traction battery overheat

hot battery doc fusco thinks in a related thread. any chance of cover for the car?

 

I wouldn't say the battery is overheated. The car babies the battery in several ways, including thermal management. Others have reported that when the battery reaches 104F, the car uses the ICE preferentially over the motors to power the AC (which I assume you're running) and limit current flow out of the battery, reducing additional ohmic heating. The result is more work for the ICE, which means higher RPM and less ICE-off time.

I had an episode last summer of sluggish performance when OAT reached 104F. The consensus on cause was a hot battery (105F).

In the midst of peak summer heat I take steps to keep the battery cool: park in the shade whenever possible, a windshield sunscreen, and cracking the windows. I also have window tinting. Once heated, the battery takes a while to cool, even with the battery fan and AC on. Better is to prevent it from getting so hot in the first place.

 

I'll add to that a form of babying I spotted with my Scangauge. My SG2 is only a few weeks old and I've found monitoring the traction battery current to be one of the most interesting uses. Going down the same long hill on most trips as the first major stretch after our house, I'd gotten used to seeing 80 to 95 Amps of regeneration current if I had to stop at a stoplight, and was starting to learn to modulate my braking to keep it below 80 as a measure to assure as little brake wear as feasible. So one time I went right back down because I'd forgotten something, and was going down the hill with a warmer car and battery than usual, and was surprised to see the regen current limiting to something under 30 Amperes. And, no, the battery fan was not on yet.

We generally don't hear it turn on for weeks at a time, but the single trip from which my wife has most often heard the battery fan is one that takes her downhill the better part of a thousand feet, then she parks for a couple of hour meeting. More than once, she has heard, and been puzzled by, the fan starting up fairly shortly after starting her return trip. As the meeting is an evening one, I suspect part of the setup conditions involve how recent and battery-strenuous here immediate previous trip was.

The SG2 is in my Audi right now, when it goes back to the Prius I hope to get one of the published traction battery temperature XGauge settings working. I suspect I'll see something to surprise me.

 

I don't know if increased humidity has anything to do with what you're experiencing but it's been a consistant 110-113 the last few weeks here in AZ and I have yet to hear my battery fan come on (although I haven't really tried to listen). I can tell you my car acts exactly like it does when it's cold. It'll run several minutes on battery, then when it gets down to 2 bars it will start up for a few minutes, then the ICE will turn off again. Acts like normal, just drains the battery a bit faster.

Mike