Two vents for Hybrid battery?

You will probably need to force the vent fan on for the tissue test.

 

Mine has both - in the first photo, you can see part of the side one.

 

three blind ones, no doubt.

 

I think TP meant just the long thin vent, we all have both.
I think it's a smelly feet extractor

 

Seems that ZVW50 prii (NiMH traction battery) have one vent in the centre, while ZVW51 (Li-on traction battery) have both or the larger one.

Maybe it is for better Li-on traction battery cooling, or controlling air flow on special occasions? If I recall ZVW51 have a hydrogen gas exhaust connected to the Li-on traction battery to comply with future regulations about safety against possible explosion and fire cases might have been happening on cars with Li-on traction batteries. Could have been possible to be part of a system related to such future regulations?

 

I believe a lithium battery only produces gasses when exposed to water. The battery then releases multiple gasses including hydrogen, carbon dioxide and carbon monoxide. Not something I'd imagine they want venting into the car. Eventually the battery catches fire in dramatic fashion. So if there is an exhaust vent for gasses from the battery I would bet (and hope) it's vented to atmosphere rather than the cabin of the car. Nickel batteries will release hydrogen if overcharged, something that occurs more often than water on a lithium, which is why they are typically vented to atmosphere.

My guess is still that the vent has to do with cooling the battery since lithium batteries are much more temperature sensitive. I don't know anything about the prius battery but my small understanding of lithium batteries comes from a few years ago when I used to play with RC cars. My understanding is that if the battery has a cobalt cathode, at 302* F they can become unstable and will begin thermal runaway resulting in a big fire. Manganese cathodes can go up to 482* F. You can mix the two materials (and others) to balance performance and temperature which is probably what we have. The possibility of thermal runway in my backseat is never far from my mind, but it's just been something I'm aware of, other than placing items behind the driver rather than the passenger (my theory is it's a blow vent not a suck, plastic bags on the floor won't block it) I don't do anything different than a normal car. I still continue to haul buckets of salt water in my trunk on a weekly basis (although I do find myself triple checking the lids) and I don't crack my windows on a regular basis. But if I ever thought I noticed something like a smell or extreme heat coming from the backseat I would run far away from this car. I wouldn't say I'm scared of this car in anyway, I'm just aware of the risk.

 

Is it to relieve cabin pressure if you slam the back hatch or a door closed quickly?

Your move quite a volume of air when you close that hatch I'll bet. Most modern cars are very well sealed around the cabin for noise reduction. Moving air needs somewhere to go or the doors would close with resistance.

The cabin heating up during the day would also increase in pressure slightly.

Many vehicles release the air from the cabin through a similar system, often out through a trim-piece into the space between the panels.

Less often some older vehicles would vent behind the wheel arch liners.

They all had a flap or reed valve that would keep it closed until needed.

If I remember, I will have a look at mine next time I'm giving it a clean out.

 

This is Li-ION layout




NiNH Battery

 

I am pretty sure it is for exhaust from the battery fan. If you look at this video, link is at the right spot, you can see the cooling duct ends there.

 

2021 Prime Ltd have 4 air vents for the high voltage battery. 2 at top and 2 at bottom of rear seats.