Warp Factor II Battery Modules

I think the silver plating is key here, along with adequate contact pressure. Silver maintains a nice low resistance connection even when tarnished.

The proof will be in the time slip. :wink:
 
Thanks for the posts Ron!
 
fechter said:
I think the silver plating is key here, along with adequate contact pressure. Silver maintains a nice low resistance connection even when tarnished.

The proof will be in the time slip. :wink:
Click to expand...
The silvered copper is only one half of the connection. !
I dont doubt the system will work, all i am saying is this method of buss bar "segmentation" results in many thousand more primary circuit connections compared to a solid buss bar system.
... and if any one of those extra thousands of connections fail it could cause a full system failure rather than a single cell failure as on a solid buss bar arrangement.
Further , i dont believe any BMS can detect that kind of "weak" connection until it fails under load ...which is too late !
 
But hillhater, every cell tab will need to be connected to a bus somehow, and that connection will have the same issues you describe. Granted there will be fewer problems with the primary series circuit, it just means some cells won't be working as hard. If there is a problem this way, it will be very obvious and easily fixed. Depends on the application really. It's probably as good as you will get for this app. at least.
 
Hi Ron,

Nice to see you on this forum, I love your packs, but I have to agree with hillhater.
In my testing of A123 pouches my first design was a block between every tab in a 3P pack (I used aluminium but I'm going to peak at 1000A not 4000A, you may have seen my crappy pictures on diyelectriccar) the voltage drop was much higher than expected, the cells were doing just fine, but it was the hundreds of extra connections each one has a tiny resistance but you add them all up and it's significant.

This was a big enough problem in my testing that I redesigned my connection method. Instead of 7 blocks making up a 3P series connection, I now have 3 blocks, two of them being outside clamps and now only one block is between the series groups, the tabs in each 3P set are all sandwiched together.

I'm not saying your method won't work, it's going to work, and it's going to work pretty well, but I think it could work better. (not from theory, from testing)

I know you don't like A123 cells, but laser welding has nothing to do with the issues that hillhater is trying to point out.

When you get the car on the track make sure you have a logging method for the battery voltage, I would suggest something at the + and - battery terminals and not at the Shiva terminals (or the shiva itself) as there will be so much noise and ripple there it's hard to say how accurate the voltage reading would be. I'll bet you a cold Canadian beer that you experience higher sag at the battery terminals than you are expecting, and it won't be the fault of your cells it will be all of the series connections contributing to significant sag at peak current.
 
Good luck at Lebanon Ron. We all love when you share your stuff with us, so please check in and share afterward to help bring in a whole new fan base to drag racing, a bunch of crazy ebikers. :lol:

John
 
rwaudio said:
Hi Ron,

Nice to see you on this forum, I love your packs, but I have to agree with hillhater.
In my testing of A123 pouches my first design was a block between every tab in a 3P pack (I used aluminium but I'm going to peak at 1000A not 4000A, you may have seen my crappy pictures on diyelectriccar) the voltage drop was much higher than expected, the cells were doing just fine, but it was the hundreds of extra connections each one has a tiny resistance but you add them all up and it's significant.

This was a big enough problem in my testing that I redesigned my connection method. Instead of 7 blocks making up a 3P series connection, I now have 3 blocks, two of them being outside clamps and now only one block is between the series groups, the tabs in each 3P set are all sandwiched together.

I'm not saying your method won't work, it's going to work, and it's going to work pretty well, but I think it could work better. (not from theory, from testing)

I know you don't like A123 cells, but laser welding has nothing to do with the issues that hillhater is trying to point out.

When you get the car on the track make sure you have a logging method for the battery voltage, I would suggest something at the + and - battery terminals and not at the Shiva terminals (or the shiva itself) as there will be so much noise and ripple there it's hard to say how accurate the voltage reading would be. I'll bet you a cold Canadian beer that you experience higher sag at the battery terminals than you are expecting, and it won't be the fault of your cells it will be all of the series connections contributing to significant sag at peak current.
Click to expand...
If he moves the main connector in each set of Cells in parallel to the Center it Would likely be a very good set up. If its not an awesome setup already... I think the cell(s) closest to the main connector will drop most but if its in the middle it will help reduce that a lot. Silver coated copper... Cool :)
 
jonescg said:
But hillhater, every cell tab will need to be connected to a bus somehow, and that connection will have the same issues you describe. Granted there will be fewer problems with the primary series circuit, it just means some cells won't be working as hard. If there is a problem this way, it will be very obvious and easily fixed. Depends on the application really. It's probably as good as you will get for this app. at least.
Click to expand...

Obviously connecting individual cells to a common buss still requires a lot of connections (but actually only half as many as Rons system ) ,..however each of those connections will only have to carry 1/10th of main circuit current ..AND none of those connections will be primary ( system critical) points if one or more does fail.
Loss of a connection would simply mean loss of one cells worth of Ahrs.
Loss of one (of 4000+) of Ron's connections will not only kill the system dead, but also most likely blow a few cells from massive current overload.
 
EVDragRacer said:
2012FebCells008.jpg
Click to expand...
I am very happy to see our BMS on you pack design, which looks awesome, by the way. :)
Feel free to contact me or Gintautas if in need for support or with suggestions.
 
Ron interested in what you have on A123 welded tab issues. I was under the impression the issue was inside the pouch with separators, secondary insulators and such...
 
Hi,
EVDragRacer said:
A123 has a 50 million dollar recall because their welding machine did not properly connect the cells, all their modules shorted out!
Click to expand...
That's incorrect. It's not an issue of improperly welded connections between cells. The problem was with a welding machine that was used to build individual cells.
 
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