the car was working great in AM and bricked in PM. please help!

I got out of work and the car was completely dead. not responding to the wireless fob whatsoever. i opened it using the manual key and nothing. no cabin light, no green power button light when pressing brakes. my son came to rescue me. i connected the booster cable myself making sure no reversed polarity. nothing, no spark, not cabin light inside, no response to brake or power button. we waited quite a while with the cable connected and his car running waiting for a miracle that didn't happen.

at the same time, i know i left no light on, and there is no reason the battery drained by itself. i'm thinking it's some major but random electrical fault. the battery was replaced 2 years ago, because the OEM was getting old (8 years) but still good.

tomorrow, i'll bring the old good battery to swap. and i'll check all the fuses. it was too cold and too dark to do it today. any other ideas before i give up and tow it somewhere?

for the record, it's 2010 with near 126,000 miles. it's was a super reliable car and never gave me a problem till now when it seems bricked in a big way.

Thanks for listening!

 

Thanks Dave! I tried to jump at the post, as the hatch was locked. I'll unlock it tomorrow and I'll bring a multimeter too.

 

update: i revived it this morning. i came well prepared with a bunch of tools, a charged spare battery, multimeters, cables, and info how to take the fuse box apart in case a hidden fusable link is dead: Reverse Polarity Jump Start - Gen3 Prius wont Start | PriusChat

the car surprised me. i expected it completely dead, but it opened with the wireless fob. i opened the hood and checked the voltage. it was 12.0V, completely discharged, but not completely dead. i attempted to start it, but it produced only dashboard lights and no ready. then i looked at the battery itself and measured the voltage at the posts. 12.0V again. but i noticed a loose nut. the one on connecting positive wire. i finger tightened it and the car started and went to ready with no problem. i made sure not to turn it off and took it back home. after running it for about 30 minutes, the battery is at 12.6V, not fully charged and i put it on a charger.

i suspect the problem was an intermittent connection at the battery and it never fully charged. last night the connection was totally gone and hence the car was completely dead. it doesn't explain why i could not get it jump start with several different attempts. before my son came, i got a security guy with a portable jumper (of course i connected the leads myself), but i assumed that thing was faulty. when i couldn't jump it with my son connecting it to his car, that made me think a lot. i need to check if his jumper cable is operational and if the crocodile teeth are working only one sided. last night, i completely forgot about it as a possibility.

when the battery is fully charged, i'll load test it and report back.

 

yeah, the loose nut surprised me. it was tight for sure when i put the new battery in over 2 years ago. maybe it wasn't tight enough? i didn't know what torque was needed for that. BTW, the battery tested OK on the analog load charger. exactly the same as it did when new (i keep notes on batteries on my cars).

thank you both for the support!

The whole thing illustrates the design flaws in this generation of prius. if you put the battery in the trunk, you need a manual release cable for the trunk and not just an electric lock. then the jumping post under the hood should be 2 sides metal. i suspect the reversed jumping accidents may happen when people connect the leads correctly, nothing happens, and then they get confused and reverse the leads. pure speculation, but makes you think. i thought i was mechanically savvy, but yet i got confused by the whole thing. YMMV

 

i just tested my son's jump cable. sure enough, it conducts electricity only on one side of the teeth.