Warp Factor II Battery Modules

[Hillhater]

By "tab" I mean the two bars with holes for connection.
When these are on opposite sides, the parasitic series resistance is shared equally between all cells.

You need to put your thinking hat on a little tighter .

 

[Hillhater]

I have built a 3P 3S module using the bus bars as a connection method. Starting at 12V I ran a load tester at 400 amps for over 10 seconds, the voltage dropped to 10.25V under load. The tabs did not get hot, a little warm. After stopping the load tester the pack is 11.84V.

but that is only 1/3 the load you are planning to use !
...and I think volt drop is proportional to current !

I think this photo of Ron's may help you get a better picture of the issue.
This is only 7 of the 54 10p modules he has in series, but you can see how the full load current ( 4000A) will have to pass through each of the cell tabs and every tab connection.
Also imagine what happens if /when one of those cells, fail under full load..
..or one of the connections half way down a 10p module !!

 

[Arlo1]

I have built a 3P 3S module using the bus bars as a connection method. Starting at 12V I ran a load tester at 400 amps for over 10 seconds, the voltage dropped to 10.25V under load. The tabs did not get hot, a little warm. After stopping the load tester the pack is 11.84V.

but that is only 1/3 the load you are planning to use !
...and I think volt drop is proportional to current !

I think this photo of Ron's may help you get a better picture of the issue.
This is only 7 of the 54 10p modules he has in series, but you can see how the full load current ( 4000A) will have to pass through each of the cell tabs and every tab connection.
Also imagine what happens if /when one of those cells, fail under full load..
..or one of the connections half way down a 10p module !!

Although its passing though the tab of the cell its though it in a matter that looks to be over 1sq inch of surface area... I cant belive the bench racers on this thread... I have seen close to 1000 amps on small over a foot long (like IM talking 2 awg and 4 awg ) for short pirods and what he has here is the = to 0000 awg I think Luke pointed out.
As well if once cell fails how is it any different any way he builds it??? Basicaly he is passing current though the equivilant of 1"x1" copper with silver coated on it how do you think that will have an issue
As for the volatge drop being proportional to currant I think it is but he did't tell the voltage drop he said the cell voltage droped to 10.25v fo that pac which is not a meusrement of voltage drops due to resistance!

 

[Hillhater]

.As for the volatge drop being proportional to currant I think it is but he did't tell the voltage drop he said the cell voltage droped to 10.25v fo that pac which is not a meusrement of voltage drops due to resistance!...

..
So, if not resistance in the connections or internal in the cells, what did cause that voltage drop (sag) ? ..
..and what do you think it would be at 3 times the current ?

..Basicaly he is passing current though the equivilant of 1"x1" copper with silver coated on it how do you think that will have an issue

The silver coated copper is fine, but its the number of joints and tab interfaces that can interfere with the current flow.
If you cannot see the difference between a continuous solid conductor and Rons "segmented" conductor with 20+ contact faces along its length, then dont worry.

 

[EVDragRacer]

.As for the volatge drop being proportional to currant I think it is but he did't tell the voltage drop he said the cell voltage droped to 10.25v fo that pac which is not a meusrement of voltage drops due to resistance!...

..
So, if not resistance in the connections or internal in the cells, what did cause that voltage drop (sag) ? ..
..and what do you think it would be at 3 times the current ?

..Basicaly he is passing current though the equivilant of 1"x1" copper with silver coated on it how do you think that will have an issue

The silver coated copper is fine, but its the number of joints and tab interfaces that can interfere with the current flow.
If you cannot see the difference between a continuous solid conductor and Rons "segmented" conductor with 20+ contact faces along its length, then dont worry.

Hillhater, not sure if your trying to help or just point out where we MIGHT have some issues? I believe the voltage drop was due to sag, I was adding a 400amp load to the small pack. Every cell on the planet will drop when a large load is applied. I was told the K2 Energy 4000 amp module will drop to 1.6 volts a cell under full 4000amp load. I believe the Haiyin cells will do much better under full load.

