flathill wrote: okashira wrote:Guys - I need an idea for plastic washers for shrink wrapped cells. I am talking about the plastic reinforcement that protects the area where the positive and negative terminal meets. Heat shrink alone works OK, but I wouldn't feel good about selling cells without the washer to ensure durability.
An OEM Panasonic cell had one that measured ~17.3mm OD x 8.4mm ID x 0.2mm THK. That's .007" THK.
I found a couple places for custom washers that will be perfect (UHMW and PTFE) but the lead time is too long so I am looking for a short term solution?
On the test data, i'll post the 1A test of a cell tonight. I wont be able to run 3A, / 9A/10A/other rates until Friday/weekend.
Here is data on how to supercharge, see link. Your algorithm is too aggressive (max charge rate is 4.4A/cell not 2C, and tapers off early)
It's constant power (16.4W/cell); then taper power at 3.8V/cell; by 4.0V per cell 8.8 W (~2.2A) continue to taper to 1.5A by 4.11V.
If you do a 100% charge at a supercharge, Tesla goes all the way to 4.20V with 50mA cut (!)
I am working on a couple ideas to implement supercharging without a custom computer controlled charger. Ideas appreciated.
I think a resistor combined and/or 2-3 CC/CV staged power supplies with different settings.
Nice is that data from a 135kW supercharger? The actual Tesla charging algorithm takes cell impedance into account (old packs won't charge as fast, cold packs won't charge as fast, etc), but the basic charge algorithm may work well enough for us. As I read it you can safely charge at 2C up to 4.0V on a new cell and then you must taper to avoid damage. The Tesla supercharger may also need to taper for other reasons. The cable and connector can not handle 135kW continuous.
That's from a 120kW supercharger.
Noone knows why the A packs can only do 90kW (my cells are from a 120kW pack)
Yes, cell temp is important.
I'd take that graph I made, any algorithm we develop to mimic that should fall below the current vs soc line to be safe. I wouldn't do 2C until 4.0V. that would be MUCH faster then how Tesla actually supercharges, and hard on the cells....
At low SOC charging is endothermic, but there is a changover around 40% soc.
Obviously at ~4.5A the net effect will be slightly exothermic (resistive heating) but, sure I will do a test and log temperature. Hell, I will do 7A until 10V to see what happens.