J-Mans project

[Korishan]

I'd say you probably had some cells warm up more than others, and the springs helped dissipate the heat. Also, depending on what the outer layer of the spring was made of, would make a difference of how much went into the cells. If they were made with zinc plating, they wouldn't transfer as much as if they are silver plated. And if they are stainless, even less.

I think silver plated spring tabs would of been better.

 

[kazbach]

...
So as I briefly mentioned I wanted to build a rig so that I can charge the 120p packs without having to solder them together as im still not sure about the format I want to arrange them in.
....
No surprise really but I had this idea in my head and I wanted to try it out

Been there - I'm trying magnets instead of springs - with similar results - I'm not giving up yet. Asolderless solution for my little system(s) will be highly advantageous as I assume I will be dissembling the packs more than once.

 

[The-J-Man]

I'd say you probably had some cells warm up more than others, and the springs helped dissipate the heat. Also, depending on what the outer layer of the spring was made of, would make a difference of how much went into the cells. If they were made with zinc plating, they wouldn't transfer as much as if they are silver plated. And if they are stainless, even less.

I think silver plated spring tabs would of been better.

It doesnt say how they are plated, or maybe stainlessbut id saythey are zinc plated.
Ahh ok, well im not going to redo it, I think i ages like 6 months doing that.....

Been there - I'm trying magnets instead of springs - with similar results - I'm not giving up yet. Asolderless solution for my little system(s) will be highly advantageous as I assume I will be dissembling the packs more than once.

Hmm interesting. Let me know how it goes, or post a thread about the build here!
cheers

 

[The-J-Man]

Greetings my friends

Im planning my build in Solidworks at the moment and Ithought about screwing the whole twisted busbar concept and having a lasercuter cut out some copper sheets with the holes in it. (see screenshot)Then buy a spot welder and attach the fusewire. So how just Tesla does it I guess.




Couple questions to you guys
Voltage drop etc. Would be it a problem?
Copper, aluminium or steel? Tesla uses Aluminium, atleast from the close up I attached it says AL 1001.
Thickness to handle the current? Currently want to set up everything to handle up to 120A. Any guesses if 0.5mm thickness would to the job? or should I be looking more into 1-2mm?

cheers

 

[Korishan]

Tesla might be using Aluminum (Aliminium) for heat dissipation and cost reasons. Not for current reasons. I would go with copper that's been nickel plated if possible.

A standard sheet of only a few mm thick would be sufficient since you are using a plate of metal, not wires. So the current is transferred differently. Doing it that way would be a great idea if you have access to a laser cutter

 

[The-J-Man]

Tesla might be using Aluminum (Aliminium) for heat dissipation and cost reasons. Not for current reasons. I would go with copper that's been nickel plated if possible.

A standard sheet of only a few mm thick would be sufficient since you are using a plate of metal, not wires. So the current is transferred differently. Doing it that way would be a great idea if you have access to a laser cutter

Could also be aluminium because spet welding copper doesn't work very well apparently, I just read that.
Nickel plated copper could work though... hmmm..

I will get offers in on the pricing for cutting the sheets.
Just finishing off doing all the CAD work.

 

[The-J-Man]

Still havent managed to carry on with my project but I had a look at my ugly test pack just yesterday and noticed some serious corrosion /oxidationon the copper busbars.
I forgot to remove the flux after soldering so thats what the ugly brown stuff is on the cells but the green oxidation on the busbar cant be missed. Thats probably also due to the flux.
Although on the positive side it looks like rust...

How much corrosion have you guys had on your packs and is it a problem?

 

[cristof]

I wont said it's corrosion, it's "oxydasion". It's a normal way for coper. After a few days/weeks/months/ coper color go to "brown". it's going faster with electric intensity or heat.
for the cells, it's not corrosion or oxydation, most of time, inside the solder, there is a "cleaner" and this cleaner become dark after a few.
sory for my poor English.

 

[Korishan]

I will go out on a limb here and say that the oxidation on the copper is because the solder connections weren't good enough. You didn't have enough heat to allow for the solder to flow fluidly as it's supposed to.
Yes, the brown gunk is the left over flux from the solder. I believe if you use something other than resin core, this won't happen (as much).

Just make sure that when you solder any joint, that the solder flows very smoothly. It should be shiny after it has set. Most of those above look to have not quite made it to the right temperature for long enough and so the solder started to cool unevenly causing a matte like finish, especially on the copper connections.

