Hi folks, Out of interest, what's the safe upper limit for battery temperature? Driving my 04 yesterday I noticed that there was a heck of a lot of noise coming from behind me. (I could hear it above the radio!) On switching to my CANview screen I noticed that the battery temperature was +56 degrees C! (133 F). Isn't that a little high? Just curious really as to what the upper limit is. I'd just been doing a long downhill and my SOC was up to 75%. Cheers, Nikki.
Wow, I've never seen it close to that. The hottest I've seen mine is 120F-ish after a long descent out of the mountains. SOC was higher than yours though: 82%. But I can't answer your question; I'm curious to hear what the experts say. My mostly uneducated guess is that with car's protective systems in place (e.g., the battery fan, using the ICE preferentially with high SOC and high battery temps), the battery will never reach an unsafe temperature. But I don't know what that temperature is.
aminorjourney, were you running the air conditioner? What was the outdoors temperature? (The noise of course was the battery fan.)
haha i've seen it up there too, on bc hottest record day! My A/C was disabled at the time, so by the time I got to recharge it, the days cooled off !! But for days like that I'd crank the A/C and ensure your driving at a decent speed to cool off the radiator and keep your power demands low so you don't create more heat from both the engine and the inverter/motors. I think personally the sweet temp for our batteries is around 20-25 degrees C when digging around phev conversions wiki.
For NiMH batteries in general, the less time spent above 45 oC, the better. I believe that temperature corresponds to the Prius battery fan going to 'high'. If the air entering the battery is not sufficiently cool, the fan can't help much. For the 2001-2003 Prius it was possible to set the HVAC to flow-through and turn the A/C on max. This combination could cool the battery by 1 oC per 3-5 minutes, can't recall the exact rate. Unfamilar with the control settings available on the newer model Prius. I don't like the sound of 50-something battery temperatures in Prius though. Do whatever you can to avoid getting them that hot.
