Hillhater
100 TW
Jack on EVTV is having some interesting times and second thoughts on the A123 pouches ..
Dow-Kokam (NMC) vs. A123 (LiFePo4) comparative analysis...
- Thread starter sangesf
- Start date
gestalt
10 kW
Thanks mitch for the suggestion, I like that brass would be corrosion resistant and especially that it's cheaper. Seems that it would deform less and also be better for tapping threads.
As for using silicone for insulating the terminations at first I was thinking to have each individual termination block with it's own neat little cube of silicone over it, but I'm thinking that it might work just fine to fill in the whole top of the pack from the tabs up. That way if you ever had to tinker or test you could just peel the whole thing off as one piece. There is a company called Reynolds Advanced Materials and they deal in all of the silicone based molding supplies. They have been very helpful when I have been working on Halloween costumes and are just a five minute bike ride away. They have a cool showroom with samples of each and every product they carry which is a whole lot. I'll stop by and see if they have anything that would be suitable.
As for using silicone for insulating the terminations at first I was thinking to have each individual termination block with it's own neat little cube of silicone over it, but I'm thinking that it might work just fine to fill in the whole top of the pack from the tabs up. That way if you ever had to tinker or test you could just peel the whole thing off as one piece. There is a company called Reynolds Advanced Materials and they deal in all of the silicone based molding supplies. They have been very helpful when I have been working on Halloween costumes and are just a five minute bike ride away. They have a cool showroom with samples of each and every product they carry which is a whole lot. I'll stop by and see if they have anything that would be suitable.
IBScootn
100 W
Brass - I remember someone using a brass bolt in a high current load and it failing prematurely. It was completely corroded and everything else was perfectly fine. Made me nervous about using brass for my connections.
Yeah i'll believe that when i see it. You know how the battery thing goes by now, dontcha arlo? 
I think some decent NMC is coming our way in the near future, though. I'd almost put money on it
Dow Kokam stuff is already here.. bit pricey though... the Chinese knockoff will come in due time
I think some decent NMC is coming our way in the near future, though. I'd almost put money on it
Dow Kokam stuff is already here.. bit pricey though... the Chinese knockoff will come in due time
oldpiper
1 kW
Haven't been following this thread closely, but I'll put in my 2c about brass. For high current applications like we're talking about (higher than normal house wiring), I would stay away. Most brass has about 3X the resistance of copper, due to the zinc in it, which means you'll get more heating. Also, zinc is a much more reactive metal, which means it will corrode more than copper. Lastly, brass is an alloy, and the corrosion is often much more porous than the "patina" on copper, so it lowers the mechanical stability of the metal and opens up more surface area to corrode faster. Remember, you're subjecting these batteries to a fair amount of vibration.IBScootn said:
Somebody also mentioned aluminum, stay away, stay *far* away. Remember the fire hazard that the "experiment" with aluminum house wiring in the 50's caused. And that was with a system (screw-tight switch connections, etc.) which saw almost no vibration.
Cameron
John in CR
100 TW
Arlo1 said:
I hope you're right, because that will drive down even further the price of stuff that is plenty good enough already, like the A123s. It may not be good for some very specific hard core performance rigs, but it's plenty good enough for oversize packs run conservatively on ebikes or even light cars. It's only price holding the revolution back, not the tech, and tech advancements push the prices down.
John
docnjoj
1 GW
Good thinking, Cameron. I just looked up the relative conductivity of various metals and this picture shows the difference. The site does mention that brass is easier to machine and stronger. It is about 1/4 the cost of copper.oldpiper said:
otherDoc
999zip999
100 TW
Silver, copper and gold solder different. Silver is very conducted of heat you must heat the whole piece to the same temp. befor the solder will flow, and is the most heat conducted. Gold you can heat a section then apply the solder. These are all hard solders. Copper is a dirty metal as pure. And a solder as if we use in electrical ( low temp. ) is used. Now what is the solder is used on aluimun ? With is a a good conducter in between the metals ?
Harold in CR
100 kW
I have been holding off posting in this thread, about soldering aluminum with lead solder.
Somewhere, and I can't find the article, I read and saw photos of a guy that solders A123 tabs using lead solder.
He say he scrapes the tab a bit, with a sharp edge of his iron, while the flux is ON the tab. This keeps the oxygen from forming the oxide. No air = good solder joint. He puts a bit of solder down, and scrubs in into the tab. Photos showed it looking as good as copper soldered tab. Once the tab is "Tinned" he just connects to it, same as a copper tab.
Wish I could find the article. Someone with a bad cell, needs to try this out. MIGHT be this simple ???
Somewhere, and I can't find the article, I read and saw photos of a guy that solders A123 tabs using lead solder.
He say he scrapes the tab a bit, with a sharp edge of his iron, while the flux is ON the tab. This keeps the oxygen from forming the oxide. No air = good solder joint. He puts a bit of solder down, and scrubs in into the tab. Photos showed it looking as good as copper soldered tab. Once the tab is "Tinned" he just connects to it, same as a copper tab.
Wish I could find the article. Someone with a bad cell, needs to try this out. MIGHT be this simple ???
999zip999
100 TW
I was told that if not the right solder it will heat on the aliumin side and melt off and just drop off ? This is an answer I looking for. Thanks
For Sale Thread coming soon...