 

[Hillhater]

Ron, I am trying to help make you aware of potential problems, so if they happen, you are prepared for them at least.
Yes, you would expect a volt drop (sag) under load, but the test data posted by you for the Hayin cells indicated a IR of 1.4mohm (and a volt drop (sag) of 0.2 V for a 120 A load ).
That is very different to the result you saw on your 3p3s , 400A, load test. ( = 133A per cell).
Crunch the numbers Ron,... you measured a 0.58V sag "per cell" at 133A..
What would you expect at 400A ?
What does that mean on a 54s pack ?

If it was me, i would do a full load test on the pack,..or at least a few modules... to know what to expect .
but maybe the only place to do that is on the track, or the dyno ?.

 

[Arlo1]

Hillhater. IM trying to understand if maybe you are not quite visualizing this all just quite right.
11.84-10.25/3= 0.53v sag per cell.
From the first or second page

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.

400 amps /3 = 133.3333 amps per cell. So if he wanted to pull 133.333 amps per cell out of 848 cell thats 113066 amps he would pull out of the whole pack.
But I have to go re-read this thread to see if I can find the pac size and I dont know if its 106s 848p so lets run the numbers from a whole pack and see what we think.

 

[Hillhater]

..I dont know if its 106s 848p

that would be some pack !
Arlo,
. Rons pack is a 10p, 54s.
IE:- he has groups of 10 cells connected in parallel to give a 60Ahr, 3,8V , module
This is 2 of them...

He then connects 54 of those modules in series giving a 60Ahr, 216 V pack when charged to 4 v per cell.
The big photo in the page above shows 7 modules connected in series giving 26.85 V

Each cell is 6 Ahr, 67C burst rate , so 400A max.
Hence a 10p module should be capable of 4000 A burst rate
so the full pack is rated for 4000A ,216 volts
..BUT ..how much voltage sag will it have at 4000A ???

 

[EVDragRacer]

..I dont know if its 106s 848p

that would be some pack !
Arlo,
. Rons pack is a 10p, 54s.
IE:- he has groups of 10 cells connected in parallel to give a 60Ahr, 3,8V , module
This is 2 of them...

He then connects 54 of those modules in series giving a 60Ahr, 216 V pack when charged to 4 v per cell.
The big photo in the page above shows 7 modules connected in series giving 26.85 V

Each cell is 6 Ahr, 67C burst rate , so 400A max.
Hence a 10p module should be capable of 4000 A burst rate
so the full pack is rated for 4000A ,216 volts
..BUT ..how much voltage sag will it have at 4000A ???

I thank you all for crunching the numbers, I am currently adding another 10P 4S module to boost the total voltage a little.
I only have a 500amp load tester, if I try it on the end of the pack (full voltage and amperage) and draw 500amps and supply the sag numbers can we calculate this figure to reach a 4000amp draw?

 

[EVDragRacer]

To be safe, I will start track testing at 3000 total BA (1500amps to each controller) and check temperatures. If all looks good them I will creep up from there.
Note: Oli's "Black Current" burned to the ground after a 1/4 mile run using Flight Power cells, I am trying to avoid this.

 

[Arlo1]

To be safe, I will start track testing at 3000 total BA (1500amps to each controller) and check temperatures. If all looks good them I will creep up from there.
Note: Oli's "Black Current" burned to the ground after a 1/4 mile run using Flight Power cells, I am trying to avoid this.

Make the pack vented and wraped in nomex.

 

[Arlo1]

I thank you all for crunching the numbers, I am currently adding another 10P 4S module to boost the total voltage a little.
I only have a 500amp load tester, if I try it on the end of the pack (full voltage and amperage) and draw 500amps and supply the sag numbers can we calculate this figure to reach a 4000amp draw?

The more numbers you collect the better as a rule. If you do this test. Can you data log it at the cell level??? Or video it at the cell level? A cheep hobby lipo display would work for video. And keep recording for about 30sec after you remove the load to see where the voltage comes back to and how long the cells take to recover.

 

[EVDragRacer]

I thank you all for crunching the numbers, I am currently adding another 10P 4S module to boost the total voltage a little.
I only have a 500amp load tester, if I try it on the end of the pack (full voltage and amperage) and draw 500amps and supply the sag numbers can we calculate this figure to reach a 4000amp draw?

