nuxland wrote:Want to build solderless pack and need some opinions.
Basically ANR26650M1 cells are sitting inside orange enclosures 10 in parallel. Connections will be made with 0,5mm thick copper like in this image but 10 in parallel. Also final size of 34s9p (will change this to 34s10p instead), together 23Ah but capable around 60kw bursts.
Question is: are these connections capable of 600A in burst and 300A continious? 0,5mm thick copper and 1cm wide for each cell should do 0,5mm2 and 10 of these should do 50mm2.
Also copper is pressed against battery with enough force (rubber ring between copper and plexiglass), so that should be enough, as right now I'm using 35mm2 wire in my kart and thats ok.
First off, Bravo ! I gotta say I'm impressed... The compression system is beautifully engeneered and progress seem to be going fast in your build !
If I use a ruler and do a rule of three (knowing 2 holders = 57 mm wide), it seems like your copper is more like 13 or 14 mm wide rather than 10 mm. Please correct me if I'm wrong...
So let's say 13 mm x 0.5 mm = 6.5 mm2.... IF you use
really really really pure copper (and please verify the %IACS of the exact copper alloy type you are using, so you know IACS is close to 100%)... I mean the electric grade kind of copper....
Then with 6.5mm^2 cross sectionnal area, you should get a resistance of around
2.60 milliOhm per meter for that strip.....
About equivalent to 9AWG pure copper wire (which ampacity rated for
64 amps by Powerstream.com -->
http://www.powerstream.com/Wire_Size.htm). So
approximating that strips will behave like
a round and insulated copper wire (which they will not because they dont have insulation and dont have a round shape but are rather flat ---> much better for thermal dissipation!), you should be good for AT LEAST 64A/PER STRIP ampacity (of course, don't just refer blindly to ampacity, as lenght of metal plays a very important role, and it also depend of what you are willing to accept in terms of heat, power loss, voltage sag, etc).
With the same
ballpark logic,If, rather that 13 mm, it is 10 mm wide x 0.5 mm (5 mm^2) PURE copper, that resistance will be 3.36 milliOhms per meter. About equivent to 10AWG in term of cross-sectional area.... the 10AWG round insulated wire being rated for 55 amps.... The flat strip with same cross-sectionnal area could probably take more amps as it might dissipate heat more easily...More amps than 55A yes, but if your will to accept bit more voltage drop and power loss...
A while back I was asking myself the same question.... So I made a table : Here it is (note that copper, nickel, tin, etc here are of the kind you would use for electric stuff.... Not the alloy that copper pipes are made of, which is usually 85% IACS).
Actually, to others benefit, here is my original file (better resolution, and with intrapolation graphics for where I came up with these numbers):
Please note :
The RESISTANCE VALUES are exact (assuming electric grade metals, not unpure alloys used for other purposes)... But
the AMPACITY VALUES are ballpark approximation (it assumes flat strips behaves the same as round isolated copper wire of identical cross-sectional area.... which it is not.... Flat stips could probably dissipate a bit more heat than round core insulated wire... So AMPACITY VALUES probably underestimates what your stips are capable of).
Dont forget also... this is all theoretical. In practice solderless connections might be the bigger problem, as a loose connection will generate very high resistance... A loose connection is your worst enemy ! All that work with heavy gauge copper, destroyed because of loose connections....
BUT, Your design seems well above other solderless packs (including my own first naive experiment with solderless), maintaining very high and evenly spread pressure... I have very high hopes on this. SUBSCRIBED!
Hope this helps and keep up the beautifull work !
PS : My own first naive experiment with solderless :
INITIALLY :
https://endless-sphere.com/forums/viewt ... 50#p121314
and
https://endless-sphere.com/forums/viewt ... 5#p1235640
WITH MORE PERPECTIVE :
https://endless-sphere.com/forums/viewt ... 8#p1236205
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