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