 

[The-J-Man]

I will go out on a limb here and say that the oxidation on the copper is because the solder connections weren't good enough. You didn't have enough heat to allow for the solder to flow fluidly as it's supposed to.
Yes, the brown gunk is the left over flux from the solder. I believe if you use something other than resin core, this won't happen (as much).

Just make sure that when you solder any joint, that the solder flows very smoothly. It should be shiny after it has set. Most of those above look to have not quite made it to the right temperature for long enough and so the solder started to cool unevenly causing a matte like finish, especially on the copper connections.

So the copper is reacting with the solder. Its not the extra flux I put on the copper thats still there and causing the oxidation?
I have this anti corrosion spray coating against electrical stuff, should I try and apply it to the busbar (when its not on the cells yet ) to stop this from happening?

I had problems soldering this thing :
ill be spot welding to the cells in my final packs.

 

[The-J-Man]

First update in quite a long time, didn't have the time or the nerve to work on my packs these last weeks or months.
Anyway so I changed my arrangement from 4x30 to 8x15 and the style of the busbars as well. Did this so I can have a more compact powerwall (it will be a wall hung unit like the original)

Built my first pack just now and im very pleased.
Spot welding just makes it look so much more professional

Took about 25mins to spot weld the entire side. Then another 5 mins cutting off the excess wire and another 8mins to solder them up to the busbar.
So just the welding and soldering for the whole pack is over an hour. Guess ill get quicker at it with time

Also took over 2 hours to make the busbar pieces, bend them to the desires shape and attach them to the cell holders. First time doing it though. Next Ill do all the parts at once for the remaining 13 packs.

Decided to try it out with my 14th pack first, the only one that will be from laptop batteries in my build. At least in the first build ;
I made sure to only use 2200-2400mAh (rated capacity cells) that tested 2200mAh-2300mAh on theOPUS. Essentially I used my best cells in in the 2200mAh range because all my hoverboard cells are exactly that.

Annoying was that the different branded cells have slightly different dimensions and therefore some are looser in the holders then others. Causing them to move when applying pressure with the spot welder. Often I couldn't excerpt enough pressure because of this and it caused a big spark. Which is why some cells have those dark spots on them.

Also haven't decided yet if I will use those crimp lugs or useall my XT60 connectors. The lugs would probably look more tidy but be slower to assemble and disassemble in the rack.

Aaaand now to the other 13...

 

[Korishan]

The cells were probably loose due to the wrapper not being uniform in thickness from brand to brand. You can take some clear scotch tape and put around the end that goes in the holder. That should add sufficient thickness to the loose ones.

About the soldering and copper. Corrosion is usually caused by differences in metals and metal interactions. So my guess would be that the solder you used may have something in it that is interacting with the copper. Or, when you soldered to the copper, you didn't get it hot enough to allow for the flux to properly clean the copper before the solder adhered to it. This causes impurities to be present and cause the metal interactions. I think if you got your copper bars hot enough during soldering, this would alleviate a lot of this from happening.
Now, if it's corroding due to oxidation, then that would still be under the aforementioned fix. Heat it up hot enough to allow for the flux to clean the metal, then the solder flows into where the flux was once at and then adheres to the copper. Essentially, the solder becomes a protective layer over the copper to keep it from oxidizing. Ie, tinned copper

---

Oh, and less I forget, nice looking pack
In those pics, it looks like you did a much better job of soldering to the copper wire. Of course, it's only 1 strand, not multiple strands like in the others.

 

[floydR]

Annoying was that the different branded cells have slightly different dimensions and therefore some are looser in the holders then others. Causing them to move when applying pressure with the spot welder. Often I couldn't excerpt enough pressure because of this and it caused a big spark. Which is why some cells have those dark spots on them.

Also haven't decided yet if I will use those crimp lugs or useall my XT60 connectors. The lugs would probably look more tidy but be slower to assemble and disassemble in the rack.

Aaaand now to the other 13...

a single layer of clear tape 1/4 wide at bottom and top of cells would tighten up the loose cells in the holder.


later floyd

didn't read Korishan's reply see he suggested the same thing.

 

[The-J-Man]

The cells were probably loose due to the wrapper not being uniform in thickness from brand to brand. You can take some clear scotch tape and put around the end that goes in the holder. That should add sufficient thickness to the loose ones.

