Nickel strips for 10S2P pack 21700

[carlbikekits]

Hi,

I'm attempting to build a 10S2P pack as at

.

There is a lot of snipping and welding.

His configuration is below


As you'll know, there are 10S2P nickel sheets available that would seem to remove the need for all this complexity, such as


So I have three questions my novice head would appreciate some feedback on please.

1. The video guy has a break every second cell but the sheets don't. What am I missing here?

2. Are the fabricated dash lines relevant or not?

3. If I can use sheets and need 0.3mm, can I spot weld 2 x 0.15 sheets together?

Many thanks

 

[matthewslack]

Hi,

I'm attempting to build a 10S2P pack as at

.

There is a lot of snipping and welding.

His configuration is below
View attachment 49087

As you'll know, there are 10S2P nickel sheets available that would seem to remove the need for all this complexity, such as
View attachment 49088

So I have three questions my novice head would appreciate some feedback on please.

1. The video guy has a break every second cell but the sheets don't. What am I missing here?

2. Are the fabricated dash lines relevant or not?

3. If I can use sheets and need 0.3mm, can I spot weld 2 x 0.15 sheets together?

Many thanks

Go back a stage and make sure you understand what 10s and 2p mean in terms of the electrical connections between the cells. When you understand that, you will see the answer to 1.

If you don't reach that level of understanding, you may well hurt yourself by shorting out cells.

 

[carlbikekits]

Go back a stage and make sure you understand what 10s and 2p mean in terms of the electrical connections between the cells. When you understand that, you will see the answer to 1.

If you don't reach that level of understanding, you may well hurt yourself by shorting out cells.

My understanding is that it means 10 cells in series (to achieve 36V) with 2 in parallel

 

[matthewslack]

My understanding is that it means 10 cells in series (to achieve 36V) with 2 in parallel

Now translate that into the connections that are needed, and don't allow yourself to be misled by that long strip of terminal strip you pictured earlier!

All that is is a convenient way to manufacture and supply in bulk a 2 wide by any length connection matrix, which needs cutting to length to suit each application. Your pack needs 2 by 2 sections, a 3p would need 2 by 3 sections and so on.

 

[carlbikekits]

Can anyone help with questions 2 and 3 please?

Many thanks

 

[matthewslack]

Can anyone help with questions 2 and 3 please?

Many thanks

3 is a yes, as long as the two layers are connected well electrically, as the cross sectional area is the same, so same resistance and current carrying capacity. A single layer is preferable.

2 I am not clear what you mean by fabricated dash lines.

 

[soundwave]

copper strip is better but costs more and you need a expensive spot welder to use it.

 

[carlbikekits]

3 is a yes, as long as the two layers are connected well electrically, as the cross sectional area is the same, so same resistance and current carrying capacity. A single layer is preferable.

2 I am not clear what you mean by fabricated dash lines.

As in that nickel strips are complete but these sets seem to be punctuated by holes, and I wonder how that affects the spot welding or has any function?

 

[saneagle]

When you do an electric weld, the current flows from one electrode to the other and it takes the easiest path, which is through the strip rather than through the strip to the battery. Some does because it goes in every direction, but most of it gets wasted. When you put a slit in the metal, the current can't find an easy path directly accross to the other electrode. Instead, it has to go through the strip into the battery metal, along the battery metal and up through the strip on the other side of the slit, which gives two nice welds at the join between the strip and the battery.

You can just about get enough current to weld a single strip to a battery when the strip has no slit in it, but if you try to weld another strip on top of that, it hardly welds with maximum current.

Always used slitted strip if you can, or make your own slits.

 

[Nealh]

Which spot welder are you using ?
As d8ve has said, the slit means the weld current is purposed to the cell rather then shorting across from one electrode ot the other.

For a neater job buy the H strip for your battery or the Z strip, which you buy depends on the cell layout and whether they are symetrically aligned or staggered.

 

[Nealh]

This is my simple p42a cell pack build using the superb molicel brand.
One can see under the nickel plated steel buss H strip that I have used squares of thin copper sheet for the better current flow, the Ni plated steel simply makes a sandwich of steel /cu/steel sandwich and adds rigidity to the weld connection, the spot welder can weld easier then using pure copper on it's own.

21700 battery build

Having bought the Moli P42's, I have quickly built the battery up ready for use. Being only 12s2p the battery is just shy of 370wh at 8.4ah, but can easily do more then 40a continuously. The first job I do is cut the first and last cell buss so I can pre solder ready for the discharge wires to...

www.pedelecs.co.uk

 

[Nealh]

Mica Toll's build quality is not very good, he talks well but the actual product delivery is poor.
He uses no cell seperation, relying totally on the mech strength of the buss's also in the pic#2 there are no card insulators used on the positive end to prevent shorting.
The whole can is a negative electrode except for the central contact on the positve end, the buss has to cross from the central positive and bridge to the next cell via the negative can rim/edge. if the can wrap shrinks due to heat or rubs bare then one will short out the cell and wipe the battery out.
Each cell has a insulator on the positive end that goes under the wrap edges but this insulator is a thin plastic one that can also melt /shrink form heat so it is always best to add the extra one on top for added safety. This can clearly be seen in my build long with adequate cell seapartion and mechanical strength via the cell holders.

The method of using strip Nickel is old hat and the slotted strips now available area lot neater and easier to apply, there is less chance of accidental shorting using the slotted strips.

 

[AntonyC]

If you don't reach that level of understanding, you may well hurt yourself by shorting out cells.

Your questions are entirely sensible but they plead for lots more reading or, much quicker, work out what result you want and who will provide it. A single cell stores 10Wh of leccy and 10x that amount in chemical energy, you have 20 of them, so at worst a momentary slip can trigger a 5 minute fireball of 25kW that the usual methods won't extinguish, or with luck... be sure to search KFF. Battery building may not be difficult but you do want deep ingrained knowledge as one among several layers of protection. HTH.

 

[harrys]

Oh my. Oh my. You have to cut those nickel sheets to achieve the same connectivity you were seeing with the discrete strips.

The construction method show in your video is also out-of-date. Cells should no longer be placed together like that. Their wrappers are not sufficient for ebike applications. Friction/vibration can wear thru the mylar and cause the cell cases to touch and short circuit. Best practices are to use cell holders, which space the cells apart, or add an insulator between adjacent cell groups.

Not my picture, but these cells have been wrapped in "fish paper" and cannot short circuit. In addition, insulating washers are used on the positive terminals for added protection.

 

[Nealh]

Fish paper also goes by the name of Barley paper, the ring insulators are made from the same material. For piece of mind the few extra quid it costs to add the extra protection isn't worth not spending the money on, if buying make sure it is the adhesive backed one.