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pip-MGX 64v max charge 14s or 16s
#11
with these DIYBMS being limited to 64 modules that would mean 4x banks of 16s , but that would only be 4v charge

so I might do 15s = 4.2v @64v just means 1 empty cell holder

or should I just do

https://www.lithiumbatterypcb.com/produc...2-2-2-2-2/
and
https://github.com/simat/BatteryMonitor

anyone know how many different banks it can display ?

mind you I already have a spare 16s 50A here for my ebike , I have a feeling it was possible to downgrade it to 15s
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#12
(08-12-2020, 04:02 AM)MasterCATZ Wrote: well what would your thoughts be on spring loaded holders ? 
I do not mind paying $1 a cell holder if it means I could build something expandable that I could start running now 

https://www.ebay.com.au/itm/18650-Cell-H...3452699433

honestly, those cell holders would be trash to use in this application. They are only good for small applications/projects, portable even. And definitely nothing that required a decent amount of current flow, anything more than 500mA (even that is pushing it). The tabs are nickel coated steel. Not very good coating at that. There's a lot of resistance build up at moderate to high amp loads. There's a video/images somewhere on here that shows the tabs heating up a LOT under 1A load.

Also, $1 per holder is expensive and would eat up all your savings you got from reclaimed cells. You'd be better off taking all the $$ and using it for brand new cells.

If you insist on cell holders, use ones that use beryllium copper alloy. Not only do they handle the current better, they also don't loose their tension over time.

Also, you do not want to run used cells to 4.2V. You have no idea how many cycles they already have and by going to 4.2V, you are assuring them a short life. Just by dropping to 4.1V you can add 100's of cycles. Dropping to 4.0V you can add over 1000 cycles.
A cycle doesn't necessarily mean from full->empty->full. A partial discharge to about half and then back to full would be considered a cycle as well.
Proceed with caution. Knowledge is Power! Literally! Cool 
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#13
that was why I was wanting to go for the higher 16S so upper cell voltage was lower and would be impossible for the mpp to over charge
now just waiting on my diybms boards to arrive
I am hoping 1 controller can do 4x 16s banks , just unsure if the controller can only do 1 bank at a time or not
min order was 5 controllers anyhow so no biggi just sucked having to order 30 batches at a time

as I have 1.2m heated bed I decided to 3d print my own cell holders inspired by https://www.thingiverse.com/thing:456900
how ever I have my positive and negative opposite of their design
used just under 50m of filament per 40 cell pack ~2hr each to print
the negative contact fingers are made directly from 2mm x 40mm x 800mm copper flat bar (should handle 300amps )
by cutting slits every 10mm and rolling back as fingers and have positives with spot welded fuse fed through the printed spring hole , this allows tension on the negatives bus bar

16s40p x4 banks

allowed me to do slide out shelves using my old server rack rails and be able to swap out single cells easily
using flexible welder cord to link the shelves ,
ended up with ~2k 3000mah cells
and a heap of others around half of that
what peaved me off the most is the cells that worked out ~1500mah cost me $15 a cell (new $800 e-bike battery packs ) while the 3000mah ones cost me $1.5 a cell (used tesla modules)

how ever now that I think about it spotting a blown fuse will be hard ... next time I will run them over the plastic spring
can only melt through it
I was going to do threaded bolt / nuts but then thought knowing my luck I would over tighten and explode
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