A question of efficiency

[CrawlingWhisper]

Hello Everybody,

Does one of You have experience with the vruzend battery kit ? If so, how much efficiency do I lose compared to spot welded battery packs, e.g. how many meters per km?

Thanks
Felix

 

[Sunder]

That's really a meaningless question. There is nothing inherently inefficient about the Vruzend battery kits, just like there is nothing inherently inefficient about spot welded battery packs.

But the Vruzend kits have been designed for 3.5A per cell, where as 0.1mm x 5mm nickle strip carries only 2.1A. If you upgraded to 0.3mm x 7mm, you could go 10A.

But that's still not the end of the story. If you were only drawing 2A per cell, all of those would be as efficient as each other. If you were drawing more than 3.5A, then the order would be thick nickel, Vruzend, thin nickel, but the differences still wouldn't be noticeable probably until 7-10A constant. if it's just an occasional burst starting from stand still or going up a short hill, and the overall impact might be less than 1%, and how are you going to notice that?

Design to spec, and you don't have to worry about these things. If you're unsure how to do that, ask here. Post what cells you're using, which configuration, what controller, and a description of your ride.

 

[MadRhino]

There may be some loss, if the contacts are making some heat. Yet there is no way to put numbers on this, for each situation is different. The only way to measure the losses in your battery assembly, would be to measure each cell draw and capacity before the assembly, then measure the total numbers after the assembly, and do the math. Then the result will include all losses, including the loss caused by the resistance of the assembly hardware and wiring.

Unless it is getting hot, I agree that you should not bother with the losses in your battery assembly. There are much more important factors of efficiency loss in your ebike.

 

[CrawlingWhisper]

Thanks for the info.

But the Vruzend kits have been designed for 3.5A per cell[...]

Does that mean that if I run a 84 cell system with 14s6p and draw 24A, I need to upgrade the connections because they can't handle 4A continuous?

I'll use these cells:
https://eu.nkon.nl/rechargeable/18650-size/samsung-inr18650-35e.html

 

[spinningmagnets]

The Vruzend system uses a "C" shaped steel connection that acts both as a compression spring, and the electrical conductor. I am glad they have been honest about the 3.5A rating that they have posted for its capabilities. However...

There is an additional upgrade that you can make. 0.25mm thick copper sheet is very cheap and available, and a slender strip of this material can be used to overlay the metal portion of the connector to increase its amperage capacity.

I found that any thickness that was thinner was too fragile when made from the relatively soft copper, but anything thicker was difficult to cut with scissors.