MSantos,
Thanks for the detailed explanation. It was helpful.

Kenny, nobody can conclusively say that you are damaging your batteries by allowing the cabin temps to reach 90 (32C). It may very well be that you'll be an exemplary statistic and never suffer from a NiMH cell failure.

However, there's also no denying that you are stressing them more than you would if the temps were a little lower. I should mention that the temps in the pack are MUCH higher than 90F (to avoid mentioning the actual scary numbers) .
The greatest enemy of a NiMH battery pack is heat - so the lower the cabin temps the greater the cooling efficiencies within the IMA power control module. Heat causes chemical erosion of the batteries and electro-migration of the surrounding electronics. These symptoms are typicaly irreversible so it is in our interest to ensure that we keep the cabin temps in check.



Cheers;


MSantos

Interesting information. If I follow correctly the A/C Unit also cools off the Battery Pack - is that correct?

Today we drove from Phx 100 miles into Central AZ and noticed that the A/C began to weaken/not cool as efficiently and the rear right seat and seat back became very warm. Too warm to sit on. If the A/C is not working efficiently then the battery Pack is not being cooled properly - would that be a fair assessment. What else would cause the battery pack to heat up that much?

We had the car in for an A/C check and they said it was working normally. I have told them that after about 1 hour of driving up hill from Phoenix the A/C struggles and now I am noticing the warm seat/seatback.

TIA

Ed

So we don't know if and external temp of 90 deg F during operation is a damaging temp to batteries.
But we do know that cooler is better.

Hmm. . .

Perhaps I'll compromise and use my AC if outside temp hits 85 instead of 90 or so.

It is possible those Honda engineers assumed humans would never tolerate a 94 deg F external temp without turning on the AC when designing their systems.

All designs are compromises based on assumptions.

Need fewer troops to support.
Drive a hybrid.
Best tank 71.65 MPG.

Before this car I spent two years learning hypermiling on my 2004 HCH1.

W-o-w. I would love to see the dealer's face when you ask him to rip apart your AC to try to save 0.2MPG! Not to be rude, but this is a dumb idea for more than a handful of reasons...

In all seriousness, this idea is only logical if you have a reputable mechanic that 1) will buy the AC parts from you for ~$1000, and 2) will do the work for almost nothing. And you probably do not have either of those situations in your favor.

Ed, you are correct.

Under normal operating circumstances, the battery pack is indirectly cooled by the AC system (or whatever other means you can cool the passenger cabin with).

It makes sense that the back seat gets warm in extremely warm days. The temps in the power control module can go much, much higher than 200F.


Cheers;

MSantos

You are quite right my friend! Quite right.


Cheers;

MSantos