explanation too , but I think now I have a dim mental model of how it works, and it resonates with a phenomenon I had seen before - two packs, wired in parallel, both charged with banks of single-cell chargers; when the first pack's charger failed, the other pack's charger charged both packs, so I thought one got a single-cell charge and the other got a series charge - now I see they both mostly got series charges .

As I wrote to Fechter, every day I see how much more I have to learn.

-JD

[Doctorbass]

JD.. This forum ia a very nice place to learn about EV!!

You just can't imagine how many people i refer to our forum!

What is imoprtant is that you correctly understand what we explain.. otherwise it mean we(guru) don't do our job correctly!!

Good evening!

Doc

[echas]

JD,

You did a really great job with the conversion and this forum! I converted a 240sx to electric and need to get the lead out. The car has 1100 lbs of batteries and is not happy. http://vintage-voltage.com/240sx You have inspired me to go for the LiFePo, but I'm concerned sea freight may take 3 - 6 months to get delivered.

Do you remember how much the FedEx shipping cost you? I counted 240 cells in your pack. Did you ship all cells using FedEx? I'd like to talk to you more about your experiences with these cells.

[oatnet]

JD,

You did a really great job with the conversion and this forum! I converted a 240sx to electric and need to get the lead out. The car has 1100 lbs of batteries and is not happy. http://vintage-voltage.com/240sx You have inspired me to go for the LiFePo, but I'm concerned sea freight may take 3 - 6 months to get delivered.

Do you remember how much the FedEx shipping cost you? I counted 240 cells in your pack. Did you ship all cells using FedEx? I'd like to talk to you more about your experiences with these cells.

Greetings Echas!

You are the first to post it, but your reaction is something I was hoping to encourage, by demonstrating with a big heavy old bus. I think there are lots of underutilized Pb conversions out there, that already have the EV infrastructure in place, the just need a battery chemistry replacement to restore them to ICE weight and handling - and exceed ICE performance thanks to electic torque.

It costs $12/kg - or $4/cell - to ship air. Victoria got the cells to me in 3 days via air - although customs interrupted the second shipment for 2 days. Even better, she matched the price of local Thundersky seller (where I could pick up cells without shipping), so cost + shipping = local pickup cost.

I am happy to talk with you or anyone else who is lurking - just send me a PM with your email address!

-JD

[headway]

Dear Mr.Doctorbass,

How are you?

Did you get our two samples of 38120P 8Ah cells?

By the way, I will be in San Diego from 22nd to 29th, March. Is it possible for our meeting there?

Best Regards
Victoria

JD.. This forum ia a very nice place to learn about EV!!

You just can't imagine how many people i refer to our forum!

What is imoprtant is that you correctly understand what we explain.. otherwise it mean we(guru) don't do our job correctly!!

Good evening!

Doc

[theyerb]

JD-

I'm thoroughly impressed (and somewhat jealous. haha!). Great work