leaking battery?

The battery compartment has been known to collect water when it rains. Somehow water is able to enter the Prius and end up in the battery area. So what you are seeing is most likely water that's been there for a while (moldy)...yikes

 

If you have the correct battery, it should be a sealed AGM battery. It won't leak

 

Nice photo....looks like that is coming from the HV hybrid batt area.
Can't tell what the heck it is. it is near the fan vent to the rear seat, so maybe some liquid got into that vent?
I think it might be a good idea to have fan cleaning service (many people get those cleaned out) and also if cost-effective shop available, someone could check your contacts in the HV batt and clean off the corrosion, may be see what is going on.

The other way liquid can come is from the exit side of the vent by the rear wheel...if you got your car washed with some problem , the liquid could be forced up that black conduit and leak out there.

OK third idea - photo almost looks like you had something (milk etc) in the rear compartment that leaked down the carpet surface and fell down over the HV batt protective structure and pooled on the floor.

 

I agree with the above. In your picture it can clearly be seen that the liquid spillage was in the area above the HV battery running down and over it's top cover. Try removing the rear seat squabs, and panel over the battery to see if there is any spillage there.

John (Britprus)

 

It's definitely isn't spills of food. I buyed used 2007 Prius and now i have practically the same yellow things. Same color, same spot, but not so much as in photos Johnny provided.

 

If you don't find an obvious source for that leak, the next step would be to remove the traction battery cover and make sure none of that mess came from or got into the battery case.

 

Ok, got to admit I also thought it looked like spilt food too.

Kinda looks like someone left a cake out in the rain,
and then tried to transport it in a Prius,
with all the sweet green icing flowing down ...

Hmm, this is getting interesting now. I thought Johnny's just looked like spilled food or something, but two the same seems like a bit of a coincidence. Now all we need is one of you two to be game enough to taste it and see.

Ok, perhaps not taste it, but what does it smell like. Does it smell corrosive, like acid or alkali?

 

Its nos smelly or something, just yellow mass. Then touching feels sticky a little bit. Adding some photos. Mine leak are much smaller then Johnny's. I must admit that the leak could be her from outside during car wash from the venting pipe.

 

The electrolyte in the HV battery is KOH "basically caustic soda used to make soap", and is colorless. It feels slippery " like soap" if you get it on your fingers not sticky. Any leak from the battery to the extent in the pictures would have dash lighting up like a Christmas tree from ground fault codes, and failing module voltages.
Wash your hands if you do get KOH on your fingers.

John (Britprius)

 

In my case yellow thing is not a liquid anymore. It's sustained like glue or something. Touching it do not do anything Two weeks ago i did ODB diagnostic and modules (pairs of cells) looked well and no battery related errors were reported. Suspect i need just to clean this thing then i will do venting fan cleanup.

 

Yours doesn't really look very much like Johnny's. Different colour, different extent, and much less corrosive looking.

Yours could be something as innocuousness as an aftermarket corrosion inhibitor being applied by the previous owner. Lots of after market corrosion inhibitor products can leave a residue like that in areas where they can accumulate and slowly dry out. The spare tyre bay is just about a classic example of where this can happen.

 

I have the same pine tree in my yard!
The two stains do look different to me.

The only thing I can think of as far as ID is to get some on a wet rag and get the pH. You'd have to get some pH paper from Amazon or something. If it was strongly basic that would say something. Sort of looks a little corrosive maybe salty water or something...guess I am still assuming prior owner had some liquid spill in the back.

 

Mindogas I’ve seen similar stuff on many other cars. Newer caused any problems don’t know what it is. No idea about OP:s case.

 

KOH dries to a white powder. It is corrosive on copper and can strip paint, but is not so corrosive on steel.

John (Britprius)

 

I wouldn't taste it, as one other Prius-owner purports to have done.

 

did you disconnect the high energy plug?