About the soldering and copper. Corrosion is usually caused by differences in metals and metal interactions. So my guess would be that the solder you used may have something in it that is interacting with the copper. Or, when you soldered to the copper, you didn't get it hot enough to allow for the flux to properly clean the copper before the solder adhered to it. This causes impurities to be present and cause the metal interactions. I think if you got your copper bars hot enough during soldering, this would alleviate a lot of this from happening.
Now, if it's corroding due to oxidation, then that would still be under the aforementioned fix. Heat it up hot enough to allow for the flux to clean the metal, then the solder flows into where the flux was once at and then adheres to the copper. Essentially, the solder becomes a protective layer over the copper to keep it from oxidizing. Ie, tinned copper

---

Oh, and less I forget, nice looking pack
In those pics, it looks like you did a much better job of soldering to the copper wire. Of course, it's only 1 strand, not multiple strands like in the others.

---

They seem different lengths as well though, was difficult putting enouch pressure on the holders as though as I had to put the copper onto the holder before putting the cells in.
Ill try the tape next time but all my other cells are identical and have a snug fit.

Ohh ok i get it now thanks :

Ive been doing so much soldering the past months at work and stuff that I really got the hang of it now :
Yeah that thick busbar was a b****. Im going to take that pack apart again now

a single layer of clear tape 1/4 wide at bottom and top of cells would tighten up the loose cells in the holder.


later floyd

didn't read Korishan's reply see he suggested the same thing.

Sweet thanks mate

 

[The-J-Man]

IM DONE!!

well with making packs at least
Finished off all 14 packs yesterday. I ended up taking about 22 mins for the spot welding and 8 mins for the soldering per pack. Add in the making of the busbars etc it was about 1hr 15mins per pack.

Super pleased with the result, love the spot welder, such a clean look!
Sadly the soldering iron on the spot welder stopped working at one stage : anyone know how to fix it?

The other 3 packs are in the house as I need to discharge them, they are full but I want them at 4 volts.Sure takes its time with the iMax B6 and 1Amp Discharge : Speaking of the iMax, anyone know how to make it more accurate? The voltage reading is off massively and it bugs me.
Ill charge up all the others packs to 4 Volts simultaneously. Ive got a big charger I can borrow so Ill just connect them up in series and blast away. All have cells of same condition so shouldn't be a problem.

Now its time to design the housing for the packs and plan other components. Need to order my Batrium too but I might wait till next year, wont have much time this month anyway. Whats the shipping time to Europe?

Any recommendation for the fuse I can put between packs 7 & 8? Id like a safety measure in there, no idea how big they are but I need to plan that in as well

thanks fellas

 

[wim]

Are those some nice looking packs or what ???
Put them in a nice plexi box, way too pretty to hide away...

 

[Korishan]

Maybe put a few led strips around them to give them some POP! (not to be confused with cristof's pop )

 

[The-J-Man]

Are those some nice looking packs or what ???
Put them in a nice plexi box, way too pretty to hide away...

That is actually a nice idea!!! Or at least a plexi front and sides. Need some structural back and bottom plates as it will be wall /wall floor mounted. What about some of that electric glass that goes transparent when pressing a button

Maybe put a few led strips around them to give them some POP! (not to be confused with cristof's pop )

Hey Siri, make my 18650s Red. Yeah that would be funny, kinda nerdy but funny hahahah. Ohhhh no I, trying not to get inspired by that pop...

 

[The-J-Man]

Discharging two packs with the iMax at the same time. Should be done in, um about 20days :
Positive part: the 14th pack from laptop cells is maintaining identical voltage to the other pack.




Forgot to post about the pack interconnects I made.
Bought some 10mm diameter copper pole. cut them into 30mm pieces, drilled 5mm holes into it and then cut and M6 thread.
Originally I wanted 12mm but for some reason I ended up ordering the 10mm, brainfart... 12mm would have looked nicer and I have no clue if the 10mm is enough for the currents but I doubt its too little....




So now I can puta M6 screw directly into the copper. Works like a charm.

 

[The-J-Man]

New Discharging Rig

Its pushing about 2.4-2,8Amps into the iPads : I leave the screens on at full brightness. If you put the brightness to low on one of them then thecurrent drops to 1.6A. Nearly 1A just to power the screen :O
Got that USB thing out of a powerbank, its only a 1A per slot model but its seems to be able to do 1.4A per slot. It was getting rather warm though so I put a USB fan there as well...

Quite a lot faster then the iMax at 1A