21700 battery pack construction advice please

Simon916

1 µW
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Dec 4, 2020
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Hi All
I am looking for some advice so I can complete the electrification of a classic motorbike.

The batteries are Samsung 40 T's ( 4000mAh , 35 amp ). There will be 4 packs. Each pack is made up of a row of 13 cells in series stacked 5 high and connected at each end with a 0.8 by 10mm copper strip/bus bar in turn connecting to 10mm2 copper wire running direct to the motor terminal ( I have not found any small 175 amp connectors but dont really see a need for them.
The motor is a 10KW DC brushless but it can take a peak of 20kw for 14 seconds ( handy for drag racing ).

I am using cell holders. I bought a welder from Ebay .

I bought the batteries from Frogstar and also purchased a roll of 0.2 by 10mm "zinc " stip although it is magnetic so possibly zinc coated steel ?
I also purchased dummy batteries to practice. At full power and max pulses the welder ( using the wand on a lead ) won't connect the battery and strip . The welder came with some 0.15 mm zinc coated steel strip but only in short strips . I get a good weld with these thinner strips.

My first question is that given I have a max 35amps at 48 volts at the end of each 13 cell strip , what size/type of "metal" strip must I have. The cell holders cater for a 10mm wide strip and looks like I can only use a 0.15 mm thickness. Frogstar declined to comment on what strip I needed as they had issues in the past. If I need a bigger welder could I solder instead ( I intend to solder the copper bus bar ) or will this overheat the battery ?

My next question is do I need to use the "Polo" insulators at the positive end.

Having solved that issue I then need advice on load balancers and a on board charger ( 13 amp ) , which ones to use and how to connect.

Any other advice / comments would be appreciated.

I attach a picture of a practice build pack , please note the cells are not in the correct orientation.

Thanks

Simonbatt 2.JPG
 
Assume you mean Nickel strips! They have ratings posted for continuous current.

So are the 4 packs going to be connected in series parallel? Creating a large 26series/10parallel pack?
 
4 packs of 13s5p= 20p
20p/170amps=8.5 amps per cell
you could get away with 1 layer of pure nickel strip for series

you have nickel plated steel, try reading this thread

https://endless-sphere.com/forums/viewtopic.php?f=14&t=108006#p1579841
 
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