Typical China battery poor power/current share !!!

[Nealh]

I opened one of my Dolphin 29E packs today to have a look at cell layout and connections and not to surprised to see the poor series connections which leads to poor power /current share amongst all cells. Cells are all connected in a long row alternating every 5 cells as it is 5p between + & -- for the series connections.
All the blue dots mark a series connection on one side which is a poor way to share current/ power. Only 5 series links per side, ideally 25 should be what we need for perfect power share The nickel strips are doubled up and look like 0,15mm though might be 0.20mm.


If I bought this this new today I would open it straight a way and ensure the power /current share is much improved and as perfect as possible. Marked by the dots above I would remove the five double layer of nickel forming the series links.
And would use 18awg silicone wire soldered (as indicated by the colours) to each cell, each of the five wire lengths need to be the same length to the next series connection, though other series connections can have different length wires to the previous or next group. For equal current share to the next cell the five distances from cell to cell in that series connection need current to flow the same distance.

 

[Woosh]

this is how it's done from one of my suppliers.
it's a 48V 12AH HL battery with 21700 cells:

 

[Nealh]

A 14s 3p so actually 52v not 48v battery, which bike is that on ?
Or is it the TSDZ kit ?

 

[Nealh]

At least they have upped their game better, my one above was originally from a Big Bear BPM kit.
It is better but still not perfect for equal current share.
Each outer cell in the series groups is receiving again half the current from the center cell so they will be getting a bit warmer and having to work a bit harder.
The center cell cannot move it's current share directly in series to the next cell opposite, instead it has to go around the houses (as to speak) and get there via both it's neighbours loading them with 50% more current.


This would be nearly perfect except for the differing shaped group.

 

[Nealh]

Everyone feel free to add your packs or builds to the thread so we can all improve our designs builds together.
The more uniform a pack is, the easier it is to make for equal current share, the layout is key and in my pack in #1 the execution/layout from the factory could have been much better.

 

[Woosh]

A 14s 3p so actually 52v not 48v battery, which bike is that on ?
Or is it the TSDZ kit ?

ah.. I shouldn't have posted these pictures. They are of a current project, still in prototype stage.
The current TSDZ2 kit comes with ordinary Samsung INR 18650 29E in 13 x 4.
We are moving to 21700 GA 5000mAH cells. They make for tidier packs.

 

[Woosh]

Everyone feel free to add your packs or builds to the thread so we can all improve our designs builds together.

I am most interested in small packs for folding bikes.

 

[Nealh]

ah.. I shouldn't have posted these pictures. They are of a current project, still in prototype stage.
The current TSDZ2 kit comes with ordinary Samsung INR 18650 29E in 13 x 4.
We are moving to 21700 GA 5000mAH cells. They make for tidier packs.

Nooo, don't be shy it is good to see even for a protoype bike.
5000mah sounds good , 21700 GA not heard of them yet ?
The wrap to me looks like Sam 50E 21700 !!!

 

[Woosh]

you are right, that pack was 14x3 INR21700-50E

 

[Nealh]

you are right, that pack was 14x3 INR21700-50E

AK will be excited by that news , that is one of his dream cells at the mo .

 

[Nealh]

Got to admit it has now peeked my interest as a 14s 3p/52v pack would be 780wh and work with my 48v controllers, 58.8v or even better 57.7v /4.12v per cell charge would be good with min discharge to 47.6/3.4v per cell. Limit the controller to 15a@52 for 780w peak controller output.

The advantages are there to be had at the mo except for the cell price per unit,
but fewer cells = a bit cheaper. Also less welding required and series connections needed, things will slowly start moving in the right direction again.
Every few years we see a bit of progress.

 

[anotherkiwi]

AK will be excited by that news , that is one of his dream cells at the mo .

Sorry I was just wiping the drool off the floor...

What is good news is that they fit in the HL case. 3P is too little for my needs though.

We need on the road testing report now Woosh, how do they hold up on a +10% climb?

 

[wheeliepete]

with 21700 cells

21700 cell holders for the hailong case, they would be nice to see available from somewhere.

Sorry I was just wiping the drool off the floor...

I think i've got the same problem as you AK when I see 21700 cells.