Battery construction etc


Vextrek

Active member
Location
Augusta, GA
View attachment 8777

I would like to see something along the lines of this. Do you think your Sunstone could do this Gary?
That’s a pretty cool design. If I’m seeing at correct it basically is a “Copper bridge” to the center of the cell. Only downside would be copper that wide would not act as an “individual cell-level fuse” because it can conduct so much current. As long as it’s .4 mm or less in thickness, the Sunstone Welder can spot weld it to that cell.
 

testus191

Member
Location
Poteau, OK
I would assume with some bench testing/loading you could find a cross sectional shape of the “bridge” as you stated that would act as a fuse. However, other than those capable of wire bonding, I don’t see any other methods being used to incorporate cell level fusing. More than than the cell level fusing, I like the idea of only connecting to the cell from one side allowing the possibility of better thermal management from the other end. I’m just not sure the best way to electrically isolate the cells from each other with any sort of cold plate or liquid cooling methods.
 

Rashid510

Well-known member
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I would assume with some bench testing/loading you could find a cross sectional shape of the “bridge” as you stated that would act as a fuse. However, other than those capable of wire bonding, I don’t see any other methods being used to incorporate cell level fusing. More than than the cell level fusing, I like the idea of only connecting to the cell from one side allowing the possibility of better thermal management from the other end. I’m just not sure the best way to electrically isolate the cells from each other with any sort of cold plate or liquid cooling methods.

Have you tried some sort of thermal interface material or coating on your cold plate? Tesla messed with E-coating back in the day.

Also could try coating your copper plating. That might provide better conductivity. Depending on your performance requirements you could potentially use a laser welder too.
 

testus191

Member
Location
Poteau, OK
Have you tried some sort of thermal interface material or coating on your cold plate? Tesla messed with E-coating back in the day.

Also could try coating your copper plating. That might provide better conductivity. Depending on your performance requirements you could potentially use a laser welder too.
I have not, I need to do some research on coating options.

Are you referring to adding the plating to the copper for better conductivity while bond cells?
 

Vextrek

Active member
Location
Augusta, GA
Interesting. Thanks for sharing. The dud cell in my pack still had all of the wire bonds secure with continuity between. I still don't know why there is a dud cell but it dragged the voltage of a p group down very low. It also dragged all of the p groups before that one in the sting down a bunch….
Generally speaking, the more cells in parallel the less impact a dead cell will have on that particular grouping. Tesla packs rarely are impacted by a dead sale because they have so many in parallel… 74 in parallel on the earlier cars if my memory serves me correctly. When you have smaller packs such as what I have on the electric go kart, a week cell with only 18 to 20 in parallel will start to be noticeable at some point. I know it’s frustrating but it’s all part of physics.
 

padu

New member
Location
San Diego, CA
We use a Sunstone Pulse Arc welder (P250i) to connect the Molicel P26A cells with .25mm thick cooper sheets. The pack performs very well with no heat issues. Using a di-lithium BMS with 10 thermistors and we routinely pull 600A of current. Disclaimer: Pack does not utilize cell-level fusing so risk of thermal runaway is greater.

View attachment 8767
This is really cool. I'm working on a conversion project and I'll need to make my own battery pack based on cylindrical cells. Are the plastic guides shown in the picture above off-the-shelf? Or you made them yourself (3D printed?) If OTS, can you share where you got them?
 

Vextrek

Active member
Location
Augusta, GA
This is really cool. I'm working on a conversion project and I'll need to make my own battery pack based on cylindrical cells. Are the plastic guides shown in the picture above off-the-shelf? Or you made them yourself (3D printed?) If OTS, can you share where you got them?
No problem. Ordered the cell holders direct from AliExpress. Took about a month to arrive but pleased with the product. Here is the link …

 

TCMB371

The Silent Assassin
Forum's Sponsor
Location
Temecula, CA
Generally speaking, the more cells in parallel the less impact a dead cell will have on that particular grouping. Tesla packs rarely are impacted by a dead sale because they have so many in parallel… 74 in parallel on the earlier cars if my memory serves me correctly. When you have smaller packs such as what I have on the electric go kart, a week cell with only 18 to 20 in parallel will start to be noticeable at some point. I know it’s frustrating but it’s all part of physics.
1/20 > 1/74 .
 

Rashid510

Well-known member
Forum's Sponsor
Thats a fancy pick and place forsure. Lots of custom automation. So they cut the top wrapper off and then put a plastic sleeve to slot into the casting, should be reallly really interesting for thermals...Also looks like there not showing off the welding/bonding process
 

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