DIY 18650 Pack: Can i mix cells?

[dogman dan]

If you are going to solder, would have been better to have left tabs on, and solder to the tab.

I never meant to say it was a good idea to mix up cells, I just said it could be done.

 

[DrkAngel]

4A fuse will be blown with <2C discharge!
Which will cause a cascade failure disabling entire pack.

Could you explain this more plz, i only ordered them because tesla uses them on their 18650 cells and many others.. why would it be different for my setup?

36V 20Ah pack = 10s ≥8p (≥2500mAh new cells)
750w motor can draw 1500w+ (≥40A controller)
1500w / 36V = 41.67A
41.67A / 8p = 5.2A per cell = blown 4A fuse

Tesla uses a battery large enough to not pull ≥4A per cell ... ?

 

[Syonyk]

Uh, Tesla very certainly pulls more than 4A per cell.

A P90D with Ludicrous upgrade will briefly pull about 6.35C during a launch.

http://syonyk.blogspot.com/2015/06/tesla-model-s-p85d-c-rate-calculations.html

 

[999zip999]

This is a hobby pack and learning step. Be careful as the little cells can short and make fire. I would use a big fat tip iron 80watt and a wet sponge to cool solder. Put sense wires for cell monitoring and balancing. Use a gasket on the positive end. And monitor your battery with a cellog or meter.

 

[Storx]

4A fuse will be blown with <2C discharge!
Which will cause a cascade failure disabling entire pack.

Could you explain this more plz, i only ordered them because tesla uses them on their 18650 cells and many others.. why would it be different for my setup?

36V 20Ah pack = 10s ≥8p (≥2500mAh new cells)
750w motor can draw 1500w+ (≥40A controller)
1500w / 36V = 41.67A
41.67A / 8p = 5.2A per cell = blown 4A fuse

Tesla uses a battery large enough to not pull ≥4A per cell ... ?

I was going to build an 48v 13s12p pack, but now im trying to figure out if i cut it down to 2 x 13s6p packs with the capability to bridge the second to the first via the 13s for longer rides..

Motor is Updated Mac 10T, 48v x 25amp controller, 1000watt hub motor... people claim it never exceeds 1200watts even on high grade hills....
1200w/48v = 25A
25A / 6p = 4.16A
25A/ 12p= 2.08A

since 4.16A exceeds the rating on the fuses i bought when the motor is pushed to its absolute max, i may go 13s8p for the pack...
25A/8p= 3.12A