Last week as I was returning home I had a strange event in my Prius. I was coasting at about 30 mph when I heard a very faint pop sound a bit like a balloon breaking. It sounded like it came from the right rear area of the car. Afterwards I thought I detected a very faint chemical smell. Could this have been something involving the HV battery? Has anyone else experienced anything similar?
You might want to check your 12 volt battery which is in the area you described (behind right rear tire and just before right rear tail lamp).
Definitely check small 12volt battery in rear for damage etc. Also there are simple diagnostics posted here to check to make sure 12v health OK. The 12v batt does evolve tiny amounts of H2 gas but this is vented via small black tube...if somehow the vent got plugged (spiders?) maybe it would pop off. Not quite sure how Gen3 vents it. Also you could take a sniff at the vent in the rear seat...that's where the hybrid batt vent intake is.
The 12V battery in your 10 Prius is a valve regulated AGM battery. Normally the battery cells never generate enough hydrogen / oxygen pressure to vent any gas, it is recombined into water and drips back into the glass mat seperators and used again. This all goes wrong when an aged battery cell shorts, in effect converting your 12V battery into a 10V battery. The 12V charging system will try the impossible task of charging the now 10V battery, up to the voltage of a working 12V battery. It will overcharge the remaining 5 battery cells to the point that the pressure relief valves open to vent the excess gas pressure. What you heard may have been the relief valves popping and smelled the vented hydrigen gas. Check uour battery for proper voltage, as a shorted battery may leave you stranded or do corrosion damage to your car from battery acid fumes.
Thanks for all the responses. My spouse wasn't in the car, but I could have farted - though I didn't (this time)! No warning indications or lights on the dash. I will definitely check the 12 volt battery and post the results.
Check that the spare hasn't blow. Rare but could account for the pop and the smell. Also see if anything is loose in there such as the jack. Failing that, whilst in that area have a smell around the HV battery (obviously not getting close enough!) to see if there's anything smelly there. The Prius would more than likely display an error message if there was any HV battery issue.
If it were mine I would remove the cargo area floor, remove the plastic storage tray above the spare tire and inspect both the 12V battery to your right and the HV battery that is just above the spare tire and behind the rear seat. As GrumpyCabbie said above check for anything loose and then smell around and see if you can find the source of the smell.
