2011 GS450H w/ 216,000 miles here. I got the error one night while delivering for Uber (my side gig). I had long suspected the battery was weak many months ago and fully expected a failure at some point, and it finally came. Months ago, I took note of the poor gas mileage (17-19mpg), inconsistent readouts on battery charge state, cells going from blue (5-6 bars) to purple (1 bar) INSTANTLY), laggy acceleration, HORRIBLE capacity, etc. After the lights came on the dash, I was still able to drive perfectly fine, but only on engine power, but I knew I needed to fix a couple of bad cells. After many many hours of research, many YouTube videos, threads and guides, I got around to opening up the battery and when I removed the outer metal case (to reveal the individual modules), the long rubber tubes used to vent the individual batteries were both MISSING... I guess this explains why there was a hose unplugged from the car when my friend and I took the car apart.

For reference, the black rubber hose running alongside the battery modules (not the stiff metal bars):



My questions is...

How vital is this part really? Car seemed to be running okay without it. I didn't notice any obvious signs of heating issues when opening the pack either. It's obvious any "exhaust" from the batteries does not vent out the car as it was designed to, but rather it's venting inside the car (which, again, never seemed to be an issue driving hundreds of hours). Is this extremely dangerous, or did the previous mechanic know something we didn't? Do we even need this? He might also just be a complete moron, dunno.

Video of my setup, with missing ventilation hose: The official part is listed at $240 here: https://www.lexuspartsoutlet.com/oem...ose-2888531080

I'm honestly thinking of just getting similar size rubber hose/tubing and cutting the appropriate sized holes myself to fit along the top of the battery. Shouldn't be that hard to attach it to the rest of the ventilation components. Would this be an awful idea? I can't find the part on eBay (makes sense, considering who's really selling these?!), and I can't justify spending $240 on two long pieces of rubber. Toyota is nuts for this price.

Thoughts? Suggestions?