20s 10p battery build, help with nickel strip needed

Hello all

I’m in the process of building my 2nd ebike, the 1st was a great success but I’m setting my sights way higher with the new one.

It’s an 8000w Qs motor on an enduro frame from our friends in China!
It’s a beast!

The part I need help with is the battery, this is my 2nd 18650 pack I’ve ever made and I don’t want to get it wrong not only due to fire hazard but even more so for my wallet! I’m sure you guys can appreciate 200 Samsung 30q cells aren’t cheap!

My question relates to the nickel strip.... how many layers of .15 7mm nickel would I need for the series and parallel connections?

I’ve scrawled this forum and watched endless videos but I can’t seem to find much info regarding how many layers of nickel I would need to make a 150amp pack that won’t burst into flames or short out the nickel under heavy loads.

I’m using a 150 amp Sabvoton controller and 150amp bms and the motor can defo handle the power!

Here is my logic....... each strip of nickel can handle 5amps, the cells can handle 15amp continuous, so would I need 1 layer for the parallel connections and 3 layers for the series connections?

Or would I need 3 layers for the 1st series connections, 6 layers for the 2nd series connections and so on? If that’s the case then I’m Gona need a trailer to carry the nickel clad battery!

Any help from you battery/electronic geniuses would be very much appreciated.

Thanks in advance...... Ian

NEVER stack strips. shit dont work that way.

use 0.25 strips and a welder capable that can hit the power needed to weld .25.
first you make the series welds, make the batter as "wide" as possible so the pos-neg connections are as short as possible.
the parralel connections dont carry any meanful currents so you can use .15 for those and only use one. no need to make more. it does nothing for current going out the pack.

with those currents i recommend using the square cell holders, dont make it honeycomb because the cells will heat up a LOT with those currents.

The guy at ebike school.com says stacking nickel is fine!?

Does stacking 2 cars make them go twice as fast?

Gross simplification but i hope it gets the point across.

flippy said:

Does stacking 2 cars make them go twice as fast?

Gross simplification but i hope it gets the point across.

Click to expand...

Not to cause too much of an argument your logic is wrong. Using your anology, speed is more like voltage than current. Current is more so how much the cars can carry. So yes, two cars stacked on top of each other can carry more than one. This is the same principle. It'd be no different than stacking two wires. One wire can only carry so much current, adding another will effectively double your capacity to carry current from A to B. Stacking nickel strips, although I've never done it, will work just fine.

Now what's really up for debate is I've read that electricity has less resistance on higher surface area objects than lower..meaning a nickel strip will have slightly more resistance than if it were the same size stranded copper strip...not sure that's true or not but that's what I've heard...so favor stranded wire instead of solid, and for obvious reasons...

What's the top speed your looking at for that setup? Obviously with 150A capability that'll be awesome acceleration, curious about top speed...?

flippy said:

Does stacking 2 cars make them go twice as fast?

Gross simplification but i hope it gets the point across.

Click to expand...

Not to cause too much of an argument your logic is wrong. Using your anology, speed is more like voltage than current. Current is more so how much the cars can carry. So yes, two cars stacked on top of each other can carry more than one. This is the same principle. It'd be no different than stacking two wires. One wire can only carry so much current, adding another will effectively double your capacity to carry current from A to B. Stacking nickel strips, although I've never done it, will work just fine.

Now what's really up for debate is I've read that electricity has less resistance on higher surface area objects than lower..meaning a nickel strip will have slightly more resistance than if it were the same size stranded copper strip...not sure that's true or not but that's what I've heard...so favor stranded wire instead of solid, and for obvious reasons...

What's the top speed your looking at for that setup? Obviously with 150A capability that'll be awesome acceleration, curious about top speed...?

You can stack as many cars on top of each other but you still only have the 4 wheels of the bottom car on the ground.
Even if you stack a dozen strips on each other you are still limited to the bottom 4 welds being abke to carry such current. Stacking welds only makes it worse.

Welding .25 nickel is not easy. For sure they need to be slotted and the welder has to be serious.

The nickel strips and the welds are like resistors in series. If you stack strips, the "resistor" at the weld end will still be the same, but the strips themselves will be in parallel. Since the weld "resistors" are very short, their resistance is very low compared to the strip part, so stacking them will prevent the strips from getting hot.

The real test would be to set it up on a bench with a high load and watch it with a FLIR to see where it gets hot.

One thing that might help is to use sheets instead of strips. You have more cross sectional area and it makes construction a lot easier. On the ends you need some seriously large copper bus bars. The challenge here is to keep the cells held rigidly and well insulated between groups. I glued these together and have fiberglass tape between groups. I've seen someone use the plastic cell holders and punch out the stops on the ends so the cells can protrude enough to attach sheets.

fechter said:

Welding .25 nickel is not easy. For sure they need to be slotted and the welder has to be serious.

The nickel strips and the welds are like resistors in series. If you stack strips, the "resistor" at the weld end will still be the same, but the strips themselves will be in parallel. Since the weld "resistors" are very short, their resistance is very low compared to the strip part, so stacking them will prevent the strips from getting hot.

The real test would be to set it up on a bench with a high load and watch it with a FLIR to see where it gets hot.

One thing that might help is to use sheets instead of strips. You have more cross sectional area and it makes construction a lot easier. On the ends you need some seriously large copper bus bars. The challenge here is to keep the cells held rigidly and well insulated between groups. I glued these together and have fiberglass tape between groups. I've seen someone use the plastic cell holders and punch out the stops on the ends so the cells can protrude enough to attach sheets.

Img_1098.jpg

Click to expand...

Pack looks excellent! Can’t believe so many still use strips?

Tom

Thanks for your reply’s!

Those are some sweet looking packs.

I didn’t even think about using wide sheets to make the series and parallel connections.
It would make construction quicker.

Why have you separated your pack into groups?
I planned on building 1 giant slab 20 cells long and 10 wide, it fits perfectly in my frame.

How would you go about fixing the rather large copper busbars to the ends of the pack? Solder?
Am I right in thinking you can’t spot weld copper?

As for top speed, it should be capable of 60 > 70mph
Me on the other hand..... capable of 50 > 60mph.
I don’t plan on setting land speed records just yet!

Thanks..... Ian

Ianrobbens said:

Those are some sweet looking packs.

How would you go about fixing the rather large copper busbars to the ends of the pack? Solder?
Am I right in thinking you can’t spot weld copper?

Click to expand...

On mine, the pack has to be split into two halves to mount on the bike.



Correct, spot welding to copper is not easy.
I soldered 8ga wire to strips of nickel first, then spot welded the strip to the pack. After welding the strip was folded over.

That’s a sweet idea, thanks for that!
Just waiting on the spot welder to arrive and I can get building!