Willard, we know the desired range of the battery temperature is from 77F to 100F from the manuals. The climate control system is used to maintain that specific range with two internal variable speed fans in the battery housing.

As the outside temperature gets colder, the need for the A/C compressor is reduced or eliminated. The HVTB monitor controls if fresh air or recirculated air is to be used and activates the battery mode door motor accordingly. It all depends on level of charging and the outsde temperature for the need for the A/C compressor to assist in cooling. With the use of repeated fake shifts in "L" to charge the HV battery for max EV use, I hear the compressor kicking in at a low outside temperatures of 60F sometimes. One HVTB climate control PinPoint test is to check the center cabin A/C vent temperature for an output of 32F - 48F. This may suggest that enough heat in the battery may require at least 48F air for cooling it down to the desired range at times.

The mileage I get depends on the temperature of the HVTB and related electrical motors and equipment because of my heavy use of EV mode. So far, a outside temperature between 50F and 60F, gives me the best FE possible. Of course this is taking into the effects of both the ICE and EV mode operation for overall performance. Not just the battery.

GaryG

"...as its final attempt..."

The question is....

At just what temperature must the batteries rise to before the system resorts to the use of A/C for cooling them.

Does anyone know for sure what type of battery is used in the FEH/MMH?

Buying a small battery of the same type and charging it fully and then using a constant load to see how it holds up "frozen" versus room temperature is a simple enough task.

You missed the point of the conversation entirely....

Just because you can run the battery at 140'F ( the manual actually says 135'F ) does not mean you should.

Just like you CAN run the ICE at redline RPM for "max output" does not mean you should do it all the time.

Once in a while, OK......

P.S. I was reading somewhere a couple weeks ago that "optimum" temperature for some new battery technology is in the 140-170'F range.
I can only imagine how poorly these would perform in Canadian or upper midwest winters. Instead of A/C refridgerant running to the back battery, we'll need to be running engine coolent water back there!!!

I assume you mean beyond Nickel Metal Hydride?

Just to jump back to the original topic, are we in agreement that using the jump start button to warm the battery every time in the winter isn't a good idea? Or did I miss something?

First 4WD Hypermiler

Have you read the FEH FAQ?

Live in Michigan? Let it be known in Michigan Roll Call

Read My Automotive Blog at Rich Rambles

"...are we in agreement...."?

Absolutely...!

Not a good idea in any case, but...

In order for this to work, and work well, you would have to begin with the hybrid battery already discharged down to, or near the 30% level.

No (re)charge required? No heating of the hybrid battery due to the charge rate.