So it begins...... Battery spot welder

[sternwake]

Hmmm.. wonder if you can integrate a gaming pc processor radiator/cooler for the battery?
Sorry.. just spitballing.. lol

My old DMEGC-26E 10s2p battery was running too hot, getting to 58C/136.4F all to easily.

This was measured on the outside of the pack, atop lots of layers of fishpaper, Kapton tape, 0.5mm  G10 fiberglass, silicone, and heatshrink.  

The actual cell temp were likely way over 60C, which is the max rated temperature of this particular cell.  

The battery was nestled in neoprene foam padding within the fiberglass enclosure, which did radiate some heat to the fiberglass enclosure, so there was some minor heatsink effect, and I did some experiments with different density foams to increase the heat transfer, but concluded that the battery was just not meant for Florida summer pavement temps and pushing nearly three hundred pounds at 16 mph for 7 miles.

The new BAK45D 10s2p battery, a few hours ago, pushed us far faster for nearly 10 miles, in very hot ambient temps, and its exterior stayed under 40C, and the battery is rated to 80C.

So my overheating battery issue is basically solved, with the Tabless cells, along with them providing  increased  torque, topspeed, and range.

My old battery, after a run, I basically had to remove enclosure, and run fans over it for a while before being able to safely recharge it, and then not recharge it too fast.

When I'd flip the  warm enclosure over, i could feel tons of heat escape, and searching with IR gun and placing Ktype thermocouples near hottest spots, revealed the extent, and safe to say the cells themselves often exceeded their 60C max operating temperature.

Battery temperature does directly affect lifespan, and performance.  The Tesla Plaid in drag race mode will heat the cells, intentionally, to lower their resistance, so they can dump more power to the motors.  

Since I can easily run at max throttle, I could tell whether the old battery was cool or warm or hot, by the throttle and torque available.

Extracting excessive heat from the Battery cells is something the EV makers have put a lot of time into.  Pumping coolant around, and ventilation, and phase change materials are all effective ways.  I kept looking at the dead air space between cells as an enemy when assembling the new  BAK pack, and filled them.with Silicone.
Not the best conductor of heat but better than dead air space.
  
I'm lucky that my heating  issue was solved with higher quality much lower resistance  Tabless cells.  It's nearly as hot as it gets here, and My ESC can't pull more than it does now, and Florida is not vgoing to grow hills I need to climb,.so I cant really heat the battery much more than I did Today.

The BAK45D does not run as cool as the EVE 40PL or Ampace JP40 cells either.

The EVE 50PL runs even cooler, and the Ampace JP50, and BAK50D, are not too far off from availability, and will have higher  capacity, higher max discharge rates,, and should run even  cooler.

Molicel.is teasing us with future cells with amazing specs,.some.of which are designed for higher operating temps and not sacrificing safety or  cycle life.

Their P50B was almost impossible to get this time last year.. It is not tabless, but can be charged at 25 amps, twice that of the BAK45D.  It has gone from 10$ each to 7$ recently. Product of Taiwan.

Hopefully these new  super high performance cells are available soon at reasonable.prices.  That topic which we cant discuss here has pushed up prices 20% or more in the last few months.  The BAK45D 2 months ago was $4.75 each.  I waited too long and paid 5.45$. They now are 6.85$ each.

I do want to build a new 10s1p for my mini lightweight grocery getter which has been backburnered.
 My Bak45d should last far more than the 3500 miles the Dmegc did.  It still works too. still good  capacity. It just runs too hot, and sags too much voltage.

A few months back I measured sag.  From garage to a patch of shade at full throttle, 42 volts sagged to 36.5 and I achieved 16mph.

Did the same exact test today with new BAK battery.  42v sagged to 41.2, and I achieved 21mph.

Not a  totally fair comparison as BAK battery  is new, was hotter, and wheel diameter is worn smaller, for more torque.

New larger hub motors were to arrive yesterday, then today.  Hopefully tomorrow.
 They will be smoother and more quiet.  Will likely lose some.torque, but gain top speed.

Fiona.is not scared to go faster.