(2 to 3 days)
If you have PMd me about cells, be ready to have funds available (soon) for ordering...
I will be posting who's ordered and update as we go along..
I will update with who's paid so far (once we start collecting monies), as well..
That's gonna be about the "trickiest" part, getting everyone to pay In a timely manner
(2 to 3 days)
If you have PMd me about cells, be ready to have funds available (soon) for ordering...
I will be posting who's ordered and update as we go along..
I will update with who's paid so far (once we start collecting monies), as well..
That's gonna be about the "trickiest" part, getting everyone to pay In a timely manner
999zip999
100 TW
How are you going to connect these cells just in seieris connections with the alumiun and copper tabs ?
agniusm
1 MW
Hi. I have done my A123 pack with brass blocks, They were easy to work with, thou it took some time to cut them, drill and thread. I dont think there is a problem for materials being less conductive than copper, in the end you are using them to clamp 2 cell tabs together and not run current through them !
Here is how i did it:
Here is how i did it:
docnjoj
1 GW
That looks excellent, agniusm, and one that I believe I can use also. What did you use for the top and how did you make it? Also are the clamps horizontal or vertical? In other words did you fold the tabs and then clamp them? Size of the brass?
otherDoc
otherDoc
agniusm
1 MW
The brass bars are 6x6mm 45mm long. Here is cad drawing for the plate: https://docs.google.com/open?id=0B56NVZIdTBFOQ2lxMXBtNlZST2V2OVBpU05uQU1CQQ . It is for 6s so u just stack them until u get the right configuration.
Mine had to be in 2 6s total 12s, but i have changed it to one stack of twelve, therefore looks a bit more rough with side bars. Here is the first intention:
The tabs are drilled and then shortened, folded and clamped.
Mine had to be in 2 6s total 12s, but i have changed it to one stack of twelve, therefore looks a bit more rough with side bars. Here is the first intention:
The tabs are drilled and then shortened, folded and clamped.
999zip999
100 TW
I like that. Did you get a bms that fits your needs ?
docnjoj
1 GW
This is getting interesting, agniusm! What material did you use for the plate. It looks like a fiber filled plastic. The closest brass bars I know of is 3/8 inch=6mm. That would work for me. Did you do the work by hand or farm out the cutting or do you have access to CNC?
otherDoc
otherDoc
Harold in CR
100 kW
Docnjoj, According to my metric-inch ruler, 6mm is about 1/4". :wink: I'm thinking maybe 1/4" masonite would work for the plates ?? That can be bought in the big box stores, cut into pieces. MIGHT even be able to work out the hole spacings in that peg masonite board ?? Can't believe the heat from the well clamped tabs will cause that stuff to catch fire ??
Just thinking out loud, until I GET my cells.
Just thinking out loud, until I GET my cells.
ohzee
100 kW
Yea I think that looks pretty freaking awesome.. right up the alley of what id like to do and how id like it to lay.
agniusm
1 MW
Harold in CR said:Docnjoj, According to my metric-inch ruler, 6mm is about 1/4". :wink: I'm thinking maybe 1/4" masonite would work for the plates ?? That can be bought in the big box stores, cut into pieces. MIGHT even be able to work out the hole spacings in that peg masonite board ?? Can't believe the heat from the well clamped tabs will cause that stuff to catch fire ??
Just thinking out loud, until I GET my cells.
It will not cause fire, no way, if it would you would class A123 tabs as useless. I bet i would hold current as high as a123 spec no problem.
docnjoj said:
I have done cad drawing, sent to a firm and they did it with CNC. It is basic PCB. stripped from copper layer.
It was done for my test project (which you can read about in standup scooter section,ze meduza project). For my full scale project, cargo bike, 24S i will be doing tracks for BMS, as well as leave copper pads on PCB where brass blocks attach.
Here is a rough sketch:
agniusm
1 MW
Forgot to metion that you can bolt same board on 10mm spacers and that will protect from any short etc
docnjoj
1 GW
Yep Harold you are correct. Gotta have coffee before I convert. Hey agniusm, that is really cool. I believe that even wood would work but PCB is a really good idea. Masonite in 1/8 or 3/16 might be the easy way and cut the slots with a clamped straightedge and rotary spiral blade, like a small router or Dremel. Thanks guys, this is getting more possible. Perhaps use crimped rings for the BMS wires to bolt on to the blocks. Thanks! I think this could be done as a one-off for a single battery by hand.
otherDoc
otherDoc
docnjoj
1 GW
Hey agniusm! Sorry to be a dummy but I just looked at this thread for your scooter and saw a bit more of the battery build. Did you put the tabs between both brass blocks on top of the PC board or is one block above the board and one below? It looks like you may have glued the blocks on top but I can't tell from the pictures. That is a neat jig for drilling the holes!
http://endless-sphere.com/forums/viewtopic.php?f=35&t=35394&start=15
otherDoc
http://endless-sphere.com/forums/viewtopic.php?f=35&t=35394&start=15
otherDoc
agniusm
1 MW
docnjoj said:
Harold in CR said:
its behind pcb. goes like that: cell, taped block, pcb, tabs and then block with through hole. Glue is to secure plastic bita, btw they are cable trunking, 10mm