Warp Factor II Battery Modules

[Hillhater]

doesnt your "bus bar" clamping system result in you having over 1000 clamped connections in series to achieve 425v ?

[EVDragRacer]

doesnt your "bus bar" clamping system result in you having over 1000 clamped connections in series to achieve 425v ?

The specs:

106 series connection bus bars.
848 parallel connection bus bars.

The parallel bus bars are bolted together on the first level, the series connections extend above the first top layer of lexan. Did you not see the pictures?
This is the most secure way to deliver 4000BA without overheating the tabs.

A123 has a 50 million dollar recall because their welding machine did not properly connect the cells, all their modules shorted out! I will not have that problem.

[999zip999]

Thanks for the pics. Looks good. Clean.

[Hillhater]

Yes Ron, i saw the pictures,..thats when i realised what you had done with your "parallel" modules.
Its just that your "Bus Bars" in each parallel pack are not actually continuous bars, but a sandwich of ten tabs and ten / eleven spacers. Each side of every tab is a "working" contact face, so each pack has 40 contact faces ( 10 +ve and 10-ve tabs) each of which will be carrying your full 2000+ Amp load. It just seems you have a lot of extra joints carrying full load current.
( 40 per pack x 106 packs = 4240 EXTRA connections ! )
...Ron, what happens if ONE of those contact faces "drys" out and goes OC. ?

[EVDragRacer]

Yes Ron, i saw the pictures,..thats when i realised what you had done with your "parallel" modules.
Its just that your "Bus Bars" in each parallel pack are not actually continuous bars, but a sandwich of ten tabs and ten / eleven spacers. Each side of every tab is a "working" contact face, so each pack has 40 contact faces ( 10 +ve and 10-ve tabs) each of which will be carrying your full 2000+ Amp load. It just seems you have a lot of extra joints carrying full load current.
( 40 per pack x 106 packs = 4240 EXTRA connections ! )
...Ron, what happens if ONE of those contact faces "drys" out and goes OC. ?

If we are to have a contact "drys" the BMS will pick-up the problem and we will replace the 10P pack. I do not think my connection method is overkill, I matter a fact I know it is a must to carry 4000+ amps safely.

Do you think crunching tabs together is a better solution? Less meat = more heat!

Ask A123 about there 55Million dollar mistake welding tabs together.

[fechter]

I've always found bolted connections to be quite reliable if properly done. The ability to repair them later is also an excellent feature. Some anti-oxidant grease might help them last longer (but in a drag racer, that probably doesn't matter much). Solid copper seems like overkill, but less resistance is better. Aluminum would be much lighter. One of the real engineer types could do the math on it to see how much more loss there would be with aluminum. Aluminum does tend to corrode and make crappy connections over time.

[Hillhater]

Ron, are you really going to install a BMS that monitors every one of your 1000+ cells individually ?
.... when they are paralleled in packs of 10 ??
I suspect the first indication of a dry joint will be a blown module from 2000+A all going through one or two cells in a pack.

We all need and use bolted connectors , ( much better than bullets etc) ....but every joint is a possible failure ( especially at 2000+ A ) and can be managed since usually those bolts are simply clamping 2 contact faces together.
But this design has resulted in an extra 4000+ bolted contact joints, with 20 contact faces per bolt, most of which are carrying the full load 2000A current !
A single , unitary ( solid) bus bar for each pack of 10 tabs would avoid that situation.

[Arlo1]

I am not here often, so I will add a few bits of info before I go.

Each 10P 28volt module weighs about 40lbs. A bit heavier that wanted, but worth it's weight in gold when you do not have to worry about bus bar resistance and heat. Our connection method with reduce heat and resistance, while making it fairly easy to remove a 10P pack at anytime in the car without removing the pack.

The whole pack weighs around 600lbs, we have replaced the older Camaro body with a 2012 Camaro body made from fiberglass, so, the added pack weight will not make much of a difference. We estimate the car will weigh 2300lbs compared to 2650lbs last year. We will have 3000amps to launch with if we want, we will start at 2000amps and work up slowly monitoring motor temps. We have geared the car for a top speed of 170mph in the 1/4 mile, 3.25 in the rear and two GearVendors overdrives to utilize the enormous amounts of torque we have available.

So whens the first run im holding my breath! Very exciting!

[EVDragRacer]

Ron, are you really going to install a BMS that monitors every one of your 1000+ cells individually ?
.... when they are paralleled in packs of 10 ??
I suspect the first indication of a dry joint will be a blown module from 2000+A all going through one or two cells in a pack.

We all need and use bolted connectors , ( much better than bullets etc) ....but every joint is a possible failure ( especially at 2000+ A ) and can be managed since usually those bolts are simply clamping 2 contact faces together.
But this design has resulted in an extra 4000+ bolted contact joints, with 20 contact faces per bolt, most of which are carrying the full load 2000A current !
A single , unitary ( solid) bus bar for each pack of 10 tabs would avoid that situation.

Each 10P cell pack will require a BMS board. Not worried about my connections, very confident in design. Better than welding, ask A123.

[EVDragRacer]

I've always found bolted connections to be quite reliable if properly done. The ability to repair them later is also an excellent feature. Some anti-oxidant grease might help them last longer (but in a drag racer, that probably doesn't matter much). Solid copper seems like overkill, but less resistance is better. Aluminum would be much lighter. One of the real engineer types could do the math on it to see how much more loss there would be with aluminum. Aluminum does tend to corrode and make crappy connections over time.

I did many weeks of research on the best aluminum for the bus bars, had Luke give me some great info. The lowest resistance aluminum can not be bought in bus bars, could not even find it in USA, after running the resistance numbers with heat build-up, copper was my choice. Silver coating was also a must. All the work was done at Storm Copper in Tenn.

[fechter]

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.

[Ykick]

Thanks for the posts Ron!

[nechaus]

Nice Connections and battery pack.

[Hillhater]

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.

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 !

[jonescg]

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.

[rwaudio]

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.

[John in CR]

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.

John

[Arlo1]

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.

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

[Hillhater]

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.

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.

[circuit]

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.

[Hillhater]

Any one know how Rons going with WF II ?
I cant seem to find any results from the ECEDRA events this season.

[bigmoose]

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...

[MitchJi]

Hi,

A123 has a 50 million dollar recall because their welding machine did not properly connect the cells, all their modules shorted out!

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.

[Hillhater]

Still no sight of the Warp Factor on the track ?
I think Ron is spending too much time arguing with the guys over on the Diy electric car forums !

[EVDragRacer]