The more numbers you collect the better as a rule. If you do this test. Can you data log it at the cell level??? Or video it at the cell level? A cheep hobby lipo display would work for video. And keep recording for about 30sec after you remove the load to see where the voltage comes back to and how long the cells take to recover.

Yes, I can video tape the BMS Monitor screen which will allow me to see each cell's voltage and each cell's temperature. Will try this Monday or Tuesday. Our first drag race will be this Saturday at Lebanon Valley Dragway.

 

[EVDragRacer]

Shoot, I just realized I cannot run this load tester on my entire pack, it is designed for 12V battery. Need to buy better equipment for higher voltage testing.

 

[nieles]

not really needed to test the whole pack. you can measure different aspects of the packs an then calculate the v-drop or whatever you want to know.
just make sure you make a plan how you are going to measure it.

below is a picture of how i would measure the contact resistance of the cell connections:


if you do the above, make sure the positive and negative of both packs are protected from eachother

 

[EVDragRacer]

not really needed to test the whole pack. you can measure different aspects of the packs an then calculate the v-drop or whatever you want to know.
just make sure you make a plan how you are going to measure it.

below is a picture of how i would measure the contact resistance of the cell connections:


if you do the above, make sure the positive and negative of both packs are protected from eachother

Thanks I will give it a try!

 

[EVDragRacer]

I want to give some weight number from our pack modules:

10P 1S (3.7n 4000amp)
10 cells = 3.5 lbs
Copper = 1.5 lbs

Each 10P = 5 lbs

35S 147V Pack = 185 lbs est..

54S 227V Pack = 280 lbs est..

80S 336V Pack = 420 lbs est..

 

[Hillhater]

I can video tape the BMS Monitor screen which will allow me to see each cell's voltage and each cell's temperature..

ron, ..You wont be able to check individual cell voltages once they are assembled into 10p modules.
You will only see the voltage of the module.
..but that is still V useful.

 

[hillzofvalp]

what kind of PPE do you employ when working with those voltages..?

 

[Doctorbass]

not really needed to test the whole pack. you can measure different aspects of the packs an then calculate the v-drop or whatever you want to know.
just make sure you make a plan how you are going to measure it.

below is a picture of how i would measure the contact resistance of the cell connections:


if you do the above, make sure the positive and negative of both packs are protected from eachother

I agree for that test. It look like a great way to test the resistive loss thru the parallel connnections !.. It would be interesting to see the results!

Doc

 

[Hillhater]

Yes a good initial test, but still only using 1/8th of the max planned 4000A load, so difficult to draw conclusions from.

Ron, if you are all ready for the track this weekend, couldn't you run her up on a dyno and monitor the pack voltage ?
or will you just get that data from your first runs.?

 

[EVDragRacer]

Yes a good initial test, but still only using 1/8th of the max planned 4000A load, so difficult to draw conclusions from.

Ron, if you are all ready for the track this weekend, couldn't you run her up on a dyno and monitor the pack voltage ?
or will you just get that data from your first runs.?

The Soliton Shiva will provide data from each run.

 

[Hillhater]

.....Our first drag race will be this Saturday at Lebanon Valley Dragway.

Any feedback.. ??

 

[EVDragRacer]

Well, just returned from the track. Good day of testing, completed two shake-down runs. Track was swamped today with Gamblers, etc....Only problem is no data, the wire was too short would not reach the computer, will have data on next test.

Results:

Test #1:
1500 BA (each controller)
2000 MA
190 Motor Volts
(Pack was at 230V.)

Time: 60' 1.5 seconds, 1/8 6.6 seconds, 1/4 10.6 @121.36 mph
__________________________________________________ ___

Test #2:
2000 BA (each controller)
2000 MA
200 Motor Volts
(Pack was at 230V)

Time: 60' 1.4 seconds, 1/8 6.5 seconds, 1/4 10.4 @123.83 mph

 

[EVDragRacer]

Additional test day information:

Battery only dropped about 7 volts per run. Cell temp remained under 50c. No sparks from motors or brushes. Controllers worked flawless (I think, no data).

Car developed a clunk in rear diff, will check ring and pinion. Might also change front springs.

Wish I could have tested at full power, but not enough time and very very very HOT day!