Better battery cooling.

eq1 said:

Are you really charging your (stock?) pack at around 60 amps, close to 190V? Isn't that bad for the cells?

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At sustained levels without supplemental cooling and done on a routine basis, yeah, it's potentially bad, but it's still basically ~11kW limited.

For the purposes of demonstrating the effectiveness of a cooling system, I think it's a worthwhile exercise. It's not like these cells are fragile flowers. In my experience it's accumulated abuse or chronic adverse conditions that take them out.

What I would like to see is the exercise repeated -

charge/discharge/charge.
Pull over and cut the cooling system for 5 minutes.
See what the soak temperature is.

That would be a really good indicator of the effectiveness of the cooling system - how much of the temperature is a function of the sensors being on the surface of the cell vs. the core temperature of the cell.

If the battery temp is a pants-s****ing 140°F after 5 minutes - probably a really bad idea to stress the pack like that and not as effective as the initial data suggests - not because of the ineffectiveness of the cooling system, but the challenges of cooling big, fat cylinders and their s****y, s****y aerodynamics...

eq1 said:

On the subject of pack cooling...

In the Insight battery space, would it be better for pack performance and longevity to have cells packed closely so each cell is more likely to be the same temperature, or packed with space for presumably more air flow between cells, better cooling, yet perhaps risk having cells at more varied temps?

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We may have our answer in the HCH2. The 06-08 with it's much tighter spaced sticks and offset/nested spacing is the second worst pack ever made with a 1 in 6 failure rate in 5-7 years. The 09-11 increased the spacing slightly. Worst pack ever made with a 1 in 3 failure rate in 3-4 years.

Both have substantially more cooling capability due to an absurdly powerful blower that is literally as effective as a leaf blower and consumes about 100W. I messed my kid's hair up from 10' away when I aimed it at him. "DAD! STOP IT!"

It may be an unfair comparison because I'm pretty sure those are Sanyo and not Panasonic cells (before Panasonic bought Sanyo). They may be less heat tolerant as the Sanyo cells performed wonderfully in the air-conditioned battery of the Ford Escape Hybrid (battery rarely over 100°F).

From an aerodynamics point of view, more spacing and slower flow is better for laminar airflow around a cylinder's surface for maximum heat transfer. In that regard the puny 120mm fan of the Insight might have more potential benefit than the massive blower on the HCH1. However, in this regard, I would expect the HCH2 packs to have better cooling because the flow is deliberately interrupted and diverted through what amount to serpentine passages vs. complete cylinders.

OH THE HUMANITY! SCREW TRYING TO RECONCILE THEORY WITH REAL-WORLD!!!!!!